KoritheMan's WunderBlog

Tropical weather analysis - June 29, 2012

By: KoritheMan, 1:59 AM GMT on June 30, 2012

Invest 97L

The unusually active north Atlantic tropics refuse to shut off the engine, and give me some much needed rest. An area of disturbed weather associated with a tropical wave located about 800 miles east of the Windward Islands was recently designated an invest ("97L"). Visible satellite images show that the associated shower activity has become a little better organized this evening, and the wave axis appears to be situated within this convection based on recent scatterometer data.



Figure 1. Latest infrared satellite image of Invest 97L. Image credit: NOAA

Strangely, there appears to be some easterly shear over the system as evidenced by the squashed outflow pattern in the right quadrant. However, synoptic data doesn't really support high level easterlies over the system. Assuming I'm not imagining things, I theorize that there's some shear beneath the outflow layer.

Personal musings aside, the system is surrounded by dry air, which should limit significant development despite the seemingly favorable shear pattern. Although some short-term development is possible, strong westerly shear awaits the wave as it moves through the Leeward Islands in a few days. None of the models develop this wave, and I don't expect development either. Nevertheless, the wave may bring some squally weather to portions of the Windward and Leeward Islands at the beginning of next week. Also, given the wave's convective vigor, I would be cognizant of the potential for long-range development in the Eastern Pacific. None of the models are currently indicating this, but we shall see. The northern portion of the wave axis may also need to be watched in about a week as it finds a more favorable environment in the western Caribbean.

Probability of development within 48 hours: 20%

Gulf of Mexico disturbance

A large area of elongated showers and thunderstorms has developed over the western Gulf of Mexico. Conditions are not favorable for development in this area, and the system is forecast to move inland over coastal Texas in about a day.

Probability of development within 48 hours: 10%

Hurricane Invest 97L

Updated: 2:00 AM GMT on June 30, 2012

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Tropical weather analysis - June 25, 2012

By: KoritheMan, 4:40 AM GMT on June 26, 2012

Debby

Debby refuses to move. As of the latest NHC advisory, the following was posted on the storm:

Wind: 45 mph, with higher gusts
Location: 29.2°N 85.1°W
Movement: NE at 2 mph
Pressure: 992 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

The low-level center, while well-defined, is exposed well to the southwest of a large band of very deep convection due to about 20 knots of southwesterly shear associated with the upper low still over the western Gulf of Mexico, and a large anticyclone over the western Atlantic extending into the Caribbean Sea.



Figure 1. Latest infrared satellite image of Tropical Storm Debby. Image credit: NOAA

The cyclone's biggest legacy will continue to be torrential rains. Doppler radar estimates indicate a swath of 15+ inches of rain south of Tallahassee. Considering most of this has fallen over the last 24 hours, there is serious flooding ongoing across the Tallahassee metro area, especially in Wakulla County, where the heaviest rainfall has occurred. With Debby moving little, additional heavy rainfall is expected, and doppler estimates reveal that 2 to 3 inches per hour has been a common motif with Debby. Since the shear is pushing all the convection east, these dangerous rains may spread eastward, creating a more widespread flood threat. There has been mention by Dr. Greg Forbes, severe weather expert with The Weather Channel, that this is the most serious flood threat he's even seen in all his years of forecasting. While I seriously doubt Debby will surpass Tropical Storm Claudette's 24-hour rainfall record of 42 inches set at Alvin, Texas in July of 1979, over 20 inches of rain have fallen in western Wakulla County, and additional rainfall continues to train over this area. As senior hurricane specialist Stacy Stewart pointed out in the most recent National Hurricane Center forecast discussion for the storm, the cyclone center will have the tendency to follow the deep convection, in the absence of any large-scale steering mechanisms. The net result should be a flood threat that slowly spreads eastward with time, unless the shear unexpectedly relaxes, which is not anticipated. Truth be told, when this is all over, I don't think 35 to 40 inch rainfall totals in some locations should be considered unreasonable. I cannot place enough emphasis on how serious the ongoing flood threat across Florida is, the worst of which is currently occurring across the Tallahassee area. If you see high water, DO NOT attempt to drive through it. High water can be especially difficult to see at night.

Tropical storm force winds are also still impacting the state, although thus far I have been unable to find any official observations of sustained tropical storm force winds. However, locations with official National Weather Service anemometers are located within areas outside the strongest doppler velocities. Isolated tornadoes remain possible, but 0z upper air data over Florida indicates that any such threat will remain marginal. Indeed, the Storm Prediction Center hasn't reported any tornadoes across Florida in association with Debby today, despite the earlier tornado watch covering much of the peninsula. Although tropical storms don't normally produce significant storm surge, the slow-moving nature of the tropical cyclone will produce a prolonged fetch of onshore flow, and surge values of 1 to 5 feet near and to the east of the center will not be uncommon. The National Hurricane Center is predicting water level rises in excess of 3 to 5 feet near Apalachee Bay. This area is notoriously vulnerable to storm surge, so this is a reasonable prognosis.

Given the shear, continued dry air, and inevitable oceanic upwelling along the projected path, Debby is not expected to intensify while over the Gulf of Mexico. In fact, slow weakening seems most likely. When the system enters the western Atlantic, global models suggest the shear could decrease, and the cyclone will have the opportunity to restrengthen. This is consistent with the global models, which show Debby intensifying as it accelerates across the western Atlantic waters between Bermuda and the United States.

5-day intensity forecast

INITIAL 0300Z 06/26 40 KT 45 MPH
12 hour 1200Z 06/26 40 KT 45 MPH
24 hour 0000Z 06/27 40 KT 45 MPH
36 hour 1200Z 06/27 40 KT 45 MPH
48 hour 0000Z 06/28 35 KT 40 MPH...JUST OFF COAST
72 hour 0000Z 06/29 35 KT 40 MPH...INLAND
96 hour 0000Z 06/30 40 KT 45 MPH...OVER WATER
120 hour 0000Z 07/01 45 KT 50 MPH

The track forecast remains challenging, but a little easier than recent days. Water vapor and upper air data over the eastern United States indicates the absence of any synoptic scale steering mechanisms. This means Debby will move little for at least the next 48 hours, with only a slow east-northeast to northeast motion toward the Big Bend region of Florida expected. A weakness between the central United States ridge and the Atlantic subtropical ridge is evident along and east of 80W. This has a been a persistent feature with this storm, and is why Debby is expected to, eventually, cross Florida. The GFS and ECMWF remain in excellent agreement on this, and have converged tighter on the forward speed since the recent run of the 0z GFS. Although Debby is most likely to follow the path of least resistance out into the Atlantic, earlier runs of the GFS hinted that the large scale blocking pattern over the central US, which has been equally persistent relative to the trough over the east, would halt the forward progress of the cyclone while over the western Atlantic. I doubt Debby swings back into the Gulf of Mexico amidst that pattern, but I think now is a good time to alert everyone on the east coast to begin monitoring the storm. Out of deference to this possibility, I am not forecasting rapid acceleration.

Interestingly, the GFDL and HWRF bring Debby west from its current location, but this is probably contingent on a weaker system moving westward in the low-level flow. Since Debby has convection, this was discounted.

5-day forecast track



Figure 2. My 5-day forecast track for Debby.

Watches and warnings


THE TROPICAL STORM WARNING HAS BEEN DISCONTINUED WEST OF MEXICO
BEACH FLORIDA.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE FLORIDA GULF COAST FROM MEXICO BEACH TO ENGLEWOOD

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE.

Hurricane Tropical Storm Debby

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Tropical weather analysis - June 24, 2012

By: KoritheMan, 4:53 AM GMT on June 25, 2012

Debby

Tropical Storm Debby remains disorganized while continuing to meander over the northeastern Gulf of Mexico. As of the latest NHC advisory, the following was posted on the storm:

Wind: 60 mph, with higher gusts
Location: 28.3°N 85.9°W
Movement: Stationary
Pressure: 991 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

Satellite imagery shows the low-level center exposed, with all of the associated weather confined to a large band north and east of the center. Not surprisingly, these are also where most of the tropical storm force winds are occurring. Debby is still battling southwesterly shear being imparted by a persistent upper low over the southwest Gulf of Mexico. Size matters not. The low, while small, has ingested dry air into Debby's circulation, essentially evaporating most of the convection. While this low continues to slowly move to the southwest, it is in no hurry to do so, and the global models have been far too adamant in relinquishing the shear.



Figure 1. Latest infrared satellite image of Tropical Storm Debby. Image credit: NOAA

A slew of radar fixes from Tallahassee show little movement of the cyclone over the last several hours, although there are faint indications of a slow westward drift in recent frames. Satellite images are less inconclusive. The largely stationary motion of Debby appears to be related to rising heights over the eastern United States in the wake of the trough in this same region.

Despite the huge eastward shift in the models toward Florida today, joined by the generally reliable ECMWF, there is still a lot of uncertainty in the future trajectory, and Debby's future hangs in the balance. Water vapor, 0z upper air data from the eastern United States, as well as UW-CIMSS real-time steering data suggest that heights are gradually rising to the east of the storm as the trough lifts out. Heights above 500 mb are being a little slower to rise, and given that Debby's central pressure is still rather low, convectiveless as it is, the lingering weakness at that level may tug the storm a little northward for a little longer before weak ridging gradually builds behind the storm. However, the large scale pattern over the US and Canada favors a continuous barrage of shortwave perturbations within the mean westerly flow to periodically deamplify the ridge over the eastern US for the next several days. The result should be very little motion for the next few days, possibly stairstepping between north and west as Debby comes under the steering influence of both the ridge and the trough. The storm may finally get moving on Wednesday, when the the steering flow may finally begin to stabilize.

At that point, the ridge over the central US will reach its highest point of amplification, and if Debby moves far enough west, or lingers to the point where it avoids most of the shortwaves, it could still move westward toward the northern Gulf Coast as per earlier prognostications. On the other hand, the trough will be persistent enough just to the east of the ridge that the cyclone could find its avenue of escape through Florida, as the GFS has been showing. Either way, any appreciable movement seems likely for the next few days. Given that the Euro, albeit wildly and unpredictably, has now joined the fray in calling for a Florida landfall, I will abide by that idea for now. However, with the 0z GFS showing a blocking pattern setting up over the western Atlantic and Gulf of Mexico, westward adjustments may have to be considered tomorrow, most likely at longer-ranges. At the same time, if the GFS, now joined by the UKMET verifies, the storm will head toward peninsular Florida, and the short-term track may have to be shifted eastward. While I did mention the northern Gulf Coast, I think the large scale pattern over the US is too amplified to allow for a motion further north than the Mississippi coast.

Interests along the Gulf Coast from Louisiana to Florida should carefully monitor the progress of this tropical cyclone, which is expected to dump heavy rains. In fact, various WSR-88D radars across Florida show bands of heavy rain still training across the state. These bands have already caused flooding in some areas, as well as several tornadoes. It's also worth mentioning that the large column of dry air that has sneaked into the center over the last several hours may actually enhance the tornado potential by sunrise tomorrow, as subsidence in the middle troposphere generally leads to high dewpoint depressions, which promotes tornadic development and locally damaging wind gusts with any storms that develop along the feeder bands. Tropical storm force winds will also continue lashing much of the northeastern and eastern Gulf for the next few days, as Debby is in no hurry to go anywhere.

Debby still has the potential to intensify, though the current structure and unfavorable environment would argue against that. The global models have are clearly having issues adequately resolving the shear pattern that is affecting Debby. Thus, it pays to be conservative, and I no longer anticipate Debby becoming a hurricane. This is also supported by cold water upwelling that will inevitably impact the cyclone at some point. This is particularly true near the coast, where the shallow shelf waters have already cooled by several degrees. However, since convection is currently nonexistent over the center, presumably so is wind. Thus, no significant upwelling is forecast to affect Debby in the near-term.

Both the track and intensity forecast remain highly uncertain.

5-day intensity forecast

INITIAL 0000Z 06/25 50 KT 60 MPH
12 hour 1200Z 06/25 50 KT 60 MPH
24 hour 0000Z 06/26 50 KT 60 MPH
36 hour 1200Z 06/26 50 KT 60 MPH
48 hour 0000Z 06/27 55 KT 65 MPH
72 hour 0000Z 06/28 50 KT 60 MPH
96 hour 0000Z 06/29 45 KT 50 MPH...NEAR COAST
120 hour 0000Z 06/30 35 KT 40 MPH...INLAND

5-day track forecast



Figure 2. My 5-day forecast track for Debby.

Watches and warnings

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE MISSISSIPPI-ALABAMA BORDER EASTWARD TO THE SUWANNEE RIVER
FLORIDA

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* SOUTH OF THE SUWANNEE RIVER TO ENGLEWOOD FLORIDA

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE LATER TODAY.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE
THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.

Hurricane

Updated: 4:58 AM GMT on June 25, 2012

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Tropical weather analysis - June 23, 2012

By: KoritheMan, 3:38 AM GMT on June 24, 2012

Debby

What was previously Invest 96L has developed into Tropical Storm Debby in the central Gulf of Mexico earlier today. Debby is the earliest occurrence of the fourth named tropical cyclone in the historical database. The previous record was held by Hurricane Dennis in 2005, which became a tropical storm in the Caribbean Sea on July 5. As of the latest NHC advisory, the following was posted on Debby:

Wind: 50 mph, with higher gusts
Location: 26.3°N 87.5°W
Movement: Stationary
Pressure: 998 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

In terms of structure, Debby is currently very reminiscent of Tropical Storm Lee last year. The center is exposed, and the west side of the cyclone is entirely devoid of convection thanks to a vigorous upper low located off the upper Texas coast. The GFS gradually pulls this feature to the southwest, and this is fairly supported by current observational trends. However, the low is moving rather slowly, and it may take up to 48 hours for it to move into Mexico and distance itself from Debby.



Figure 1. Latest infrared satellite image of Tropical Storm Debby. Image credit: NOAA

Debby remains disorganized, with several vorticity centers rotating around the large-scale cyclonic circulation associated with the cyclone. However, there are signs that the shear is beginning to decrease, as a recent convective burst, while still quite distant from the low-level center, has developed closer to the central gyre for the first time.

Although the shear is forecast to decrease, any such relenting could be slow to occur, due to the aforementioned upper low. The GFS still wants to build a weak anticyclone over Debby as the upper flow gradually becomes more conducive to strengthening, but this model has done a rather poor job at forecasting the vertical shear pattern over the Gulf with this storm. At the risking of being wrong for the sake of being conservative, I anticipate little change in strength for the next 12-24 hours, followed by slow strengthening after that. I do think the shear will relax enough that Debby will become a hurricane prior to landfall, especially if it does so along the Texas coast, where it will have a longer duration over water.

5-day intensity forecast

INITIAL 0300Z 06/24 45 KT 50 MPH
12 hour 1200Z 06/24 45 KT 50 MPH
24 hour 0000Z 06/25 50 KT 60 MPH
36 hour 1200Z 06/25 50 KT 65 MPH
48 hour 0000Z 06/26 55 KT 70 MPH
72 hour 0000Z 06/27 60 KT 75 MPH
96 hour 0000Z 06/28 65 KT 80 MPH
120 hour 0000Z 06/29 70 KT 80 MPH

Debby is by far one of the most difficult tropical cyclones I've had to forecast. There remains little to no model agreement in where the storm will go subsequent to this point. The 0z suite was just released, and, to nobody's surprise -- least of all mine, there remains a remarkable spread, with some calling for a strike anywhere from Texas to Florida. Same news, different day.

Water vapor images show a large ridge over the central United States building downstream behind the east coast trough. A secondary trough, the key player in the landfall location of Debby, is currently moving into the west coast. This trough looks like it could be rather deep, with weak southwesterly flow already evident as far south as 25N in the eastern Pacific. Little movement is expected from the large upper low attendant to the trough in the short-term, which currently extends horizontally over a distance of about 800 miles. By tomorrow afternoon, the low is forecast to get moving, and begin plowing across the United States. At this point, there are two possibilities: the first is that the upper low remains farther north so that the trough/cold front doesn't appreciably erode the ridge. The second is for the low to sneak farther southward, erode the ridge, and potentially allow for a more northward hook to the forecast track at longer-ranges.

Unfortunately, it remains impossible to determine which of these scenarios is the more likely one. However, given the large amplitude of the ridge, which has thus far shown little signs of budging, as well as the reliable ECMWF model still walloping the Texas coast, I will side with the former scenario. Strong blocking patterns, like the one currently over the central US, are typically very hard to break.

Although I eventually expect a landfall somewhere along the Texas coast, due to uncertainty in where Debby will ultimately make landfall, and the unpredictable nature of the trough, I will keep the system offshore throughout the forecast period. This is an extremely low-confidence forecast, and I will not possess much confidence until the models finally converge on a consistent solution in any given direction.

5-day track forecast



Figure 2. My 5-day forecast track for Debby.

In the meantime, since most of the precipitation is still east of the center, Debby will continue to generate tropical storm force winds, dangerous sea conditions, periods of heavy rainfall, and isolated tornadoes across the southern half of the Florida peninsula through at least the next 12 hours. Thereafter, Debby may begin to consolidate, and the large wind field could flatten somewhat. Doppler radar still shows northerly-moving bands of heavy rain moving across the central and western Florida peninsula. These bands have had a history of producing tornadoes, as well as gusty winds.

By tomorrow night or early Monday, Debby should be close enough to the southeastern coast of Louisiana to deliver tropical storm force winds. These winds should not be able to permeate too far inland over the northern Gulf Coast, especially if Debby strengthens as predicted. However, they will likely persist over the coastal waters and adjacent coastal areas for some time. For this reason, tropical storm warnings have been posted (see below).

Watches and warnings

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE COAST OF LOUISIANA FROM THE MOUTH OF THE PEARL RIVER WESTWARD
TO MORGAN CITY...NOT INCLUDING THE CITY OF NEW ORLEANS OR LAKE
PONTCHARTRAIN

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

Hurricane

Updated: 3:42 AM GMT on June 24, 2012

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Tropical weather analysis - June 22, 2012

By: KoritheMan, 2:43 AM GMT on June 23, 2012

Invest 96L

A large tropical disturbance located over the southeastern Gulf of Mexico ("96L") is producing a widespread area of precipitation to the east, but the western side continues to struggle amidst unfavorable upper-level winds, and the system as a whole remains disorganized.



Figure 1. Latest infrared satellite image of Invest 96L. Image credit: NOAA

Convection is slowly wrapping, however, so 96L is definitely trying to organize. In fact, the overall circulation appears a little tighter today than yesterday, and this is supported by analysis of satellite imagery as well as real-time vorticity data from UW-CIMSS. This fact notwithstanding, there remains little sense to deny the continued broad nature of the circulation. This should at least slow development in the near-term. Westerly shear also continues to inhibit development, and while there are indications on water vapor imagery that this shear is decreasing, it is going to be a gradual process, not a rapid one, and the global models have been too quick to move the shear over 96L. SHIPS doesn't show the shear decreasing much, but considering the 18z run was a little more lenient, and there are actual signs of a more favorable upper environment, I do not have a proclivity toward belief in this regard.

I still anticipate this low to become a tropical depression and eventually, a tropical storm. A hurricane is still possible, but the GFS suggests an upper air pattern over the Gulf that is not quite as anticyclonic as we'd like if we want to get a hurricane out of this system. On the other hand, none the global models show anything less than a slow-moving large circulation traversing the central Gulf of Mexico. Given the enormous size of the circulation already preexisting with the system, one possible outcome is for the latent heat release to generate a more substantial, well-defined anticyclone atop the circulation, which would help the system strengthen, possibly to hurricane strength. The longer the system remains in the Gulf, the more favorable the upper-level flow will become.

The track forecast is anything but straightforward. Water vapor imagery shows a distinct mid-level ridge over the central United States, with a weakness downstream over the western Atlantic. The ridge is gradually shifting eastward and flattening out as a developing trough over the western United States pivots eastward. The global models show this ridge more or less remaining in place between two troughs -- one over the west, and one over the east. This is where the biggest forecast challenge arises, and what has still yet to be resolved within the models. The GFS continues to insist on a strike on the Florida west coast near Tampa, while the ECMWF has been consistent in tracking the system toward the lower to central Texas coast. I've mentioned for several days now, particularly yesterday, that I don't buy the sharp, almost immediate recurve toward Florida considering the time of year. In addition, for the GFS solution to verify, the trough over the western Atlantic would have to be in the process of picking up the system now, which it is not.

I still do not know where this system will ultimately make landfall, but interests along the entire Gulf Coast should follow the progress of this disturbance. I still don't think western Florida is at the risk the GFS claims it is. I really want to place the Texas coast at greatest risk given the model trends in that direction. A stall near the northern Gulf Coast before heading toward the Texas coast underneath the central US ridge is also possible. Another trough is forecast to arrive on the US west coast by Tuesday, which, if it moves faster than predicted, could bend the track more to the east. At the very least, much of the Gulf Coast could receive some heavy rains, and possibly gusty winds as well.

A reconnaissance aircraft is scheduled to investigate this system tomorrow, if necessary. Although today's flight was canceled due to the disorganized nature of the system, I suspect they will fly tomorrow. Hopefully, a NOAA G-IV synoptic surveillance mission will be launched, and help to resolve some of the track issues within the global models.

Probability of development in 48 hours: 80%

Hurricane

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Tropical weather analysis - June 21, 2012

By: KoritheMan, 1:11 AM GMT on June 22, 2012

Chris

Chris briefly became a hurricane earlier today, the first of the 2012 season. I wasn't quite expecting this, as I had the inkling that the cool water the storm is sitting underneath would prevent full mixing of the winds from aloft to the surface. Perhaps the eye persisted long enough so that the winds in the eyewall were ultimately able to support hurricane force winds. It would have been most interesting to have a reconnaissance aircraft and a couple of dropsondes in the storm during the time of peak intensity this morning. As of the most recent NHC advisory on the storm, the following was posted:

Wind: 70 mph, with higher gusts
Location: 42.4°N 42.9°W
Movement: NNE at 14 mph
Pressure: 990 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

I should note that three named storms and a hurricane before July, while highly unusual, is not necessarily indicative of an active season. History has shown that early season storms forming in the MDR typically portends an active season, but all of our storms have formed outside this region, in a small hole of lighter wind shear outside the westerlies. Indeed, even the potential Gulf tropical storm will form outside this region, in a climatologically favored area. If El Nino develops as predicted, even a weak one should be enough to stagnate (relatively speaking) activity a little later in the season.

And for those of you doubting that there are any actual signs of an El Nino, I present you with this fanciful graph from NOAA:



Figure 1. Latest sea surface temperature (SST) anomalies for the Northern Hemisphere. Notice the large swath of warm waters extending along the equatorial Pacific, the classic signature of an El Nino. Image credit: NOAA

I'm not really expecting a strong El Nino, and if by some chance we see most of the warming in the central Pacific, there would theoretically be less wind shear over the Atlantic. This was the case in 2002 and 2004, where the former saw Lili hit the central Louisiana coast, and the latter saw four major hurricanes impact the Florida coast.

Anyway, satellite images show that Chris retains a well-defined and symmetrical wind field, but the cold waters are clearly taking their toll. There is virtually no deep convection anywhere within the circulation, and the cyclone appears to be becoming entangled in the developing extratropical low to its south.



Figure 2. Latest infrared satellite image of Tropical Storm Chris. Image credit: NOAA

There have been no recent AMSU microwave overpasses to assess the vertical temperature profile in the storm, but I imagine that Chris is quickly losing its warm core. Personally, I feel Chris will be declared extratropical in the next advisory. Global models continue to indicate that Chris will become absorbed into the baroclinic system in about 24-36 hours. In the meantime, the cyclone, or its extratropical remnants, are forecast to execute a broad cyclonic loop around this low.

5-day intensity forecast

INITIAL 0000Z 06/22 60 KT 70 MPH
12 hour 1200Z 06/22 55 KT 65 MPH...EXTRATROPICAL
24 hour 0000Z 06/23 50 KT 60 MPH...EXTRATROPICAL
36 hour 1200Z 06/23...ABSORBED BY LARGER EXTRATROPICAL SYSTEM

5-day track forecast



Figure 3. My 5-day forecast track for Chris.

Invest 96L

A large area of disturbed weather over the southern Gulf of Mexico north of the Yucatan Peninsula has the potential to become a tropical depression or tropical storm over the next day or two as it moves toward the central Gulf of Mexico. I mentioned yesterday that the low might try and relocate along the Yucatan Peninsula. I just wasn't buying a convectiveless swirl being the dominant system. Interestingly, the models have generally come west today, although the GFS still shows a threat to the west coast of Florida.

Satellite images show a large but slowly organizing disturbance. Indeed, the system is beginning to develop an outflow channel to the north and west, which probably heralds the onset of more favorable upper-level winds. An upper low over Brownsville is moving westward, which should lessen the shear over the Gulf. This should allow the system to continue to organize, and I anticipate that this system will be a tropical depression by tomorrow evening. The global models generally support this.



Figure 4. Latest infrared satellite image of Invest 96L. Image credit: NOAA

One thing to note about this disturbance is that it is large. While such systems usually take awhile to spin up, they are also more resilient to vertical shear and subtle changes in the surrounding environment. A belt of westerly shear is forecast to be over the Gulf of Mexico north of about 25N, but it is unclear how much of this is related to 96L, or to the subtropical jet. A thorough examination of the GFS upper-level forecast fields indicates that a weak cyclonic shear axis could remain over the northern Gulf of Mexico for the next few days. This feature was evident in the model at 300 mb, but not further down the troposphere. This suggests that it is not storm relative. However, vertical shear conditions can change rather quickly, and with the system as large as it is, the moisture associated with it is causing a lot of latent heat energy to be released. As such, it remains possible that, when and if 96L builds an anticyclone (which the GFS does forecast to happen, at least for the first 48 hours), it could quickly change the surrounding environment and push the shear further north. Nevertheless, I doubt the system retains an anticyclone all the way to the coast, and there is likely to be some westerly shear over the northern and central Gulf Coasts, which would probably weaken the system in the event it makes landfall that far north. The shear is forecast to be weaker farther west, closer to the western Gulf Coast, which would potentially allow for a stronger system to impact that area.

If the system moves slower than anticipated and meanders before it actually gets moving, a hurricane cannot be ruled out. But I would rather remain conservative considering the time of year, the large size of the disturbance, and the uncertainty in the intricacies of the upper-level shear.

The track forecast for this system is much more difficult. One positive sign is that we finally have a well-defined center to track, which theoretically will make things easier. However, I do not like the initialization in most of the models. The closest to reality appears to be the ECMWF, but even that model is a bit too slow. The CMC also had a fairly good initialization, but flunked shortly afterward. I think the GFS threat to Florida is based on a faulty premise -- examination of the forecast fields indicate that the low was initialized about a degree or so too far east. As I said, it is not climatologically favored to get a sharp recuravture toward the western Florida coast this early in the year, and I think areas farther west, from northeast Mexico to the Florida panhandle, are at greater risk. The westward shift in the guidance gives me more confidence in this. However, it is simply impossible to delineate a specific threat area this far in advance. All we can be certain of in the meantime is a slow northward movement toward the central Gulf of Mexico. Water vapor imagery and real-time steering data show the ridge over Texas weakening with the approach of a shallow trough. Although this trough is forecast to lift out, a residual weakness is forecast to remain in western Atlantic, which favors a slow motion toward the north or northwest. Thereafter, the system will either slide under the ridge over the central plains and move into Texas, or it will become entangled with a secondary trough forecast to dive out of Canada and into the Ohio Valley.

There is no absolutely no way to determine which location along the Gulf Coast will see a landfall from this, and despite my claims, the Florida coast is still at risk.

Regardless of development, heavy rainfall should continue over portions of the Yucatan Peninsula, western Cuba, the Florida Keys, and perhaps extreme south Florida over the next day or so. Long-range radar out of Key West shows bands of heavy rain moving cyclonically around coastal areas. Observations in these areas indicate some gusty winds, 30 to 35 mph.

A reconnaissance aircraft is scheduled to investigate the system tomorrow, if necessary.

Probability of development in 48 hours: 70%

Hurricane

Updated: 2:15 AM GMT on June 22, 2012

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Tropical weather analysis - June 20, 2012

By: KoritheMan, 1:18 AM GMT on June 21, 2012

Chris

Tropical Storm Chris strengthened a little today. As of the most recent advisory from the National Hurricane Center, the following was posted:

Wind: 60 mph, with higher gusts
Location: 38.5°N 49.0°W
Movement: E at 21 mph
Pressure: 997 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

Well, what do we have here? Is Chris sporting an eye? I think he is. Over the last several hours, and shortly after the release of the current advisory, the cyclone began to exhibit a large eye-like feature in the central convection. This feature has since persisted, and the thunderstorm activity is wrapping cyclonically around this feature in all directions. I daresay Chris may be trying to make a shot at hurricane strength.



Figure 1. Latest infrared satellite image of Tropical Storm Chris. Image credit: NOAA.

Chris is at the base of an upper low. Southwesterly mid- to upper-level flow on the east side of this low is helping to promote upper-level diffluence, and thus convection. This may be why the cyclone has been able to strengthen over SSTs of about 22C. However, this low is forecast to amplify and eventually move away from Chris. As this happens, there are two possibilities: the first is that Chris remains the dominant system; the second is that the cyclone becomes absorbed by the developing baroclinic system to its west. Lacking any obvious reason why I shouldn't, I'll continue the trend in the previous forecast of the cyclone merging with said extratropical cyclone in a few days.

While Chris definitely looks healthy, and the feature seen on satellite images probably is an eye, I am doubtful that the cyclone will be able to adequately transport the hurricane force winds -- which likely exist aloft -- down to the surface. I will forecast a little more strengthening, but not to hurricane strength.

The track forecast remains straightforward. Chris is moving around the eastern periphery of the aforementioned upper low, and the global models suggest that it will continue to move in a broad cyclonic fashion around this low.

5-day intensity forecast

INITIAL 0000Z 06/20 50 KT 60 MPH
12 hour 1200Z 06/20 55 KT 65 MPH
24 hour 0000Z 06/21 50 KT 60 MPH...EXTRATROPICAL
36 hour 1200Z 06/21 45 KT 50 MPH...EXTRATROPICAL
48 hour 0000Z 06/22 45 KT 50 MPH...EXTRATROPICAL
72 hour 0000Z 06/23...ABSORBED BY DEVELOPING BAROCLINIC LOW

5-day track forecast



Figure 2. My 5-day forecast track for Chris.

Caribbean disturbance

A large area of disturbed weather continues over the northwestern Caribbean Sea in association with a sharp surface trough. The National Hurricane Center hasn't officially designated this system an invest yet, because that requires a definitive low pressure center, of which there currently is none.

Satellite and CIMSS real-time vorticity data suggest that there are two distinct circulation centers within the overall cyclonic gyre. The first of these is a convectionless swirl moving over the eastern Gulf of Mexico west of the Florida Keys; the second is located inland over the northern Yucatan Peninsula. While both of these lows are still primarily mid-level, a couple of surface observations from the Yucatan Peninsula suggest that the secondary vortmax may become the dominant system; Merida recently reported northeasterly winds, and Campeche, located about 100 miles to the southwest, reported northerly winds, and there were even a few reports of westerly winds in the area. Both these locations lie along the western coast of the peninsula, and their respective locales and finely spaced so that such observations bear mentioning. However, I can't ignore the convection afflicting the western Caribbean from the Yucatan Peninsula to the Isle of Youth, which, although will likely due once the diffluent flow aloft over the Gulf of Mexico lifts northward, may try to combine with the Yucatan center, and form a center closer to the north or northeast coast, rather than in the Bay of Campeche. I am not confident enough to say anything else right now.

The models continue to indicate a Florida landfall, but as I said yesterday, until we get a definitive center established, this track isn't set in stone. It would also be climatologically favored for a more gentle recurvature, not the sharp one the models are portraying. At this time, interests along the entire Gulf Coast should be attentive to the progress of this system, which the models develop into a tropical cyclone over the central Gulf of Mexico in a few days, underneath more favorable upper-level winds.

Regardless of development, heavy rains will continue affecting the western Caribbean and neighboring nations, including Mexico's Yucatan Peninsula, western and central Cuba, and possibly south Florida and the Florida Keys at times.

Probability of development within 48 hours: 40%

Hurricane

Updated: 1:22 AM GMT on June 21, 2012

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Tropical weather analysis - June 20, 2012

By: KoritheMan, 5:51 AM GMT on June 20, 2012

Chris

Tropical Storm Chris formed earlier today from an area of disturbed weather of subtropical origin that had been tracked across the central Atlantic for the last several days. As of the most recent advisory from the National Hurricane Center, the following was posted:

Wind: 45 mph, with higher gusts
Location: 38.8°N 56.0°W
Movement: ESE at 13 mph
Pressure: 1005 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

Chris is generating rather deep convection for a high latitude system. Satellite imagery indicates that this convection is attempting to wrap cyclonically into the low-level center, and Chris may be trying to strengthen. In fact, CIMSS ADT numbers have recently plateaued to 3.5, or 55 kt.



Figure 1. Latest infrared satellite image of Tropical Storm Chris. Image credit: NOAA

I should note that Chris is underneath 22-23C SSTs, so it is hard to imagine that it could get much stronger. However, I would be a fool to assert that it couldn't, as several tropical cyclones in the past have attained hurricane strength at such latitudes. Olga in 2001 and Karl in 1980 come to mind. Sometimes the upper troposphere can become so cold relative to the surface center possessing the shallow warm core that it effectively counteracts what is normally considered a baroclinic environment. None of the intensity guidance calls for strengthening, and SHIPS analyzed it as extratropical. However, in this instance I don't care about that, and will forecast a bit of strengthening prior to extratropical transition. I am sure the models will catch on eventually.

5-day intensity forecast

INITIAL 06/20 0000Z 40 KT 45 MPH
12 hour 06/20 1200Z 45 KT 50 MPH
24 hour 06/21 0000Z 45 KT 50 MPH
36 hour 06/21 1200Z 40 KT 40 MPH...EXTRATROPICAL
48 hour 06/22 0000Z 40 KT 45 MPH...EXTRATROPICAL
72 hour 06/23 0000Z 35 KT 40 MPH...EXTRATROPICAL
96 hour 06/24 0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW

It should be noted that Chris is likely to become absorbed prior to the 96 hour mark, but due to inherent sensitivities involved in the 5-day forecast format, it is not explicitly shown.

Chris is becoming embedded in mid-latitude westerly flow, as evidenced by the east-southeast movement on satellite pictures. Chris is forecast to execute a broad cyclonic loop around an upper low forecast to cut off from the trough west of the storm. This same low is the one forecast to absorb the system. Model guidance is in excellent agreement on this scenario, and surprisingly, they initialized the Chris vortex rather nicely, putting more confidence in the track forecast.

5-day track forecast



Figure 2. My 5-day forecast track for Chris.

Caribbean disturbance

No longer is this disturbance within the global models just speculation. A large area of cloudiness and showers now extends across the northwestern Caribbean Sea, associated with a surface trough interacting with an upper-level trough over the Gulf of Mexico. Surface observations do not yet suggest any real organization of the system, which is to be expected given westerly shear of about 35 kt. Do not be deceived by the large convective cloud cluster impacting the Cayman Islands, central and eastern Cuba -- there is no vorticity center there, and this area is being supported by upper-level diffluence associated with a weak upper low south of the western Florida panhandle.

Water vapor imagery shows this low lifting northward, and the GFS forecasts it to be inland in by about 0z Thursday. This should lessen the diffluence over the convective complex, and allow the surface center, if there is one, to begin to generate convection. It is also possible that a new surface center will develop underneath the convection overnight, in which case the regression of the upper low would be irrelevant, and the actual track would be considerably farther east. However, upper-level winds are forecast by the GFS to slowly become more conducive for development of this disturbance during the next couple of days, and there are some hints on water vapor imagery of the core of the westerly flow moving northward away from the disturbance.

Track models are somewhat diverse, with the CMC recurving the system over southeast Louisiana in about 120 hours, while the GFS and ECMWF carry it to the west or central Gulf of Mexico, then shoot it northeast into the Florida peninsula. Given that a fairly deep closed low is already developing over Alberta, Canada, and getting ready to move into the intermountain west, this trough promises to be a strong one. The fly in the ointment is pinpointing just where and when a surface low will form. As previously alluded to, if one were to form amidst the fancy-looking convective complex drenching Cuba, a track closer to the northeastern Gulf Coast and eastern United States would be plausible. On the other hand, if the center is farther west, closer to the Isle of Youth, a more westerly path would result, placing the northern and central Gulf Coasts at greater risk. I have trouble believing the trough is going to be as strong as the GFS and ECMWF are saying. Climatologically, it is highly unusual for a storm to penetrate the central or western Gulf of Mexico, and recurve all the way to Florida.

I am also not comfortable painting a precise landfall location for a disturbance that doesn't even have a well-developed center, and if you live anywhere in the aforementioned Gulf Coastal areas -- and even the western Atlantic, you should pay close attention to this disturbance, which the global models do transform into a large tropical cyclone over the central Gulf of Mexico in a few days.

Regardless of development, heavy rainfall is possible across the Cayman Islands, much of Cuba, south Florida, and the Bahamas over the next couple of days. These rains could produce flooding in low-lying areas, especially considering soils in this region have already been saturated by recent rains.

Probability of development within 48 hours: 10%

Invest 95E

A large tropical disturbance located off the southwest coast of Mexico has become considerably less organized, and development now appears unlikely. Satellite imagery indicates that this system is embedded within a large-scale cyclonic circulation associated with a weak low- to mid-level trough over southwest Mexico, and the Intertropical Convergence Zone (ITCZ) to the south. Northerly shear, dry air entrainment, and competition within the larger gyre is expected to prevent significant development as the low moves slowly east to east-northeast. The system is then forecast to veer away from the coast, but high-level moisture associated with the remnant mid-level vorticity center could locally enhance precipitation across portions of southwest Mexico during the next couple of days.

Probability of development within the next 48 hours: 10%



Figure 3. Latest infrared satellite image of Invest 95E. Image credit: NOAA.

Hurricane

Updated: 5:58 AM GMT on June 20, 2012

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Tropical weather analysis - June 16, 2012

By: KoritheMan, 3:46 AM GMT on June 17, 2012

Invest 95E

With Carlotta officially gone, our attention can now turn to Invest 95E, located several hundred miles west-southwest of Manzanillo, Mexico. This low briefly tried to organize several days ago, but quickly succumbed to unfavorable environmental conditions. Earlier in the day, convection was showing signs of organization, but recent satellite frames show disorganization.



Figure 1. Latest infrared satellite image of Invest 95E. Image credit: NOAA

Although this system is currently leering from easterly to northeasterly shear, this flow is forecast to become lighter as the system moves slowly northwestward. Although some of the models suggest another long-range threat to Mexico, the large-scale pattern is simply too up in arms, and I am not ready to bite off on this just yet. In fact, many of the global models bring this system to at least a minimal tropical storm in about four days. One limiting factor could be the large area of subsidence that lies to the west of the disturbance, as seen in water vapor imagery.

As a precaution, interests along the southwest coast of Mexico, as well as southern Baja, should monitor the progress of this system, which has the potential to slowly develop over the next couple of days.

Probability of development within 48 hours: 20%

Still watching for Gulf of Mexico development

I continue to carefully monitor the possibility of a tropical cyclone forming in the western Gulf of Mexico per the global models. Satellite imagery does reveal a large mass of cloudiness and thunderstorms overspreading the Bay of Campeche, Central America, and the western Caribbean at this time, so it's not as if the disturbance being carried in the models is fake. Broad cyclonic turning is noted in this area based on satellite and scatterometer data, but there is currently no focal point of organization, and westerly shear is rather strong. Although development is possible in this region, it will take some time. Indeed, many of the models don't actually develop the system until about five days, which is a reasonable expectation.

Theoretically, the synoptic pattern should be relatively straightforward, but apparently it's not. In general, the consensus still appears to be aimed at northeast Mexico or south Texas. However, glancing at the occasional wobble and eccentricities within the models, I cannot help but notice a northward turn. Dependent in part on where the system originates, a more poleward motion is not impossible. However, I am not apt to go against a consensus, and I recall similar turns being forecast for Nate and Alex. I suppose it's worth noting that, although the consensus is aimed at the aforementioned areas, every model shows some sort of trough over the central plains which would be capable of turning the system northward. Hopefully once a definite center forms, we will have a better handle on things. For now, let's just kick back, watch, and let nature do the talking.

Hurricane

Updated: 3:48 AM GMT on June 17, 2012

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Tropical weather analysis - June 15, 2012

By: KoritheMan, 5:21 AM GMT on June 16, 2012

Carlotta

After operationally peaking at 90 kt (105 mph) earlier in the day, Hurricane Carlotta is on the decline as it makes landfall on the southern coast of Mexico. The National Hurricane Center had the following to say about the storm in their latest advisory:

Wind: 90 mph, with higher gusts
Location: 15.9°N 97.2°W
Movement: NW at 10 mph
Pressure: 978 mb
Category: 1 (Saffir-Simpson Hurricane Scale)

I say operationally because I think I'll find, and perhaps so will the National Hurricane Center, that the cyclone briefly became a major hurricane. This is based on CIMSS ADT satellite intensity estimates, which entered into the major hurricane threshold around 2000 UTC, and remained that way for several hours. In fact, raw T Numbers actually reached 6.3 near 2100 UTC, corresponding to a Category 4 hurricane. While satellite animations show that this was probably excessive, I do think Carlotta was a Category 3 hurricane for a several hour period prior to landfall.



Figure 1. Latest infrared satellite image of Hurricane Carlotta. Image credit: NOAA

Latest satellite pictures show that the center is just inland between Acapulco and Puerto Angel. The cloud pattern has begun to deteriorate, and, assuming the hurricane continues along the current trajectory, rapid weakening is the most likely scenario. However, as National Hurricane Center senior hurricane specialist Lixion Avila mentioned in the latest forecast discussion for the hurricane, one must always remain cognizant of the possibility that Carlotta might emerge back over the water. If so, this would significantly delay the expected dissipation, which at the moment is forecast to occur in about two days. Current analysis of satellite and water vapor supports the former evolution. The global models also agree on quickly dissipating the hurricane overland. Although the forecast keeps a circulation through five days, it is possible -- perhaps likely -- that Carlotta will not survive that long.

Carlotta is expected to turn westward in about 18-24 hours as a mid-level ridging develops north of the tropical cyclone. There are already supportive indications of such a pattern shift over the Gulf of Mexico. Thereafter, the cyclone -- then much weaker, is forecast to turn back to the east as lower to middle level cyclonic turning develops in the western Caribbean western Gulf of Mexico in association with a large area of disturbed weather forecast to manifest itself in advance of the upward MJO pulse moving into this area of the world. Satellite imagery already shows the initial stages of this disturbance. Ironically, Carlotta is actually forecast to enhance this area. A vertical decoupling of the low- to mid-level circulations appears plausible as the Sierra Madre mountain range disrupts the hurricane.

In the meantime, sustained winds to hurricane force are likely still occurring near and just inland from the coast near the eye. Tropical storm force winds extend out up to about 90 miles from the center, so Carlotta is a relatively small circulation. The hurricane force winds will likely persist for another 6-12 hours, and should slowly permeate inland. The threat for tropical storm force winds in inland areas will probably be existent for perhaps another 24 hours. Heavy rainfall, flash flooding, and mudslides in areas of mountainous terrain is also anticipated. These hazards are of course life-threatening. Storm surge should gradually subside along coastal areas as the center moves farther inland and the winds decrease.

5-day intensity forecast

INITIAL 0300Z 06/16 80 KT 90 MPH...INLAND
12 hour 1200Z 06/16 70 KT 80 MPH...INLAND
24 hour 0000Z 06/17 40 KT 45 MPH...INLAND
36 hour 1200Z 06/17 30 KT 35 MPH...INLAND
48 hour 0000Z 06/18 30 KT 35 MPH...POST-TROP/REMNANT LOW
72 hour 0000Z 06/19 25 KT 30 MPH...POST-TROP/REMNANT LOW
96 hour 0000Z 06/20 25 KT 30 MPH...POST-TROP/REMNANT LOW
120 hour 0000Z 06/21 20 KT 25 MPH...POST-TROP/REMNANT LOW

5-day forecast track



Figure 2. My 5-day forecast track for Carlotta.

Watches and warnings

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* THE PACIFIC COAST OF MEXICO FROM SALINA CRUZ TO PUNTA MALDONADO

A HURRICANE WATCH IS IN EFFECT FOR...
* THE PACIFIC COAST OF MEXICO WEST OF PUNTA MALDONADO TO ACAPULCO

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE PACIFIC COAST OF MEXICO WEST OF PUNTA MALDONADO TO ACAPULCO

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. PREPARATIONS TO PROTECT LIFE
AND PROPERTY SHOULD HAVE BEEN COMPLETED.

A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE
WITHIN THE WATCH AREA.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

Gulf of Mexico development possible

The global models continue to anticipate the possibility of tropical development in the western Gulf of Mexico in about five days. As mentioned earlier, the incipient system is already beginning to exist over the Bay of Campeche and adjacent western Caribbean, possibly associated with a tropical wave which has been moving through the Caribbean Sea for the last several days. With another tropical wave passing south of Puerto Rico, and the remnants of Carlotta, synoptic parameters appear rather favorable for some homegrown mischief, especially when one stops to consider the looming threat of the MJO, and the forecast pattern of upper-level winds. The models do appear to be converging better on the location of origin with this disturbance, with development now anticipated, both by me and by them, in the Bay of Campeche, or at least somewhere in the western Gulf of Mexico.

Based on the forecast synoptic pattern over the United States, and of course climatology, any system originating here would likely affect Mexico, Texas, and perhaps western Louisiana. Although this will probably change until a definite center forms (if it does), right now the model consensus is, in general, aimed at the northeast Mexican coast as a shallow trough over the central plains bypasses the system. However, there is enough uncertainty so that any of the aforementioned areas are at roughly equal risk. Tropical development notwithstanding, it appears that at least some heavy rainfall is on tap for this area next week.

Hurricane

Updated: 5:27 AM GMT on June 16, 2012

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Tropical weather analysis - June 14, 2012

By: KoritheMan, 3:56 AM GMT on June 15, 2012

Carlotta

Tropical Storm Carlotta continues to intensify. As of the latest NHC advisory, the following information was posted on the storm:

Wind: 65 mph, with higher gusts
Location: 12.5°N 94.7°W
Movement: NNW at 10 mph
Pressure: 994 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

Earlier satellite pictures showed a hole near the low-level center, perhaps an eye, but this is inconclusive on recent images. Upper-level outflow remains well-defined, except to the east, where it remains restricted by weak northeasterly shear.



Figure 1. Latest infrared satellite image of Tropical Storm Carlotta. Image credit: NOAA

Alas, it is times like these where I wish I had decent microwave imagery. Unfortunately, the only one available for the whole panorama -- an AMSU-B overpass, is about four hours old. I checked the Puerto Angel radar as well, and it appears Carlotta is out of range. Lacking a distinct definition of the inner core structure, I am loath to forecast rapid intensification. However, if what I think I saw earlier was in fact an eye, then the cyclone has developed an inner core, and a quicker pace of intensification could soon begin. Beyond 48 hours, strengthening is likely to be inhibited -- by land and eventually by shear, which is forecast to come from the east near the end of the forecast period. Obviously, if Carlotta decides to play tricks and moves inland, it will just dissipate instead.

5-day intensity forecast

INITIAL 06/15 0300Z 55 KT 65 MPH
12 hour 06/15 1200Z 60 KT 70 MPH
24 hour 06/16 0000Z 70 KT 80 MPH
36 hour 06/16 1200Z 80 KT 90 MPH
48 hour 06/17 0000Z 65 KT 75 MPH
72 hour 06/18 0000Z 45 KT 50 MPH
96 hour 06/19 0000Z 40 KT 45 MPH
120 hour 06/20 0000Z 35 KT 40 MPH

Denoted quite well in water vapor imagery, a large mid- to upper-level trough and attendant frontal zone over the central United States continues to erode the ridge to the north of the tropical cyclone. This evolution, in combination with a weak trough aloft to the west, is moving Carlotta toward the north-northwest. This general motion is expected to continue through about another 36 hours, bringing the center near or perhaps over the coast. After that, mid-level ridging is forecast to develop to the north of the tropical storm and force it back to the west. The models, unlike yesterday, continue to insist that Carlotta will not make landfall. With such a strong consensus aimed at me, I am forced to do the same. However, given the usual uncertainty in tropical cyclone track predictions, interests anywhere within the cone should carefully monitor the progress of Carlotta, as any deviation to the right -- like the northward jog this morning -- could bring the center over Mexico. Beyond the point where Carlotta turns west, the models diverge significantly, which generally indicates slow motion. I will compromise by predicting a quasi-stationary motion, with perhaps a gentle eastward crawl. Indeed, some of the models suggest that Carlotta will eventually come back toward the coast, albeit as a much weaker cyclone.

Regardless, Carlotta is expected to produce torrential rainfall, hurricane force winds along the coast (with tropical storm conditions inland), and locally damaging storm surge as it makes its point of closest approach to the coast on Saturday. The rains in particular will be exacerbated by the forecast slow movement of the storm, which is expected to remain within 150 miles of the Mexican coast for the next five days. These rains could cause life-threatening flash floods and mudslides, particularly over mountainous regions. If Carlotta rapidly intensifies, there is the potential for a brief period of winds to near 100 kt (115 mph) -- major hurricane strength -- along portions of the coast brushed by the northern eyewall.

5-day track forecast



Figure 2. My 5-day forecast track for Carlotta.

Watches and warnings

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* THE PACIFIC COAST OF MEXICO FROM SALINA CRUZ TO PUNTA MALDONADO

A HURRICANE WATCH IS IN EFFECT FOR...
* THE PACIFIC COAST OF MEXICO EAST OF SALINA CRUZ TO BARRA DE TONALA
* THE PACIFIC COAST OF MEXICO WEST OF PUNTA MALDONADO TO ACAPULCO

INTERESTS ALONG THE COAST OF MEXICO WEST OF ACAPULCO TO CABO
CORRIENTES SHOULD MONITOR THE PROGRESS OF CARLOTTA.

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. A WARNING IS TYPICALLY ISSUED
36 HOURS BEFORE THE ANTICIPATED FIRST OCCURRENCE OF
TROPICAL-STORM-FORCE WINDS...CONDITIONS THAT MAKE OUTSIDE
PREPARATIONS DIFFICULT OR DANGEROUS. PREPARATIONS TO PROTECT LIFE
AND PROPERTY SHOULD BE RUSHED TO COMPLETION.

A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE
WITHIN THE WATCH AREA. A WATCH IS TYPICALLY ISSUED 48 HOURS
BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL-STORM-FORCE
WINDS...CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT OR
DANGEROUS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

Atlantic development still possible

There's not much to say at this point. But to risk sounding like a broken record, I'll say it again -- the global models continue to insist on the potential for tropical cyclone formation in the western Caribbean or Gulf of Mexico in 5 - 7 days. Recently, they have shifted their point of origin farther to the west, over the Bay of Campeche. Presumably, this comes in response to Carlotta's remnant mid-level circulation. Given the fact that some of the reliable models pull the system inland beyond day five, this is not impossible, but I favor development farther east based on the 6-10 day GFS 500 mb height anomalies. Should the system originate in the Bay of Campeche as forecast, Mexico and Texas would probably be the primary targets.

Hurricane

Updated: 3:58 AM GMT on June 15, 2012

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Tropical weather analysis - June 13, 2012

By: KoritheMan, 12:50 AM GMT on June 14, 2012

Invest 94E

An organized and potentially dangerous tropical disturbance ("94E") located about 360 miles south of the Mexico/Guatemala border appears likely to become a tropical depression. The center appears to be closed and within the convection, and the system appears to be on the verge of becoming a tropical depression.



Figure 1. Latest infrared satellite image of Invest 94E. Image credit: NOAA

Upper tropospheric shear over the system isn't strong, although the large scale flow pattern does not yet resemble an anticyclone. Interestingly, water vapor imagery shows a small upper low over southeast Mexico. Since this low appears to be moving westward away from 94E, it is unlikely to alter its chance at becoming a tropical cyclone. Luckily the global models recognized this vortex, otherwise I would be concerned about a busted intensity forecast due to unexpected shear. They quickly elongate and weaken this low over the next 12-24 hours. It should be noted that the HWRF makes the system a major hurricane prior to moving inland. While experience has taught me to be cautious, forecasting hurricanes is hardly an art, and once an inner core becomes established, there is definitely the potential for rapid strengthening.

The model consensus is in surprising agreement on the track for a system that hasn't even developed yet, although they differ a bit on the timing of landfall. The GFS is about 12-18 hours ahead of the other models, apparently seeing more pull from the trough. Since the large scale pattern over the United States looks rather zonal at the moment, I tend to side with the other models, comprised of the generally reliable ECMWF. Amusingly, but perhaps unsurprising, the 12z NOGAPS initialization was terrible, spinning the system around, and eventually weakening it because of, an adjacent vortex to the west. Since the latter system is quite weak, this solution was ignored. I am to the left of the GFS, in best agreement with the ECMWF. This should pull the system inland over central Mexico by late Saturday afternoon.

Interests along the Mexican coast from Acapulco to Puerto Angel should closely monitor the progress of this potentially dangerous system. Tropical storm warnings or hurricane watches could be required rather quickly tonight for a portion of the coast. I would also like to note that the potential for abrupt weakening or dissipation before landfall in a fashion mimicking Bud last month does not seem feasible this time around. Bud was in an area of cooling sea surface temperatures, and was also ingesting the very dry marine layer airmass that is typically found over the eastern Pacific west of 110W. That is not the case with this system. This system will probably become a strong tropical storm, and even that is probably conservative. A much more dangerous system is certainly possible.

Probability of development within the next 48 hours: Near 100%

Invest 95E

Another area of low pressure, the one the NOGAPS initialized as the stronger of the two, is located several hundred miles west of 94E. This system is embedded in a large cyclonic circulation within the ITCZ, and is undergoing easterly shear, which is not forecast to abate. Development is not anticipated with this system, and I probably won't mention it again.

Probability of development within the next 48 hours: Near 0%

Atlantic development still possible

While I have ceased monitoring the Carolinas system, there is still the potential for some development in the northwest Caribbean or southern Gulf of Mexico beginning in about 5 days. It appears that the mechanism by which this development will arise is the mid-level remnants of 94E/Carlotta, which could combine with a tropical wave to enhance cloudiness and showers over this area. Although the incipient wave is already approaching 85W, with 94E forecast to become a deep system, the typical easterly flow found in this region of the basin may temporarily become halted due to large scale cyclonic flow surrounding 94E. This could slow the forward progression of the tropical wave some, and allow it to stick around until 94E moves inland, and into the Caribbean.

Hurricane

Updated: 12:52 AM GMT on June 14, 2012

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Tropical weather analysis - June 12, 2012

By: KoritheMan, 2:19 AM GMT on June 13, 2012

Invest 94E

An area of low pressure located in the far eastern Pacific about 500 miles south-southeast of the Guatemala/El Salvador border ("94E") is showing signs of organization. Last light visible satellite imagery and Dvorak enhancement imagery from RAMMB suggests the low-level center is located on the northeastern edge of the convection. This was also confirmed by an earlier ASCAT pass, showing the strongest winds west of a sharp cyclonic wind shift assumed to be the trough axis.



Figure 1. Latest infrared satellite image of Invest 94E. Image credit: RAMMB imagery Colorado State University (CSU).

Atmospheric and oceanic parameters appear favorable for continued development over the next few days, and this low has the potential to become a tropical depression during the next day or so. I think the most likely timeframe for this to occur is around 0z Thursday. It is possible that this system could become a hurricane before moving inland.

As just mentioned, the synoptic pattern favors a gradual turn into southeast Mexico. Model guidance suggests this, and their theory is supported by the current large-scale pattern over the United States; water vapor imagery shows the ridge over the central US shifting eastward as a weak upper-level trough develops over the Rockies. Cyclonic flow is forecast to linger in this area for the next several days, which in combination with the ridge should induce a west-northwest motion, followed by a turn to the northwest toward the coast. This system is forecast to move inland late Friday or early Saturday.

Interests along the coast of southeast Mexico should monitor the progress of this disturbance.

Probability of genesis within the next 48 hours: 60%

Invest 95E

A secondary of low pressure lies several hundred miles west of 94E. This low is not nearly as well organized, and any development here should be slow. This low is expected to move generally westward over the next few days. It poses no threat to land areas.

Probability of genesis within the next 48 hours: 20%

Atlantic development possible late this week and into next

The global models continue to portray two areas of interest across the Atlantic basin over the next 7 - 10 days: the first is off the waters of the western Atlantic, where they are unanimous in developing a weak surface low off the coast of North Carolina from the large trough moving across the eastern seaboard. Unlike with Alberto and Beryl, the synoptic pattern does not favor US peril, as a large trough is forecast to amplify over the western Atlantic, which favors a slow turn out to sea through the break in the subtropical ridge. I am not particularly confident on development, as northwesterly shear and dry air are present.

Demanding more immediacy is the potential for some sort of tropical development in the northwestern Caribbean or Gulf of Mexico next week. The models have been hinting at this for awhile, albeit with minimal consistency on the specifics -- i.e., whether we get a tropical cyclone. Without going into explicit detail, the large-scale pattern forecast over the United States and western Atlantic does favor development in this region, especially considering the MJO is forecast to move back into our basin soon. We are already seeing overt signs of this in the eastern Pacific. It is important not to let your guard down in regards to the potential for some sort of tropical cyclone forming in this region, the lack of consistency amongst the global models notwithstanding. This current upward pulse is fairly strong. As such, the models will probably have a little bit of difficulty in resolving it.

At the very least, a large surge of moisture will probably manifest over the waters of the western Caribbean, Gulf of Mexico, and portions of the western Atlantic over the next 7 - 10 days. Height anomalies over the US favor the development region over the Gulf of Mexico or northwest Caribbean. It is uncertain where such a system would go, but based on the large-scale pattern in the models, I feel like a north to northwest track into the Gulf of Mexico would be possible. The system's exact point of origin cannot yet be known, so there is enough uncertainty that the entire Gulf Coast could see something. It is also possible, as per the GFS, that the system could originate farther east, closer to Jamaica, get caught up in a trough, and move off to the northeast.

Hurricane

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Tropical weather analysis - June 10, 2012

By: KoritheMan, 4:58 AM GMT on June 11, 2012

Invest 93E

A broad area of low pressure continues to spin in the vastness of the eastern Pacific, centered about 850 miles south of the southern tip of Baja California.



Figure 1. Latest infrared satellite image of Invest 93E. Image credit: NOAA's Satellite Services Division (SSD).

This system actually looks less organized than 24 hours ago due to easterly shear, which is why I wasn't in the mood to call for rapid intensification in the previous forecast. The SHIPS analyzes 19 kt of easterly shear over the system as of 0z. Normally in this basin, such shear would not cause a signification disruption of the cloud pattern -- at least to the point where strengthening is downright inhibited -- since most systems here tend to move relatively fast, offsetting the net shearing effect of the Pacific ridge. However, 93E is moving at only about 10 mph, slower than the shear vector. Using a combination of satellite and microwave fixes, the low-level center appears to be located east of the convection. The banding isn't particularly impressive, either.

SHIPS still wants to make this system a hurricane in about four days, yet keeps a distinct shearing mechanism in place. This seems mysterious to me, but it is not the first time I've seen SHIPS incorrect. The current cloud pattern notwithstanding, water vapor imagery suggests that the large scale environment is not yet unfavorable enough to deter slow strengthening. It is most interesting that none of the models, in sharp contrast to yesterday, want to develop this system into anything more than a weak tropical storm. One thing I've learned over the years is to not jump the gun based on a new day -- or cycle -- of model runs, and I will make no such exception here. Since there is little apparent reason, other than easterly shear, why this system should not strengthen, I am still calling for slow development over the next couple of days, and this low could still become a tropical depression or tropical storm.

The system is expected to continue to track slowly west to west-northwest over the next several days. A southwestward motion is still possible in the long-term, but I am not ready to commit to this.

Probability of genesis within the next 48 hours: 50%

More Eastern Pacific development possible

The global models continue to insist that another tropical cyclone will develop behind 93E in a few days. There is no obvious reason why this should not happen, and at the very least I am confident in an organized area of disturbed weather developing. The synoptic pattern favors an eventual turn toward the Mexican coast, but the details are too broad and variable to be adequately worked out at this time.

Atlantic development still possible in the long-range

Based on the forecast of the large scale pattern over the United States and western Atlantic, there is still the potential for some type of tropical development in the western Caribbean beginning late this week into early next week. Although the models are less enthusiastic about this today, I am not ready to back off on this just yet, given the widespread influence of the upward MJO forecast to make its way into our segment of the world at those ranges. In addition, global models still have immense difficulty in properly resolving large scale perturbations within the synoptic scale pattern, so that daily fluctuations in prognostications are not uncommon. I still believe a Caribbean system, at least a tropical disturbance, is possible in six to seven days, but there is enough uncertainty that it may not become a tropical cyclone. These models also hint at possible mischief off the eastern seaboard, presumably from a portion of the energy from the Caribbean disturbance interacting with a decaying frontal trough.

Hurricane

Updated: 5:00 AM GMT on June 11, 2012

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Tropical weather analysis - June 9, 2012

By: KoritheMan, 4:51 AM GMT on June 10, 2012

Invest 93E

An area of disturbed weather developed late Friday evening several hundred miles south of Manzanillo, Mexico. This disturbance has shown signs of gradual organization over the last 24 hours. The system is decently organized on satellite imagery, though earlier microwave data suggested that the center was along the eastern edge of the convection.



Figure 1. Latest infrared satellite image of Invest 93E. Image credit: RAMMB imagery Colorado State University (CSU).

There could still be a little bit of easterly shear over the system, but any negative effect from this is deemed to be negligible. In fact, the current cloud outflow pattern is rather impressive, and objective upper wind analyses from the CIMSS-UW laboratory suggest that an anticyclone may be forming over the system. If true, the system will likely develop quicker than the models are indicating. However, since I am not completely convinced the system isn't experiencing easterly shear, I will not forecast rapid intensification.

With ample instability and adequate shear values, there is little reason why this system should not steadily develop.

Although some of the guidance appears to have initialized the circulation a little prematurely, the general agreement is for a west-northwest track under the influence of a ridge to the north. This seems supported by water vapor imagery, as well. Later in the forecast period, the GFS suggests the system could turn southwest. Presumably, this is the model responding to the anomalous northwesterly flow on the western side of a secondary tropical cyclone the global models develop to the east of 93E in a few days enhancing the ridge to the north. Since the incipient system is now evident entering the far eastern Pacific, a possible, although aclimatological, southwestward motion later in the period cannot be fully ignored. It should be noted that the ECMWF loses the circulation in about three days, becoming absorbed by the larger cyclonic gyre to the east. Although the secondary system is moving faster than 93E, it is quite distant, and most likely, the abrupt demise of the vortex in this model is related to poor initialization. However, I find it hard to believe this system will not have at least some impact on 93E. For now, I will side with the GFS and keep a separate entity throughout the forecast period.

Probability of genesis within the next 48 hours: 40%

Possible tropical cyclone behind 93E?

As alluded to earlier, the large disturbance encompassing the far eastern Pacific and southwestern Caribbean could eventually become the season's next tropical depression. The global models are unanimous in developing a large hurricane out of this system, with some even bringing it to the coast of Mexico late next week. There is no obvious meteorological reason why this cannot happen.

Atlantic development possible

I've neglected to mention this, but the global models, particularly the GFS, have been forecasting the development of a tropical disturbance forming in the western Caribbean in the next 7 - 10 days, and then becoming a tropical storm as it up moves up the western Florida coast. All meteorological facets appear supportive of this: the MJO is returning to our area of the world (hence the activity in the eastern Pacific), ridging is forecast to develop in the eastern portion of the nation, and upper-level winds are forecast to become lighter. That's all that can be said for now. Stay tuned.

Lastly, the ECMWF has been consistent in developing a weak tropical cyclone in the Bay of Campeche in about 10 days, but none of the other models show this.

Hurricane

Updated: 4:54 AM GMT on June 10, 2012

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

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