Dr. Jeff Masters' WunderBlog

93L Fighting Dry Air, But Could be a Tropical Depression

By: JeffMasters, 1:47 PM GMT on July 31, 2014

An area of disturbed weather located near 11°N, 52°W at 8 am EDT Thursday, about 650 miles east of the Lesser Antilles Islands (93L), has maintained a well-organized surface circulation and has now developed enough heavy thunderstorms to potentially be classified as a tropical depression later today. Visible satellite loops on Thursday morning showed that the surface circulation of 93L was exposed to view, with a modest clump of heavy thunderstorms on the south side. The storm was fighting moderate wind shear of about 15 knots, due to strong upper-level winds out of the north. These winds were driving dry air to the north of 93L into the circulation, keeping heavy thunderstorms from forming on the north side. An ASCAT pass at 9:11 pm EDT Wednesday night showed top surface winds near 35 mph, just below tropical storm-force. Water vapor satellite loops and the Saharan Air Layer analysis showed that a large amount of dry air lay to the north and west of 93L. Ocean temperatures were about 28°C, which is 2°C warmer than the typical 26°C threshold for development. An Air Force C-130 hurricane hunter aircraft will investigate 93L on Thursday afternoon, and the NOAA Gulfstream IV jet is scheduled to fly a dropsonde mission on Thursday afternoon around the storm.


Figure 1. Latest satellite image of 93L.

Forecast for 93L
Moderate wind shear of 10 - 20 knots is expected to affect 93L for the next five days, according to the 12 UTC Thursday forecast from the SHIPS model. With the atmosphere around 93L now quite dry, the storm will have to work hard to insulate itself from disruptive dry air incursions. Sea Surface Temperatures (SSTs) will stay roughly constant at 28°C. The models agree that 93L will arrive in the northeast Lesser Antilles Islands on Friday evening, move over Puerto Rico on Saturday evening, and approach the Southeast Bahamas and Turks and Caicos Islands on Sunday evening. Our three reliable models for predicting tropical cyclone genesis, the GFS, European, and UKMET models, predicted in their 00Z Thursday runs that 93L would be no stronger than a 40 mph tropical storm as it passed through the islands, and then dissipate early next week near the Southeast Bahama Islands. The GFDL and HWRF models predicted in their 06Z Thursday runs that 93L would be a weak tropical storm as it passed through the islands, intensify some after passing over Puerto Rico on Saturday night, but turn to the north, missing the Bahamas. In their 8 am EDT Thursday Tropical Weather Outlook, NHC put the 2-day and 5-day odds of development at 70%. The Thursday morning runs of our top four models for predicting intensity, the LGEM, DSHIPS, GFDL, and HWRF models, predicted that 93L would have top sustained winds between 40 - 55 mph on Friday - Saturday as it affects the Lesser Antilles Islands, Virgin Islands, and Puerto Rico. I predict that 93L will continue to struggle with dry air as it passes through the islands on Friday and Saturday, with top sustained winds between 35 - 50 mph.

The GFS and European models continue to agree on the long-range fate of 93L. The great majority of the 20 members of the 00Z Thursday runs of the European and GFS ensemble models (which run at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed 93L taking a northwesterly track early next week in response to a strong trough of low pressure over the Eastern United States, then recurving to the north without hitting the mainland U.S. coast.

Jeff Masters

Hurricane

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Little Change to 93L

By: JeffMasters, 2:47 PM GMT on July 30, 2014

An area of disturbed weather located near 9°N, 45°W at 8 am EDT Wednesday, about 1150 miles east of the Lesser Antilles Islands (93L), has the potential to develop into a tropical depression by Thursday, but is struggling with high wind shear today. Visible satellite loops on Wednesday morning showed 93L had a well-defined surface circulation and some low-level spiral bands. However, infrared satellite images showed heavy thunderstorm activity was very limited, and the storm is fighting high wind shear of about 20 knots. Water vapor satellite loops and the Saharan Air Layer analysis showed that while there was some dry air in the vicinity of 93L, the bulk of the dry Saharan Air Layer lay to the north. Ocean temperatures had warmed since Tuesday, and were about 28°C, which is 2°C warmer than the typical 26°C threshold for development.


Figure 1. Latest satellite image of 93L.


Figure 2. Analysis of the Saharan Air Layer (SAL) made at 8 am EDT Wednesday July 30, 2014 using data from the Meteosat-9 satellite. Dry, dusty air was present from the coast of Africa westwards across the tropical Atlantic, but was fairly well separated from tropical disturbance 93L. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.

Forecast for 93L
The high levels of wind shear affecting 93L on Wednesday morning were expected to diminish to a moderate 10 - 15 knots by Wednesday night, according to the 12 UTC Wednesday forecast from the SHIPS model. With the atmosphere around 93L reasonably moist, this may allow the system to become a tropical depression as early as the 11 pm EDT Wednesday NHC advisory. Thursday morning is probably a more likely time for classification as a TD, though. Sea Surface Temperatures (SSTs) will stay roughly constant at 28°C. Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Wednesday runs that the disturbance would develop into a tropical depression by Friday, but were much less aggressive about strengthening the storm than in previous runs. In their 8 am EDT Wednesday Tropical Weather Outlook, NHC put the 2-day and 5-day odds of development at 70% .

All of the models predict that the disturbance will continue west-northwest at 13 - 19 mph for the next four days. The UKMET and the European models offer the fastest solution, predicting that the disturbance will arrive in the northeast Lesser Antilles Islands on Friday evening, move over Puerto Rico on Saturday evening, and approach the Southeast Bahamas and Turks and Caicos Islands on Sunday evening. The GFS is slower and more to the northeast, predicting a Saturday morning arrival in the northern Lesser Antilles, with passage about 100 miles northeast of Puerto Rico occurring on Sunday morning. Dry air to the north of 93L will likely interfere with development throughout the week, and the atmosphere surrounding 93L will grow drier as the storm progresses west-northwest. The moderate levels of wind shear forecast to occur will be capable of driving this dry air into the core of the system, disrupting formation. The Wednesday morning runs of our two top statistical models for predicting intensity, the LGEM and DSHIPS models, forecast that once 93L became a tropical depression, it would intensify into a hurricane within 3.5 days. However, the dynamical GFDL and HWRF models, which made good intensity forecasts for Hurricane Arthur, were much less bullish. The Wednesday morning runs of these models predicted that 93L would never reach hurricane strength. I give a 10% chance that 93L will be a hurricane on Saturday when it makes its closest approach to the Lesser Antilles Islands. If 93L hits the Northern Lesser Antilles as a wet Tropical Storm Bertha (not a hurricane), the storm could be more boon than bane for the islands. The Northeast Caribbean suffered its driest June in recorded history last month, according to NOAA, and many of the islands have significant drought problems.

The GFS and European models continue to agree on the long-range fate of 93L. The great majority of the 20 members of the 00Z Wednesday runs of the European and GFS ensemble models (which run at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed 93L taking a northwesterly track early next week in response to a strong trough of low pressure over the Eastern United States, then recurving to the north without hitting the mainland U.S. coast.

The Hurricane Hunters to study 93L
Originally, a fleet of five hurricane hunter aircraft were headed to the Caribbean today to intercept 93L, according to the NOAA/HRD blog and the NHC recon Plan of the Day. Two Air Force C-130s are still headed to the islands, and will begin flying alternating missions into 93L on Thursday afternoon. The three NOAA aircraft that were scheduled to deploy today have now had their missions cancelled.


Figure 3. Image taken at 8:50 pm EDT July 29, 2014, from the Guam radar, showing the eye of Tropical Storm Halong over the island of Rota, north of Guam.

Tropical Storm Halong hits Guam
In the Western Pacific, Tropical Storm Halong passed just north of Guam on Tuesday night (EDT), with sustained winds near 65 mph. Anderson AFB recorded a top wind gust of 53 mph, and 11.82" of rain. The eye of the storm passed over the island of Rota, where a wind gust of 58 mph was recorded. Guam radar shows that Halong is now moving to the northwest away from Guam, and the storm may be a long-range threat to Japan.

Sharknado 2 Airs Tonight!
The much-anticipated sequel to the ridiculous "Sharknado", "Sharknado 2: The Second One" is scheduled to hit the air on the Syfy Channel at 9pm EDT/8 pm CDT on July 30, 2014. Yes, after terrorizing Los Angeles, once again bloodthirsty people-eating tornado-hurled sharks will hit a major American city--this time, New York. "Even the sharknadoes are tougher in New York," quips the hero of the movie, actor Ian Ziering, reprising his role from "Sharknado." According to the production studio, The Asylum, Al Roker will make a cameo appearance in the film as himself. Billy Ray Cyrus, Matt Lauer, the Subway guy, and Kelly Osbourne are also listed as cast members. As I wrote last year in my review of "Sharknado", the movie seriously challenged The Day After Tomorrow for greatest number of impossible meteorological events packed into a single film. Wunderground, for now, has decided not to create a new "Sharknado" weather icon for the web site, due to the low probability of such an event occurring with the laws of physics being what they currently are. But, if you are in a masochistic mood for a campy low-budget parody of both disaster and horror movies, "Sharknado 2" is likely to be a hoot.


Video 1. Watch out, New York! It's the official Sharknado 2 trailer.

Jeff Masters

Hurricane

Updated: 3:36 PM GMT on July 30, 2014

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93L in Middle Atlantic Close to Tropical Depression Status

By: JeffMasters, 2:22 PM GMT on July 29, 2014

An area of disturbed weather located near 10°N, 39°W at 8 am EDT Tuesday, about 1600 miles east of the Lesser Antilles Islands, (93L), has the potential to develop into a tropical depression by Wednesday, but is struggling with high wind shear today. Visible satellite loops on Tuesday morning showed improved organization to 93L with more spin and some low-level spiral bands beginning to form. A 7:30 am EDT July 29 pass from the ASCAT satellite showed plenty of west winds on the south side of 93L's center of circulation, so the storm is close to having a well-defined closed surface circulation. However, infrared satellite images showed that the system's heavy thunderstorm activity had diminished somewhat since Monday, and the storm is now fighting high wind shear of about 20 knots. Water vapor satellite loops and the Saharan Air Layer analysis showed that 93L had more dry air to contend with than on Monday, with some tendrils of the dry Saharan Air Layer to the north encroaching into the circulation. Ocean temperatures have cooled since Monday, and are now marginal for development, about 27°C.


Figure 1. Analysis of the Saharan Air Layer (SAL) made at 8 am EDT Tuesday July 29, 2014 using data from the Meteosat-9 satellite. Dry, dusty air was present from the coast of Africa westwards across the tropical Atlantic, and was beginning to encroach from the north into tropical disturbance 93L. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.

Forecast for 93L
Given the high levels of wind shear affecting 93L today, it is more likely that NHC will classify it as a tropical depression on Wednesday than today. The 12 UTC Tuesday forecast from the SHIPS model predicted that the current high wind shear affecting 93L will relax to the moderate level, 5 - 15 knots, Wednesday afternoon through Friday, aiding development. Sea Surface Temperatures (SSTs) will slowly warm as the system approaches the Caribbean, reaching 28°C by Friday and Saturday. Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Tuesday runs that the disturbance would develop into a tropical depression by Thursday. The fact that two out of three of the reliable genesis models predict development bolsters the odds that development will actually occur. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC put the 2-day and 5-day odds of development at 70% and 80%, respectively.

All of the models predict that the disturbance will continue west or west-northwest at 10 - 15 mph for the next four days. The UKMET and the European models offer the fastest solution, predicting that the disturbance will arrive in the northeast Lesser Antilles Islands on Friday evening, move over Puerto Rico on Saturday evening, and approach the Southeast Bahamas and Turks and Caicos Islands on Sunday evening. The GFS is slower and more to the northeast, predicting a Saturday morning arrival in the northern Lesser Antilles, with passage a few hundred miles northeast of Puerto Rico occurring on Sunday morning. Dry air to the north of 93L will likely interfere with development throughout the week, and we will have to see if the moderate levels of wind shear forecast to occur will be capable of driving this dry air into the core of the system, disrupting formation. The disturbance may also have trouble disentangling itself from the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, which lies just to the south of the disturbance. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance. The Tuesday morning runs of our two most reliable models for predicting intensity, the LGEM and DSHIPS models, forecast that once 93L became a tropical depression, it would intensify into a hurricane within 72 hours. However, the dynamical GFDL and HWRF models, which made good intensity forecasts for Hurricane Arthur, were much less bullish. The Tuesday morning runs of these models predicted that 93L would never reach hurricane strength. I give a 10% chance that 93L will be a hurricane on Saturday when it makes its closest approach to the Lesser Antilles Islands. If 93L hits the Northern Lesser Antilles as a wet Tropical Storm Bertha (not a hurricane), the storm could be more boon than bane for the islands. The Northeast Caribbean suffered its driest June in recorded history last month, according to NOAA, and many of the islands have significant drought problems.

The GFS and European models have come into better agreement on the long-range fate of 93L. The great majority of the 20 members of the 00Z and 06Z Tuesday runs of the European and GFS ensemble models (which run at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed 93L taking more of a northwesterly track early next week, passing to the north of Hispaniola and not making an extended track through the Caribbean Sea. This raises the odds that the strong trough of low pressure over the Eastern U.S. will be able to recurve 93L out to sea without the storm hitting the mainland U.S. coast.


Figure 2. Image taken at 9:54 am EDT July 29, 2014, from the Guam radar, showing heavy rains from an outer spiral band of Tropical Storm Halong affecting Guam. The eyewall of the intensifying storm is visible to the east.

Tropical Storm Halong approaching Guam
In the Western Pacific, Tropical Storm Halong is close to becoming a Category 1 typhoon, and is expected to pass within 50 miles of Guam near 12 UTC (8 am EDT) on Wednesday. Guam radar is showing that heavy rains from an outer spiral band of Halong have already arrived. Halong may be a long-range threat to Japan.

Jeff Masters

Hurricane

Updated: 2:32 PM GMT on July 29, 2014

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93L in Eastern Atlantic Growing More Organized

By: JeffMasters, 2:43 PM GMT on July 28, 2014

An area of disturbed weather located near 10°N, 33°W at 8 am EDT Monday, about 500 miles southwest of the Cape Verde Islands, was designated Invest 93L by NHC early Monday morning. This disturbance is a more serious threat than Tropical Depression Two of last week, and has the potential to develop into a strong tropical storm before reaching the Lesser Antilles Islands on Friday or Saturday. Visible satellite loops on Monday morning showed that the disturbance had only a modest amount of spin, but infrared satellite images showed that the system's heavy thunderstorm activity had increased significantly since Sunday. Wind shear was light, 5 - 10 knots, which should aid development. Ocean temperatures were decent for development, about 27.5°C. Water vapor satellite loops showed that the atmosphere was reasonably moist in the area, though a large area of dry air lay a few hundred miles to the north.


Figure 1. Analysis of the Saharan Air Layer (SAL) made at 8 am EDT Monday July 28, 2014 using data from the Meteosat-9 satellite. Dry, dusty air was present from the coast of Africa westwards across the tropical Atlantic, but was located well to the north of tropical disturbance 93L. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.


Figure 2. MODIS true-color image of 93L from approximately 9:30 am EDT July 28, 2014, when the storm was about 500 miles southwest of the Cape Verde Islands. The disturbance was embedded in the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics. Image credit: NASA.

Forecast for 93L
The 12 UTC Monday forecast from the SHIPS model predicted that wind shear will remain low to moderate, 5 - 15 knots, for the remainder of the week, aiding development. Sea Surface Temperatures (SSTs) will cool a bit to 27°C on Tuesday and Wednesday, which will tend to slow development. Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Monday runs that the disturbance would develop into a tropical depression by Thursday. Several of our less reliable models, the NAVGEM and Canadian models, also predicted development. The only reliable model that did not predict development was the European model, which historically has had the highest incidence of failing to predict development when development actually occurs. The fact that two out of three of the reliable genesis models predict development bolsters the odds that development will actually occur. In their 8 am EDT Monday Tropical Weather Outlook, NHC put the 5-day odds of development at 70%, up from their 40% forecast from Sunday.

All of the models predict that the disturbance will continue due west or west-northwest at 10 - 15 mph for the next five days. The UKMET is the fastest of the models, predicting that the disturbance will arrive in the Lesser Antilles Islands on Friday evening. The GFS is slower, predicting a Saturday morning arrival in the islands. Once the disturbance crosses west of about 55°W longitude on Thursday, ocean temperatures will warm to about 28°C, which should aid development. Dry air to the north will likely interfere with development late in the week, and we will have to see if the moderate levels of wind shear forecast to occur over the tropical Atlantic will be capable of driving this dry air into the core of the system, disrupting formation. The disturbance may also have trouble disentangling itself from the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, which lies just to the south of the disturbance. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance.

The long-range fate of 93L remains highly uncertain, and will depend upon exactly how far south the center ends up consolidating when the storm develops. Most of the 20 members of the 06Z Monday run of the GFS ensemble model (which runs the GFS model at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed the disturbance missing the U.S. East Coast and recurving out to sea next week; four of the members showed 93L hitting the Southeast U.S. coast. Most of the members of the 00Z Monday run of the European ensemble model showed 93L moving into the Eastern Caribbean on a more southerly trajectory without recurving.

Jeff Masters

Hurricane

Updated: 3:40 PM GMT on July 28, 2014

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Disturbance off the Coast of Africa a Potential Threat to the Lesser Antilles

By: JeffMasters, 5:57 PM GMT on July 27, 2014

An area of disturbed weather near 11°N, 31°W, about 500 miles southwest of the Cape Verde Islands, has the potential to develop into a tropical depression later this week as it heads west at 10 - 15 mph towards the Lesser Antilles Islands. Visible satellite loops on Sunday morning showed that the disturbance had only a minor amount of spin. Infrared satellite images showed that the system's heavy thunderstorm activity was modest at best, and had not changed significantly since Saturday. Wind shear was moderate, 10 - 15 knots, which should allow slow development. Ocean temperatures were marginal for development, about 27°C. Water vapor satellite loops showed that the atmosphere was reasonably moist in the area, though a large area of dry air lay a few hundred miles to the north.


Figure 1. MODIS true-color image from approximately 11:30 am EDT July 27, 2014, showing a tropical disturbance (marked with an "L") about 500 miles southwest of the Cape Verde Islands. The Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, is also apparent. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance. Image credit: NASA.

Forecast for the disturbance
Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Sunday runs that the disturbance would develop into a tropical depression by Thursday. Several of our less reliable models, the NAVGEM and Canadian models, also predicted development. The only reliable model that did not predict development was the European model, which historically has had the highest incidence of failing to predict development when development actually occurs. The fact that two out of three of the reliable genesis models predict development bolsters the odds that development will actually occur. In their 2 pm EDT Sunday Tropical Weather Outlook, NHC put the 5-day odds of development at 40%, up from their 20% forecast from Saturday evening.

All of the models predict that the disturbance will continue due west or just north of due west at 10 - 15 mph for the next five days. The UKMET is the fastest of the models, predicting that the disturbance will arrive in the Lesser Antilles Islands on Friday. The GFS is slower, predicting a Saturday arrival in the islands. Once the disturbance crosses west of about 50°W longitude, ocean temperatures will warm to about 28°C, which should aid development. Dry air to the north will likely interfere with development by the middle of the week, and we will have to see if the moderate levels of wind shear forecast to occur over the tropical Atlantic will be capable of driving this dry air into the core of the system, disrupting formation. The disturbance may also have trouble disentangling itself from the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, which lies just to the south of the disturbance. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance. Most of the 20 members of the 06Z Sunday run of the GFS ensemble model (which runs the GFS model at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed the disturbance missing the U.S. East Coast and recurving out to sea early next week, but it is too early to assess the odds of this.

Jeff Masters

Hurricane

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The Record Quiet Hurricane Season of 1914: Could it Happen Again in 2014?

By: JeffMasters, 4:08 PM GMT on July 25, 2014

This year marks the 100th anniversary of the slowest Atlantic hurricane season on record--1914, which had no hurricanes and only one tropical storm. Is it possible that the 2014 hurricane season could match 1914 for the lowest activity ever recorded, with Hurricane Arthur ending up as our only named storm? I think that is highly unlikely, even though the atmospheric and oceanic conditions in the Atlantic are looking hostile for development for the coming two weeks.



A re-analysis of Atlantic tropical cyclones finds only one storm in 1914
In 2005, a reanalysis effort was made of all Atlantic tropical cyclones between 1911 - 1914, using historical weather maps, ship reports, and newspaper accounts. I talked to the leader of the reanalysis project, NHC's Dr. Chris Landsea, about the 1914 reanalysis. He told me, "We went into the re-analysis process for 1914 knowing that this was the quietest year on record, with only one tropical storm and no hurricanes. I thought for sure we'd find some storms that were missed, since so many of the other years we re-analyzed came up with new storms that were missed. But when we analyzed the data and looked for missing storms, we couldn't find any. The year 1914 remained with just one named storm--truly a remarkable year in the annals of the Atlantic hurricane database."

The only tropical storm of 1914 developed in the Bahamas on September 15--the latest formation date for an Atlantic season's first storm in the official HURDAT database, which goes back to 1851. The storm moved slowly northwestward and made landfall near the Florida/Georgia border on September 17. Two other systems were formally considered for inclusion into the hurricane database in 1914: a potential late-October tropical depression that was identified in the Western Caribbean, but was too weak to be considered a tropical storm; and a storm that brought gale-force winds on September 30 - October 1 to the coasts of Alabama, Mississippi, and the Florida Panhandle, but which was deemed to be an extratropical storm. The reanalysis effort found that the only other Atlantic hurricane season that did not produce any hurricanes was 1907.



Figure 1. Top: August - October 1914 departure from average of relative humidity at middle levels of the atmosphere (near the 700 mb pressure level, which is roughly 10,000 feet above the surface.) Bottom: August - October 1914 departure from average of sea level pressure. The August - October peak part of hurricane season in 1914 had a very dry atmosphere with a relative humidity 4 - 8% lower than average (yellow, orange and red colors), and was dominated by high pressure (1 - 2 mb higher than average.) Images plotted using the NOAA/ESRL 20th Century Reanalysis.

Reasons for the Exceptionally quiet hurricane season of 1914
1) El Niño. Not surprisingly, 1914 was an El Niño year, judging by the Southern Oscillation Index Archives from Australia's Bureau of Meteorology. It is well-know that during an El Niño event, an atmospheric circulation that brings strong upper-level west-to-east winds over the tropical Atlantic typically sets up, and these winds tend to create high wind shear, discouraging tropical storm formation.

2. Sea Surface Temperatures (SSTs.) Ocean temperatures in the Main Development Region (MDR) for Atlantic hurricanes, from the coast of Africa to Central America, between 10°N and 20°N, including the Caribbean, were -0.4°C (-0.7°F) from average during August - October 1914, according to the Hadley Centre SST data set (HadSST2). This ranks as the 12th coolest such departure from average since 1900, and this sort of temperature anomaly would have definitely tended to squelch tropical storm formation by limiting the amount of heat energy available to developing storms. The record coldest SST anomaly in the MDR since 1900 was -0.8°C during the 1913 hurricane season, which was a very quiet year with six named storms and four hurricanes, all of which were Category 1 hurricanes.

3. Dry air and high pressure. It is well known that dry air at middle levels of the atmosphere (near the 700 mb pressure level, which is roughly 10,000 feet above the surface) discourages tropical storm formation. During August - October 1914, there was plenty of dry air over the Caribbean and Gulf of Mexico which would have made it difficult for tropical storms to form. The Atlantic was also dominated by higher than average pressure, so an atmosphere featuring large-scale dry, sinking air associated with persistent high pressure systems was likely in place during the 1914 hurricane season.

Why the quiet hurricane season of 1914 will be hard to duplicate
Is it possible in our new climate and with the modern weather observing system to have just one named storm in an Atlantic hurricane season? It's not impossible, but the odds of such an event are much lower than they were in 1914, for two reasons:

1) The globe has warmed about 0.8°C (1.4°F) since 1914. That extra heat in the oceans makes it much more difficult to maintain a Sea Surface Temperature (SST) anomaly of -0.4°C during the peak part of hurricane season in the Main Development Region (MDR) for hurricanes, as occurred during the 1914 hurricane season. The MDR SST anomaly has averaged about -0.2°C in June and July 2014, and I would be surprised if it managed to sink as low as -0.4°C and maintain that level of coolness during all of August, September, and October. The quietest Atlantic hurricane seasons typically occur in years when MDR SSTs are much below average, so the extra heat in the ocean due to global warming should cut down on the number of seasons with very low named storm counts.

2) Back in 1914, we did not have weather satellites or the Hurricane Hunters, which meant that weak, short-lived tropical storms far out at sea may have been missed. Landsea et al. (2010) showed that the increasing trend in North Atlantic tropical storm frequency over the past 140 years was largely due to the increasing trend in short‐lived storms (storms lasting 2 days or less, called “shorties”), after the 1940s (Figure 2, top). The researchers did not detect a significant increasing trend in medium‐ to long‐lived storms lasting more than 2 days. Looking at Figure 2, it looks quite plausible that 2 - 4 of these "shorties" were missed in 1914, due to the inferior observing system. They wrote that “while it is possible that the recorded increase in short‐duration TCs [tropical cyclones] represents a real climate signal, we consider it is more plausible that the increase arises primarily from improvements in the quantity and quality of the observations, along with enhanced interpretation techniques.” Villarini et al. (2011), in a paper titled, "Is the recorded increase in short-duration North Atlantic tropical storms spurious?", agreed. They attempted to correlate increases in tropical Atlantic sea surface temperatures in recent decades to the increase in short-lived Atlantic tropical storms, and were unable to do so.


Figure 2. Atlantic tropical cyclones between 1878 - 2013 that spent two days or less at tropical storm strength (top) and more than two days at tropical storm strength or hurricane strength (bottom.) Figure updated from Villarini, G., G. A. Vecchi, T. R. Knutson, and J. A. Smith (2011), "Is the recorded increase in short-duration North Atlantic tropical storms spurious?", J. Geophys. Res., 116, D10114, doi:10.1029/2010JD015493.

My conclusion: we will see a Tropical Storm Bertha in the Atlantic in 2014, but don't expect it until mid-August.

References
Landsea, C. W., C. Anderson, N. Charles, G. Clark, J. Dunion, J. Fernandez‐Partagas, P. Hungerford, C. Neumann, and M. Zimmer (2004), "The Atlantic hurricane database re‐analysis project: Documentation for 1851–1910 alterations and additions to the HURDAT database," in Hurricanes and Typhoons ‐ Past, Present, and Future, edited by R. J. Murnane and K. B. Liu, pp. 178–221, Columbia Univ. Press, New York.

Landsea, C. W., (2007), "Counting Atlantic tropical cyclones back to 1900," Eos, 88(18), 197-202.

Villarini, G., G. A. Vecchi, T. R. Knutson, and J. A. Smith (2011), "Is the recorded increase in short-duration North Atlantic tropical storms spurious?", J. Geophys. Res., 116, D10114, doi:10.1029/2010JD015493

Have a great weekend, everyone, and if the Atlantic stays quiet, I'll wait until Monday to make a new post.

Jeff Masters

Hurricane

Updated: 4:10 PM GMT on July 25, 2014

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June 2014: Earth's 3rd Consecutive Warmest Month on Record

By: JeffMasters, 5:22 AM GMT on July 24, 2014

June 2014 was Earth's warmest June since records began in 1880, said NOAA's National Climatic Data Center (NCDC) this week. NASA rated June 2014 a bit cooler: the 3rd warmest June on record. According to NOAA, the planet has now had three consecutive warmest months on record--April (which was tied for the warmest April), and now May and June of 2014. This is the first time Earth has experienced three consecutive warmest months on record since a four-month stretch during March, April, June, and June 2010. Global ocean temperatures during June 2014 had the greatest departure from average for warmth of any month in recorded history: 0.64°C (1.15°F) above the 20th century average. The previous record of +0.59°C (1.06°F) was set in June 1998 and tied in October 2003, July 2009, and May 2014. Global land temperatures in June 2014 were the 7th warmest on record, and the year-to-date January - June period was the 3rd warmest on record for the globe. Global satellite-measured temperatures in June 2014 for the lowest 8 km of the atmosphere were the 4th warmest in the 36-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH).


Figure 1. Departure of temperature from average for June 2014, the warmest June for the globe since record keeping began in 1880. Large regions of Earth’s oceans experienced record-warm conditions. New Zealand had its warmest June since records began in 1909. No record cold was observed on the planet. Image credit: National Climatic Data Center (NCDC) .

Notable weather events of June 2014
According to wunderground's weather historian, Christopher C. Burt, June 2014 was the wettest June on record for portions of Minnesota, South Dakota, and Iowa. A COOP weather station four miles west-northwest of Canton, SD received 19.65” of rain during the month, setting an official new state monthly precipitation record. Previous record: 18.61” in Deadwood, SD in May 1946. India had the opposite problem: the monsoon brought anemic rains that were just 57% of average for the month.



One billion-dollar weather disaster in June 2014
Only one billion-dollar weather-related disaster hit the Earth during June 2014, a severe thunderstorm outbreak across Germany, France and Belgium, according to the June 2014 Catastrophe Report from insurance broker Aon Benfield. The total number of billion-dollar weather disasters for the first half of 2014 is eleven, which is well behind the record-setting pace of 2013, which had seventeen such disasters by the end of June, and ended up with a record 41 by the end of the year.


Disaster 1. An outbreak of severe thunderstorms across Germany, France and Belgium on June 8 - 10, 2014 killed six people in Germany and did $2.75 billion in damage. Hail up to 7.0 cm (2.75") in diameter and winds beyond 145 kph (90 mph) were recorded. Extensive crop damage was also noted in southwestern France around Bordeaux, Cognac, and Languedoc where swaths of vineyards were destroyed. In this image, a boy walks next to a tree that fell on a building on June 9, 2014 in Cognac, France a few hours after a violent thunderstorm. Image credit: NICOLAS TUCAT/AFP/Getty Images.

An El Niño Watch continues
June 2014 featured neutral El Niño conditions in the equatorial Eastern Pacific, and sea surface temperatures have been hovering near the threshold for El Niño, +0.5°C from average, from late April through mid-July. However, the atmosphere has not been behaving like it should during an El Niño event. The Southern Oscillation Index (SOI)--the difference in surface pressure between Darwin, Australia and the island of Tahiti--tends to drop to negative values during the presence of an El Niño atmosphere, but was positive during June. However, the SOI became negative at the beginning of July, and has remained negative through this week, which may be an indication that the atmosphere is beginning to respond. NOAA is continuing its El Niño Watch, giving a 70% chance that an El Niño event will occur this summer, with an 80% chance by fall.

Arctic sea ice falls to 6th lowest June extent on record
Arctic sea ice extent during June was the 6th lowest in the 36-year satellite record, according to the National Snow and Ice Data Center (NSIDC). Average June temperatures over parts of the Arctic Ocean were from 1 to 2 degrees Celsius (2 to 4 degrees  Fahrenheit) below the 1981 to 2010 average, keeping extreme ice melt from occurring. This is in stark contrast to the unusually warm summers of many recent years, particularly 2012 and 2007, when air temperatures over the Arctic Ocean were up to 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit), respectively, above average.

Most impressive weather video of June 2014

Video 1. An EF-4 tornado hit a farm near Woonsocket, South Dakota, on June 18, 2014. The tornado had a dramatic set of suction vorticies--smaller vortices embedded within the tornado’s circulation, which can add over 100 mph to the ground-relative wind. The suction vortices are particularly striking about 2:00 into the video, and contribute to heavy damage to a farm about 3:00 in. Video taken by Dick McGowan and Shay Phillips of Team Dominator of TVNWeather.com.

Jeff Masters

Climate Summaries

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Atlantic Tropical Depression #2 Weakens to TROF as it Heads for Caribbean

By: JeffMasters, 5:17 PM GMT on July 23, 2014

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)

Former Tropical Depression #2 is estimated to be near 14.1N / 56.2W or about 300NM east of the CARIB, and is heading westward (290ᵒ) at 17Kts. Imagery loops along with a few surface OBS any clearly indicate TD #2 opened-up into an inverted TROF early this AM; and one with a minimum of significant convection.


Fig 1: The above VIS (left) and Enhanced IR (right) image of former TD #2 depicts an extremely weak and poorly organized area of convection.

Although the decrease in convection was partially due to typical diurnal variation, the disturbance encountered stronger wind shear and drier air that ultimately destroyed the already borderline circulation. In addition, the disturbance will be encountering even stronger wind shear over the next 48 hours, and the chances of re-development are NIL.


Fig 2: TD-2 ran into increasing shear overnight, and this appears to be the primary reason TD-2 is no longer…

Anything up Elsewhere in the Atlantic?


Fig 3: The precipitable water graphic shows an increase in moisture associated with the ITCZ, though drying due to the intrusion of the SAL is also shown over the Cape Verdes ahead of the next, albeit somewhat weaker wave now emerging off the African coast.


Fig 4: This unique ‘convective’ image for northern Africa (along with related loop imagery and 850mb Vorticity analysis – not shown) helps identify the next set of upstream tropical waves over central and western Africa.

The tropical wave analysis using the above Convective imagery indicates a moderately strong wave with some mid-level turning over west central Africa (2nd from the coast) and a much stronger wave developing over east central Africa (far right in above image) with significant low to mid-level rotation evident. Both of theses waves will be moving over the Atlantic next week. However, in the meantime, no cyclone formation is currently expected for the next 6 or more days.

Typhoon MATMO over mainland China

MATMO crossed Taiwan yesterday with numerous wind reports supporting CAT 2 intensity at landfall. While crossing Taiwan, it weakened to a CAT 1, with additional weakening due to friction affects and increasing wind shear as it crossed the Taiwan Strait. The storm made it’s 2nd landfall along the SE coast of China between 06Z and 07Z today. The system is now moving northward, and will transition to a non-tropical Low as it moves more rapidly N/NE during the next 2 days – with heavy rainfall it’s primary threat.


Fig 6: MATMO is seen ‘unwinding’ rapidly in the above IR image, with most of the significant convection far removed from the center of the cyclone.


Fig 7: The latest color enhanced IR image of MATMO indicates very strong convection remains along the coast and over the open waters well south of the storm center.

Winds are likely still gusting to tropical storm intensity over land, while winds are likely near CAT 1 intensity in the stronger convective bands over the open water.

Although there are 3 other ‘Invests’ over the West Pacific – none of these are expected to develop into cyclones during the next 48 hours.

The next update will be coming from Dr. Jeff Masters on Thursday.

For those interested , I will once again be providing my own Weather Updates starting the week of AUG 18 at Steve Gregory

Steve Gregory


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MATMO Approaches Taiwan Coast as Atlantic TD#2 continues Westward

By: JeffMasters, 3:42 PM GMT on July 22, 2014

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)

Latest SAT and Radar imagery shows Typhoon MATMO approaching the Taiwanese east coast and is currently about 65 NM S-SE of Taipei. With a NW movement at 16 Kts, MATMO should hit the east coast within the next hour or so. Radar indicates strong convective bands have been impacting the Island for the last 4-6 hours.



Fig 1: IR imagery clearly shows MATMO has gotten much better organized since yesterday, but with so little time left for higher level winds to work their way to the surface, MAX winds are almost certainly still under true, CAT 2 intensity.

Imagery has also depicted a partial but distinct eye feature for the last 8 hours, with very good outflow to the north and south of the storm. This, combined with Dvorak estimates of over 80Kts, and JMA estimates of a central pressure near 965mb means MATMO should still be able to hit the coast near CAT 2 intensity.

Although conditions are still quite favorable for further intensification, interaction with Taiwan’s mountainous terrain, and effects of friction with the China mainland even as the storm traverses the Taiwan Strait, MATMO should weaken rapidly once it makes landfall and will almost certainly make its second and final landfall on the SE coast of China in 24 hrs at Tropical storm intensity. As the storm makes landfall on mainland China, it will turn northward in response to an approaching long wave TROF followed by acceleration towards the N-NE on THU as it transitions rapidly to a non-tropical Low.



Fig 2: Radar depiction from Taiwan shows a reasonably well-defined eye, with convective banding already over the central portion of Taiwan. The strongest convection appears to be in the S-SW quadrant which corresponds with the overall ‘history’ of this cyclone in which the strongest convection has generally been in the southern semi-circle.




TROPICAL DEPRESSION #2 OVER CENTRAL ATLANTIC

Very small Tropical Depression #2 is located near 12.5N / 47.8W or about 700NM east of the CARIB, moving westward (285ᵒ) at 16Kts. With the system embedded in deep easterlies, and convection remaining relatively weak, this trajectory should continue for the next 48-72 hrs.



Fig 3: TD#2 remains quite small, with a general 'circulation' diameter estimated at about 200NM (This estimate is based on VIS and microwave imagery shown in Fig 4 below.)

Despite relatively low wind shear (approximately near 10Kts), there has been very little change in the overall size and structure of TD#2 during the last 24 hours. In addition, the small cyclone will soon begin encountering significantly drier air, and as the system approaches the eastern CARIB Thursday, it is expected to encounter stronger wind shear which is likely (though not with 100% certainty) to prevent any significant intensification despite warmer SST’s that will support stronger convection. In addition, the shear may be strong enough to cause the system to open up into a wave.



Fig 4: The 85Ghz microwave image continues to support a closed low or mid-Level circulation which has been more difficult to locate on VIS or IR imagery than it was yesterday.

The large scale global models still cannot resolve/initialize this small system, but the specialized Tropical Cyclone models, initialized at 12Z, forecast the storm to continue tracking towards the CARIB, reaching the eastern CARIB late on Thursday. Interestingly, a few of the dynamical models show a slow intensification of the system to Tropical Storm intensity – though the most reliable models, and the Official NHC forecast, call for dissipation in 48-60 hours





Fig 5 & 6: The Early 12Z cycle model runs are generally a bit more aggressive in developing TD#2 into a Tropical Storm compared to yesterday's runs – but the most reliable dynamic models continue to forecast dissipation and admittedly have a high probability of verifying.



Fig 7: The official NHC Track forecast is in excellent agreement with the model consensus, but calls for dissipation prior to the system reaching the CARIB.

ELSEWHERE in the Atlantic, there are 2 Tropical Waves over the far eastern Tropical Atlantic that have brought along more ‘moisture laden air’ (versus dry, Saharan air). In addition, there are now several somewhat stronger appearing Tropical waves upstream over Africa (only 2 are shown in Fig 9) that will reach the Atlantic later this week and early next week, with one of these systems having a significantly higher potential for development next week.



Fig 8: Aside from TD#2, only 2 significant Tropical Waves are present over the eastern most Atlantic, and they are entangled in the African Monsoonal TROF and/or ITCZ.



Fig 9: Tropical Waves over Africa have become somewhat stronger over the past week, with the easternmost one in the above image showing a mid-level 'turning' on imagery loops.

In the meantime, however, no new tropical cyclone formation is expected during the remainder of the week.

The next update will be Wednesday afternoon unless conditions in the Atlantic warrant an earlier posting.

Steve Gregory

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Atlantic Invest 92L Likely Depression

By: JeffMasters, 8:08 PM GMT on July 21, 2014

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)

SPECIAL UPDATE

Latest VIS and IR imagery suggests INVEST 92L is now a Tropical Depression, though NHC has not yet ‘called it’.



Fig 1: Latest VIS image of INVEST 92 about 1,200 NM east of the Lesser Antilles.

The low level circulation near 11.1N / 43.5W (about 1,200NM east of the Lesser Antilles) appears ‘closed’, with significant, though weak convection noted within 25NM of the center, along the S-SE side of the center.



Fig 2: The 85Ghz microwave image from a pass earlier today indicates convection is located very close to the low level circulation which I believe supports designating this system as a Depression.

The quite small developing cyclone is moving westward at 18 Kts, and is embedded in a relatively moist environment with low wind shear (<10Kts). However, the system is still located over relatively cool SST’s, and this does not support strong convection. Until the system gets closer the CARIB in about 48 hours, where SST’s exceed 28ᵒC, it is doubtful the system will be able to intensify beyond a minimal Tropical storm.



Fig 3: The latest SST analysis in the vicinity of 92L indicates SST’s are significantly below the threshold needed for deep convection and intensification beyond minimal storm intensity.

The large scale global models do not have a handle on this small system, but the specialized Tropical Cyclone models, initialized at 18Z, forecast the storm to track towards the CARIB, reaching the eastern CARIB late in the day THU or by early Friday. The statistically based intensity models show the cyclone becoming a tropical storm by then, though the more reliable dynamical models are NOT forecasting the system to show significant intensification – and at this time, this seems like the most likely solution as wind shear and drier air are likely to be encountered by the time the cyclone approaches the CARIB.



Fig 4: The Early 18Z cycle model runs are little changed from the early morning runs, but now show the system reaching the CARIB a bit earlier, reflecting the relatively fast forward motion that should continue as long as there is no deep convection.



Fig 5: The more reliable dynamical models do NOT intensify the cyclone – and this seems to be the most likely solution as the system should encounter a more hostile environment by the time it reaches the CARIB.

Update on CAT 1 MATMO

The latest GFS model run shows MATMO moving somewhat faster than earlier progged, and the Typhoon should reach the eastern coast of Taiwan as a strong CAT 2 Typhoon around 00Z Wednesday.

The next full update will be Tuesday afternoon unless conditions in the Atlantic warrant an earlier posting. Steve Gregory

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Atlantic ‘Wakes-Up’ / Typhoon Matmo Heads For Taiwan

By: JeffMasters, 3:40 PM GMT on July 21, 2014

ATLANTIC ‘WAKES-UP’ / TYPHOON MATMO HEADS FOR TAIWAN


(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)

Morning VIS imagery shows a well defined low level closed circulation has formed about 1,200 NM east of the CARIB near 11.6N / 42.6W and is westbound (280ᵒ) at 20Kts – and is now being carried by NHC as INVEST 92L.



Fig 1: A relatively small but well-defined Low level circulation has formed within a small area of weak convection.

Convection remains fairly weak, but does exist just to the SE of the center of rotation, and high level wind analysis from CIMSS does NOT show significant outflow. That said, wind shear is believed to be quite low (est. under 10Kts)




Fig 2: With limited derived values for high level winds associated with INVEST 92L, there is currently little evidence of significant outflow associated with the tropical Low. (More data should become available if/when convection deepens.)



Fig 3: Likewise, what wind data is available in the vicinity of the Low, wind shear is likely quite low (under 10 Kts) and this should enable INVEST 92L to slowly intensify once deeper convection is able to develop.

Global models still have not resolved this system, but after manual initialization by NHC, Early Track and Intensity model forecasts call for the system to become a Depression today and possibly reach Tropical Storm intensity during the next 48-72 hours once the system moves over waters that are warm enough to support storm formation.



Fig 4: Early 12Z model runs show a W/WNW track, with the system reaching the Northeast CARIB Friday.




Fig 5: Early 12Z model runs (primarily based on CLIMO and limited dynamical / statistical forecasts) show the system becoming a Tropical storm, and POSSIBLY a minimal CAT 1 by the time it reaches the NE CARIB. Confidence is Low for this forecast.

ASSUMING this developing cyclone manages to become a Tropical storm or Hurricane near the eastern CARIB, extended global model forecasts depict a weakening of the sub-tropical ridge north of the system by then, and an approaching large-scale long wave TROF in the eastern US suggests the system will eventually turn northward away from the US mainland. However, this assumes that the system does in fact reach the northern CARIB as currently forecast by the early model runs. That said, should the cyclone stay on a more westerly track into the central CARIB AND manage to find a low shear environment this weekend - track / intensity forecasts beyond then become quite problematic. And, of course, the developing system could simply turn northward prior to reaching the CARIB and would simply head out sea by the weekend.


CAT 1 MATMO HEADING FOR TAIWAN


Typhoon MATMO is located about 485 NM South of Okinawa, Japan, heading NNW at 15 Kts. With Dvorak T numbers near 5.0 and the JAM estimating a central pressure near 970mb, MATMO’s Max sustained winds are estimated near 75Kts.



Fig 6: A tightly 'wound up' and small-to-average size storm is depicted in the last VIS image of MATMO.




Fig 7: Deep convection is especially prominent in this color enhanced IR image.

Overall, recent Imagery depicts a bit more symmetrical storm signature with strong, deep convection (with typical diurnal variation) - especially in the southern semi-circle. As anticipated, wind shear has fall off to near 15 Kts, with a continuing decline to near 10 Kts expected during the next 12 hours. This has allowed for a much improved outflow to develop, with moderate to strong outflow channels noted pole-ward and equator-ward, with MAX speeds near 50 Kts.



Fig 8: Wind shear has decreased since yesterday and should promote intensification during the next 24 hrs.



Fig 9: Strong Outflow channels are clearly seen to the north and south of the cyclone's center.

With this overall improvement in outflow – and a projected track over quite warm SST’s – MATMO should reach CAT 2 intensity within 12-18 hrs, and may approach CAT 3 intensity in 24-36 hrs.

There has been virtually no change in the forecast track for MATMO for the past 2 days, with both the GFS and specialized hurricane track models showing the storm center passing across the northern Taiwan east coast WED around 06Z,

With the approach of an upper air TROF over eastern China, wind shear should then increase as the storm continues NNW towards the SE China coast. Combined with cooler SST’s and interaction with the mountainous terrain of Taiwan (and additional interaction with the China mainland) MATMO should approach the SE coast of China around 06Z THU as a minimal CAT 1, or strong Tropical Storm. At this time, there is minimal risk that MATMO will be stronger than a CAT 3 when it reaches Taiwan.



Fig 10: The official Track forecast from JTWC (above) is in excellent agreement with all track forecast models, and now, the track and intensity forecast from the JMA.


I will have another update on the ATLANTIC INVEST late this afternoon.

Steve Gregory

Updated: 5:52 PM GMT on July 21, 2014

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MATMO SLOWLY INTENSIFIES

By: JeffMasters, 11:55 PM GMT on July 20, 2014

TYPHOON MATMO HEADS FOR TAIWAN / ATLANTIC STIRRING

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)


Typhoon MATMO is located about 650 NM SSE of Taipei and is now heading NNW at 12Kts. Although convection has increased some since yesterday (with a fairly strong convective burst over the last 2 hours), wind shear of nearly 20 Kts has continued to inhibit major intensification over the last 24hrs. OTH, outflow appears to have improved some, though remains somewhat restricted in the NE semi-circle. Latest intensity estimates (Dvorak approaching T-5) support 75Kt sustained winds.



Fig 1: Enhanced IR image of Typhoon MATMO. Despite major convective burst during the last few hours, there is no indication that MATMO is intensifying 'rapidly'.

With very warm SST’s ahead and lowering of wind shear to near 10 Kts expected during the next 24-72 hrs., MATMO should intensify to near CAT 3 intensity just prior to reaching the Taiwan coast at around 09Z Wed.



Fig 2: There has been very little change in track or intensity forecasts for MATMO since yesterday, with landfall along the east coast of Taiwan expected WED at near CAT 3 intensity.

TROPICAL ATLANTIC

Although a broad area of Low pressure has formed near 35W, none of the global models is forecasting cyclone formation. In general, there has not been any significant change in environmental conditions across the tropical Atlantic since yesterday, however, the general ‘trend’ towards a more conducive environment for cyclone formation during the next 10 days continues.

The next complete update will be Monday afternoon.

Steve Gregory

Updated: 1:43 PM GMT on July 21, 2014

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RAMMASUN MAKES WAY FOR MATMO AS TROPICAL STORM WALI GOES ‘POOF' & ATLANTIC 'STIRS'

By: JeffMasters, 6:20 PM GMT on July 19, 2014

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)




Just before 00Z today, Typhoon Rammasun made it’s final landfall in northern-most Vietnam as a CAT 2 (my analysis) and is QUICKLY weakening and losing its identity as it continues moving inland.

Meanwhile, Tropical Storm MATMO (10W) continues to become better organized, and is currently approaching Typhoon intensity. The cyclone has an estimated pressure of 975 mb, and was last located near 11.9N / 130W, or about 600 NM East-Southeast of Manila, Philippines, moving WNW at about 5Kts



Fig 1: Color enhanced IR image of Tropical Storm MATMO. The storm has had several convective bursts over the last 24 hours, and has gradually intensified to near Typhoon intensity, based on Dvorak estimates of T3.5 earlier today. However, ‘Experimental’ satellite derived wind estimates show a considerably weaker system, with MAX winds around 50Kts.

Microwave imagery shows a somewhat elongated structure to the convective banding in the southern semi-circle, but satellite imagery loops show a definite improvement in the over all symmetry of the storm, and there is good consensus between the various agencies that MATMO has sustained winds of 60 Kts.



Fig 2: The upper air wind analysis shows good equatorward outflow, and improved outflow to the west. However, at this time, outflow from the NW – N – E is poor.



Fig 3: Wind shear over the storm center is a moderate 20Kts, which is slowing the rate of intensification.

As the storm moves northwestward, the cyclone will find a region of lowering wind shear, with all dynamic models now in agreement that the high level anti-cyclone now centered about 100 NM to the north of the storm, should become vertically aligned with the lower level circulation center (LLCC). This general fall-off of wind shear along with the overall improvement in the outflow pattern, should support a more rapid intensification phase beginning in about 24-36 hours. In addition to a more conducive atmospheric environment, SST’s and total Ocean Heat Content (OHC) in the vicinity of the storm – including the projected track - will also support a faster intensification rate for the next 72 hours.



Fig 4: The last available HWRF track guidance continues to be in excellent agreement with the last several GFS and EURO model predictions taking the storm across Taiwan around 03Z-06Z Wednesday. It should be noted that the official Forecast from the Japan Meteorological Agency (not shown) calls for the storm to pass well south of Taiwan on Wednesday.

As shown in the below figure, there is nearly unanimous agreement of all specialized hurricane forecast intensity models that MATMO will reach CAT 2 intensity in 36-48 hours, with the HWRF calling for a solid CAT 3 intensity in 72 -84 hours. This forecast seems quite likely to verify.



Fig 5: Last available run of the intensity model forecast suite show MATMO reaching CAT 3 intensity Monday, and this is closely supported by the most recent 12Z GFS global model run that has just come in.

All of the specialized hurricane forecast models are in generally good agreement that MATMO will intensify to CAT 2 by the time it approaches Taiwan by the middle of next week. A couple models are calling for a much stronger storm – though these appear to be outliers at this point (as are some of the Japanese models that originally showed a more northerly track towards Japan). It is worth noting that after 6 model runs forecasting only minor development, the GFS has come back into excellent agreement with the Hurricane models in forecasting a vigorous cyclone, tracking it towards Taiwan.



Fig 6: The official forecast track from JTWC calls for MATMO to make landfall along the central east coast of Taiwan around 06Z Wednesday as a very strong CAT 2. *** Based on the most recent GFS model run – this still appears ‘on track’ ***.

It should be noted that the latest 12Z GFS forecast calls for the storm to take a more westward track after making landfall on Taiwan, eventually making a second landfall on the east coast of China about 24 hrs later. This ‘westward’ turn is likely a contributing factor for the JMA track forecast that now calls for MATMO to pass SOUTH of Taiwan on WED.

WALI ‘VANISHES’




By 00Z last night, ‘WALI’ essentially fell apart. (This assumes it actually ‘existed’ as a Tropical Storm to begin with.)

ATLANTIC REMAINS UNEVENTFUL BUT IS BECOMING MORE ‘INTERESTING’



Fig 7: There are 4 significant waves traversing the tropics – with the CARIB wave (that brought some significant convection to the SE CARIB yesterday) weakening significantly over the last 12 hours. The next wave in the central ATL will reach the SE CARIB by Monday.

The most significant waves of interest today is the fairly significant wave to the West/Southwest of the Cape Verdes along 30W that brought a moisture surge along with it, and the wave just now coming off the West African coast. This second wave along the African coast has an elongated Vorticity pattern associated with it, though no rotation of any type can be discerned in SAT imagery. The lead wave near 30W which brought a large moisture surge (see below 2 figures) with it, is currently moving westward at 12 Kts, while the second wave is westbound at 15Kts. Warm air associated with the Saharan Air Layer has effectively capped convection within the moisture ‘surge’ and is also stifling convection with the wave right along the coast.



Fig 8: The derived precipitable water image shows the large moisture surge associated with the wave near 30W, and in general, the increasing aerial extent of moisture laden air associated with all of the easterly waves.



Fig 9: The overall increase in moisture throughout the tropics – and the general decrease in dry air intrusion into the tropics, is evident in this AM’s water vapor image of the ATL basin.



Fig 10: The last image shows the large scale decrease in adverse wind shear from the CARIB to the African coast.

What makes these waves especially ‘interesting’ is the GFS models' handling of them – with the latest run attempting to spin up a small circulation center by Monday in the vicinity of 40W. While the development of a cyclone seems very unlikely considering the overall stability of the atmosphere and lack of rotation, it does represent a general evolution towards a more conducive environment for the formation of cyclone during the next 7-14 days.

Indeed, the last few GFS model runs have shown a trend towards stronger easterly waves, and ones that are coming off the African coast at somewhat higher latitudes. Combined with a slow but steady decrease in observed wind shear across the ATL tropical basin – and a general moistening of the atmosphere – stability should decrease over the coming 10-15 days, which will provide a more favorable environment for cyclone development.


I will have a brief update tomorrow evening, with a complete update Monday afternoon.

Steve Gregory

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Super Typhoon Rammasun Makes Landfall – Next Up Tropical Storm Matmo

By: JeffMasters, 5:49 PM GMT on July 18, 2014

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)



Figure 1: NEXSAT image showing both Rammasun and newly formed T.S. Matmo just a couple hours before Rammasun made landfall.

Super Typhoon Rammasun has made landfall on the Luichow Peninsula just north of Hainan most likely as a low end CAT 4 Typhoon. (Officially, JTWC has carried it as a borderline CAT 5). Haikou on the north coast of Hainan, about 50NM SSE of the storm center, reported a sustained wind of 68Kts with gusts to 88Kts (100mph) as the storm passed just to their north, and a minimum pressure of 955mb. Winds continue to gust to tropical storm strength as of the writing of this report.

Rammasun intensified rapidly during the past 12-18 hrs as a strong outflow channel developed equatorward of the storm, and wind shear decreased to about 15kts. With an east-west ridge line just north of the storm, Rammasun should develop a more westward track during the next few hours and is expected to make its final landfall in northern Vietnam by around 03Z Saturday.



Figure 2: One final WV image clearly showing Rammasun’s eye and very large circulation field.

UP NEXT: MATMO

Since yesterday, TD 10W has become slightly better organized and is now being carried as Tropical Storm Matmo. The slowly developing cyclone is about 235 NM north of Koror, Palau, and is drifting WNW at about 3-5 kts. Dvorak estimates and imagery loops suggest Matmo remains a borderline storm, but the marginally conducive environment is expected to become more favorable for intensification during the next 72 hours as the storm begins to track northwestward at a somewhat faster forward motion.

All of the specialized hurricane forecast models are in generally good agreement that Matmo will intensify to CAT 2 as it approaches Taiwan by the middle of next week. A couple models are calling for a much stronger storm – though these appear to be outliers at this point (as are some of the Japanese models that show a more northerly track towards Japan). It is worth noting that after 6 model runs forecasting only minor development, the GFS has come back into excellent agreement with the Hurricane models in forecasting a vigorous cyclone, tracking it towards northern Taiwan.



Figure 3: The above product depicts satellite derived winds, with strong outflow channels to the south of Rammasun. However, only a weak outflow exists to the northwest of MATMO, and poor outflow in all other quadrants around the cyclone..



Figure 4: The 06Z HWRF model run shows a somewhat more eastward track projection for Matmo compared to the GFS, but other models (not shown) show a track closer to that of the GFS.



Figure 5: Interpreting the Intensity forecast models is somewhat more problematic – with the typically more reliable models calling for Matmo to eventually become a CAT 1 or CAT 2, but a couple models are calling for a far more intense storm. Considering the EURO and GFS global model solutions, I tend to believe a low end CAT 2 to be the most likely outcome.



Figure 6: The official JTWC forecast calls for Matmo to be a CAT 2 Typhoon as it approaches northern Taiwan on Wednesday.

TROPICAL STORM WALI

An unusual (but certainly not rare) Tropical Depression formed yesterday in the central Pacific, about 1,100 NM ESE of the Hawaiian Islands. By early today, better organization of the small cyclone prompted NOAA forecasters to officially designate the system Tropical Storm ‘Wali with 40Mph winds. The storm is currently located about 950 NM ESE of Hilo.

The storm is moving slowly W-NW, and while it may intensify a bit more, cooler SST’s and most notably, stronger wind shear and drier air should significantly weaken the system prior to it reaching the Big Island on Tuesday.



Figure 7: Enhanced IR imagery of Tropical Storm WALI. It’s relatively deep convection and symmetrical signature prompted NOAA forecasters to upgrade the storm early today, but the storm remains quite small and is heading towards a more hostile environment.



Figure 8: Wali is currently located in a relatively low wind shear environment, but a deep TROF NW of the Hawaiian Islands is generating strong, southwesterly wind shear over the eastern Islands and will impact Wali as it heads towards the Big Island in a couple days.



Figure 9: Official Track forecast for Wali

TROPICAL ATLANTIC

The Tropical Atlantic remains fairly quiet – but continues to trend towards a more seasonal pattern as wind shear continues to ease off, and more distinctly, the environment has continued to 'moisten' up.

The Tropical Wave that first emerged off the African coast early yesterday has moved westward, loosing most of its deep convection. However, the wave has brought a strong moisture surge to the eastern Atlantic, though the warm Saharan air has stifled convection.

The more significant wave approaching the Windward Islands and is bringing showers and some heavier convection to the Islands, which will continue westward over the weekend. While wind shear as fallen off considerably compared to last week, it remains relatively high across the southern CARIB, especially in the SW CARIB, and this fact alone will prevent the Tropical wave near the Windward Islands from developing.

While none of the global models are forecasting any cyclone development during the next 10-14 days, the environment is expected to become a bit more conducive to cyclone formation during the last week of the month.



Figure 10: Todays 'big picture' shows the wave bringing significant rainfall to the Windward Islands, with the eastern Atlantic wave representing the leading edge of a significant moisture surge. (While not clearly shown, another large wave over west Africa should reach the coast by tomorrow.



Figure 11: The above enhanced water vapor image highlights the moisture surge over the eastern Atlantic that has accompanied the large tropical wave that came off the coast early yesterday.



Figure 12: The wide view water vapor imagery shows the continuing ‘moistening’ across the Tropical Atlantic Basin – a dramatic change compared to the first 10 days of July.



Figure 13: Wind shear continues to decline across the basin, but remains relatively strong across the southern CARIB which will inhibit any development of the wave near the Windward islands.

Next update will be Saturday afternoon.

Steve Gregory

Updated: 7:29 PM GMT on July 18, 2014

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Rammasun Nears South China – Atlantic Remains ‘Quiet’ As Record Cold / Heat Affect US

By: JeffMasters, 5:50 PM GMT on July 17, 2014

(By Steve Gregory - Substituting for Dr. Masters who is on Vacation.)

Deadly Typhoon Rammasun is located about 440NM NW of Manila heading towards the South China Island of Hainan (population of 9 million). Latest satellite imagery estimates indicate the central pressure is near 955mb, with Max sustained winds of 80Kts. Over the last 6 hours, both IR and water vapor imagery has shown a significant improvement in the convective banding structure and a clearing out of the eye – both indicative of re-intensification.



Figure 1: Latest Enhanced IR image of Rammasun clearly shows a well defined eye within a more symmetrical imagery signature. Banding is evident with extremely cold cloud tops to the North/Northeast of the center.

Until last night, official and model forecasts pointed towards a re-intensification of Rammasun to a solid CAT 3 or Cat 4 prior to reaching Hainan. However, despite the significant improvement in the satellite signature, most forecast models have trimmed the intensity forecast to a strong CAT 2 or minimal CAT 3 within 12 hours, with a slow weakening thereafter. Model projections call for a strong CAT 1 or low end CAT 2 by the time the storm makes landfall along the north coast of the Island near Haikou around 10Z on Friday due to its interaction with land and somewhat cooler SST’s near the South China coast.

The China Meteorological Administration has issued a "orange warning for typhoon" for the provinces of Hainan, Guangdong, and Guangxi, all in southern China. The three provinces have a combined population of over 150 million people. An orange warning is the second-highest level in China's four-tier warning system. Once the cyclone passes by Hainan, the storm is expected to make its final landfall in extreme northern Vietnam with Tropical Storm strength winds. (Note: Vietnam's National Center for Hydro-Meteorological Forecasting has also issued a typhoon warning for portions of northern Vietnam.)



Figure 2: The latest available JTWCTrack forecast for Rassmasun shows the cyclone passing across the northern coast of Hainan as a CAT 2 Typhoon between 06Z and 18Z Friday.

Meanwhile, up on deck is TD#10 which has formed near 10N / 135E with estimated max winds of 30Kts. Imagery indicates the system is essentially stationary, with a slight westward drift noted over the last 12 hours. As late as yesterday, most of the reliable forecast models had forecast this system to become a strong Typhoon over the next 3-5 days with a slow forward acceleration towards the WNW and then NW towards Taiwan. However, the last 4 global model forecast cycles have dramatically changed, with most models now depicting a weak Tropical storm development. Nonetheless, latest official forecasts still call for the development of a CAT 1 typhoon over the weekend, with a track that continues to take aim on Taiwan. This forecast appears to be the most likely scenario based on the most recent SAT imagery.



Figure 3: The above NEXSAT image from last night shows both Rammasun and what is now, TD #10



Figure 4: Track/Intensity forecast for TD #10 shows the cyclone intensifying to CAT 1 as it approaches Taiwan on Tuesday. However, please note that the latest GFS model run does NOT forecast this system to intensify; contrary to yesterday’s model runs calling for a significant typhoon.

TROPICAL ATLANTIC

The Tropical Atlantic remains quiet – but there are continuing signs that conditions are trending towards a more ‘seasonal’ environment, as the first relatively significant Tropical wave emerges off the west African coast – and one that isn’t embedded in the Saharan Air Layer (SAL)! Deep convection is associated with the tropical wave – though the latest animated SAT imagery indicates relatively weak Vorticity associated with this system.

In general, Water Vapor imagery shows a general moistening across the CARIB eastward to the African coast – though wind shear, while falling off during the past few days, remains relatively high across much of the CARIB. In addition, with SST’s still slightly below normal, an overall stable environment persists across much of the CARIB eastward to the African coast. Bottom line: no cyclone formation is expected during the next 7 days



Figure 5: The most significant tropical wave is shown emerging off the West African coast earlier this morning, with waves clearly seen over the central Tropical Atlantic and a more complex wave structure approaching the eastern CARIB. These latter waves MAY may manage to bring some well needed showers to portions of the CARIB over the weekend and next week.




Figure 6: Strong and deep convection associated with the Tropical Wave near the African coast, with minor, but significant convection observed with the central AT and near CARIB waves.




Figure 7: The SAL is well north of the tropical wave off the African coast – the first time this has happened this summer; reflecting the typical intra-seasonal trend that typically begins by late JUL.




Figure 8: This derived image depicts total precipitable water – with somewhat greater totals now shown extending across the deep tropics from just east of the CARIB to the African coast, while some ‘moistening’ of the atmosphere noted over the CARIB as well.



Figure 9: The 850mb Vorticity analysis over the eastern ATL shows a minimal VORT structure associated with the wave that has just emerged off the African coast – while also indicating a far more significant VORT signature associated with the next tropical wave expected to reach the coast late FRI.

RECORDS FALL ACROSS THE NATION

The major upper level TROF that dug southward over the eastern US during the past few days has brought unseasonably ‘cold’ air to much of the central and eastern US during the last couple of days, while the persistent western ridge has led to numerous record highs, especially to the PAC NW northward into portions of western Canada. At the same time, severe drought conditions continue across much of the west, with numerous wild fires in the PAC NW.

Some notable Record Lows reported over the past 2 days include:

Springfield, IL: 52ᵒ
Ottumwa , IA: 49ᵒ
International Falls, MN: 39ᵒ
Little Rock, AR: 62ᵒ
St. Joseph, MO: 51ᵒ
Norfolk, NE: 47ᵒ
Lincoln, NE: 48ᵒ
Moline, IL: 52ᵒ
Mobile, AL: 64ᵒ
Pensacola, FL 66ᵒ

Some Record Low ‘MAX’ Temps on Tuesday:

Goodland, KS: 62ᵒ
Appleton, WI 66ᵒ
Rhinelander, WI 62ᵒ

Some Record Highs:

Moses Lake, OR: 106ᵒ
Pendleton, OR: 105ᵒ
Seattle, WA: 89ᵒ
Yakima, WA: 101ᵒ
Redmond, WA: 100ᵒ
Hanford, WA: 105ᵒ
Pasco, WA: 109ᵒ

Record High ‘MIN’ Temp:

Elko, NV: 71ᵒ - (Also the second warmest Low ever recorded!

And to round it all out – an amazing RAINFALL Record of 0.85” was set yesterday at Tonopah, Nevada.

Steve Gregory

Updated: 7:57 PM GMT on July 17, 2014

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Quiet in the Atlantic; Typhoon Rammasun Kills 12 in the Philippines

By: JeffMasters, 3:33 PM GMT on July 16, 2014

Category 2 Typhoon Rammasun hit the Philippines’ capital city of Manila, where 12 million people live, near 6 pm EDT Tuesday night (22 UTC). The center of the typhoon passed within 40 miles of the city, and had top winds rated at 105 mph by the Joint Typhoon Warning Center (JTWC) at the time. This makes Rammasun one of the most powerful typhoons ever to directly affect Manila; according to NOAA's historical hurricane web page, the strongest typhoon ever to make a direct hit on Manila was Typhoon Angela of 1995, which was a strong Cat 1 or weak Cat 2 when it passed over the city (sustained winds of 90 - 105 mph, according to JTWC's annual report). Fortunately, Rammasun’s eyewall collapsed as it approached Manila, and top winds at the Manila airport reached only 20 mph. However, Rammasun is being blamed for twelve deaths elsewhere in the Philippines. The typhoon came ashore in the Philippines in the Bicol Region of Luzon Island near 5 am EDT on Tuesday, as a Category 3 storm with sustained winds near 125 mph. Rammasun was the first typhoon to strike the Philippines since devastating Category 5 Super Typhoon Haiyan in November 2013, which left over 7,300 people dead or missing. Rammasun's eye passed just north of Samar Island where Haiyan initially made landfall, and brought sustained winds of 40 mph to Haiyan's ground zero, the city of Guiuan. The high winds blew down many of the tents of the people whose homes were destroyed in Tacloban after Super Typhoon Haiyan, but Rammasun’s winds and flooding were not extreme there, and most of the people who evacuated to temporary shelters during the typhoon have now returned.


Figure 1. In this MODIS image from 02:40 UTC July 16, 2014, Category 1 Typhoon Rammasun is looking very disorganized after passing through the Philippine Islands. Image credit: NASA.


Figure 2. Tracks of all typhoons to pass within 75 miles of the Philippines’ capital city of Manila, according to NOAA's historical hurricane web page. The strongest typhoon ever to make a direct hit on Manila was Typhoon Angela of 1995, which was a strong Cat 1 or weak Cat 2 when it passed over the city (sustained winds of 90 - 105 mph, according to JTWC's annual report).

Rammasun will have the opportunity to re-strengthen over the South China Sea before making a second landfall in China near Hainan Island on Friday. Given the typhoon’s current state of disorganization, it will take at least a day for it to take advantage of moderate wind shear of 10 - 20 knots and very warm water temperatures and regain Category 2 strength. I don’t think the storm has time to reach Category 3 strength, as the official JTWC forecast is calling for. Our two top track models, the GFS and European, predict a landfall in China between 03 - 9 UTC on Friday. Rammasun, which has a different name, "Glenda", in the Philippines, is the Siamese word for thunder god.

ATLANTIC REMAINS QUIET - FOR NOW

The tropical Atlantic Basin remains rather quiet, as relatively dry air dominates the CARIB eastward to the west African Coast. One reasonably discernible Tropical Wave located from near 8N / 31W to 14N / 29W is west bound at about 20Kt. The 850mb Vorticity analysis shows some modest tendency for ‘spinning’ with isolated convection associated with this disturbance. However, the tropical wave appears to be inter-twined with the ITCZ which is likely enhancing what little convection there is.

All of the more reliable global models, along with some of the more experimental forecast tools that rely on the MJO (Madden-Julian Oscillation) and CCKW (Convectively Coupled Kelvin Waves) are not forecasting any tropical cyclone spin-ups during the next 10-14 days, and none is expected. (I’ll have bit more information on how CCKW may influence Tropical Cyclone formation and deepening this weekend.)



Fig. 3 There are only a couple easily discernible Tropical Waves – with only the one in the far eastern Atlantic of even minimal interest.



Fig. 4 There is a significant Vorticity Max associated with the wave in the far eastern Atlantic, but it is tracking due west at a very low latitude, and has almost no chance of enhancing the probability that this wave will develop as it tracks westward.



Fig. 5 For much of the summer, wind shear in the CARIB has been very high, but the shear has begun to ease a bit over the past day or two, and there are indications this shear will continue to fall off during the next 1-2 weeks.

Welcome Steve Gregory back!
Today's post was written with the help of meteorologist Steve Gregory, who recently retired as a weather expert for the commodities industry. Steve is also a hurricane expert, and made over 200 posts as a wunderground blogger during the epic hurricane season of 2005. Steve will make several posts in my blog during the coming week, as I will be taking some vacation.

Jeff Masters and Steve Gregory

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Category 3 Typhoon Rammasun hits the Philippines

By: JeffMasters, 2:43 PM GMT on July 15, 2014

Category 3 Typhoon Rammasun powered ashore in the Philippines in the Bicol Region of Luzon Island near 5 am EDT on Tuesday, bringing sustained winds near 125 mph and torrential rains. Rammasun was the first typhoon to strike the Philippines since devastating Category 5 Super Typhoon Haiyan in November 2013, which left over 7,300 people dead or missing. Rammasun's eye passed just north of Samar Island where Haiyan initially made landfall, and brought sustained winds of 40 mph to Haiyan's ground zero, the city of Guiuan. The storm's main fury was felt farther to the north, though, on the southeastern portion of Luzon Island. Rammasun passed just north of Legaspi on Luzon, dropping the pressure to 966 mb near 10 UTC. Maximum sustained winds were 52 mph, and 7.13" of rain fell. Storm chaser James Reynolds is in Legaspi, and tweeted at 3:35 am EDT, "Big mall we're in being shredded, front breaking off into sea. We're safe surrounded by lots of concrete!"


Figure 1. In this MODIS image from 05 UTC July 15, 2014, Category 2 Typhoon Rammasun is enveloping virtually all of the Philippine Islands. Image credit: NASA.

Rammasun was intensifying rapidly as it approached landfall, and it is a good thing that interaction with land was able to halt this process when it did. The Japan Meteorological Agency put Rammasun's central pressure at 965mb at 06Z (2am EDT) Tuesday, then dropped it to 945mb at 09Z (5am EDT) as the storm was making landfall. The pressure rose to 950 mb by 12Z (8 am EDT) after the eye of the storm had spent three hours over land, but the Joint Typhoon Warning Center (JTWC) still rated the storm at Category 3 strength with 125 mph winds. Satellite loops show the typhoon has weakened since landfall: the eye is much less distinct, and the heavy thunderstorms now have warmer cloud tops. Philippines radar shows the typhoon is bringing very heavy rains to much of Luzon, including the capital of Manila, where 12 million people live. Flooding is already occurring in Manila, and flood and wind damage in the city have to potential to make Rammasun one of the top ten most expensive natural disasters in Philippine history. According to NOAA's historical hurricane web page, the strongest typhoon ever to make a direct hit on Manila was Typhoon Angela of 1995, which was a strong Cat 1 or weak Cat 2 when it passed over the city (sustained winds of 90 - 105 mph, according to JTWC's annual report).


Figure 2. Rainfall rate of Typhoon Rammasun as estimated by the Special Sensor Microwave Imager Sounder (SSMIS) instrument on the DMSP F-17 polar orbiting satellite at 5:12 am EDT Tuesday July 15, 2014. Rainfall rates in excess of 1"/hour (orange colors) were indicated in the eyewall of the typhoon. Image credit: Navy Research Lab, Monterey.

After crossing Luzon, Rammasun will have the opportunity to re-strengthen over the South China Sea before making a second landfall in China near Hainan Island on Friday. Our two top track models, the GFS and European, predict a landfall in China between 03 - 12 UTC on Friday. Rammasun, which has a different name, "Glenda", in the Philippines, is a Siamese word of thunder god.

Jeff Masters

Hurricane

Updated: 6:44 PM GMT on July 15, 2014

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Philippines' First Typhoon Since Haiyan Approaching

By: JeffMasters, 3:20 PM GMT on July 14, 2014

The Philippines Islands are bracing for the impact of Typhoon Rammasun, the islands' first typhoon since the devastating strike by Category 5 Super Typhoon Haiyan in November 2013. Haiyan was the deadliest and most expensive natural disaster in Philippines history. Fortunately, Rammasun is much weaker--a mere Category 1 storm. Top winds were 85 mph (1-minute average from the Joint Typhoon Warning Center), and the central pressure was 975 mb (as rated by the Japan Meteorological Agency) at 8 am EDT on Monday morning--a far cry from the incredible 195 mph sustained winds and central pressure of 895 mb of Haiyan at its peak. Rammasun is intensifying, though. Satellite loops on Monday morning showed a steady increase in the intensity and areal coverage of the typhoon's heavy thunderstorms. With wind shear a light 5 - 10 knots and Sea Surface Temperatures a very warm 30°C, further intensification is likely until landfall occurs. Philippines radar showed the outer spiral bands of Rammasun were already affecting Samar Island, where Haiyan initially made landfall. The core of Rammasun will pass north of Samar Island and strike the main Philippines island of Luzon, with the center passing very near the capital of Manila early Wednesday (local time). The main concern will be flash flooding and mudslides over Luzon and Samar, but wind damage also has the potential to be considerable, since the typhoon is passing over the most heavily populated part of Luzon.

After crossing Luzon, Rammasun will have the opportunity to re-strengthen over the South China Sea before making a second landfall in China near Hainan Island on Friday. Our two top track models, the GFS and European, predict a landfall in China between 03 - 12 UTC on Friday.


Figure 1. Rainfall rate of Typhoon Rammasun as estimated by a microwave sounding instrument on NOAA's F-18 polar orbiting satellite at 6:44 am EDT Monday July 14, 2014. Rainfall rates in excess of 1"/hour (orange colors) were indicated in the northern eyewall of the typhoon. Image credit: Navy Research Lab, Monterey.

Extreme heat in Western Canada, unusual coolness in Midwest U.S.
The remnants of Super Typhoon Neoguri, which pushed northeastwards into Alaska after the storm hit Japan last week, set in motion a chain-reaction set of events that has dramatically altered the path of the jet stream and affected weather patterns across the entire Northern Hemisphere. Neoguri caused an acceleration of the North Pacific jet stream, which amplified a trough low pressure over Alaska, causing a ripple effect in the jet stream over western North America, where a strong ridge of high pressure developed. The ridge helped push temperatures as high as 106°F (41.1°C) in British Columbia on Sunday. A compensating strong trough of low pressure formed over the Midwest U.S., and that trough is now pumping cool, polar air southwards into the Upper Midwest. The high temperature in Minneapolis on Monday is predicted to be in the low 60s, about 15°F below average. This jet stream pattern is similar to the nasty "Polar Vortex" pattern that set up during the winter of 2014 over North America, but calling it the polar vortex in this case is not technically correct.


Figure 2. Forecast for the departure of surface temperature from average for 5 pm EDT July 14, 2014, as predicted by the GFS model at 00 UTC July 14, 2014. A strong trough of low pressure is predicted to bring high temperatures much below average over portions of Minnesota and Wisconsin, while much above average temperatures are predicted over much of British Columbia and Alberta, Canada. Data/image obtained using Climate Reanalyzer™ (http://cci-reanalyzer.org), Climate Change Institute, University of Maine, Orono, Maine.

Quiet in the Atlantic
None of the reliable models for predicting genesis of Atlantic tropical cyclones is predicting development over the next five days, and there are no threat areas to discuss. The tropical Atlantic is dominated by dry air and high wind shear, and SSTs are 0.2°C below average in the Hurricane Main Development region between the coast of Africa and Central America, between 10°N - 20°N. If we get another tropical storm this month, the most likely area for formation would be off the Southeast U.S. coast or in the Gulf of Mexico.

Jeff Masters

Hurricane

Updated: 5:29 PM GMT on July 14, 2014

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Upgraded HWRF and GFDL Hurricane Models Excelled During Hurricane Arthur

By: JeffMasters, 12:04 PM GMT on July 11, 2014

Today's guest post is by Dr. Morris Bender of NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) in Princeton, New Jersey, and Dr. Vijay Tallapragada of NOAA's National Center of Environmental Prediction Environmental Modeling Center (NCEP/EMC), with help from GFDL's Timothy Marchok. They outline some very encouraging news on the ability of the latest versions of the GFDL and HWRF hurricane models to significantly improve hurricane track and intensity forecasts.

- Jeff Masters


The landfall last week of Hurricane Arthur, the first named tropical system in the Atlantic for 2014, brought a quick start to this year’s hurricane season. Perhaps lost in the predictions and preparations for Arthur’s landfall was the fact that there have been major upgrades this year to the two operational National Weather Service (NWS) regional hurricane prediction systems, the GFDL and HWRF models. Here we will provide background on each of those models and highlight the forecast improvements achieved from recent upgrades to both models.

Since 1995, the GFDL hurricane model has been an official operational product of the NWS, providing forecast guidance on track and intensity for the National Hurricane Center (NHC). The model was originally developed as a research tool, by scientists at NOAA’s Geophysical Fluid Dynamics Laboratory in Princeton (GFDL), to help understand the behavior and structure of tropical cyclones, including hurricane formation, decay and intensification. To adequately represent the structure of the hurricane and its inner core, the GFDL hurricane model required high resolution (distance between the individual grid points where the atmosphere equations of motion are solved), compared to other models of the atmosphere that define processes over the entire globe (typically called general circulation or global models--for example, the GFS and European models). Also, advanced physics were required to correctly reproduce the processes that occur in the hurricane core, as well as the interaction with the ocean below (Figure 1).


Figure 1. Inner core structure of Hurricane Katrina of 2005 simulated from the GFDL hurricane forecast model. Sea Surface Temperatures (SST) are denoted by the color shading, with the darker colors of blue showing the cooling of the SSTs due to the hurricane winds mixing the cooler waters from below to the surface.

In the early 2000s scientists at the NWS National Center for Environmental Prediction (NCEP) began to develop a new state of the art hurricane model using the most advanced numerical techniques available, to more accurately solve the mathematical equations that represent the processes of the atmosphere. This model (named HWRF, or Hurricane Weather Research Forecast model) became operational in 2007, as an official product of the National Weather Service. Since then, improvements have been made to the HWRF modeling system every year, resulting in a steady reduction in track and intensity forecast errors. The recently upgraded HWRF model implemented for the 2014 hurricane season has shown much reduced track forecast errors compared to the 2013 version of HWRF for a large sample of North Atlantic basin tropical cyclones, with performance comparable to the NHC Official Forecasts (Figure 2).


Figure 2. Track forecast errors from 2014 HWRF upgrades (H4FI, red) compared to previous year’s operational HWRF (2013 version, H3FI, blue) and NHC Official Forecasts (OFCL, purple) shown for a large sample of North Atlantic storms from 2008 to 2013.

A major accomplishment is the significant reduction of intensity errors from the HWRF model in the past three years since the model was upgraded to run using cloud-permitting, 3 km resolution nests (see Figure 3), making it a primary model for intensity forecast guidance for NHC. Much of the increased skill seen in the HWRF model over the past 3 years was due to the successful collaboration between agencies within NOAA (GFDL, NCEP, AOML, ESRL) and partners within the academic community (such as the University of Rhode Island), that was made possible through the coordinated efforts and support from NOAA’s Hurricane Forecast Improvement Project (HFIP). Apart from providing operational forecast guidance to the NHC for the Atlantic and Eastern Pacific basins, the HWRF model is also run in real-time for all global oceanic basins, providing forecast guidance to the US Navy’s Joint Typhoon Warning Center (JTWC). All real-time forecast products can be accessed from the HWRF website.


Figure 3. HWRF model intensity forecast improvements from 2011 to 2013 for North Atlantic basin. The intensity errors shown here are collected from hundreds of retrospective simulations for each upgraded HWRF configuration since 2011. The 2011 version of HWRF (blue) was run at 9km resolution, while the model was upgraded to run at 3km resolution in 2012 (purple). The 2013 HWRF (red) was able to meet or exceed the HFIP intensity error baseline whereas the 2014 HWRF (green) further reduced the intensity errors, approaching the HFIP 5-year intensity error goal.

At the same time, scientists at GFDL have also upgraded the GFDL hurricane modeling system, with major improvements made operational in 2014, particularly to improve the prediction of hurricane intensity as shown in Figure 4. Note that the improvements made to the GFDL hurricane model reduced the error in the prediction of the storm maximum wind by about 15% in the 3 to 5 day forecast time period, for a set of forecasts rerun from the 2008, 2010, 2011, and 2012 Atlantic hurricane seasons, using both the 2013 version of the GFDL model and the newly upgraded model.

The National Hurricane Center continues to support both of these operational regional hurricane models (HWRF and GFDL) since the forecast error of both models is often not correlated (individual model errors often go in different directions). Numerous scientific studies suggest that the average forecast from models that are well behaved produce errors that are less than those from the individual models. This has led to an increase in the use of model ensembles (models with slightly different initial conditions or different physics). For example, as shown in Figure 5, a consensus made up of the average of the intensity forecasts from the 2014 versions of the GFDL and HWRF (solid black line) results in an intensity forecast error that is significantly less than either the HWRF or GFDL model at every forecast lead time. Note that the average intensity forecast error of the 2-model consensus at days 4 and 5 is even less than the HFIP 5-year goal established in 2009.


Figure 4. Comparison of the intensity forecasts errors (in knots) from 12 to 120 hours in the future, for Atlantic storms rerun from the 2008, 2010, 2011 and 2012 Atlantic hurricane season. Plotted are the forecast errors for the version of the GFDL hurricane model used in 2013 (black line), compared to the version recently made operational in 2014 (red line).


Figure 5. Intensity forecast errors at hours 12 through 120, for the 2014 versions of the GFDL (blue) and HWRF (red) models for over 800 forecasts from the 2008, 2010, 2011 and 2012 Atlantic hurricane seasons, compared to the forecast error for the consensus model made up of the average intensity prediction of GFDL + HWRF.

Both the upgraded GFDL and HWRF modeling system did well for track and intensity forecasts for Hurricane Arthur, the first hurricane of the 2014 Atlantic hurricane season (Figure 6). The new GFDL and HWRF had very low track errors although the sample size was small, with the average intensity errors comparable to the other two top NWS intensity prediction models (Decay SHIPS and the LGEM).

With continuous advancements to the NCEP hurricane models supported by HFIP, and enhanced computational resources available for operational models, we anticipate further improvements in track and intensity forecasts through improved hurricane physics, advanced inner core data assimilation, and increased horizontal and vertical resolutions. Apart from coupling the atmospheric model to the ocean model, future efforts also include coupling to wave, land surface, hydrology, and surge and inundation models for improved prediction of land falling storms.



Figure 6. Average track forecast error (top) and average errors in the forecast maximum surface winds (bottom) for the upgraded GFDL model (green), the upgraded HWRF (red), compared to the official forecast of the National Hurricane Center (black), and other NWS operational models, for all forecasts of Hurricane Arthur (2014).

Morris Bender and Vijay Tallapragada

Hurricane

Updated: 3:24 PM GMT on July 14, 2014

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Tropical Storm Neoguri Hits Japan; NOAA Holds Summer El Niño Odds at 70%

By: JeffMasters, 1:50 PM GMT on July 10, 2014

Tropical Storm Neoguri made landfall near the city of Akune in southwest Japan's Kagoshima Prefecture on the island of Kyushu just before 7 a.m. Japanese time Thursday (6 p.m. Wednesday Eastern time in the U.S.). Once a mighty super typhoon with 155 mph winds, the Japan Meteorological Agency estimated that Neoguri weakened to maximum 10-minute sustained winds of 60 mph at landfall (equivalent to maximum winds of about 65 to 70 mph using the U.S. 1-minute sustained wind standard.) Neoguri will track along the east coast of Japan on Thursday, and Japan Meteorological Agency radar showed very heavy rains in excess of one inch (25.4 mm) per hour were affecting portions of the country this morning. On Kyushu, Ebino reported 13.20 inches (335.5 mm) of rain in the 24 hours ending at 8 a.m. Japanese time Thursday, and a 72-hour rainfall total of 398 mm (15.67 inches) was recorded at Ushibuka. Public broadcaster NHK said parts of central Japan, including Nagoya, could see up to 16 inches (400 mm) of rain by Friday morning. Neoguri killed two people and injured 32 in Japan's Ryukyu Islands, which include Okinawa. The islands may have another typhoon to worry about next week--recent runs of the GFS model have been predicting that tropical disturbance 92W will develop into a tropical cyclone and potentially affect the Ryukyu Islands by the middle of next week.


Figure 1. A wooden house collapsed during strong winds in Naha on Japan's southern island of Okinawa on July 8, 2014. (Jiji Press/AFP/Getty Images)

NOAA Holds El Niño Odds at 70% for this Summer
NOAA's monthly El Niño discussion, issued on Thursday July 10, maintains an El Niño watch, and continues to project a 70% chance of El Niño forming this summer, and an 80% chance by fall. The forecasters anticipate El Niño will peak at weak-to-moderate strength during the late fall and early winter, with 3-month values of the Niño-3.4 index between 0.5°C and 1.4°C. The Niño-3.4 index is a measure of the departure from average of sea surface temperatures (SSTs) along the Equator in the Pacific between 120°W - 170°W, 5°N - 5°S. SSTs in this region have been hovering near the threshold for El Niño, +0.5°C from average, from late April through mid-July. However, the atmosphere has not been behaving like it should during an El Niño event. The Southern Oscillation Index (SOI)--the difference in surface pressure between Darwin, Australia and the island of Tahiti--tends to drop to negative values during the presence of an El Niño atmosphere. The SOI has been trending downwards the past 50 days, but was still positive in June. Heavy thunderstorm activity over Indonesia and near the International Date Line is typically enhanced during an El Niño event, and has been picking up over the past month, but must increase more before we can say the atmosphere is responding in an El Niño-like fashion.


Figure 2. Forecasts of the departure of SST from average along the Equator in the Pacific between 120°W - 170°W, 5°N - 5°S as made by computer models that forecast ENSO (the El Niño/Southern Oscillation.) Forecasts above the thick red line indicate an El Niño event; forecasts below the thick blue line are for a La Niña event; forecasts between the red and blue line are for neutral conditions. None of the models are predicting La Niña, and about 2/3 are predicting El Niño. Image credit: IRI/NOAA.

Quiet in the Atlantic
None of the reliable models for predicting genesis of Atlantic tropical cyclones is predicting development over the next five days, and there are no threat areas to discuss. The tropical Atlantic is dominated by dry air and high wind shear, and SSTs are 0.3°C below average in the Hurricane Main Development region between the coast of Africa and Central America, between 10°N - 20°N. If we get another tropical storm this month, the most likely area for formation would be off the Southeast U.S. coast or in the Gulf of Mexico.

Jeff Masters

Hurricane

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Neoguri Weakens to a Tropical Storm, Brings Torrential Rains to Japan

By: JeffMasters, 2:32 PM GMT on July 09, 2014

Tropical Storm Neoguri continues its steady weakening trend as it closes in on the large southern Japanese island of Kyushu. Landfall of the center is expected to occur near 6 am local time on Thursday (Wednesday night in the U.S.) Once a mighty super typhoon with 155 mph winds, Neoguri has now weakened to a tropical storm with 70 mph winds as of 11 am EDT on Wednesday. Satellite images Wednesday morning showed a continued deterioration of Neoguri's heavy thunderstorms as high wind shear of 20 knots tore at the storm and the storm moved over cooler sea surface temperatures. Neoguri passed through Japan's Ryukyu Islands on Monday, killing two people and injuring 30. Japan Meteorological Agency radar showed that very heavy rains of up to two inches per hour (50.8 mm/hr) were affecting southern Kyushu Wednesday night local time (Wednesday morning EDT), and Tahiro recorded 55 mm (2.16") in the two hours ending at 10 pm local time on Wednesday. Some mountainous areas of southern Japan are predicted to receive 20 - 28" of rain from Neoguri. With soils already saturated from a week of heavy rains prior to Neoguri's arrival, damaging flooding is expected.


Figure 1. ESA astronaut Alexander Gerst tweeted this photo of Typhoon Neoguri at 22 UTC July 8, 2014. At the time, Neoguri was a weakening Category 2 typhoon with 100 mph winds.


Figure 2. Radar image of rains from Neoguri affecting southern Japan, at 10:50 pm local time Wednesday, July 9, 2014. Image credit: Japan Meteorological Agency.

Links
Japanese radar
Official Neoguri forecasts from the Japan Meteorological Agency

Impact of Neoguri on U.S. weather
While the remnants of Typhoon Neoguri will not impact the U.S. directly, the large and powerful nature of this storm has set in motion a chain-reaction set of events that will dramatically alter the path of the jet stream and affect weather patterns across the entire Northern Hemisphere next week. Neoguri will cause an acceleration of the North Pacific jet stream, causing a large amount of warm, moist tropical air to push over the North Pacific. This will amplify a trough low pressure over Alaska, causing a ripple effect in the jet stream over western North America, where a strong ridge of high pressure will develop, and over the Midwestern U.S., where a strong trough of low pressure will form. This jet stream pattern is similar to the nasty"Polar Vortex" pattern that set up during the winter of 2014 over North America, and will cause an unusually cool third week of July over the portions of the Midwest and Ohio Valley, with temperatures 10 - 20°F below average.



Figure 3. One-week forecast for the departure of surface temperature from average for July 16, 2014, as predicted by the GFS model at 00 UTC July 9, 2014. A strong trough of low pressure is predicted to form over the Midwest U.S., bringing temperatures 10 - 20°F below average. Data/image obtained using Climate Reanalyzer™ (http://cci-reanalyzer.org), Climate Change Institute, University of Maine, Orono, Maine.

Jeff Masters

Hurricane

Updated: 9:05 PM GMT on July 09, 2014

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Typhoon Neoguri Weakens to Category 3, But Still a Major Flood Threat to Japan

By: JeffMasters, 3:37 PM GMT on July 08, 2014

The outer spiral bands of Typhoon Neoguri are lashing the large southern Japanese island of Kyushu as the storm heads north at 15 mph towards Japan. Despite seemingly favorable conditions for intensification on Monday and Tuesday morning, with low wind shear, very warm sea surface temperatures of 30 - 31°C, very warm waters extending to great depth, good upper-level outflow, and only modest amounts of dry air, Neoguri mysteriously weakened from a 155 mph super typhoon to a Category 3 storm with 120 mph winds in the 30 hours ending at 11 am EDT Tuesday morning. Satellite images Tuesday morning showed a continued reduction in the intensity and areal coverage of Neoguri's heavy thunderstorms. Neoguri passed through Japan's Ryukyu Islands over the past day, killing one person and injuring 25, but the eyewall missed making a direct hit on any island. Some notable wind and rainfall reports from the islands:

Peak winds: Sustained winds of 79 mph, gusting to 118.6 mph at Tokashiki Island (according to the Japan Meteorological Agency)
Peak winds at Kadena AB (Okinawa): 74 mph, gusting to 101 mph
Kadena AB rainfall since 8am Monday: 24.03 inches, with 10.02 inches in 6 hours from roughly 3-9 p.m. JST today, and another 12.73 inches from 9 a.m. - 3 p.m. JST today


Figure 1. Radar image of the outer bands of Typhoon Neoguri affecting southern Japan, at 12:10 am local time Wednesday, July 9, 2014. Image credit: Japan Meteorological Agency.

Forecast for Neoguri
Neoguri has been caught by a trough of low pressure and is expected to turn northeast towards the Japanese island of Kyushu, where the city of Nagasaki lies. A stalled stationary front over the island has been bringing flooding rains to Kyushu since Thursday; Ushibuka (in far southwest Japan) picked up 14.72 inches of rain over the past 48 hours. Nagasaki had upwards of 8 inches of rain on Thursday. With the soils already saturated from these heavy rains, the torrential rains from Neoguri are sure to cause significant flooding on Wednesday and Thursday. The latest 00Z and 06Z Tuesday runs of the European and GFS models showed landfall occurring between 00 - 04 UTC on Thursday. Ocean temperatures will cool and wind shear will rise as Neoguri approaches Japan, weakening the storm, and Neoguri is likely make landfall as a strong tropical storm or Category 1 typhoon. At this intensity, major wind damage would not occur; flood damage from heavy rains will be the main concern. Neoguri, pronounced "NAW-guh-ree", is named after the Korean word for raccoon dog. It is also a brand of ramen noodle in Korea.

Links
Japanese radar
Official Neoguri forecasts from the Japan Meteorological Agency

Neoguri's eye has a wrinkle
Neoguri's displayed an unusual "wrinkle" in satellite images taken the past three days--a sharp line radiating out from the northern eyewall, where an interesting "cliff" of clouds had formed. The cause of this "cloud cliff" is unknown, but it is not uncommon to see them in Western Pacific Super Typhoons. Similar eyewall "cloud cliffs" were observed in 2012 in Super Typhoon Bopha (visible on the south side of the eye in this blow-up image from the University of Wisconsin CIMSS Satellite Blog ), and in Super Typhoon Jelawat (visible on the north side of the eye.)


Figure 2. ESA astronaut Alexander Gerst tweeted this photo of Typhoon Neoguri's "cloud cliff" from the International Space Station at 7am EDT July 8, 2014. At the time, Neoguri was a Category 3 typhoon with 125 mph winds.


Figure 3. ESA astronaut Alexander Gerst tweeted this photo of Typhoon Neoguri's "cloud cliff" from the International Space Station at 5am EDT July 8, 2014. At the time, Neoguri was a Category 3 typhoon with 125 mph winds.


Figure 4. NASA astronaut Reid Wiseman tweeted this photo of Typhoon Neoguri's "cloud cliff" from the International Space Station at 5:55 pm EDT July 7. At the time, Neoguri was a Category 3 typhoon with 125 mph winds.


Figure 5. Infrared VIIRS image of Neoguri taken at 12:53 am EDT July 7, 2014, showing the "cloud cliff" along the northern eyewall. Image credit: Dan Lindsey, NOAA/CIRA.

Jeff Masters

Hurricane

Updated: 8:20 PM GMT on July 08, 2014

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Super Typhoon Neoguri Lashing Okinawa, Headed for Japan

By: JeffMasters, 4:01 PM GMT on July 07, 2014

The outer spiral bands of Super Typhoon Neoguri are pounding the Japanese Ryukyu Islands, which include Okinawa, as the mighty storm heads north-northwest at 12 mph towards Japan. At 11:30 pm local time (13:30 UTC) Monday, Naha City in southern Okinawa was reporting heavy rain and wind gusts of 43 mph. At 8 pm local time Monday, Miyako-jima reported sustained winds of 33 mph, gusting to 53 mph. On Sunday, Neoguri strengthened to 155 mph winds, crossing the 150 mph threshold needed to be labeled a Super Typhoon. As of 8 am EDT on Monday, the typhoon had weaker slightly to 150 mph winds, and infrared satellite images showed a reduction in the intensity and areal coverage of Neoguri's heavy thunderstorms. Recent microwave satellite images showed that the weakening may be due to the onset of an eyewall replacement cycle, a common occurrence in intense tropical cyclones. In an eyewall replacement cycle, the inner eyewall shrinks to the point of instability, collapses, and is replaced by a larger-diameter outer eyewall that forms from a spiral band. This process can take several days, and typically reduces the peak winds by 10 - 20 mph. With wind shear light, 5 - 10 knots, sea surface temperatures a very warm 30 - 31°C, and very warm waters extending to great depth along the storm's path, the typhoon will have the opportunity to re-strengthen once the eyewall replacement cycle is done.


Figure 1. MODIS image from NASA's Terra satellite of Typhoon Neoguri taken at 02:05 UTC July 6, 2014. At the time, Neoguri was a Category 4 storm with 140 mph winds. Image credit: NASA.


Figure 2. Radar image of Super Typhoon Neoguri approaching Miyako-jima Island, Japan, at 12:45 am local time Tuesday, July 8, 2014. Image credit: Japan Meteorological Agency.

Forecast for Neoguri
The official Joint Typhoon Warning Center forecast calls for Neoguri to complete its eyewall replacement cycle and intensify into a Category 5 typhoon with 160 mph winds by Tuesday. The official Japan Meteorological Agency forecast also calls for intensification, with the typhoon dropping from its current 930 mb pressure to 915 mb by 03 UTC on Tuesday. While intensification is certainly possible, I think it is more likely that Neoguri has peaked in intensity, given the level of disruption to the storm apparent on satellite images. The 00Z Monday runs of our two top track models, the GFS and European models, showed Neoguri passing about 150 miles southwest of Okinawa near 00 UTC Tuesday. Okinawa will be in the right front quadrant of Neoguri, but if the present track forecast holds, the top winds on the south end of the island will stay below hurricane force. Stronger winds will be felt on Miyako-jima island, south of Okinawa, which may see the weak (left) eyewall of the typhoon.


Figure 3. Tropical Cyclone Heat Potential (TCHP) for Neoguri will be as high as 100 J/kg/cm^2 on Monday, a level which is favorable for rapid intensification. Forecast positions from the 5 am EDT Joint Typhoon Warning Center advisory from July 7, 2014, are superimposed. Image credit: NOAA/RAMMB.

Neoguri has been caught by a trough of low pressure and is headed for the Japanese island of Kyushu, where the city of Nagasaki lies. Nagasaki had upwards of 8 inches of rain on Thursday, and parts of Kyushu saw 10 inches of rain on Friday, thanks to a stalled stationary front over the island. With the soils already saturated from these heavy rains, the torrential rains from Neoguri are sure to cause major flooding on Wednesday and Thursday. The latest 00Z and 06Z Monday runs of the European and GFS models showed a delayed arrival in Kyushu compared to earlier runs, with landfall now expected to occur between 00 - 04 UTC on Thursday. Although ocean temperatures will cool and wind shear will rise as Neoguri approaches Japan, weakening the storm, the typhoon is so large and powerful that it will likely make landfall with at least Category 2 strength, causing major damage in Japan. Neoguri is the 7th named storm and 3rd typhoon of the 2014 Western Pacific typhoon season. The other two typhoons of 2014--Typhoon Faxai and Typhoon Tapah--were both Category 1 storms. Neoguri, pronounced "NAW-guh-ree", is named after the Korean word for raccoon dog. It is also a brand of ramen noodle in Korea.

Links
Storm chasers Josh Morgerman, Mark Thomas, and James Reynolds, who intercepted Super Typhoon Haiyan at its peak fury when it devastated the Philippines last year, are on Miyako-jima island, south of Okinawa. Miyako-jima appears likely to receive a visit by the weak (left) eyewall of Neoguri, and you can follow their experience at http://www.icyclone.com/.

Japanese radar

Kadena AFB, Okinawa Facebook page

Jeff Masters

Hurricane

Updated: 4:38 PM GMT on July 07, 2014

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Category 4 Typhoon Neoguri Headed Towards Japan

By: JeffMasters, 4:51 PM GMT on July 06, 2014

In the Western Pacific, Typhoon Neoguri has strengthened into a dangerous Category 4 storm with 140 mph winds this Sunday morning, and is headed west-northwest at 12 mph towards a Tuesday brush with Okinawa in Japan's Ryukyu island chain. Satellite images show a huge and well-organized system, with a prominent eye, and very intense eyewall thunderstorms with cold cloud tops. WInd shear is light, 5 - 10 knots, sea surface temperatures are a very warm 30 - 31°C, and very warm waters extend to great depth along the storm's path, giving the typhoon plenty of heat energy to power potential intensification into a Category 5 Super Typhoon. The 00Z Sunday runs of our two top track models, the GFS and European models, showed Neoguri passing about 50 - 100 miles south of Okinawa near 00 UTC Tuesday. Okinawa will be in the right front quadrant of Neoguri, but if the present track forecast holds, the top winds on the south end of the island will be barely hurricane force, 70 - 75 mph. The ocean is very deep offshore of Okinawa, which will allow huge waves to crash against the coast. Shortly after passing Okinawa, Neoguri will get caught by a trough of low pressure and begin curving to the north, and likely hit the Japanese island of Kyushu, where the city of Nagasaki lies, between 12 - 22 UTC on Wednesday. Although ocean temperatures will cool and wind shear will rise as Neoguri approaches Japan, weakening the storm, the typhoon is so large and powerful that it will likely make landfall at Category 2 or 3 strength, causing major damage in Japan. Neoguri is the 7th named storm and 3rd typhoon of the 2014 Western Pacific typhoon season. The other two typhoons of 2014--Typhoon Faxai and Typhoon Tapah--were both Category 1 storms. Neoguri is named after the Korean word for raccoon dog.


Figure 1. NASA astronaut Reid Wiseman tweeted this photo of Typhoon Neoguri from the International Space Station at 7 pm EDT July 5, 2014. At the time, Neoguri was a Category 4 typhoon with 140 mph winds.

Links
Kadena AFB, Okinawa Facebook page

Jeff Masters

Hurricane

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Arthur Hits Nova Scotia, Becomes Post-Tropical; Cat 4 Typhoon Neoguri Forms

By: JeffMasters, 3:23 PM GMT on July 05, 2014

Hurricane Arthur is no more. Its circulation has been absorbed by a trough of low pressure over the Canadian Maritime provinces after Arthur made landfall in Nova Scotia on Saturday morning near 10 am EDT as a tropical storm with 65 mph winds. On Friday night, Arthur skirted Nantucket and Cape Cod, Massachusetts, bringing a swath of 3 - 5" of rain across Southeast Massachusetts and Eastern Maine. Top winds at Nantucket were 50 mph, gusting to 59 mph, at 9:53 pm EDT.


Figure 1. Boston radar image of Arthur on Friday night July 4, 2014, as it brushed Nantucket and Cape Cod, Massachusetts.


Figure 2. Total radar-estimated rainfall for the Northeast U.S. from Arthur from the Boston radar. Arthur brought a swath of 3 - 5" of rain across Southeast Massachusetts.

Category 4 Typhoon Neoguri a threat to Japan
In the Western Pacific, Typhoon Neoguri has strengthened into a Category 4 storm with 135 mph winds this Saturday morning, and is headed northwest towards a Tuesday rendezvous with Okinawa in Japan's Ryukyu island chain. Satellite images show a huge and well-organized system, with a prominent eye, and very intense eyewall thunderstorms with cold cloud tops. WInd shear is light, 5 - 10 knots, and Neoguri is expected to be a Category 5 storm by Sunday. Neoguri will get caught by a trough of low pressure on Monday and begin curving to the northwest. The 00Z Saturday runs of our two top track models, the GFS and European models, showed Neoguri passing about 50 - 100 miles south of Okinawa near 00 UTC Tuesday, then curving to the north and hitting the Japanese island of Kyushu, where the city of Nagasaki lies, between 10 - 22 UTC on Wednesday. Neoguri is the 7th named storm and 3rd typhoon of the 2014 Western Pacific typhoon season. The other two typhoons of 2014--Typhoon Faxai and Typhoon Tapah--were both Category 1 storms. Neoguri is named after the Korean word for raccoon dog, and was also used for a 2002 typhoon that passed near Japan, and a 2008 typhoon that hit China.


Figure 3. NASA astronaut Reid Wiseman tweeted this photo of Typhoon Neoguri from the International Space Station on July 4, 2014. At the time, Neoguri was a Category 2 typhoon with 105 mph winds.

Links
Kadena AFB, Okinawa Facebook page

Jeff Masters

Hurricane

Updated: 4:16 PM GMT on July 05, 2014

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Hurricane Arthur Pounds North Carolina, Heads for Nova Scotia

By: JeffMasters, 5:20 PM GMT on July 04, 2014

Hurricane Arthur has weakened to a Category 1 storm with 90 mph winds on Friday morning, after delivering a direct hit to the barrier islands of eastern North Carolina on Thursday night. Officially, Arthur made landfall at Shackleford Banks between Cape Lookout and Beaufort, North Carolina at 11:15 pm EDT July 3, 2014 as a Category 2 hurricane with 100 mph winds. It was the first Category 2 hurricane to make U.S. landfall since Hurricane Ike of 2008 (which had 110 mph winds at landfall.) Arthur is only the fourth July hurricane to hit North Carolina since accurate records began in 1851, and the earliest in the year to hit the state. Other July hurricanes to hit the state occurred in 1901, 1908, and 1996. Fortunately, no deaths or injuries were reported due to Arthur, and damage was minimal, said North Carolina governor Pat McCory at a 9:30 am EDT July 4 press conference, though 44,000 customers lost power. The vast majority of the 60,000 permanent residents who live on the Outer Banks did not evacuate. Highway 12 connecting the Outer Banks to the mainland was flooded and covered with sand, but is scheduled to re-open on Saturday. The Bonner Bridge crossing Oregon Inlet on Highway 12 needs to be inspected before it can re-open, since there is concern that the 4.5' storm surge that roared though the inlet early Friday morning may have scoured sand away from the support pilings. Luckily, the highest surge occurred at low tide.


Figure 1. NASA astronaut Reid Wiseman tweeted this photo of the storm from the International Space Station taken through a 10.5mm fish eye lens at 9:30 am EDT July 4, 2014. At the time, Arthur was a Category 1 hurricane with 90 mph winds.


Figure 2. Radar out of Wilmington, North Carolina at 11:22 pm EDT July 3, 2014, as Arthur made landfall at Cape Lookout, NC.


Figure 3. Total radar-estimated rainfall for North Carolina from Arthur from the Wilmington, North Carolina radar.

Wind, wave, storm surge, and tornado reports

Here are the top winds measured in North Carolina from Arthur:

Cape Lookout CMAN, 71 mph gusting to 84 mph at 10 pm (though NHC reported that this station had sustained winds of 77 mph, gusting to 101 mph between the regular hourly reporting times)
Beaufort, 54 mph gusting to 69 mph at 10:24 pm
Cape Hatteras USCG, 64 mph gusting to 78 mph at 1:36 am
Oregon Inlet Marina, 54 mph gusting to 69 mph at 5:24 am

A significant wave height of 21.3' was observed at Oregon Inlet at 4:47 am EDT.

Here are the top storm surge levels measured at NOAA tide gauges from Arthur:

4.5' at Oregon Inlet, NC
2.5' at Hatteras, NC USCG Station
2.4' at Beaufort, NC
2.1' at Duck, NC
2.1' at Sewells Point, VA
2.1' at Chesapeake Bay Bridge Tunnel, VA

NOAA's Storm Prediction Center recorded one tornado in North Carolina on Thursday from Arthur; the tornado did only minor damage.


Figure 4. Aerial view of Highway 12 to the North Carolina Outer Banks on the morning of July 4, 2014 after the storm surge of Hurricane Arthur had scoured the coast. Image credit: U.S. Coast Guard.

Forecast for Arthur
Satellite loops on Friday afternoon showed that Arthur's eye had filled with clouds, and the storm had expanded in size. Top winds of the hurricane at 11 am EDT were still a formidable 90 mph, with the central pressure a respectable 976 mb. With wind shear a high 25 knots and sea surface temperatures a chilly 24°C, Arthur will steadily weaken, but is still expected to have 70 - 75 mph winds when it makes landfall in Western Nova Scotia between 5 am - 8 am EDT Saturday, July 5. By late morning Saturday, Arthur will complete the transition to a powerful extratropical storm with tropical storm-force winds. The 11 am EDT Friday wind probability forecast from NHC gave Yarmouth, Nova Scotia a 12% chance of hurricane-force winds, and a 93% chance of tropical storm-force winds. Nantucket and Cape Cod, Massachusetts were given 88% and 54% chances of tropical storm-force winds, respectively.

Arthur's formation is not a harbinger of an active hurricane season
The first hurricane of the season typically occurs on August 10, so Arthur is quite a bit ahead of schedule. Arthur was able to form so early because it was over the very warm waters of the Gulf Stream Current, and these waters happened to be over 1°F warmer than usual for this time of year. Formation of a June or July hurricane like Arthur off the U.S. coast is typically not a harbinger of an active hurricane season, since these storms do not form from African tropical waves. Arthur spun up from a cluster of thunderstorms and their associated low pressure system that moved off the Southeast U.S. coast, and hurricanes that get their start this way are typically too far north and too close to land to be able to intensify into major hurricanes. The bigger threat are hurricanes that get their start from tropical waves traversing Main Development Region (MDR) for hurricanes (from the coast of Africa to Central America between 10° - 20°N, including the Caribbean Sea.) Tropical waves that traverse the MDR are responsible for 85% of all major (Category 3 and stronger) hurricanes. When June and July hurricanes and tropical storms form in the MDR, it usually does portend an active hurricane season, since it shows that atmospheric and oceanic conditions are primed to assist development of tropical waves coming off the coast of Africa during the peak mid-August through mid-October part of hurricane season.

A better way to evaluate whether or not this will be an active hurricane season is to look at sea surface temperatures (SSTs) in the MDR, and the status of El Niño. MDR SSTs are currently very close to average, and are thus unlikely to contribute to an above-average hurricane season. The very warm equatorial waters currently off the coast of South America suggest that an El Niño event is in the process of developing. When an El Niño event occurs during hurricane season, it tends to create an atmospheric circulation that brings unusually strong upper-level winds to the tropical Atlantic. These strong winds create a shearing action (wind shear) on any tropical storms or hurricanes that may be attempting to form, disrupting their circulation. Thus, the pre-season predictions of a below-average or near-average hurricane season still look good.


Video 1. ‪Hurricane Arthur at The Frying Pan Tower Adventure B&B‬ (thanks to Skyepony for posting this link in my blog comments.)

Jeff Masters

Hurricane

Updated: 5:24 PM GMT on July 04, 2014

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Hurricane Arthur Shifts Left, Aims for a DIrect Hit in Eastern North Carolina

By: JeffMasters, 9:25 PM GMT on July 03, 2014

Hurricane Arthur has shifted to the left inside its cone of track uncertainty, and is poised to deliver a direct hit to the barrier islands of eastern North Carolina on Thursday night and Friday morning. The hurricane's 90 mph winds and 979 mb pressure from the 5 pm EDT Thursday NHC advisory make Arthur as strong as the strongest hurricane of 2013, Hurricane Humberto. Humberto peaked as a Category 1 storm with 90 mph winds and a central pressure of 979 mb as it traversed the waters a few hundred miles northwest of the Cape Verde Islands off the coast of Africa. The strongest winds measured at a buoy today in Arthur were 52 mph, gusting to 67 mph, measured at buoy 41004 offshore from Charleston, SC, at 12:50 pm EDT. Heavy rains from Arthur brought radar-estimated rainfall amounts of 3 - 4" as of 4:30 pm EDT near Wilmington, in southern North Carolina. Radar out of Wilmington shows that Arthur has developed an imposing area of heavy rains, but dry air is still infiltrating its core, creating a large gap in the eyewall. Satellite loops on Thursday afternoon showed a moderate-sized hurricane with a prominent eye surrounded by intense thunderstorms with very cold cloud tops. An excellent outflow channel has developed on the east side, but outflow is still restricted on the west side, where dry air is interfering with the storm. Wind shear a light 5 - 10 knots. Arthur's core has moved north of the axis of the Gulf Stream, and the hurricane is no longer able to take full advantage of the heat energy this narrow ribbon of very warm waters carries.


Figure 1. MODIS satellite image of Tropical Storm Arthur, taken at approximately 16:30 UTC (12:30 pm EDT) on Thursday, July 3, 2014. At the time, Arthur was a Category 1 storm with 90 mph winds. Image credit: NASA.


Figure 2. Radar out of Wilmington, North Carolina at 4:39 pm EDT July 3, 2014.

Forecast for Arthur
With the eyewall still showing gaps due to dry air infiltration, rapid intensification into a Category 3 hurricane appears unlikely. The 18Z Thursday run of the SHIPS model predicted that wind shear will remain light to moderate, 5 - 15 knots, between now and Friday morning, then rise steeply. The model also predicted a 20% chance of rapid intensification--a 30 mph increase in winds in 24 hours. I put the odds Arthur becoming a Category 3 or stronger storm at 10%. The 5 pm EDT Thursday wind probability forecast from NHC gave Cape Hatteras a 80% chance of experiencing hurricane-force winds, and Morehead City a 92% chance. The 12Z Thursday runs of our top two track models, the GFS and European (ECMWF), showed the eye of Arthur hitting Cape Lookout, North Carolina between midnight and 1 am, with the strongest winds of the eyewall's right front quadrant affecting Cape Hatteras between 3 am - 5am.


Figure 3. Radar-estimated rainfall from Wilmington, North Carolina as of 4:44 pm EDT July 3, 2014.

Arthur's storm surge
Along with wind damage, the biggest threat from Arthur is coastal flooding due to storm surge. A surge of 2 - 5 feet will peak late Thursday night through early Friday morning from Morehead City, NC, to the North Carolina/Virginia border. Low tide will occur near 6:30 - 7 pm EDT Thursday night, and again at 7 - 7:30 am Friday morning. High tide will be between 12:30 - 1:00 am Friday, and this is when the highest water levels (storm tide) will occur along much of the North Carolina coast south of Cape Hatteras, due the combined effect of the storm surge and tide. Tidal range between low and high tide is about 2 feet along much of the North Carolina coast, though it is only about 0.5' along portions of the Outer Banks. Tidal range at the Hatteras USCG station, which isn't far from the lighthouse, is only 0.3', so it doesn't matter much when the surge arrives there. At 4 pm EDT on Thursday, Arthur was bringing a storm surge in excess of one foot to portions of the South Carolina and North Carolina coasts:

1.7' at Oyster Landing, SC
1.6' at Wrightsville Beach, NC
1.3' at Wilmington, NC
1.1' at Beufort, NC
0.8' at Charleston, SC

I highly recommend NHC's Potential Storm Surge Flooding Map to evaluate how high above high tide the storm surge is likely to inundate the coast.


Figure 4. Observed storm surge from previous Category 1 and 2 hurricanes to hit North Carolina. Isabel of 2003 brought the most dangerous surge of these historic storms, since it was a very large storm that took an unusual north-northeasterly track into the coast near the North Carolina/Virginia border. Image credit: Western Carolina University Program for the Study of Developed Shorelines Storm Surge Database.

Arthur's tornadoes
Tornadoes are another threat from Arthur, and NOAA's Storm Prediction Center recorded three preliminary tornado sightings in North Carolina between 3:20 and 4:40 pm EDT. A tornado watch continues through 2 am EDT Friday for coastal North Carolina.

Arthur's impact on Canada and New England
As Arthur accelerates northeastwards towards Nova Scotia, Canada, large waves of 4 - 5 feet will begin to pound coastal Massachusetts on Friday night. Sustained tropical storm-force winds of 39 mph and higher are likely on Cape Cod and Nantucket, Massachusetts between 8 pm Friday - 2 am Saturday, and the 5 pm EDT NHC wind probability forecast gave Nantucket an 82% chance of seeing tropical storm-force winds. By 8 am EDT Saturday, Arthur will be merging with a cold front and transitioning to a hurricane-strength extratropical storm, and is expected to make landfall in Nova Scotia later that morning. The 5 pm EDT NHC wind probability forecast gives Halifax, Nova Scotia an 80% chance of seeing tropical storm-force winds of 39 mph or higher, and a 9% chance of hurricane-force winds.

Arthur's formation is not a harbinger of an active hurricane season
The first hurricane of the season typically occurs on August 10, so Arthur is quite a bit ahead of schedule. Arthur was able to form so early because it was over the very warm waters of the Gulf Stream Current, and these waters happened to be over 1°F warmer than usual for this time of year. Formation of a June or July hurricane like Arthur off the U.S. coast is typically not a harbinger of an active hurricane season, since these storms do not form from African tropical waves. Arthur spun up from a cluster of thunderstorms and their associated low pressure system that moved off the Southeast U.S. coast, and hurricanes that get their start this way are typically too far north and too close to land to be able to intensify into major hurricanes. The bigger threat are hurricanes that get their start from tropical waves traversing Main Development Region (MDR) for hurricanes (from the coast of Africa to Central America between 10° - 20°N, including the Caribbean Sea.) Tropical waves that traverse the MDR are responsible for 85% of all major (Category 3 and stronger) hurricanes. When June and July hurricanes and tropical storms form in the MDR, it usually does portend an active hurricane season, since it shows that atmospheric and oceanic conditions are primed to assist development of tropical waves coming off the coast of Africa during the peak mid-August through mid-October part of hurricane season.

A better way to evaluate whether or not this will be an active hurricane season is to look at sea surface temperatures (SSTs) in the MDR, and the status of El Niño. MDR SSTs are currently very close to average, and are thus unlikely to contribute to an above-average hurricane season. The very warm equatorial waters currently off the coast of South America suggest that an El Niño event is in the process of developing. When an El Niño event occurs during hurricane season, it tends to create an atmospheric circulation that brings unusually strong upper-level winds to the tropical Atlantic. These strong winds create a shearing action (wind shear) on any tropical storms or hurricanes that may be attempting to form, disrupting their circulation. Thus, the pre-season predictions of a below-average or near-average hurricane season still look good.

Stay safe tonight, all of you in North Carolina!

Jeff Masters

Hurricane

Updated: 9:51 PM GMT on July 03, 2014

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Hurricane Arthur Intensifying as it Approaches North Carolina

By: JeffMasters, 1:34 PM GMT on July 03, 2014

Hurricane warnings are flying for most of the North Carolina coast as Hurricane Arthur accelerates north-northeastwards. Arthur is the first Atlantic July hurricane since Hurricane Alex of 2010, and arrives over a month prior to the typical August 10 arrival of the season's first hurricane. Heavy rains from the intensifying hurricane have already begun this morning along the southern North Carolina coast at Wilmington, and will spread northeastwards along the North Carolina coast today. Long-range radar out of Wilmington shows that Arthur has developed an imposing area of heavy rains, and is expanding in size. The Hurricane Hunters were in Arthur this morning, and an Air Force aircraft measured a minimum pressure of 983 mb at 7:03 am EDT. At 7:36 am EDT, a NOAA aircraft measured 82 mph winds at the surface using a dropsonde, but stronger winds of 109 mph were recorded just 110 meters above the surface. The Air Force aircraft noted that the eyewall had a gap in the southwest quadrant, so Arthur is still having issues with dry air infiltrating its core. Satellite loops on Thursday morning showed a much more impressive storm than yesterday, with a large area of intense thunderstorms with cold cloud tops, and an intermittent eye. An excellent outflow channel has developed on the east side, but outflow is still restricted on the west side, where dry air is interfering with the storm. Wind shear continued to be a light 5 - 10 knots. Arthur is riding along the axis of the Gulf Stream, taking advantage of the narrow ribbon of very warm waters the current carries.


Figure 1. Long-range radar out of Wilmington, North Carolina at 11:14 am EDT July 3, 2014.

Forecast for Arthur
Given the Category 2 winds of 109 mph that the Hurricane Hunters found just above the surface, we can expect that these winds will begin to mix down to the surface later today as the storm continues to organize, bringing the storm to the threshold of Category 2 strength: 95 - 100 mph winds. With the eyewall still showing gaps due to dry air infiltration, rapid intensification into a Category 3 hurricane appears unlikely. The 12Z Thursday run of the SHIPS model predicted that wind shear will remain light to moderate, 5 - 15 knots, between now and Friday morning, then rise steeply. The model predicted a 21% chance of rapid intensification--a 30 mph increase in winds in 24 hours, and I put the odds Arthur becoming a Category 3 or stronger storm at 20%. The four main intensity models used by NHC--the LGEM, SHIPS, GFDL, and HWRF--continue to be in remarkable agreement, predicting that Arthur will be a borderline Category 1/Category 2 hurricane with 95 - 100 mph winds at 8am EDT on Friday. The models are also in good agreement on the track of Arthur. A trough of low pressure passing to the north accelerate the storm northeastwards Thursday night and Friday, and the Outer Banks of North Carolina are at risk of a direct hit. The 11 am EDT Thursday wind probability forecast from NHC gave Cape Hatteras a 72% chance of experiencing hurricane-force winds, and Morehead City a 51% chance. The 00Z Thursday runs of our top two track models, the GFS and European (ECMWF), showed the eye of Arthur passing over North Carolina's Outer Banks between 3 am - 7 am EDT Friday, July 4.


Figure 2. Screenshot of the experimental NHC Potential Storm Surge Flooding Map for the North Carolina Outer Banks, generated at 5 am EDT Thursday July 3. Inundation of the land to a depth of 3 - 6 feet (yellow colors) has a 10% chance of occurring near the vulnerable section of Highway 12 near Rodanthe, and at the Bonner Bridge over Oregon Inlet. The bridge was forced to close in December 2013 for 12 days of emergency repairs due to dangerous scouring around the support pillars. The image was generated using using NOAA's Probabilistic Hurricane Storm Surge (P-Surge 2.0) model. P-Surge 2.0 uses multiple runs of the NWS Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model to create an ensemble of possible inundations, by varying the hurricane's landfall location, intensity, size, forward speed, and angle of approach to the coast. The image shows where the storm surge has a 10% chance of inundating the coast at 3, 6, and 9 feet above ground level. The model does not take into account wave action, freshwater flooding from rainfall, and breaching or overtopping of levees.

North Carolina's Outer Banks at risk of getting cut off
Hurricane Sandy pummeled the Outer Banks of North Carolina in late October 2012, causing $13 million in damage, and wiping out the protective dunes along a long section of coast. Coastal Highway 12 that connects North Carolina's Outer Banks to the mainland was cut for nearly two months, until repairs were completed in December 2012. Residents of the Outer Banks were forced to take a 2-hour ferry ride to get to the mainland when Highway 12 was cut. Nor'easters and storms repeatedly caused overwash and road damage to NC-12 during the winter of 2012 - 2013, but a temporary barrier was erected in 2013 that has been successful at keeping the road open during the past year (though minor overwash occurred during storms on October 10, 2013 and March 18, 2014, and Tropical Storm Andrea closed the road to all but 4-wheel drive vehicles on June 7, 2013.) Emergency post-Sandy federal funding of $20.8 million was secured to construct a barrier designed to last three years, but the project is up for bid, and has not yet begun.



Figure 3. Top: Coastal Highway 12 in North Carolina, which connects the Outer Banks to the mainland, as seen at 5:43 pm EST on Tuesday, November 13, 2012, near Rodanthe. Hurricane Sandy wiped out most of the protective dunes along the coast, allowing the ocean to directly pound the road during high tide. Bottom: the same view as seen in June 2014, after a temporary repair was made to the beach destroyed by Sandy. Image credit: North Carolina DOT. Live views of Highway 12 road cams are available from the NCDOT web site.

NC 12 is once again in danger of being cut, due to the storm surge and wave action of Arthur. Also at risk is Highway 12's Bonner Bridge over Oregon Inlet on the Outer Banks, which was forced to close for 12 days in December 2013 for emergency repairs, when scans revealed excessive sand erosion (scour) around some of the support columns. The bridge will be subjected to a double storm surge from Arthur--one when the hurricane approaches, as onshore winds drive water into Pamlico Sound, and another as the storm passes, when the winds will reverse to offshore, driving the accumulated water out of the sound and back into the ocean. It is often this reverse surge that causes the greatest erosion to barrier islands. With sea level rise steadily increasing the damage that storms like Arthur can do to the vulnerable Highway 12, some very expensive long-term solutions are being studied for keeping Highway 12 open.

Links
Wrightsville Beach, NC webcam
Carolina Beach, NC webcam

Jeff Masters

Updated: 3:19 PM GMT on July 03, 2014

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Arthur Nears Hurricane Strength

By: JeffMasters, 9:03 PM GMT on July 02, 2014

Tropical Storm Arthur has formed a large, 30-mile diameter eye, and appears destined to be a hurricane by early Thursday morning, as the storm heads towards a rendezvous with the North Carolina coast on Friday. An Air Force hurricane hunter aircraft was in the storm Wednesday afternoon, and measured top surface winds of about 70 mph with their SFMR instrument. Arthur's central pressure was 995 mb at 3:10 pm EDT, then dropped to 992 mb during their second eye penetration an hour later, at 4:04 pm. Radar out of Melbourne, Florida and satellite loops on Wednesday afternoon showed that Arthur had closed off an eye, though portions the northwestern portion of the eyewall had a gap due to infiltration of dry air. Arc-shaped bands of low cumulus clouds are no longer spreading out to Arthur's north, indicating that the storm has walled off its center from dry air. An impressive "hot tower"--a powerful eyewall thunderstorm with a high top--developed along the eastern side of the eye at 4 pm EDT. Wind shear continued to be a light 5 - 10 knots. Water vapor satellite loops showed dry air to the north and west of Arthur, and some of this dry air was still filtering into the circulation.


Figure 1. MODIS satellite image of Tropical Storm Arthur, taken at approximately 16:30 UTC (12:30 pm EDT) on Wednesday, July 2, 2014. Note the arc-shaped lines of low clouds to Arthur's north, caused by dry air at mid-levels of the atmosphere getting ingested into Arthur's heavy thunderstorms, creating strong downdrafts that spread out along the ocean surface. This process robs a tropical storm of moisture and energy. Image credit: NASA.


Figure 2. Melbourne, Florida radar image of Tropical Storm Arthur at 4:37 pm EDT July 2, 2014.

Forecast for Arthur
Now that Arthur has mostly closed off an eye and walled off much of the dry air to its north, we can expect some modest intensification, with perhaps a 20 mph increase in strength by Thursday afternoon. The 18Z Wednesday run of the SHIPS model predicted that wind shear will remain light to moderate, 5 - 15 knots, between now and the time Arthur makes is closest approach to North Carolina on Friday morning. There will still be dry air to the storm's north and west, and the SHIPS model predicted a 17% chance of rapid intensification--a 30 mph increase in winds in 24 hours. I put the odds Arthur becoming a Category 3 or stronger storm at 10%. The four main intensity models used by NHC--the LGEM, SHIPS, GFDL, and HWRF--continue to be in remarkable agreement, predicting that Arthur will reach hurricane strength on Thursday, and peak at maximum sustained winds between 80 - 95 mph about the time Arthur is making its closest pass to the Outer Banks of North Carolina, on Friday morning. The models are also in good agreement on the track of Arthur. A trough of low pressure passing to the north will turn the storm northeastwards by Thursday, and cause Arthur to pick up speed. The Outer Banks of North Carolina will be the land area at greatest risk of a direct hit, and the 5 pm EDT Wednesday wind probability forecast from NHC gave Cape Hatteras a 26% chance of experiencing hurricane-force winds. Given the degree of model unanimity, the cone of uncertainty is likely thinner than presented. The latest 12Z Wednesday runs of our top two track models, the GFS and European (ECMWF), showed the eye of Arthur passing over Cape Hatteras, North Carolina between 5 am - 8 am EDT Friday, July 4.


Figure 3. Screenshot of the experimental NHC Potential Storm Surge Flooding Map for the North Carolina Outer Banks, generated at 11 am EDT Wednesday July 2. Inundation of the land to a depth of 3 - 6 feet (yellow colors) has a 10% chance of occurring near the vulnerable section of Highway 12 near Rodanthe, and at the Bonner Bridge over Oregon Inlet. The bridge was forced to close in December 2013 for 12 days of emergency repairs due to dangerous scouring around the support pillars. The image was generated using using NOAA's Probabilistic Hurricane Storm Surge (P-Surge 2.0) model. P-Surge 2.0 uses multiple runs of the NWS Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model to create an ensemble of possible inundations, by varying the hurricane's landfall location, intensity, size, forward speed, and angle of approach to the coast. The image shows where the storm surge has a 10% chance of inundating the coast at 3, 6, and 9 feet above ground level. The model does not take into account wave action, freshwater flooding from rainfall, and breaching or overtopping of levees.

North Carolina's Outer Banks at risk of getting cut off
Hurricane Sandy pummeled the Outer Banks of North Carolina in late October 2012, causing $13 million in damage, and wiping out the protective dunes along a long section of coast. Coastal Highway 12 that connects North Carolina's Outer Banks to the mainland was cut for nearly two months, until repairs were completed in December 2012. Residents of the Outer Banks were forced to take a 2-hour ferry ride to get to the mainland when Highway 12 was cut. Nor'easters and storms repeatedly caused overwash and road damage to NC-12 during the winter of 2012 - 2013, but a temporary barrier was erected in 2013 that has been successful at keeping the road open during the past year (though minor overwash occurred during storms on October 10, 2013 and March 18, 2014, and Tropical Storm Andrea closed the road to all but 4-wheel drive vehicles on June 7, 2013.) Emergency post-Sandy federal funding of $20.8 million was secured to construct a barrier designed to last three years, but the project is up for bid, and has not yet begun.



Figure 4. Top: Coastal Highway 12 in North Carolina, which connects the Outer Banks to the mainland, as seen at 5:43 pm EST on Tuesday, November 13, 2012, near Rodanthe. Hurricane Sandy wiped out most of the protective dunes along the coast, allowing the ocean to directly pound the road during high tide. Bottom: the same view as seen in June 2014, after a temporary repair was made to the beach destroyed by Sandy. Image credit: North Carolina DOT. Live views of Highway 12 road cams are available from the NCDOT web site.

NC 12 is once again in danger of being cut, due to the storm surge and wave action of Arthur. Also at risk is Highway 12's Bonner Bridge over Oregon Inlet on the Outer Banks, which was forced to close for 12 days in December 2013 for emergency repairs, when scans revealed excessive sand erosion (scour) around some of the support columns. With sea level rise steadily increasing the damage that storms like Arthur can do to the vulnerable Highway 12, some very expensive long-term solutions are being studied for keeping Highway 12 open.


Figure 5. A small boy plays with a toy donated by Portlight on September 5, 2012. His home in Pearlington, Mississippi was demolished by Hurricane Isaac. Image credit: Portlight.org.

Portlight disaster relief charity ready to respond during the 2014 Atlantic hurricane season
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, is asking for donations as the 2014 hurricane season gets underway. This year, Portlight has already deployed staff to help victims of the April 27 EF-2 tornado that devastated Quapaw and Baxter Springs, Oklahoma, and is still active in New Jersey in the aftermath of Hurricane Sandy. This hurricane season, they hope to deploy a disaster shelter trailer which will help them assist shelter operators in making their facilities fully accessible to people with all types of disabilities. This will include ramping, railings, cots, dinner- and drinkware, and assistive technologies for those with vision, hearing, cognitive and developmental delays. Check out the Portlight Blog , and consider a donation to Portlight's disaster relief fund at the portlight.org website.

Jeff Masters

Hurricane

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Tropical Storm Warnings for North Carolina as Arthur Heads North

By: JeffMasters, 3:27 PM GMT on July 02, 2014

Tropical Storm warnings are up for the coast of North Carolina as Tropical Storm Arthur heads north at 7 mph. The heaviest weather associated with Arthur is on its east and south sides, and a buoy 128 miles east of Cape Canaveral, Florida, on Arthur's east side, recorded sustained winds of 47 mph, gusting to 60 mph at 6:50 am EDT on Wednesday. Significant wave heights at the buoy were an impressive 17.4' this morning. Radar out of Melbourne, Florida on Wednesday morning showed that Arthur had built about 1/2 of an eyewall, on the northeast to southwest side of the center. Bands of heavy rain were affecting the east coast of Florida near Cape Canaveral Wednesday morning, but rainfall amounts from the storm have generally been less than one inch over Florida. Satellite loops on Wednesday morning showed a slow but steady increase in the intensity and areal coverage of Arthur's heavy thunderstorms, with the potential beginning of a Central Dense Overcast (CDO) of high cirrus clouds forming on the east side of the center. A CDO is a classic sign of an intensifying tropical storm that is approaching hurricane strength. However, the visible satellite loops also showed signs that Arthur is struggling with dry air. Arc-shaped bands of low cumulus clouds were racing away from the storm to the north of the center, indicating that dry air had gotten ingested into Arthur's heavy thunderstorms, creating strong downdrafts that were spreading out along the ocean surface. This process robs a tropical storm of moisture and energy, and means that Arthur has considerable work to do in order to moisten its environment before the storm can close off an eyewall and attain hurricane strength. The clockwise circulation of an upper level high pressure over Florida was bringing northerly winds over Arthur at high altitude, and these winds were creating light wind shear of 5 - 10 knots. Water vapor satellite loops showed dry air to the north and west of Arthur.


Figure 1. Tropical Storm Arthur as seen from the International Space Station at 6:42 am EDT Wednesday, July 2, 2014. Image credit: Reid Wiseman.


Figure 2. Melbourne, Florida radar image of Tropical Storm Arthur at 10:47 am EDT July 2, 2014.

Forecast for Arthur
The 12Z Wednesday run of the SHIPS model predicts that wind shear will remain light to moderate, 5 - 15 knots, between now and the time Arthur makes is closest approach to North Carolina on Friday morning. There will still be dry air to the storm's north and west, so I put the odds of rapid intensification into a Category 3 or stronger storm at just 10%. The presence of surface-based arc clouds radiating away from Arthur this morning likely means that the storm will not achieve hurricane strength on Wednesday. However, the four main intensity models used by NHC--the LGEM, SHIPS, GFDL, and HWRF--continue to be in remarkable agreement, predicting that Arthur will reach hurricane strength on Thursday, and peak at maximum sustained winds between 80 - 100 mph about the time Arthur is making its closest pass to the Outer Banks of North Carolina, on Friday morning. The models are also in good agreement on the track of Arthur. A trough of low pressure passing to the north will turn the storm northeastwards by Thursday, and cause Arthur to pick up speed. The Outer Banks of North Carolina will be the land area at greatest risk of a direct hit, and the 11 am EDT Wednesday wind probability forecast from NHC gave Cape Hatteras a 21% chance of experiencing hurricane-force winds. Given the degree of model unanimity, the cone of uncertainty is likely thinner than presented. The latest 0Z Wednesday runs of our top two track models, the GFS and European (ECMWF), showed Arthur passing very close to Cape Hatteras, North Carolina between 2 am - 8 am EDT Friday, July 4.

Rip Current Danger
Rip currents are typically the biggest killer in shore-hugging tropical storms like Arthur, as the big waves pounding the coast create very strong currents flowing away from the shore that can drown even strong swimmers. High surf of 6 - 8 feet was affecting portions of the east coast of Florida from West Palm Beach to Jacksonville on Wednesday morning, and these waves were creating dangerous rip currents; five swimmers stranded by strong currents were rescued in Fort Pierce, Florida. The high surf will reach the South Carolina coast by Wednesday night, and begin affecting North Carolina on Thursday morning. The Wednesday morning run of NOAA's Wavewatch III model predicted that high surf of 6 - 8 feet capable of generating dangerous rip currents would affect the Mid-Atlantic coast from Virginia northwards beginning on Friday morning, and reach New England late Friday night.


Figure 3. Screenshot of the experimental NHC Potential Storm Surge Flooding Map for the North Carolina coast. Inundation of the land to a depth of 3 - 6 feet (yellow colors) has a 10% chance of occurring near Wilmington and Beaufort. The image was generated using using NOAA's Probabilistic Hurricane Storm Surge (P-Surge 2.0) model. P-Surge 2.0 uses multiple runs of the NWS Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model to create an ensemble of possible inundations, by varying the hurricane's landfall location, intensity, size, forward speed, and angle of approach to the coast. The image shows where the storm surge has a 10% chance of inundating the coast at 3, 6, and 9 feet above ground level. The model does not take into account wave action, freshwater flooding from rainfall, and breaching or overtopping of levees.

New NHC Potential Storm Surge Flooding Maps Being Generated
Arthur is the first storm for which a fantastic new experimental National Hurricane Center product is being issued, the Potential Storm Surge Flooding Map. This is an interactive zoomable map that shows where the storm surge has a 10% chance of inundating the coast at 3, 6, and 9 feet above ground level. The map is available only on the NHC web site.


Figure 4. A small boy plays with a toy donated by Portlight on September 5, 2012. His home in Pearlington, Mississippi was demolished by Hurricane Isaac. Image credit: Portlight.org.

Portlight disaster relief charity ready to respond during the 2014 Atlantic hurricane season
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, is asking for donations as the 2014 hurricane season gets underway. This year, Portlight has already deployed staff to help victims of the April 27 EF-2 tornado that devastated Quapaw and Baxter Springs, Oklahoma, and is still active in New Jersey in the aftermath of Hurricane Sandy. This hurricane season, they hope to deploy a disaster shelter trailer which will help them assist shelter operators in making their facilities fully accessible to people with all types of disabilities. This will include ramping, railings, cots, dinner- and drinkware, and assistive technologies for those with vision, hearing, cognitive and developmental delays. Check out the Portlight Blog , and consider a donation to Portlight's disaster relief fund at the portlight.org website.

Jeff Masters

Hurricane

Updated: 3:30 PM GMT on July 02, 2014

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Which Intensity Model Should You Trust for Tropical Storm Arthur?

By: JeffMasters, 6:55 PM GMT on July 01, 2014

The Atlantic's first storm of 2014 is here, as Tropical Storm Arthur was named at 11 am EDT Tuesday by NHC. Arthur's formation date of July 1 comes a week before the typical July 8 appearance of the Atlantic's first named storm, but is the latest the first named storm of the season has appeared since 2009, when Tropical Storm Ana formed on August 12.


Figure 1. Melbourne, Florida radar image of Tropical Storm Arthur at 2:20 pm EDT July 1, 2014.

Arthur was drifting northwest at 5 mph towards the east coast of Central Florida early Tuesday afternoon. Long-range radar out of Melbourne, Florida on Tuesday afternoon showed that bands of heavy rain from Arthur were affecting the Northwest Bahamas, and the top sustained winds observed in the Bahamas as of 2 pm EDT Tuesday were 36 mph, gusting to 41 mph at Settlement Point in the Northwest Bahama Islands at 8 am EDT. Top winds Tuesday morning and early afternoon at the buoy 23 miles east of Cape Canaveral, Florida were 22 mph, gusting to 26 mph, with a significant wave height of 4.3'. Satellite loops showed heavy thunderstorms were limited to the south side of Arthur's center of circulation early Tuesday afternoon, and were slowly increasing in intensity and areal coverage, with new spiral bands forming. The clockwise circulation of an upper level high pressure over Florida was bringing northerly winds over Arthur at high altitude, and these winds were creating moderate wind shear of 10 - 15 knots. Water vapor satellite loops showed dry air to the north of Arthur, and the northerly winds were driving this dry air into the storm, interfering with development. However, Arthur has moistened its environment considerably since Monday, and the storm is beginning to wall off the dry air to the north.


Figure 2. Water vapor satellite image of Arthur taken at 1:15 pm EDT Monday July 1, 2014. A large area of dry air (black colors) was to the north of the system, and was interfering with development. Image credit: NOAA/NESDIS.

Forecast for Arthur
The models are in good agreement that a trough of low pressure passing to the north of Arthur will turn the storm northwards by Tuesday night and northeastwards by Wednesday. On this track, the Outer Banks of North Carolina will be the land areas at greatest risk of a direct hit, though the cone of uncertainty encompasses the entire coast of North Carolina. Given the degree of model unanimity, the cone of uncertainty is likely thinner than presented. The latest 12Z Tuesday runs of our top two track models, the GFS and European (ECMWF) models, both show Arthur passing very close to Cape Hatteras, North Carolina between 8 am - 2 pm EDT Friday, July 4.

Which Intensity Model Should You Trust?
According to the 2013 National Hurricane Center Forecast Verification Report, issued in April 2014, the official NHC intensity forecasts in 2013 for Atlantic storms were their best ever. However, this success is likely because of the lack of any rapidly intensifying major hurricanes in 2013, which are typically the source of the largest forecast errors. NHC 72-hour intensity forecasts errors in 2013 averaged about 10 mph, and were biased too high at most forecast times. As shown in Figure 3, over the past three years, the official NHC intensity forecast has generally outperformed their four main intensity models. These four models were the dynamical HWRF and GFDL models, which subdivide the atmosphere into a 3-D grid around the storm and solve the atmospheric equations of fluid flow at each point on the grid, and the statistics-based LGEM and DSHP models (DSHP is the SHIPS model with inland decay of a storm factored in.) The top-performing global dynamical models for hurricane track, the GFS and European (ECMWF) models, are typically not considered by NHC forecasters when making intensity forecasts. The GFS model has done a decent job at making intensity forecasts over the past three years, but the European model has made poor intensity forecasts. In 2013 and for the period 2011 - 2013, the HWRF model was the best-performing intensity model for forecasts of 48 hours or less. The LGEM statistical model was the best one at longer-term intensity forecasts of 3 - 5 days.


Figure 3. Skill of computer model intensity forecasts of Atlantic named storms in 2011 - 2013, compared to a "no skill" model called "Decay-SHIFOR5" that uses just climatology and persistence to make a hurricane intensity forecast (persistence means that a storm will tend to maintain its current behavior.) NHC=Official NHC forecast; GFS=Global Forecast System model; GFDL=Geophysical Fluid Dynamic Laboratory model; HWRF=Hurricane Weather Research Forecasting model; ECMWF=European Center for Medium Range Weather Forecasting model; LGEM=Logistic Growth Equation Model; DSHP=Statistical Hurricane Intensity Prediction Scheme with inland Decay. Image credit: 2013 National Hurricane Center Forecast Verification Report.

The official NHC 72-hour intensity forecast issued at 11 am EDT Tuesday makes Arthur a Category 1 hurricane with 80 mph winds on Friday morning at 8 am EDT, when the storm is expected to make its closest pass to the North Carolina coast. The two best models we have for making 72-hour intensity forecasts, the LGEM and DSHP models, predicted in their 8 am EDT runs that at 8 am EDT Friday Arthur would be a tropical storm with 70 mph winds or a Category 1 hurricane with 95 mph winds, respectively. NHC typically relies on consensus models that average together several of the intensity models, so it is not a surprise that the official forecast of an 80 mph storm at 72 hours is close to the result gotten by averaging together the two top intensity models for making 72-hour forecasts, the LGEM and DSHP models.

Sources of Model Data
You can view 7-day ECMWF and 16-day GFS forecasts on wunderground's wundermap with the model layer turned on.
FSU's experimental hurricane forecast page (CMC, ECMWF, GFDL, GFS, HWRF, and NAVGEM models)
NOAA's HFIP model comparison page (GFS, ECMWF, FIM, FIM9, UKMET, and CMC models.)
Experimental HFIP models

Links
Webcam on the buoy 23 miles east of Cape Canaveral, FL

I'll have a new post on Wednesday morning at the latest.

Jeff Masters

Hurricane

Updated: 8:05 PM GMT on July 01, 2014

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Tropical Depression One Forms off the Coast of East Florida

By: JeffMasters, 7:36 AM GMT on July 01, 2014

The Atlantic's first tropical depression of 2014 is here, as Tropical Depression One finally formed at 11 pm EDT Monday evening from disturbance 91L. TD 1 was drifting southwest at 2 mph towards the east coast of Central Florida early Tuesday morning. Long-range radar out of Melbourne, Florida on Tuesday morning showed that bands of heavy rain from TD 1 were affecting the Northwest Bahamas, and sustained winds of 33 mph gusting to 36 mph were observed at Settlement Point in the Northwest Bahama Islands at 2 am EDT. Satellite loops showed heavy thunderstorms were limited to the south side of TD 1's center of circulation, and were slowly increasing in intensity and areal coverage. The counter-clockwise circulation of an upper level high pressure over Florida was bringing northerly winds over TD 1 at high altitude, and these winds were creating moderate wind shear of 10 - 15 knots. Water vapor satellite loops showed very dry air to the north of TD 1, and the northerly winds were driving this dry air in the heart of the storm, interfering with development, and keeping any heavy thunderstorms from developing on the north side of the circulation. The Air Force Hurricane Hunters will investigate TD 1 on Tuesday morning, and the NOAA jet is scheduled to fly Tuesday afternoon.


Figure 1. MODIS satellite image of 91L, taken at approximately 16:30 UTC (12:30 pm EDT) on Monday, June 30, 2014. Image credit: NASA.

Forecast for TD 1
Steering currents are weak off of the Southeast U.S. coast, but the models are in good agreement on the track. The disturbance should continue a slow southwesterly motion through Tuesday morning, then turn northwards or north-northwestwards on Tuesday afternoon, and move parallel to the Florida coast without making landfall in Florida, as the storm responds to a trough of low pressure passing to the north. Heavy rains of 2 - 4" will likely affect the Northwest Bahamas and eastern coast of Florida Tuesday through Wednesday. By Wednesday, the models are in agreement that TD 1 will turn northeast without hitting the coast of South Carolina, but potentially pass very near the Outer Banks of North Carolina on Friday morning. The 6Z Tuesday run of the SHIPS model showed the atmosphere surrounding TD 1 will stay dry this week, with the wind shear staying light to moderate, near 10 knots. This dry air, in combination with potentially moderate wind shear, should keep development slow. The storm will be over the warm waters of the Gulf Stream, so the extra heat energy available to the storm will help counteract to dry air and wind shear, though. The official NHC forecast of a high-end 70 mph Tropical Storm Arthur on Friday, as the storm makes its closest approach to North Carolina, is a reasonable one. A much weaker storm is also possible, if dry air and wind shear continue to interfere with development this week.

I'll have a new post by Tuesday afternoon.

Jeff Masters

Hurricane

Updated: 7:40 AM GMT on July 01, 2014

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.