Dr. Jeff Masters' WunderBlog

Katrina is gone

By: JeffMasters, 6:56 PM GMT on August 31, 2005

Katrina lost its tropical characteristics this morning and is no longer a tropical depression, just a regular low presssure system. She continues to dump 2 - 4 inches of rain along her path, and is a threat to bring minor flooding to northern New England today and tomorrow. Katrina-spawned tornadoes killed two in Georgia and damaged 13 homes in Marshall, Virginia yesterday, but the threat of tornadoes has diminished today. Katrina is no more, a blessing we can use right now!

Blessings are very hard to find in the catastrophe zones of Louisiana and Mississippi today. We are only just now beginning to hear from the areas that the calm of the eye passed over. Slidell, on the western side of the eye's passage, received a 15-foot storm surge. Only foundations are left of a large portion of the buildings, and the bridge to New Orleans is broken in multiple places, according to news reports. Pass Christian, unlucky holders of the U.S. record-highest storm surge of 24.7 feet from 1969's Hurricane Camille, received a 20-foot storm surge. The storm surge at nearby Bay St. Louis was 22 feet, and both areas have extensive areas of complete destruction.

Why did the New Orleans flood walls fail?
The 325-mile long series of flood walls and levees surrounding New Orleans were engineered to withstand the storm surge from a Category 3 hurricane. No Category 3 or higher hurricane has hit New Orleans in the past 150 years, a strange quirk one would not expect based on the pattern of hurricane strikes elsewhere along the Gulf Coast. New Orleans should get a Category 3 hurricane passing within 80 miles every 32 years, a Category 4 hurricane every 70 years, and a Category 5 hurricane every 180 years. However, the strongest hurricanes ever to hit the city were two Category 2 hurricanes--a 1893 hurricane that killed 2000, and Hurricane Betsy of 1965, which killed 75 and put parts of the city under 8 feet of water. Hurricane Camille, although it was a Category 5 hurricane and took almost the same track as Katrina, was a very small hurricane with hurricane force winds extending out only about 50 miles from the center. Camille brought 100 mph gusts to the eastern side of New Orleans. Katrina was a huge storm whose hurricane force winds extended a full 110 miles from the center, and probably brought 130 mph wind gusts to the same area. Katrina piled up a much larger storm surge wave onto the flood walls than Camille. According to the Army Corps of Engineers, "What failed were actually floodwalls, not levees. This was caused by overtopping which caused scouring, or an eating away of the earthen support, which then basically undermined the wall. These walls and levees were designed to withstand a fast moving category 3 hurricane. Katrina was a strong 4 at landfall, and conditions exceeded the design." The flood wall breaks lie along Lake Pontchartrain, whose water is 4.5 feet above sea level. Thus, since New Orleans lies 6 feet below sea level, we can expect the city to flood to a depth of at least 10 feet.

I highly recommend reading an October 2001 article from Scientific American, titled: Drowning New Orleans, to learn more about the vulnerabilities of the levee system.


The tropics today
The most significant threat in the tropics I can see is the potential this weekend for a tropical depression to develop in the coastal waters surrounding Florida. This is the same location that Katrina developed. However, this time the development might come at the tail end of a cold front that is expected to push off of the East Coast, instead of from a tropical wave. If a depression does form in this area, the possible track is impossible to guess at this point.



Tropical Depression 13 is nothing to worry about, as it is over the open Atlantic Ocean and heading out to sea. The well-organized wave 1300 miles east of the Lesser Antilles will probably become Tropical Depression 14 in the next day or two, but it is probably too far north to threaten any land areas. This system will probably recurve out to sea. The tropical wave that pushed off of the coast of Africa yesterday and is now south of the Cape Verdes Islands has some potential for development later in the week, and the GFS model projects that this wave will become a hurricane and a potential threat to the Leeward Islands a week or so from now.


On August 19, I posted the image below showing a long-range forecast for August 31 from the GFS model.



As you recall, mid-August was a time of relative quiet in the tropics, but the GFS model was calling for an end to this quiet period. The 12-day GFS forecast called for 3 tropical cyclones for August 31. Well, the GFS was correct in calling for an end to the quiet period! While there is only one tropical cyclone (TD 13) out there, the other two strong tropical waves seen in the satellite image above certainly have the potential to become tropical depressions over the next few days. The GFS did miss the formation of Katrina, but the general 12 day forecast showing a big increase in hurricane activity was pretty accurate.

Dr. Jeff Masters

Updated: 7:52 PM GMT on August 31, 2005

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Katrina a tropical depression

By: JeffMasters, 9:54 PM GMT on August 30, 2005

Just a quick update on the current state of tropics for now. The incredible stories of Katrina's devastation playing on the news now leave me stunned, and my heart goes out to all the victims and their loved ones.

Katrina now
Katrina is a tropical depression, racing northeastward through Indiana and Ohio at 27 mph, and will be gone tomorrow. No major flooding due to Katrina's rains is occurring in the areas north of the coastal devastation zone. The flooding and rains associated with Katrina's second landfall have been fairly low for a major hurricane, since the storm has been moving quickly and the soils the rain have been falling on are not saturated from previous storms. Katrina should continue to produce rain amounts in the 2-4 inch range for the rest of its track, which should only cause localized flooding problems. A few tornadoes are still possible. So far, Katrina has produced two damaging tornadoes in Georgia, one in the tourist town of Helen that ripped the roof off of an Econolodge.


Figure 1.Total estimated precipication from Katrina from the Mobile radar. Maximum amounts were in the 8-12 inch range. Data from 6 NWS radar sites is still not available, due to the failure of over 100 fiber lines in Louisiana and Mississippi. No repair date is available.

What's behind Katrina
We are watching two areas in the Atlantic that may become tropical depressions in the next day or two, but neither are expected to be a threat to land. Tropical Depression 13 dissipated yesterday, but is looking more organized and may regenerate. If it does regenerate, this system is probably only a threat to Bermuda. Another strong tropical low pressure area is midway between Africa and the Lesser Antilles Islands. This low has a large circulation and a small amount of deep convection trying to build over it. The low has some modest wind shear it is fighting, and a large area of dry, dust-laden air surrounding it. The dry air and shear will probably keep the low from developing into a depression today, but the shear may lessen enough tomorrow to let a depression form. If the low does develop, the early track models forecast the system to track northwestward over the open Atlantic Ocean and not threaten land.



Dr. Jeff Masters

Updated: 9:58 PM GMT on August 30, 2005

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The Katrina catastrophe

By: JeffMasters, 12:53 PM GMT on August 30, 2005

As news reports begin to filter in from the hardest hit areas, the scope of Katrina's destruction is slowly being realized. Remember in the aftermath of Hurricane Andrew, how there was a lot of relief about how much worse it could have been, and how well Miami fared? This cheerfulness faded once the search teams penetrated to Homestead and found the near-total devastation there. The fact we have not heard at all from the areas hardest hit by Katrina--Slidell, Bay Saint Louis, Pass Christian--means that these areas have probably been mostly destroyed, with substantial loss of life of those who failed to evacuate. While the winds of Katrina were only of Category 3 strength when the storm moved through these areas, Katrina's 20 - 22 foot storm surge was still characteristic of a Category 5 storm. Remember, the all-time record for a storm surge in the U.S. is 26 feet--from Hurricane Camille--and Katrina's storm surge was close to that level, but covered an area three times larger. And with a two block long breach in the Lake Pontchartrain levee allowing the entire city of New Orleans to flood today, we are witnessing a natural disaster of the scope unseen in America since the great 1938 Hurricane devastated New England, killing 600. Damage from Katrina will probably top $50 billion, and the death toll will be in the hundreds.

Katrina now
Katrina is still a tropical storm, but is rapidly losing her ability to cause destruction. Her top winds are only about 40 mph at 9am EDT, and the storm is moving quickly enough to the north-northeast that extensive damage from flooding is unlikely over the Tennessee valley. Rainfall amounts in this area have been in the 2-4 inch range so far, which will cause localized flooding problems. A few tornadoes are still possible, mainly over Georgia and Tennessee.

What's behind Katrina
Tropical Depression 13 dissipated yesterday, but is being watched for signs of regeneration. If it does regenerate, this system is probably only a threat to Bermuda. Another area of concern is a strong tropical low pressure area midway between Africa and the Lesser Antilles Islands. This low has a large ciculation and a small amount of deep convection trying to build over it. The low has some modest wind shear it is fighting, but the real impediment to its development is a very large area of dry, dust-laden air surrounding it. The dry air will probably keep the low from developing into a depression today. If the low does develop, the early track models forecast the system to track northwestward over the open Atlantic Ocean.



Dr. Jeff Masters

Updated: 12:58 PM GMT on August 30, 2005

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Katrina a Category 1, still incredibly destructive

By: JeffMasters, 7:27 PM GMT on August 29, 2005

Katrina continues to move northwards and accelerate through Mississippi. Katrina is now a Category 1 hurricane with 95 mph winds, but still causing massive storm surge flooding, tornadoes, wind damage, and rain water flooding. Numerous tornadoes continue to be spawned out of Katrina's spiral bands, and the National Weather Service is also issuing tornado warnings for "destructive winds near 110 mph in the eyewall and inner rain bands of Hurricane Katrina." This is a new warning technique that is used to trigger the emergency response needed for a tornado-like threat. There are not actually tornadoes occurring for these tornado warnings.

Storm surge and rainfall
According to NHC and NWS sources, peak storm surge values were 22 feet in Bay Saint Louis, MS, and 20 feet along many areas of eastern Louisiana. Southwest Lake Pontchartrain received a 10-12 foot storm surge. Mobile Bay received a 9-12 foot storm surge, and Biloxi at least 10 feet. Exact surge heights have been difficult to measure since most of the tide gauges were destroyed by the hurricane. Peak rainfall from Katrina was over the central coast of Mississippi, where radar estimated 8-12 inches fell.

Six weather radars fail
As of 11am EDT, communications with six National Weather Service radar sites failed. No radar information is available from the New Orleans, Lake Charles, and Fort Polk stations in Louisiana, Jackson and Columbus AFB stations in Mississippi, and the Red Bay station in the Florida Panhandle. The NWS offices are still able to send out warnings and forecasts.

What's behind Katrina?
Tropical Depression 13 died early this morning, the victim of wind shear. The remains of TD 13, located about 700 miles east-northeast of the Lesser Antilles, do have the potential to re-develop into a depression later in the week as they move northwest over the open ocean.

A new tropical wave near 10N 35W is large, well-organized, and has developed a circulation. I expect this wave will become a tropical depression in the next day or two as it moves west-northwest towards the Leeward Islands.

Dr. Jeff Masters

Updated: 7:31 PM GMT on August 29, 2005

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Category 3 Katrina pounding Gulf coast

By: JeffMasters, 3:17 PM GMT on August 29, 2005

Katrina has spared New Orleans a direct hit. Although the damage will be incredible, it could have been much, much worse. At 10am CDT the eyewall of Hurricane Katrina moved ashore along the Louisiana-Mississippi border between New Orleans and Gulfport, almost the exact spot Hurricane Camille devastated in 1969. The worst of Katrina is now being experienced everywhere along the coast. The National Weather Service is reporting that the levees in Orleans and St Bernard parishes have been overtopped by the storm surge, and there are reports of life-threatening flooding, roof damage, and building collapses in the city. However, the storm's passage to the east of the city means that New Orleans has escaped the catastrophic blow a direct hit would have delivered, and heavy loss of life is not expected in New Orleans.

Bay Saint Louis, Biloxi, and Gulfport Mississippi will take the full force of Katrina's right eyewall, and a storm surge of 15-20 feet is likely along the west and central Mississippi coast. Katrina will continue to weaken as she interacts with land, but will maintain hurricane intensity until about midnight tonight, when she will be nearly 200 miles inland. Tornado warnings have been issued for Louisiana, Mississippi, Alabama, and Florida in the past hour, and tornadoes will continue to be a serious threat throughout the day. Heavy rains will also be a major problem, and rainfall amounts of 8 inches have already occurred near the Louisiana-Mississippi border.

As of 11am EDT, communications with four National Weather Service offices have failed. No radar information is available from the NWS offices in New Orleans and Lake Charles in Louisiana, and Jackson in Mississippi. The NWS offices are still able to send out warnings and forecasts.

Now that Katrina is moving ashore, the Hurricane Hunters have flown their final flight into the storm. A special thanks need to be given to the Air Force Hurricane Hunters based at Keesler Air Force Base in Biloxi, Mississippi, who have flown Katrina around the clock while their families remained on the ground in Biloxi. Biloxi will suffer Katrina's harshest blow, and many of the Hurricane Hunters will see their homes destroyed or heavily damaged.

Dr. Jeff Masters


Updated: 4:30 PM GMT on August 29, 2005

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Katrina's weakening--worst missing New Orleans

By: JeffMasters, 11:39 AM GMT on August 29, 2005

Katrina is due south of the Mississippi-Louisiana border, and moving northward at 15 mph. On this course, the western edge of the eyewall will pass some 20 miles to the east of New Orleans, sparing that city a catastrophic hit. As the eye passes east of the city later this morning, north winds of about 100 mph will push waters from Lake Pontchartrain up to the top of the levee protecting the city, and possibly breach the levee and flood the city. This flooding will not cause the kind of catastrophe that a direct hit by the right (east) eyewall would have, with its 140 mph winds and 15-20 foot storm surge. New Orleans will not suffer large loss of life from Katrina.

Biloxi and Gulfport Mississippi will take the full force of Katrina's right eyewall, and a storm surge of 15-20 feet is likely along the central Mississippi coast. Katrina is a strong but weakening Category 4 hurricane, and will probably come ashore about noon CDT near Gulfport as a weak Category 4 hurricane with 135 mph winds. The storm has been slowly weakening the past 12 hours, with the central pressure rising more than 1mb/hour on average. The central pressure measured by the Hurricane Hunters has been oscillating the past three hours, jumping from 918 mb to 925, then back to 920, and now 921 mb at 7:30am EDT. The winds measured at flight level on the east side of the eyewall were 134 kt, which translates to 140 mph at the surface. The cloud pattern in satellite imagery has decreased on the west side due to dry air entrainment, and the eyewall has opened up to the south and southwest in radar imagery. With the center passing over mixed swamplands and water, much of the energy that sustains the hurricane will be cut off, making any further intensification unlikely. Katrina is not hitting at maximum intensity and is sparing New Orleans a direct hit, and although the damage will be incredible, it could have been much, much worse.

Tropical Depression 13
A new tropical depression formed in the mid-Atlantic yesterday, and is headed northwest over open ocean. This is one we definitely do not need to worry about for now. The storm may even dissipate due to hostile wind shear within the next few days.

Dr. Jeff Masters

Updated: 12:21 PM GMT on August 29, 2005

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Katrina weakening--but still of catastrophic intensity

By: JeffMasters, 4:31 AM GMT on August 29, 2005

The 10:36pm EDT Hurricane Hunter mission found a central pressure of 908 mb, up 6 mb since this afternoon's minimum of 902 mb. The maximum flight level winds in the northwest quadrant were 122 knots, which translates to a Category 3 intensity at the surface (130 mph). However, Katrina's strongest winds are in the northeast quadrant, and the Hurricane Hunters have not sampled that quadrant yet. Winds of 160 knots were found there by the previous mission at 8pm EDT. The rising pressure implies that we should see some diminishing of the winds in the next few hours, making Katrina a strong Category 4 hurricane. Hurricanes rarely maintain Category 5 intensity for more than 12 hours, and that is how long Katrina has been at Category 5.

I have been expecting Katrina to undergo a shrinking of the eye and an eyewall replacement cycle tonight, but instead the eye diameter has increased to 30 nm (35 miles). This is an incredibly large eye for a storm with a pressure this low, and makes me very uncertain about what intensity fluctuations Katrina may undergo in the next few hours before landfall. I see nothing to change the label of "catastrophic" for Katrina at landfall.

The eye is now clearly visible on long-range New Orleans radar. This view may not be around too much longer, I expect Katrina will destroy the radar site. This happened to the Miami radar during Hurricane Andrew, when a 160 mph wind gust ripped the radar ball from its rooftop mooring. When one looks at this radar image animate, considers the forecast track, and sees the huge size of the eye, it is very difficult to imagine that New Orleans will not get a portion of the eyewall. New Orleans will likely flood, causing immense destruction and heavy loss of life.

I just received this email from user Adam Henderson: "My friend is stuck on I-10 and has just called me saying there is a 12 car pile up. His CB is buzzing with news that a 18 wheeler is involved." At this stage, it might be best not to try to evacuate. Being stuck in a traffic jam on I-10 when the winds start blowing 130 mph is probably more dangerous than riding out the storm in the Superdome.

Tropical Depression 13
A new tropical depression formed in the mid-Atlantic today, and is headed northwest over open ocean. This is one we definitely do not need to worry about for now. The storm may even dissipate due to hostile wind shear within the next few days.

See you in the morning. My prayers to all in the path of Katrina.

Dr. Jeff Masters

Updated: 4:32 AM GMT on August 29, 2005

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Katrina stronger than Camille

By: JeffMasters, 10:52 PM GMT on August 28, 2005

The 6:30pm EDT NOAA Hurricane Hunter mission found a central pressure of 904 mb, up from the 902 measured at 3:30pm. These pressures make Katrina the fourth strongest hurricane ever, and the strongest hurricane ever observed in the Gulf of Mexico, surpassing Camille. However, the winds of Katrina are 165 mph, far from Camille's 190 mph winds at landfall.

Although the pressure has stopped falling, there is no indication that Katrina is about to undergo weakening, like we saw yesterday during her eyewall replacement cycle. When that cycle started, the eye diameter was 9 nm, but the present eye diameter is 28 nm. Eyewall replacement cycles usually begin when the eye shrinks below 10 nm, and there are no indications that Katrina's eye is going to shrink.

The list of strongest hurricanes of all time now reads:

Hurricane Gilbert (888 mb, 1988)

The Great Labor Day Hurricane (892 mb, 1935)

Hurricane Allen (899 mb, 1980)

Hurricane Katrina (902 mb, 2005)

Hurricane Camille (905 mb, 1969)

Landfall location and intensity
Katrina has continued to expand in size, and now rivals Hurricane Gilbert and Hurricane Allen as the largest hurricanes in size. When hurricanes reach such enormous sizes, they tend to create their own upper-air environment, making them highly resistant to external wind shear. The global computer models are not really hinting at any wind shear that might affect Katrina before landfall, and the only thing that might weaken her is an eyewall replacement cycle. Even if one of these happens in the next 12 hours, the weakest Katrina is likely to get before landfall is a Category 4 hurricane with 145 mph winds. Katrina is so huge and powerful that she will still do incredible damage even at this level. The track forecast has not changed significantly, and the area from New Orleans to the Mississippi-Louisiana border is going to get a catastrophic blow. I put the odds of New Orleans getting its levees breached and the city submerged at about 70%. This scenario, which has been discussed extensively in literature I have read, could result in a death toll in the thousands, since many people will be unable or unwilling to get out of the city. I recommend that if you are trapped in New Orleans tomorrow, that you wear a life jacket and a helmet if you have them. High rise buildings may offer good refuge, but Katrina has the potential to knock down a high-rise building. A 25 foot storm surge and 30 - 40 foot high battering waves on top of that may be able to bring down a steel-reinforced high rise building. I don't believe a high rise building taller than six stories has ever been brought down by a hurricane, so this may not happen Monday, either. We are definitely in unknown waters with Katrina.

I have focused on New Orleans in much of my discussions about this storm, but Katrina will do tens of billions in damage all along the coast of Louisiana, Mississippi, Alabama, and Florida. Mobile Bay could well see a 10-foot storm surge. And inland areas will take heavy damage as well; Katrina will still be a hurricane 180 miles inland, and cause widespread flooding throughout the Tennessee Valley.

My thoughts and prayers go out to all of you in Katrina's way, and I urge all readers of this blog to do the same.

Jeff Masters

Updated: 11:28 PM GMT on August 28, 2005

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Katrina: Category 5

By: JeffMasters, 12:24 PM GMT on August 28, 2005

Katrina is in the midst of a truly historic rapid deepening phase--the pressure has dropped 34 mb in the 11 hours ending at 7am EDT, and now stands at 908 mb. Katrina is now the sixth strongest hurricane ever measured in the Atlantic. At the rate Katrina is deepening, she could easily be the third or fourth most intense hurricane ever, later today. The list of strongest hurricanes of all time includes:

Hurricane Gilbert (888 mb, 1988)

The Great Labor Day Hurricane (892 mb, 1935)

Hurricane Allen (899 mb, 1980)

Hurricane Camille (905 mb, 1969)

Hurricane Mitch (905 mb, 1998)

Hurricane Ivan (910 mb, 2004)

Katrina's winds and storm surge
Maximum sustained winds at flight level during the 7am Hurricane Hunter mission into Katrina were 153 knots, which translates to 160 mph at the surface, making Katrina a minimal Category 5 hurricane. The winds are likely to increase to "catch up" to the rapidly falling pressure, and could approach the all-time record of 190 mph set in Camille and Allen. Winds of this level will create maximum storm surge heights over 25 feet, and this storm surge will affect an area at least double the area wiped clean by Camille, which was roughly half the size of Katrina. Katrina has continued to expand in size, and is now a huge hurricane like Ivan. Damage will be very widespread and extreme if Katrina can maintain Category 5 strength at landfall.

Landfall projections
The computer models are very tightly clustered and have been so for almost a day. The data used to initialize the models is excellent, since all available hurricane hunter aircraft have been in the air continuously making measurements for several days. Katrina has already made her turn northward, which makes the task of landfall prediction for the models much easier. The offical NHC forecast of a landfall in SE Louisiana, on the western edge of New Orleans, is thus a high-confidence forecast. The spread in the landfall location is just 90 miles, meaning the eye of Katrina is very likely to hit somewhere between New Orleans and a point just east of the Mississippi-Louisiana border.

Intensity forecast
Katrina's intensity at landfall is likely to be Category 4, but could easily be Category 3 or 5. She will undergo another eyewall replacement cycle before landfall, and this will weaken her maximum winds by 20 - 30 mph for a 12-hour period. Additionally, some increase in shear is possible in the 12 hours prior to landfall, which could weaken Katrina's winds another 10 - 20 mph. If we are extrememly lucky, both factors will conspire to knock Katrina down to a Category 3 and she will hit at low tide. Given that the storm is so large and is already pushing up a huge storm surge wave in front of it, even a weakened Category 3 Katrina hitting at low tide will cause an incredible amount of damage. A stretch of coast 170 miles long will experience hurricane force winds, given the current radius of hurricane force winds around the storm. A direct hit on New Orleans in this best-case scenario may still be enough to flood the city, resulting in heavy loss of life and $30 billion or more in damage.

Dr. Jeff Masters

Updated: 12:36 PM GMT on August 28, 2005

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Eyewall replacement done, Katrina intensifying

By: JeffMasters, 1:40 AM GMT on August 28, 2005

The eyewall replacement cycle that began at about 8am this morning has ended. The 8pm EDT Hurricane Hunter pressure reading was 942 mb, down 2mb from the pressure at 6:45pm. No inner eyewall was found, just an elliptical 30-40nm eyewall. We may be on the verge of a rapid deepening phase, since the shear and dry air on the northwest side of the hurricane appear to be lessening, and the hurricane is moving over a deep layer of warm water of almost 90F. The areal size of the hurricane continues to expand, and Katrina is growing from a medium sized hurricane to a large hurricane. Where the pressure will bottom out after this deepening phase is anyone's guess, and I believe something in the 915 - 925 mb range is most likely, which would make Katrina a strong Category 4 or weak Category 5 hurricane by tomorrow afternoon. The deepening phase may last longer than usual for a major hurricane, since Katrina is expanding in size and thus has more mass to spin up.

After this phase of deepening, another eyewall replacement cycle will occur, and the timing of that cycle will be worth billions of dollars and perhaps many lives. There is no way to predict when this eyewall replacement cycle will occur. Another factor will be the timing of the tides--if Katrina hits at high tide, there may be billions more in damage. Tidal range (difference between high and low tide) at Bay St. Louis near New Orleans is two feet. High tide will occur around 8am Monday, and low tide at 8pm. There is still the possibility, too, that the trough that is now steering Katrina to the north will also create enough shear to reduce her to a Category 3 storm at landfall. This is what happened to Hurricane Ivan last year.

New Orleans finally got serious and ordered an evacuation, but far too late. There is no way everyone will be able to get out of the city in time, and they may be forced to take shelter in the Superdome, which is above sea level. If Katrina makes a direct hit on New Orleans as a Category 4 hurricane, the levees protecting the city will be breached, and New Orleans, which is 6 - 10 feet below sea level, will fill with water. On top of this 6 feet of water will come a 15 foot storm surge, and on top of that will be 20 foot waves, so the potential for high loss of life is great. Given the current track and intensity forecast, I'd put the odds of this at about 20%.

What's behind Katrina?
A very large tropical wave way out in the Atlantic, 1300 miles east of the Leeward Islands, has a low level circulation, a large and increasing amount of deep convection, and an improving upper level outflow. Shear over the system is light, waters under it are warm, and I expect a tropical depression to form tomorrow from this system. If this happens, the depression will move west-northwest towards the northernmost Leeward Islands, and possibly affect them by Thursday.


Dr. Jeff Masters

Updated: 2:04 AM GMT on August 28, 2005

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New Orleans to Pensacola at high risk from Katrina

By: JeffMasters, 4:05 PM GMT on August 27, 2005

The Hurricane Hunters measured a central pressure of 949 mb at 11:14am EDT, up from the cental pressure of 941 mb measured at 7:07am EDT. Concentric eyewalls with diameters of 13 and 40 nm were reported, satellite images show that the eye has filled in with clouds and the cloud top temperatures have warmed. These observations indicate that an eyewall replacement cycle has begun. This was expected, since the 7:07am Hurricane Huneter report indicated that the eye diameter had shrunk to 9 nm, about the smallest diameter one gets before an eyewall replacement cycle begins.

The maximum winds may fall below 115 mph while Katrina undergoes this eyewall replacement cycle, as the inner eyewall collapses and a new outer eyewall forms. This would make Katrina a strong Category 2 storm, and indeed the maximum winds seen so far by the Hurricane Hunters were only 87 knots (100 mph) at 10,000 feet. This is a temporary affliction, since Katrina is in nearly ideal conditions for strengthening, and is expected to reach Category 4 status by Sunday. The convection and outflow are starting to look better on the north side of the hurricane, and Katrina should have a more symmetrical shape typical of Category 4 hurricanes by Sunday. As seen in the cumulative wind image below, Katrina has increased markedly in size the past 12 hours, and will deliver a widespread damaging blow wherever she comes ashore.



The favorable intensification conditions for Katrina are expected to last up until landfall, when some increase in shear may occur. Intensification forecasts are highly unreliable, though, and it would be no surprise if Katrina were a Category 2, 3, or 4 landfall. The track forecast is getting more believable, as Katrina's westerly motion shows that it has begun it recurvature, pretty much where NHC and the models were predicting. A landfall between New Orleans and Pensacola is on track for Monday morning or afternoon. I expect a Category 3 storm at landfall.

I'd hate to be an Emergency Management official in New Orleans right now. Katrina is pretty much following the NHC forecast, and appears likely to pass VERY close to New Orleans. I'm surprised they haven't ordered an evacuation of the city yet. While the odds of a catastrophic hit that would completely flood the city of New Orleans are probably 10%, that is way too high in my opinion to justify leaving the people in the city. If I lived in the city, I would evacuate NOW! There is a very good reason that the Coroner's office in New Orleans keeps 10,000 body bags on hand. The risks are too great from this storm, and a weekend away from the city would be nice anyway, right? GO! New Orleans needs a full 72 hours to evacuate, and landfall is already less than 72 hours away. Get out now and beat the rush. You're not going to have to go to work or school on Monday anyway. If an evacuation is ordered, not everyone who wants to get out may be able to do so--particularly the 60,000 poor people with no cars.

Dr. Jeff Masters

Hurricane

Updated: 7:18 PM GMT on November 30, 2012

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Katrina--costliest hurricane ever?

By: JeffMasters, 11:49 AM GMT on August 27, 2005

The Hurricane Hunters measured a cental pressure of 941 mb at 7:07am EDT, up 2mb from the 940 mb pressure recorded at 5:32am. The maximum winds recorded at flight level (10,000 feet) were just 106 knots, which meaning that Katrina is still a Category 3 storm, even though the pressure implies she could be a Category 4. The reason for this is that a significant increase in the areal extent of the storm has occurred in the past six hours, so Katrina needs to spin up a much larger area of winds, which will take time. It is likely that by this afternoon, the winds will "catch up" to the pressure, and Katrina will go from being a small, weak Category 3 storm to a medium-sized strong Category 3 hurricane. Recon noted that the eye diameter has shrunk to 9 nm, which is about as small as the eye can get before an eyewall replacement cycle begins. If this is the case, Katrina will probably not attain Category 4 status until eyewall replacement cycle ends and a new round of intensification begins, which would likely not happen until Sunday. A few of the NHC intensification models from last night suggested the possibility that Katrina could reach Category 5, which is not unrealistic, given the warm waters and light wind shear over the storm. Katrina still has a way to go to reach Category 5; the convection and outflow are still looking restricted on the north side of the hurricane, and this area will have to "catch up" before we can talk about Category 4 or Category 5.



The favorable conditions for Katrina are expected to last up until landfall, when some increase in shear may occur. But as usual, intensification forecasts are highly unreliable, and we don't really know how strong Katrina will be at landfall. The track forecast is also problematic, until Katrina makes its northward turn. She is apparently beginning to do so now, as the track has been wobbling more westward that west-southwest the past few hours.

Emergency management officials in New Orleans are no doubt waiting to see where Katrina makes her turn before ordering evacuations. However, if I lived in the city, I would evactuate NOW! The risks are too great from this storm, and a weekend away from the city would be nice anyway, right? GO! New Orleans needs a full 72 hours to evacuate, and landfall is already less than 72 hours away, so I would get out now and beat the rush. If an evacuation is ordered, not everyone who wants to get out may be able to do so.

Insurers estimate that Katrina already did about $1 to $4 billion in damage (total damage is roughly double insured damage). This is a shocking number for a Category 1 hurricane, and bodes ill for the residents of New Orleans and the U.S. insurance industry if Katrina makes a direct hit on New Orleans as a Category 4 storm, which would likely cost $100 billion. But, New Orleans' amazing run of luck could well continue at the expense of Mississippi or Alabama or Florida. Like Camille in 1969, Katrina may come ashore far enough east of New Orleans to largely spare it.

Dr. Jeff Masters

Updated: 12:03 PM GMT on August 27, 2005

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Threat to New Orleans grows

By: JeffMasters, 9:36 PM GMT on August 26, 2005

Latest compter model runs have shifted significantly west in the past six hours, and the threat of a strike on New Orleans by Katrina as a major hurricane has grown. The official NHC forecast is now 170 miles west of where it was at 11am, and still is to the east of the consensus model guidance. It would be no surprise if later advisories shift the forecast track even further west and put Katrina over New Orleans. Until Katrina makes its northward turn, I would cast a very doubtful eye on the model predictions of Katrina's track. So much for the model prediction being high confidence, as I was surmising at 8am this morning! Recurvature is a difficult situation to forecast correctly.

The pressure of Katrina has continued to slowly drop, to 965mb. Dry air on the northwest side of the hurricane has interfered with the strengthening process, and may continue to do so over the next day. I still expect Katrina to attain Category 3 status Saturday, but Category 4 is looking less likely due to the dry air to the north. As one can see from the latest long range radar out of Key West, the northwest side of the eyewall is fragmented.

Some fairly prodigious rain amounts fell in the Miami area today. Homestead south of Miami measured 13.2 inches, and isolated amounts of 15 - 20 inches were observed between Homestead and Miami. The 7.55 inches at Key West was its 10th heaviest rainy day in history.

Jeff Masters

Updated: 7:39 PM GMT on August 28, 2007

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Katrina a Category 2 storm

By: JeffMasters, 3:45 PM GMT on August 26, 2005

Recent Hurricane Hunter measurements show the pressure has dropped significantly, and is now down to 971 mb. Surface winds have increased to 100 mph, making Katrina a Category 2 hurricane. It would be no real surprise to see Katrina attain Category 3 status by this evening, and probably a Category 4 on Saturday.

The forecast track has not changed significantly, with a landfall Monday morning still expected along the end of the Gulf of Mexico's bowling alley, the Florida Panhandle between Pensacola and Panama City. However, two key computer models--the NOGAPS and GFDN--have made a large jump to the west, bringing Katrina over Louisiana. New Orleans can definitely not breathe easy until Katrina makes its turn north and we have a better idea where she is going.

Jeff Masters

Updated: 7:39 PM GMT on August 28, 2007

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Katrina batters Miami, and is back to hurricane status

By: JeffMasters, 12:09 PM GMT on August 26, 2005

Katrina is a hurricane again, after spending just seven hours over land, and briefly (for a four hour stretch) weakening to a 70 mph tropical storm. The unexpected southwestward path taken by Katrina (but hinted at for a long time by the GFDL model) put Miami in the bullseye for Katrina's strongest winds and heaviest rains. The eye passed directly over the National Hurricane Center and the Miami radar site, and Doppler Radar estimates of rainfall amounts show over ten inches of rain in a narrow band extending over the Hurricane Center. Some modest wind and flooding damage was reported by the media, consistent with typical Category 1 hurricane conditions. Four deaths, three from falling trees have been reported so far. Overall, Miami is extremely lucky--had Katrina had an additional 12 - 24 hours over water, she may have some ashore as a Category 3 hurricane.

Katrina has those 12 - 24 hours now, and more. The Miami radar loop continues to a well-organized storm, with a plainly visible eye. Upper level outflow is improving and slowing expanding. Katrina is in an almost ideal environment for intensification--31 to 32C waters, light shear, and no dry air. Katrina will likely be a Category 3 hurricane by Saturday night, and possibly a Category 4.

Although Katrina is currently moving just south of due west, the computer track models unanimously agree that a trough moving across the central U.S. this weekend will "pick up" Katrina and force it on a northward path towards the Florida Panhandle. These model predictions are high-confidence predictions, as the upper air environment around the hurricane is well-characterized thanks to the NOAA jet dropsonde mission flown last night. The NOAA jet is scheduled to fly another mission tonight. While New Orleans centainly needs to keep a wary eye on Katrina, it seems that the Florida Panhandle has its usual hurricane magnet in place, and the same piece of coast punished by Ivan and Dennis is destined for another strike by a major hurricane.

What's behind Katrina?
A large area of disturbed weather north of Hispanolia has diminished since yesterday. This disturbance lies in an area of high wind shear of 20 - 25 knots, and is not a threat to develop into a tropical depression in the next few days. The tropical wave spinning 900 miles east of the Leeward Islands is still experiencing wind shear, but still has the potential to develop into a tropical depression this weekend.

Katrina blogs
For observations of what's happening now in Southwest Florida, we have several bloggers writing today:

labsr4me (Naples, SW Florida)

Zeenster (Cape Coral, SW Florida)

evolution (Charlotte Harbor, SW Florida)

Dr. Jeff Masters

Updated: 7:40 PM GMT on August 28, 2007

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New computer model runs for Katrina

By: JeffMasters, 7:11 PM GMT on August 25, 2005

The 1:18pm EDT Hurricane Hunter mission found the pressure of Katrina remained constant at 990mb, but the maximum winds were now on the northwest side at 64 knots (73 mph) at the airplane's flight level of 5000 feet. Radar from Miami confirms that the north side of Katrina has greatly increased in the amount and intensity of precipitation the past two hours as the storm continues to strengthen. It is a very good thing that Katrina does not have an extra 12 hours to intensify before landfall! However, the very favorable environment for intensification that Katrina is currently in is expected to still exist once she is in the Gulf of Mexico Saturday. I expect Katrina will become at least a Category 2 hurricane before its second landfall.

The latest computer model runs, performed using the 8am EDT upper air data, have made a major shift. Katrina is expected to push much farther west off of the western coast of Florida, and make a delayed turn to the north. These latest model runs show a much reduced risk to Tampa, and put an area from New Orleans to Cedar Key, Florida at risk. In the center of this risk area lies the U.S.'s very own hurricane magnet, the Pensacola region, where Ivan and Dennis struck.

Katrina continues to intensify at a modest pace, and if present trends continue will hit Florida near Fort Lauderdale tonight as a minimal Category 1 hurricane with 75 - 80 mph winds. The northwest side of the storm continues to suffer from dry air intrusions, and the primary intense thunderstorms and strongest winds are on the south side. Thus, the usual rule about the right front quadrant (north side) of the storm being the most dangerous is not neccesarily the case with Katrina. The highest storm surge will still be to the north of where the center comes ashore, but wind damage may be equally distributed on both sides of the storm.

The Miami radar loop continues to show an increase in low-level banding, and an eye-like feature trying to form. Upper level outflow is improving and slowing expanding.

As I discussed in the previous blog entry, the major threat to South Florida from Katrina is freshwater flooding from her rains. Rainfall amounts of 6 - 10 inches are expected from this slow-moving storm. For comparison, Hurricane Irene of 1999, which hit South Florida as a Category 1 hurricane, dumped 10 - 20 inches of rain. Damage from Irene was over $800 million in Florida. Damage from Katrina will probably be much lower, in the $30 - $100 million range, since Katrina's rainfall will be half of what Irene's was.

What's that behind Katrina?
A large area of disturbed weather even bigger than Katrina lies to her east, just north of Hispanolia. This disturbance lies in an area of high wind shear of 25 - 35 knots, and is not a threat to develop into a tropical depression in the next few days.

Katrina blogs
For observations of what's happening now in South Florida, we have several bloggers writing today:

turtlehurricane (Weston, Broward County)

sngalla (Fort Lauderdale)

MrJ76 (Okeechobee)

Zeenster (Cape Coral, SW Florida)

evolution (Charlotte Harbor, SW Florida)

Dr. Jeff Masters

Updated: 7:40 PM GMT on August 28, 2007

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Katrina modestly intensifying

By: JeffMasters, 5:28 PM GMT on August 25, 2005

Katrina continues to intensify at a modest pace, and if present trends continue will hit Florida near Fort Lauderdale tonight as a minimal Category 1 hurricane with 75 - 80 mph winds. The northwest side of the storm continues to suffer from dry air intrusions, and the primary intense thunderstorms and strongest winds are on the south side. Thus, the usual rule about the right front quadrant (north side) of the storm being the most dangerous is not neccesarily the case with Katrina. The highest storm surge will still be to the north of where the center comes ashore, but wind damage may be equally distributed on both sides of the storm.

The Miami radar loop continues to show an increase in low-level banding, and an eye-like feature trying to form. Upper level outflow is improving and slowing expanding.

As I discussed in the previous blog entry, the major threat to South Florida from Katrina is freshwater flooding from her rains. Rainfall amounts of 6 - 10 inches are expected from this slow-moving storm. For comparison, Hurricane Irene of 1999, which hit South Florida as a Category 1 hurricane, dumped 10 - 20 inches of rain. Damage from Irene was over $800 million in Florida. Damage from Katrina will probably be much lower, in the $30 - $100 million range, since Katrina's rainfall will be half of what Irene's was.

Katrina's path once she makes landfall and crosses over the Florida Peninsula is highly uncertain, and the various computer models project a landfall anywhere between Pensacola (GFDL model) and Tampa (UKMET model). If her path in the Gulf allows her to remain over water for at least a day, Katrina could easily strengthen to a Category 1 or 2 hurricane before making her second landfall in the Florida Panhandle. If Katrina tracks right up the west coast of Florida, she would likely remain a tropical storm due to the interference of land.

What's that behind Katrina?
A large area of disturbed weather even bigger than Katrina lies to her east, just north of Hispanolia. This disturbance lies in an area of high wind shear of 25 - 35 knots, and is not a threat to develop into a tropical depression in the next few days.

Katrina blogs
For observations of what's happening now in South Florida, we have several bloggers writing today:

turtlehurricane (Weston, Broward County)

sngalla (Fort Lauderdale)

MrJ76 (Okeechobee)

Zeenster (Cape Coral, SW Florida)

evolution (Charlotte Harbor, SW Florida)

Dr. Jeff Masters

Updated: 7:39 PM GMT on August 28, 2007

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Katrina falters, does not intensify overnight

By: JeffMasters, 12:04 PM GMT on August 25, 2005

The chances for Katrina undergoing a major rapid intensification and reaching Category 2 or Category 3 status now appear very dim. Katrina faltered overnight, and increased only slightly in intensity. Dry air on the west side continued to prevent convection from wrapping all the way around the storm, and some shearing also appeared to be occurring on the storm's west side.

However, Katrina is still expected to intensify today and reach Category 1 hurricane status by tonight or early Friday morning, when it makes landfall over South Florida. The storm slowed in forward speed some, giving it more time today over the very warm (31C) waters of the Gulf Stream. Other than the small amount of shear noted on her west side overnight, Katrina is in a low-shear environment, and the shear may decrease today. The combination of low shear and warm water may allow Katrina to strenthen rapidly into a Category 1 hurricane just before landfall. The Miami radar loop shows an increase in low-level banding during the past two hours, and an eye-like feature trying to form. Katrina is getting more organized. Upper level outflow looks pretty ragged on satellite imagery, but appears to be improving and slowing expanding.

The major threat to South Florida from Katrina is freshwater flooding from her rains. Rainfall amounts of 6 - 10 inches are expected from this slow-moving storm. For comparison, Hurricane Irene of 1999, which hit South Florida as a Category 1 hurricane, dumped 10 - 20 inches of rain. Damage from Irene was over $800 million in Florida. Damage from Katrina will probably be much lower, in the $30 - $100 million range, since Katrina's rainfall will be half of what Irene's was.

Once Katrina makes landfall early Friday morning, the storm will cross over the Florida Peninsula and re-emerge into the Gulf of Mexico. If her path in the Gulf allows her to remain over water for at least a day, Katrina could easily strengthen to a Category 1 or 2 hurricane before making her second landfall.

I'll make several updates today as new Hurricane Hunter data becomes available; I was unable to make many updates yesterday, as I was travelling.

For observations of what's happening now in South Florida, we have several bloggers writing today. If you're in South Florida and are blogging today, let me know where you are at so I can add you to this list:

turtlehurricane (Weston, Broward County)

sngalla (Fort Lauderdale)

MrJ76 (Okeechobee)

Zeenster (Cape Coral, SW Florida)

evolution (Charlotte Harbor, SW Florida)

Dr. Jeff Masters

Updated: 6:42 PM GMT on August 28, 2007

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Katrina may intensify rapidly

By: JeffMasters, 10:36 PM GMT on August 24, 2005

The NHC 5pm discussion mentions that an experimental intensification model is forecasting a 57% chance that Katrina will undergo rapid intensification Thursday just before landfall in South Florida. The GFDL model is also calling for rapid intensification. This means that Katrina could be a Category 3 hurricane when it hits South Florida. The current thinking is still that there is enough dry air around Katrina to make it a strong tropical storm or weak Category 1 hurricane at landfall, but keep in mind that hurricane intensity forecasts are very unreliable.

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Katrina forms

By: JeffMasters, 1:42 PM GMT on August 24, 2005

Slow-to-organize TD 12 (now Katrina) continues to look better on satellite imagery, with deep convection on the east side continuing to build. The upper level outflow has improved considerably today, and there does not appear to be any major shearing of the system happening. Water vapor imagery does show some dry air to the northwest of the storm, and this dry air is currently the main obstacle that has slowed Katrina's development this morning. The latest Hurricane Hunter report at 7:30am EDT found a not-too-impressive central pressure of 1007 mb, but a respectable 45 knots of wind at flight level (1500 feet). The Hurricane Hunters noted some low-level banding beginning to occur, and it is a very safe bet that this system will continue to intensify today.

The track of the storm will take it over Florida by Friday, all the computer models agree. The exact landfall point is unclear, since the depression is moving slowly and erratically, and may undergo a reorganization where the center relocates under the main area of convection later today. The models forecast a landfall intensity anywhere from 35 mph winds to 70 mph winds. The higher range is possible if the convection on the east side manages to overcome the dry air on the west side and wrap all the way around the system by Thursday morning. Let's call it a 30% chance Katrina will be a Category 1 hurricane by landfall on Friday.

Once over Florida, the GFS model forecasts that the system will stall and not move for several days. All of the other models disagree, and push the system into the Gulf of Mexico by Sunday, where it has an excellent chance of intensifying into a hurricane. Since the GFS it the only model calling for this stall, it is more believable to assume that Katrina will push into the Gulf of Mexico and threaten the U.S. Gulf coast early next week.

Dr. Jeff Masters

Updated: 1:53 PM GMT on August 24, 2005

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Will TD 10 rise again?

By: JeffMasters, 3:38 PM GMT on August 23, 2005

The remains of TD 10 continue to fester over the Bahama Islands, and the clouds have taken on that decidedly messy pattern associated with a tropical depression in the formative stages. An exposed low level circulation center is apparent in both visible satellite imagery and winds from the Quikscat satellite. The circulation was north of eastern Cuba and south of the central Bahama Islands, near 22.5N, 76W at 11am EDT. Deep convection is all east of the low level circulation center, and Quickscat winds as high as 30 knots were measured in this area. Observation stations in the vicinity are sparse, and I have not yet seen any pressure falls in those stations close to the system.

The environment surrounding the system is good but not ideal. Water temperatures are quite warm--about 29C, and closer to 31C near the western Bahamas. However, wind shear levels have been increasing somewhat over the past 12 hours and are about 10 - 15 knots (5 -10 knots would be much better.) A small upper-level low just north of the system may act bring some dry air into the system and hamper any upper-level outflow that tries to develop. Another possible problem is the presence of the large landmass of Cuba to the south, which may disrupt the system's circulation if it tracks more westerly. I expect the storm to continue to torment us by very slowly continuing to organize as it moves towards Florida.


The system appears to be tracking west-northwest at a very slow 5 to 10 mph, and the latest "early guidance" shows the storm moving more northwesterly towards Florida over the next few days. However, steering currents are weak and more westerly motion towards Cuba or the Straights of Florida would not be a surprise. Some of the computer models such as the Canadian model strengthen the system into a hurricane over the Gulf of Mexico later in the week. Some very warm water (32C, or almost 90F) lies off the west coast of Florida that model believes will fuel the storm into a hurricane. The GFS model makes the system a weak tropical storm that moves over Florida by Friday, then keeps the system a weak tropical storm as it recurves past the Carolinas. If the system does become a tropical storm, it is unlikely the upper level winds will allow intensification into a hurricane for at least the next three days. By that time, it's anybody's guess what might happen. One thing is for sure--the remains of TD 10 will be a around for a lot longer, they're going nowhere very fast. I expect I'll still be talking about this system next week!

A Hurricane Hunter aircraft is scheduled to visit the remains of TD 10 at 5pm this afternoon to see if a new tropical depression has formed. If so, it will be interesting to see if they call it TD 10 again, since the NHC discussions have been refering to this system as "possibly the remnants of TD 10".

African Tropical Waves
The large tropical wave 700 miles west of the Cape Verde Islands has gained some deep convection on its east side since yesterday, but has struggled to maintain its convection in the face of some increasing wind shear this morning. The system is also battling some dry air to its norhtwest that is getting entrained into the center. This system could still become a depression in a day or two as it moves west to west-northwest. Global models forecast that this storm will recurve before it threatens any land.
Jeff Masters

Updated: 3:47 PM GMT on August 23, 2005

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Update on remains of TD 10

By: JeffMasters, 7:40 PM GMT on August 22, 2005


I've been reluctant to pay much heed to the remains of TD 10 after declaring the system dead forever and seeing it struggle to maintain its identity as a tropical wave the past few days. However, recent visible satellite images (as of 3pm EDT) indicate the remains of TD 10 may have developed a surface circulation centered just north of Haiti. The cloud pattern continues to look disorganized, but could show some development as the system approaches Florida by Wednesday. The latest "early" track guidance for this system shows it roughly paralleling the coast of Cuba, so development of this system may be substantially hindered by interaction with land. Some of the computer models indicate development of this system into a tropical storm when it reaches the Gulf of Mexico later this week, when the large upper level high anchored over Mississippi that has been creating high shear over the Gulf finally moves off to the west. I'm not a believer, I think the environment for the remains of TD 10 will still be too hostile to permit a tropical storm from developing.



Jeff Masters

Updated: 7:40 PM GMT on August 22, 2005

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TD 11, TD 10, and African waves

By: JeffMasters, 5:41 PM GMT on August 22, 2005

Tropical Depression 11
TD 11 will be the 4th tropical cyclone to hit the east coast of Mexico this year, and the 3rd weak system to affect the extreme southern Bay of Campeche. It looks almost exactly like Tropical Storm Gert of July. TD 11 will probably intensify enough be called Tropical Storm Jose before landfall tonight, but will be quickly forgotten.

The Hurricane Hunters will investigate the system at 5pm EDT, and one might wonder why NHC bothers with the expense of sending a plane out to an obviously low-threat storm with only a few hours to live. The answer is that these storms are full of surprises, and it is NHC's policy to have an airplane in a storm anytime one threatens land just in case sudden strengthening happens.

Remains of TD 10
The remains of TD 10 are still hanging around the Bahamas-Cuba-Hispanolia area, but continue to look disorganized. Expect this activity to continue moving west at 10 mph with no development over the next two days.

East Coast frontal boundary
Some development is possible off the East Coast later this week near the Carolinas at the trailing edge of a cold front that moved off the coast yesterday. This kind of development is common this time of year.

African waves
The large tropical wave that moved off the coast of Africa Friday night continues to spin and track west-northwest, and is now about 400 miles west of the Cape Verde Islands. The convection associated with this wave has not increased at all the past few days. If the wave does develop, it will probably recurve in the center of the ocean and not affect any land.



I've been calling attention the past few days to the GFS model's prediction of increased hurricane activity over the mid-Atlantic beginning late this week. This morning's GFS model run is now backing off from that prediction, and only shows one instead of three tropical cyclones in the Atlantic on August 31 (the one cyclone is the current wave 400 miles east of the Cape Verde Islands, which the GFS forecasts to recurve north of the Azores Islands). The GFS does show that the ITCZ will be very active, with many stong tropical waves pushing off of the coast of Africa. A new tropical wave is pushing off of the coast of Africa today, but it is too early too see if this wave has potential to develop.

The level of tropical activity we are seeing this week is typical of what one sees during the peak of an average hurricane season (hurricane season peaks on about September 10). It will be interesting to see if the GFS's earlier prediction of much-above average activity by next week will come back with newer runs of the model.

Jeff Masters

Updated: 5:58 PM GMT on August 22, 2005

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TD 11 forms in Bay of Campeche

By: JeffMasters, 2:44 PM GMT on August 22, 2005

Satellite, radar, and surface data indicate a tropical depression is forming within the disturbed weather in the Bay of Campeche. The National Hurricane Center will issue a special advisory on this system by 11:30am EDT today. This system is expected to move ashore over the Mexican coast and not present a threat to the U.S. A Hurricane Hunter aircraft is scheduled to investigate the system at 5pm EDT today to see if the depression has strengthened into Tropical Storm Jose.

Jeff Masters

Updated: 2:45 PM GMT on August 22, 2005

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Tropics beginning to heat up

By: JeffMasters, 5:20 PM GMT on August 21, 2005

The tropics are beginning to heat up again, and the current period of calm will likely be short-lived. There are three areas of possible tropical development worth mentioning today, and we will also discuss the possibility of extremely active conditions developing 7-10 days from now.

Yucatan and southern Gulf of Mexico
A strong tropical wave crossing Mexico's Yucatan Peninsula has an impressive and increasing amount of deep convection, and already appears to be gaining some rotation. Once the center of this circulation moves out over the warm waters of the Gulf of Mexico on Monday, chances are good that a tropical depression will form. An Air Force hurricane hunter aircraft will investigate tomorrow afternoon, if neccessary. If a depression does form, it will move west-northwest and probably make landfall in Mexico, under the steering flow of a strong upper-level high located over the southern Gulf states. This quasi-stationary high has been in place for a number of days, and is not forecast to move much the next few days. This high will act to protect the Gulf Coast of the U.S. both by steering potential tropical storms westward towards Mexico, and by using its strong shearing winds to tear apart any systems that venture too close to the Gulf Coast.

Cape Verdes Islands tropical wave
The vigorous tropical wave that pushed off the coast of Africa Friday night is now just southwest of the Cape Verdes Islands. The wave has a large circulation centered at 13N, and some strong deep convection to the south over the ITCZ with surface winds of 15-20 knots. Waters are warm, shear is light, and some computer models predict this wave will develop into a tropical storm. The GFS model predicts that a tropical storm will form from this wave on Wednesday and recurve in the center of the Atlantic Ocean towards the Azores Islands by early next week.

Remains of TD 10
The remains of TD 10 are just north of Hispanolia, and kicking up some moderate convection there. No circulation is apparent on satellite imagery, and surface pressures are not falling in the region. Although shear values are currently low, the remains of the depression are tracking due west towards Cuba and towards the shearing winds of the strong upper-level high over the southern Gulf states. This system will bring strong winds and heacy rain to the Bahamas and Cuba, but for now appears unlikely to develop into a tropical storm.

Forecast for 7-10 days from now
The GFS has been consistently predicting a very active period of hurricane development beginning late this week and running through the the end of the 16-day forecast period of the model. In my previous blog entry from Friday, I posted the GFS forecast for August 31, showing its prediction of three simultaneous tropical cyclones in the Atlantic. One and a half days later, the GFS is still predicting three tropical cyclones for August 31--although the northernmost one wasn't predicted last Friday, and is in fact the storm that is predicted to form from the current tropical wave just southwest of the Cape Verde Islands.


It bears repeating that computer forecasts of specific tropical storms developing are VERY unreliable--particularly out seven days and more from now. The GFS is likely to be dead wrong about the specific timing of the tropical waves moving off the coast of Africa, which waves might develop into hurricanes, and where in the ocean they may develop. What is believable is the GFS's forecast of a fundamental shift in the general atmospheric circulation leading to an enhanced period of hurricane activity starting later this week.

Jeff Masters

Updated: 5:33 PM GMT on August 21, 2005

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The calm before the storms

By: JeffMasters, 8:24 PM GMT on August 19, 2005

The tropics are quiet today. The only area worth mentioning is the large tropical wave pushing off of the coast of Africa, which the UKMET model develops into a tropical cyclone by Tuesday. However, the GFS, Canadian, and NOGAPS models are all pretty ambivalent about the system and do not develop it much.

No hurricane season has ever gone at full tilt all the way from July to October. Active seasons have always had quiet periods when the large scale wind patterns alternate to a different mode, creating more wind shear over the tropics. This year, that quiet period is here now, and is forecast to continue for at least a few more days. However, this may change next week. The GFS model predicts that the high shear values that have dominated the Caribbean for the past few weeks will finally relax. And beginning Friday August 26, shear values may relax over the rest of the primary hurricane genesis area in the mid-Atlantic. The GFS shows an endless succession of tropical storms developing from tropical waves moving off of the coast of Africa beginning late next week. And from August 30 continuing through the end of the GFS's 16-day forecast period, the model predicts two and sometime three simultaneous tropical cyclones in the Atlantic. This prediction has been maintained over at least the past four runs of the GFS model, so it is not a fluke one can blame on a single bad model run.



Keep in mind that computer forecasts of specific tropical storms developing are VERY unreliable--particularly out seven days and more from now. The GFS is likely to be dead wrong about the specific timing of the tropical waves moving off the coast of Africa, which waves might develop into hurricanes, and where in the ocean they may develop. What is believable is the GFS's forecast of a fundamental shift in the general atmospheric circulation leading to an enhanced period of hurricane activity. If the GFS model is correct, the current time of calm will transition to a time of storms late next week.

Jeff Masters

Updated: 8:36 PM GMT on August 19, 2005

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TD 10 is dead, and will rise no more!

By: JeffMasters, 9:24 PM GMT on August 18, 2005

The Air Force Hurricane Hunters flew into the remnants of TD 10 east of Puerto Rico this afternoon, and found that the system no longer had a closed circulation. Satellite images show that the system has deteriorated significantly this afternoon, with very little deep convection occurring. Surface winds measured by the Quikscat satellite are under 20 knots and TD 10's remains have become a tropical wave over the Atlantic. Regeneration into a tropical depression is very unlikely, as this would take several days, and the system will be experiencing increasing shear by Sunday.

I can't see any obvious reason why the system fell apart today; vertical wind shear values have continued to decrease, and are now down to 5-10 knots. Water vapor satellite imagery shows no dry air around the system. Situtations like this emphasize how little we understand about the formation process of tropical storms.

The remainder of the tropics are quiet. There is considerable cloud cover over portions of the southern Caribbean, but wind shear levels are near 20 knots over most of the region--too high to permit tropical development.

Jeff Masters

Updated: 9:34 PM GMT on August 18, 2005

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Remains of TD 10 reorganizing

By: JeffMasters, 2:16 PM GMT on August 18, 2005

The remains of TD 10 continue to spin and track west-northwestward at 10-15 mph towards the northernmost Leeward Islands. Wind shear over the remains of TD 10 has continued to decrease, and is now near 10 knots. The reduced wind shear has allowed convection near the center of the storm to persist, and the satellite presentation has improved markedly today. Surface winds measured by theQuikscat satellite show peak velocities below tropical depression strength--20 knots north of the center. Global models indicate that shear may continue to decrease, allowing TD to reform today or Friday. A Hurricane Hunter flight is scheduled for 2pm EDT today to investigate.


If TD 10 does reform, it will continue to the west-northwest under the influence of a strong high pressure ridge over Bermuda. This track would bring the system north of Puerto Rico and near the Bahama Islands by early next week. Several of the global models forecast strong shearing winds to affect the system Sunday and Monday, and both the GFDL and GFS models dissipate the system by Monday. If the storm survives this shear, a strong trough forecast to move off the East Coast of the U.S. on Monday or Tuesday may induce a more northerly motion five days from now.

Elsewhere in the tropics, Tropical Storm Irene is racing towards Iceland and will no longer be a tropical storm by this evening. The rest of the tropics are quiet.

Dr. Jeff Masters

Updated: 2:18 PM GMT on August 18, 2005

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TD 10 poised to make a comeback

By: JeffMasters, 5:39 PM GMT on August 17, 2005

The remains of TD 10 have survived some pretty significant shearing winds, and the system continues to spin and track west-northwestward at 10 mph towards the northernmost Leeward Islands. Wind shear over the remains of TD 10 has decreased substantially over the past 24 hours--from 15-25 knots yesterday down to 10-20 knots today. The satellite presentation has improved considerably, with frequent bursts of deep convection firing up to the north and east of the center. However, the strong upper-level winds from the west to southwest that are shearing the system are not letting any of the convection that fires up persist. Surface winds measured by theQuikscat satellite show peak velocities below tropical depression strength--20-25 knots north of the center. Global models indicate that the system may enter a region of lower wind shear tonight or Thursday, which will likely allow the convection in the system to persist and the system to re-organize into Tropical Depression 10 again.


If TD 10 does reform, the current thinking of the track models is that the system will continue to the west-northwest under the influence of a strong high pressure ridge over Bermuda. This track would bring the system north of Puerto Rico and near the Bahama Islands by early next week. A strong trough is forecast to move off the East Coast of the U.S. on Monday, which may induce a more northwesterly motion five days from now. However, there may be some hostile winds and dry air for the storm to overcome on its trek towards the U.S.--both the GFDL and GFS models dissipate the system by Saturday. The SHIPS intensity model disagrees, strengthening the system into Tropical Storm Jose with 60 mph winds by Saturday.

Elsewhere in the tropics, Hurricane Irene has begun its gradual weakening as it encounters cooler waters and high wind shear. It will likely be downgraded to a tropical storm this evening as it races towards Greenland and becomes an extratropical storm tomorrow. The rest of the tropics are quiet.

Dr. Jeff Masters

Updated: 5:51 PM GMT on August 17, 2005

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Remains of TD 10 still spinning

By: JeffMasters, 4:33 PM GMT on August 16, 2005

As of 4pm EDT, the remains of TD 10 are still spinning, but the system is definitely suffering from strong west to southwesterly winds aloft that are shearing it. There is a low level circulation at about 17N 53W, and the shearing winds have ripped away a mid-level circulation that is about 100 miles to the east of the surface circulation. Some very isolated convection on the northeast and northwest sides of the surface circulation indicate that this system still has the potential to become a tropical depression. However, it is traversing the base of a large trough with some dry air and 20 - 25 knots of wind shear, so development today is unlikely. By Wednesday, the remains of TD 10 will have a better chance, as shear values will probably drop to the 10-20 knot range as it moves to the WNW between 10 and 15 mph and escapes the trough. I'd put the odds of it redeveloping into a tropical depression again at 50/50. The shear today may very well completly disrupt the circulation, making it an open wave that won't develop again.


Figure 1. Wind shear values over the remains of TD 10 were 20 - 25 knots at 8am EDT today (12 GMT), but are lower to the WNW.

Irene
Irene is looking the best it has ever looked, and latest satellite intensity estimates put it as a strong Category One hurricane with 90 mph sustained winds. Irene doesn't have much time left as a hurricane, though, as shearing winds and cold water will convert it to a regular extratropical storm by Thursday.

The Mid-Atlantic and Caribbean
The latest big cloud of African dust is now halfway between Africa and the Lesser Antilles Islands. Thunderstorm activity in the ITCZ area just south of this dust cloud is unimpressive today. Stong upper-level winds associated with a large upper-level low pressure system cover most of the Caribbean, and tropical development here is unlikely today.

Jeff Masters

Updated: 7:49 PM GMT on August 16, 2005

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Quiet tropics

By: JeffMasters, 5:50 PM GMT on August 15, 2005

Except for Irene, which has a nice satellite presentation with a clearly visible eye, the tropics are quiet today. Irene continues to steam out to sea, and is only a threat to shipping.

TD 10
The remains of TD 10 are near 15N 55W at noon EDT today, moving WNW at about 10 mph. One can see a clearly defined spin on satellite images, but there is no deep convection associated with the system. It is moving through the base of a huge trough that extends several thousand miles northeast to southwest across the central Atlantic, almost to the coast of South America. This trough is creating lots of wind shear over the remains of TD 10, keeping any re-development from happening. The GFS model indicates that the remains of TD 10 will take at least two days to traverse the trough and arrive in an area of lighter wind shear, which may happen by Wednesday night or Thursday as the system approaches Puerto Rico. By that time, it is questionable if there will be anything left of TD 10 to re-develop.

African Dust
The large cloud of African dust that moved off the coast yesterday is now nearly 1/3 of the way across the Atlantic. There is a fair bit of activity in the ITCZ south of this dust cloud, but anything that forms in the mid-Atlantic from the ITCZ this week will have a tough time overcoming the dry air associated with this dust cloud.

Caribbean
Strong upper-level westerly winds cover the Caribbean, and tropical development is unlikely here until these westerly winds subside. The GFS model is forecasting these winds to subside by mid-week, but the upper level winds across the Caribbean will still not look as favorable as they did in July when Dennis and Emily formed.

Jeff Masters

Updated: 5:52 PM GMT on August 15, 2005

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TD 10 dies, Irene moving out, more African dust

By: JeffMasters, 4:55 PM GMT on August 14, 2005

Irene
Irene has begun its turn, and is now moving out to sea on a NNE course. Recent satellite images show a decrease in convective clouds over her, and I expect the 2pm EDT Hurricane Hunter mission will find a weaker storm. Irene still has a chance to make it to hurricane status over the next day or so, but that would be a surprise.

TD 10
TD 10 got ripped apart by winds from a big trough that penetrated unusually far south for this time of year. The current wind shear forecast shows relatively high shear hanging around the vicinity of TD 10's remains, so regeneration of this system is unlikely over the next few days.

African Dust
Another big area of Saharan dust is moving off of the coast of Africa today between latitiudes 12N and 17N, and has pushed as far west as the Cape Verde Islands. The associated dry air will cause problems later in the week for any tropical storms that try to develop in the mid-Atlantic.

It looks like a quiet beginning of the week in the tropics!

Jeff Masters

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So long Irene, hello TD 10

By: JeffMasters, 4:35 PM GMT on August 13, 2005

Irene
The Hurricane Hunters just paid a visit to Irene, and found a substantially weaker tropical storm. The central pressure was just 1000 mb, and maximum flight-level winds were 40 mph on the west side of the storm. Satellite imagery shows a decrease in deep convection and warming of the cloud tops.

Last night's mission by NOAA's G-IV aircraft gathered a large high-resolution set of data surrounding Irene, and this data was used to initialize this morning's models. These models continue to show that Irene will turn to the north and northeast, missing the U.S. coast by a wide margin. This is a high-confidence forecast, due to the excellent data used to initialize the models and the continuity of the model forecasts from yesterday to today.

TD 10
An impressive low pressure area in the mid-Atlantic near 12N 44W appears to be developing into a tropical depression. Deep convection near the center has increased markedly in the past few hours, spiral banding has increased, and upper-level outflow has improved. Quikscat satellite winds show a circulation center near 12N 44W as of 10:43am EDT, with the strongest winds not contaminated by rain at 20 kt. Rain-contaminated winds as high as 35 kt exist north of the center, suggesting that the low may indeed be a tropical depression. NHC will probably start issuing advisories on TD 10 at 5pm EDT today.



The storm will continue to move to the northwest or west-northwest over the next few days, not posing a threat to any islands until perhaps Wednesday. The GFS model moves the storm northwest, bypassing the Caribbean islands, then tracks it on a more westerly course towards the U.S. late next week. The storm is headed into an area of very dry air to its northwest, which may inhibit its growth and intensification. However, water temperatures are warm (28 - 30C) ahead of it and vertical wind shear is light, so it is likely that it will attain at least tropical storm status. If so, it will be named Jose.

Jeff Masters

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TD 10?

By: JeffMasters, 11:14 PM GMT on August 12, 2005

The low pressure system in the mid-Atlantic continues to look impressive on IR satellite imagery tonight, with good deep convection near the center and an improving upper-level outflow. The latest Quikscat satellite winds show a well-defined surface circulation at 10.5N 45W, with maximum winds of 20 kt. The early model run tracks are divergent, with the BAM Medium model taking the system west then west-southwest, and the GFDL taking the system northwest. The GFDL solution can be discounted, given that the steering flow appears to be solidly west to west-northwest. The SHIPS intensity model brings the storm to near hurricane strength by Monday. Keep in mind that early computer models done before a tropical depression forms are very unreliable.

Updated: 11:16 PM GMT on August 12, 2005

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Irene and TD 10

By: JeffMasters, 8:17 PM GMT on August 12, 2005

Hello all, I'm back after a long vacation to Yellowstone--a great place to tune into nature and forget the hassles of civilization and your job and just live day-to-day in appreciation of the amazing beauty of a truly extraordinary place. I'll upload a few of my photos and share some reflections of my Yellowstone trip this weekend. It was great to forget about the tropics for a while, but I'm happy to be back to daily blogging as we enter the peak two-month stretch of what has been an already very long hurricane season.

Irene
Irene is almost a hurricane. The deep convection at the center of Irene has increased markedly the past few hours, and the first Hurricane Hunter mission into the storm at 2:15pm EDT found an 8 nm wide center with central pressure of 997 mb, and peak surface winds of 70 mph. Irene is over warm 29 - 30C waters, is in a low shear environment, and has good upper-level outflow in all quadrants except the southeast. Irene is sucking in some dry mid-level air from the southeast, which is inhibiting her development some. She is moving to the northwest, which will soon put her in an area of cooler sea surface temperatures (SSTs), left behind by Franklin and Harvey when they churned up these same waters earlier this month. These cooler SSTs should act to keep Irene from rapid intensification, and I expect she will attain Category 1 hurricane status but intensify no further the next two days. Once Irene moves closer to the U.S. coast, there is a narrow area of warmer SSTs along the Gulf Stream that may help intensify her, though. I won't speculate on Irene's track at this point, since steering currents will become weak and Irene may enter a period of erratic motion by Sunday. I'd estimate the chances of Irene getting her name retired by becoming a major hurricane and hitting the U.S. at about 5%. It's pretty rare for a storm this far north to develop into a major hurricane and hit the U.S. Too many things can go wrong--the storm can hit cool SSTs, experience high wind shear, or get recurved out to sea by a fast-moving trough.


Figure 1. Irene's motion to the northwest will soon put her in an area of cooler SSTs left behind by Franklin and Harvey. However, the tropical disturbance at 12N 43W was plenty of warm water in front of it as it moves WNW at 10-15 mph. Image credit: U.S. Navy.

TD 10?
The system that might have a greater chance of developing into a serious threat lies in the middle tropical Atlantic near 12N 43W. A closed low pressure with central pressure of 1012 mb has developed here from a tropical wave, and although convection has declined a bit this afternoon, this system has an excellent chance of becoming TD 10 this weekend. Buoys in the vicinity already report winds of 20-25 knots, and the low lies in an area of light wind shear and warm waters (28 - 29C), with plenty of warm water in front of it as it moves WNW at 10-15 mph. The low is far enough south to avoid entraining in some dry Saharan air that lies to the north.

Jeff Masters

Updated: 8:21 PM GMT on August 12, 2005

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World's Largest Weather Instrument

By: JeffMasters, 5:05 PM GMT on August 05, 2005

If you've driving the stretch of I-15 between Los Angeles and Las Vegas and get off at the Baker exit near Death Valley, you have the opportunity to see the ultimate tacky weather object--the world's tallest thermometer. Rising a full 134 feet above the dusty streets of Baker (population: 700),
the working thermometer is the brainchild of Baker resident Willis Herron, who spent $700,000 erecting the huge instrument. In an article in the June 2005 issue of the Bulletin of the American Meteorological Society, Willis says: "Awww, I know it's tacky. But I also know people won't be able to pass it more than four or five times without saying, 'What is that?'". And hopefully pull off the expressway to take a look--and buy a burger at the Mad Greek restaurant or a slice of strawberry pie at the original Bun Boy restaurant, now owned by Steve Carter, whom Herron sold the thermometer to in 2000.

The thermometer weighs 76,812 pounds, sports 4900 light bulbs, and is held together by 125 cubic yards of concrete--much of this added after 70-mph winds snapped the thermometer in half shortly after it was built in 1991. The 134 foot height is symbolic of the 134 degree maximum temperature recorded in Death Valley in 1913--the all-time record for North America.

Dr. Jeff Masters

Humor

Updated: 10:11 PM GMT on March 24, 2008

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Hurricane season 2005--why so active?

By: JeffMasters, 7:31 PM GMT on August 01, 2005

This will be my last blog entry until August 12; I'm vacationing far from the tropics (Yellowstone!) to appreciate some mountain weather.

Today's monthly summary of hurricane activity for July issued by the National Hurricane Center (NHC) states:

"The month of July saw unprecedented tropical cyclone activity in the Atlantic Basin...with the development of five named storms...Tropical Storm Cindy...Hurricane Dennis...Hurricane Emily... Tropical Storm Franklin...and Tropical Storm Gert. The previous record for named storms that formed in July was four. The two major hurricanes that developed during the month tied a record set in 1916. The July activity follows an unusually active month of June ...And the seven named storms that have formed thus far in 2005 represent a record level of activity for the first two months of the season."

Why has this hurricane season been so active? Part of the reason lies in a decades-long natural cycle in hurricane activity that in 1995 switched to a high-hurricane activity mode. Hurricane activity has been above normal since 1995, and will likely continue to be for the rest of this decade and the next.

Additionally, there are six key ingredients are necessary for tropical cyclone formation (you can read about these in full detail in the Tropical Cyclone FAQ. We'll focus on three of them in particular that have been highly conducive to tropical cyclone formation during this remarkable hurricane season of 2005.


Vertical Wind Shear
Hurricanes need low values of vertical wind shear between the surface and the upper atmosphere (the jet stream level, typically 35,000 - 40,000 feet high in the tropics). Vertical wind shear is the magnitude of wind change with height. High vertical wind shear can disrupt a tropical cyclone trying to form by literally tearing it apart. High wind shear also can weaken or destroy a healthy tropical cyclone by interfering with the organization of deep convection around the cyclone center. Typically, 20 knots (23 mph or 10 m/s) or less difference in wind speed between the surface and upper atmosphere is considered favorable for hurricanes. In June and July of 2005, wind shear values were 20 - 40% below normal for the Gulf of Mexico and Caribbean Sea, the primary genesis locations for the seven tropical cyclones that formed. Wind shear values this low are highly favorable for tropical cyclone formation (see plots below).



Figure 1. Average amount of vertical wind shear (in black) and observed wind shear (in blue) for 2005 for the western Caribbean. Credit: Colorado State University (NOAA/CIRA)



Figure 2. Average amount of vertical wind shear (in black) and observed wind shear (in blue) for 2005 for the eastern Caribbean. Credit: Colorado State University (NOAA/CIRA)

Sea Surface Temperatures
Hurricanes need ocean waters of at least 26.5C (80 F) through a depth of about 50 meters to form or maintain their strength. The warmer the water, the better, since a hurricane is a huge heat engine. Sea surface temperatures (SSTs) are at the highest levels ever observed in the Atlantic, for the 50 years we have records. As of July 31, typical tropical Atlantic SSTs were about 2F (1.1C) above normal.



Figure 3. The Sea Surface Temperature departure from normal (in degrees C) for July 31, 2005. A large area of above normal SSTs (yellows and light greens) covers virtually the entire North Atlantic Ocean. The cold wake of Hurricane Emily is still apparent between the Yucatan Peninsula and southern Texas. Credit: U.S. Navy.

Moist Air
Hurricanes need moist air in the mid-troposphere (5 km or 3 mi altitude). Dry air interferes with the development of the large thunderstorm complexes needed to get a tropical storm going. Until the last week of July, the air over the tropical Atlantic and Caribbean Sea has been very moist. Since then, several large dust storms have moved off of the coast of Africa, accompanied by copious amounts of dry air that has interfered with tropical storm formation. TOMS aerosol data shows a large area of dust covering the entire tropical eastern Atlantic today.

Is Global Warming to Blame?
How much, if any, of this year's activity is due to global warming? That's a difficult question to answer. The research published so far shows that global warming cannot be linked to an increase in the number of hurricanes. So, this season's exceptional number of storms is probably unrelated to global warming. However, there is considerable debate whether or not sea surface temperatures and hurricane intensity have been affected by global warming. It is possible that the remarkable intensity of the hurricanes seen so far this season can be partially blamed on global warming. However, much more research needs to be done on this subject before we can link global warming with hurricane intensity. I plan to write a detailed article on the subject later this season, after I've had time to read the new research linking hurricane intensity to global warming, due to be published in Nature magazine on Sunday, August 7.

Dr. Jeff Masters

Updated: 9:45 PM GMT on August 01, 2005

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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.