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Atlantic Tropical Weather Update 9/2/08

Lots of changes in the Atlantic basin since yesterday. Gustav has continued to weaken, from Hurricane strength down through Tropical Storm and is a Tropical Depression this morning over the TX/LA border. Hanna strengthened to a Hurricane, then weakened back to a Tropical Storm. Then, Tropical Depression Nine formed between the Leeward Islands and the Cape Verde Islands. Then T.D. 9 strengthened and was named Tropical Storm Ike. Then T.D. 10 organized from Invest-99 between the Cape Verde Islands and Africa. Development didn’t stop there: T.D. 10 strengthened and Tropical Storm Josephine formed. That’s all in less than 18 hours. The Atlantic basin is pretty much full of storms.

Let’s start with Tropical Depression Gustav’s vitals: center located at 31.7N, 93.4W; maximum sustained winds of 35mph; moving NW @ 10mph; minimum pressure of 985mb. Gustav’s main threat now is lots of rain that could cause flooding. A secondary threat remains tornadoes. Gustav is forecasted to curve toward the northeast over the next five days, but the distance covered shouldn’t be too great. He should move into northeast Texas, southeast Oklahoma, then western Arkansas by early Friday morning.

Yesterday, Hanna was a Category 1 hurricane. She stalled off the eastern side of the Bahamas as her steering currents weakened. She followed by weakening back to a Tropical Storm, where she remains this morning. Steering has picked back up this morning and Hanna is back on the move. Her vitals: center located at 21.0N, 73.5W; maximum sustained winds of 70mph; moving WSW @ 5mph; minimum pressure of 987mb.

Hanna is forecasted to begin moving back toward the northwest later today, then continue that general movement through the next few days. She is also forecasted to regain hurricane strength by tomorrow afternoon as she moves through the Bahamas. From Thursday to Friday, Hanna should be moving by the east coast of Florida, but no landfall is expected on that state. Sometime during the day on Friday, Hanna is expected to come ashore along the Georgia border, an event that is very rare due to the orientation of the coast and the climatological movement of storms along the eastern seaboard. By the time Hanna reaches the Georgia/South Carolina border, the model track solutions diverge. Some show her moving into West Virginia before curving toward the northeast. Some show her moving through the Carolinas before turning northeast and along the east coast. That’s some time away, so the details will have to wait.

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Atlantic Tropical Weather Update 9/1/08

[Update 11:45A MDT]:

Tropical Storm Hanna has strengthened to a Category 1 hurricane.  An Air Force reconnaisance plane investigating the storm found winds strong enough at flight level to support the decision to characterize the storm as a hurricane.  Her updated vitals:

Center located at 22.4N, 72.6W; maximum sustained winds of 75mph (just over category 1 threshold); moving WSW @ 4mph; minimum pressure of 985mb (9mb less than the previous update).  The lowering pressure should allow Hanna to continue to slowly strengthen into a moderate Category 1 hurricane.  The intensity forecast has been updated to reflect this status in the short term.  At this time, the models are not indicating a strengthening to Category 2 strength.

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Hurricane Gustav made landfall within the past hour or two (currently 9:30A MDT) on Louisiana’s southern coast, near Cocodrie, Louisiana, which is south of Houma, Louisiana.  He made landfall as a strong Category 2 storm.  Reports are coming in that levees in New Orleans, to Cocodrie’s north, are being overtopped by the storm surge and waves.  I’m sure additional reports will come in throughout the day.  His vitals:

Center located near 29.2N, 90.8W; maximum sustained winds of 110mph; moving NW @ 14mph; minimum pressure of 955mb.  Those sustained winds are the threshold between a Category 2 and Category 3 storm.

Gustav’s future looks radically different than it did last night in the long-term.  He is expected to slow down over the next day or so as he moves across Louisiana and eastern Texas, weakening the entire way.  Between Tuesday and Wednesday, Gustav should turn toward the north (instead of the south, as was indicated last night) and his forward speed should continue to decrease.  Friday could see Gustav still moving slowly to the north into Oklahoma.  By the end of the week, another synoptic trough should be moving across the United States.  That trough right now looks less robust than the one currently making its way from west to east, but Gustav’s remnants should get caught up in the larger scale flow and advected out of the Texas/Oklahoma region.

So beyond additional levee failures in the New Orleans area, the main threat from Gustav will gradually shift toward flooding as he stalls and rain falls over the same area for many hours.

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Atlantic Tropical Weather Update 8/31/08

Hurricane Gustav came off the western portion of Cuba last night as a Category 4 hurricane and maintained that strength while continuing northwest. It appears that interaction with the landmass caused Gustav to weaken slightly since then. As of this morning, Gustav has weakened to a still very dangerous Category 3 storm. Starting with his vitals:

Center located at 25.3N, 86.0W; maximum sustained winds of 120mph; moving NW @ 17mph; minimum pressure of 960mb, about 20mb higher than the last time I looked near 12A MDT.

Gustav’s impressive satellite signature yesterday has degraded so far today. There is no longer a clear eye portion of the storm. Also, the convection and outflow isn’t as symmetric as it was late last night. The strongest convection looks to be confined to the southwestern portion of the storm.

What’s next for Gustav? He is still heading straight for the northern Gulf coast. As the hours tick away, his most likely landfall site is being forecasted with more confidence. Somewhat surprisingly, that location remains southern Louisiana, perhaps a bit to the east of where I thought he would strike the past two days. It looks more likely that the site will be close to New Iberia, LA. Models are forecasting a slight re-increase of strength back to Category 4 status while Gustav is still over the Gulf. Prior to landfall, his strength should begin slowly decreasing and continue to do so after landfall. Landfall is expected to occur during the day on Monday, currently sometime after 8A CDT. Due to the influence of the ridge of high pressure over the eastern U.S., his forward speed should decrease and the possibility of him stalling over Louisiana or Texas remains high.

Storm surge from Gustav is expected all along the northern Gulf coast. A maximum of 12-15 feet of storm surge is possible near the mouth of the Mississippi River and east of New Orleans. The height of surge east and west of this region decreases from there, with up to 12 feet forecasted a good distance away from the River, out toward Abbeville to the west and Biloxi, MS to the east. Combined with rain from convective bands, flooding then becomes a major risk from this storm across a very wide area. The initial storm surge and winds will weaken infrastructure and a stalled storm will only add to the challenges facing those who live and those who will help clean up in the region. Based on Gustav’s current projected path and expected effects, I don’t think the situation looks good for the New Orleans area. Damage from wind and flooding should occur once again. It is obviously too early to tell just how extensive that damage will be, which means that officials along the Gulf coast should be congratulated on acting promptly to move residents away from the area.

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Atlantic Tropical Weather Update 8/30/08

Hurricane Gustav has passed over the deep, very warm waters between Jamaica and Cuba. In doing so, he rapidly strengthened overnight from a Category 1 hurricane to a Category 3 storm this morning, making him the second major hurricane of the 2008 Atlantic season. Bertha was the other major hurricane, but remained well out to sea her entire lifetime. Gustav’s vitals as of 8:30A MDT:

Center located at 20.8N, 81.6W; maximum sustained winds of 120mph; moving NW @ 11mph; minimum pressure is down all the way to 955mb, which is 33mb less than the reading yesterday. That is quite the rapid intensification. In fact, since the pressure has continued to drop steadily this morning, expect Gustav to strengthen even further today before eye-wall replacement cycles, a slightly cooler pool of water and the island of Cuba work to weaken him somewhat.

Gustav should still make landfall over Cuba later tonight as a Category 3 storm. A solid eye-wall did develop overnight. Gustav has an impressive outflowing cloud shield. Hurricane force winds were found on the northeast quadrant on an earlier hurricane hunter flight. As they get going again today, a clearer picture of where they are found will be available. Tropical Storm force winds extend all the way to Cuba, a decent distance from the storm’s center. Western Cuba is under a Hurricane Warning today.

Model solutions have come to closer agreement as of today. There is a much narrower band encompassing the solutions through the Gulf of Mexico, which Gustav will enter 12-24 hours from now. While Gustav crosses the central Gulf, he is still forecasted to overrun the Gulf Loop Current’s warmest stretch. The model intensity forecast has him strengthening to a Category 4 hurricane during this time, but I wouldn’t be surprised to see him go all the way to a Category 5. After that, there is very good agreement about the likely landfall location: the middle of the Louisiana coast. He should make landfall between Morgan City and Lake Charles. The timing is coming into better focus. The suite of models are also in pretty good agreement that the landfall could occur Monday night.

Post-landfall may not offer a better story than during landfall. Due to the strength and orientation of the ridge that will remain over the eastern U.S., Gustav could stall over Louisiana. We’ve already dealt with one slow moving storm: Fay dropped incredible amounts of rainfall over Florida just a week or so ago. Gustav shouldn’t dump quite that much rain, but the longer he lingers, the more flooding far inland will be a concern. New Orleans residents are smartly already evacuating. I’m sure other Gulf coast residents will follow similar measures throughout the next two days.

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Atlantic Tropical Weather Update 7/24/08

Dolly made landfall yesterday as a Category 2 hurricane. Since then, she’s produced a good deal of rain, and a few tornadoes. She’s currently nearing the Texas-Mexico border as she continues to move inland.  Her vitals:

27.5N, 99.3W; moving WNW @ 9mph; maximum sustained winds of 45mph; minimum pressure of 992mb.

The models are in agreement with the outlier yesterday: a continued WNW/NW movement, more or less hugging the Texas-Mexico border.  By the time the storm system gets to the TX-NM border, a more NWN movement is likely.  Finally, the system should get caught up in the mid-latitude flow and move northerly, then north-easterly.

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Tropical Storm Cristobal is no more.  He’s been caught up in the extratropics.

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Invest-97 hasn’t changed much since yesterday.  Dry air has stalled development of what was a very impressive wave that came off the coast of Africa.  Model solutions from yesterday afternoon don’t look much different than they did the day before.  The system is expected to slowly make its way west across the Atlantic.  At some point, a turn toward the NW could occur.  At some point, intensification could occur.  The mid-Atlantic ridge’s strength and location will determine where the system goes.  The location of dry air around the storm will determine if it gets a chance to strengthen.

Another cluster of convection has emerged off Africa’s coast.  This system is located about 10N, or 5S further than Invest-97.  It hasn’t been classified as an area of interest by the NHC yet.


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Atlantic Tropical Weather Update 7/23/08

Hurricane Dolly is the big news of the day again. Hurricane Dolly strengthened since last night to a Category 2 hurricane. Her vitals:

26.0N, 97.0W; maximum sustained winds of 100mph (gusts to 120mph); moving NW @ 6mph (she finally slowed down over-night); minimum pressure of 964mb.

Dolly could strengthen a little more before making landfall, but likely won’t make Category 3 status. We’ll see though. Her eye is currently just off the Texas coast, with massive rain bands having moved over Texas all night dropping a lot of rain. I haven’t seen anything official, but I would guess the eye will make landfall within the next couple of hours, to the north-east of Brownsville (which means her track shifted slightly to the north since yesterday).

Her future movement is likely to take her further inland, across southern Texas and over Mexico. Only one model solution takes her to the NW, tracking close to the Texas-Mexico border before moving over New Mexico. She should keep hurricane-force winds a ways into Texas before weakening to a Tropical Storm tomorrow morning and a Tropical Depression tomorrow night.

One thing that frustrates me is the continued lack of preparedness, despite massive disasters like Hurricane Katrina in 2005. Every time a storm makes US landfall, we hear reports of people rushing to stores to stock up on materials. That shouldn’t be happening still.

[Update 2:00P MDT]:

Dolly has made landfall.  Her winds have decreased slightly to 95mph sustained, weakening her back to Category 1 strength.  A few tornadoes have been reported.  As I talked about above, the main problem will be with rain: 8-12 inches in many places, with as much as 20 inches in more localized regions.  Flash floods are a major concern; a couple flash flood warnings have already been issued.

***

Onto Tropical Storm Cristobal, which continues to churn away in the northern Atlantic. He’s at 44.7N, 55.9W; moving ENE @ 31mph; maximum sustained winds of 45 mph; minimum pressure of 1003mb.

He’s expected to turn toward the SE later today. The models are pretty consistent in forecasting a track between 40N and 45N across the Atlantic on its way to Europe. He should be downgraded to a Tropical Depression sometime tomorrow.

***

Invest-97 hasn’t changed much since yesterday. It’s location is west of the Cape Verde islands now. The environmental conditions aren’t great for development, thus the NHC has given it <20% chance of organizing into a Tropical Depression. Model solutions from today don’t seem to be available. I’ll keep watching it’s progress.


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Atlantic Tropical Weather Update 7/22/08

Today, Tropical Storm Dolly remains the top news. Let’s start with her vitals:

24.0N, 94.5W; moving NW @ 11mph; maximum sustained winds of 70mph; minimum pressure of 991mb.

Just a little more sustained wind speed and Dolly will become a Category 1 hurricane. In fact, she is expected to do so by sundown tonight. She is moving over very warm Gulf of Mexico waters and has upper-air support in the form of a 200mb anticyclone, which aids her outflow of rising air.

The biggest change from yesterday is with her forecasted track. The two models indicating a more southerly landfall appear now to have been correct. Thus, the eyewall should come over land very near the Texas-Mexico border, right around Brownsville. I’ll repeat what I wrote yesterday: more importantly, hurricane force and tropical storm force winds will extend for many miles away from the eyewall. Those are the features that folks need to pay attention to as Dolly comes ashore. She should do so as a Category 1, then weaken back to Tropical Storm strength for about a day before degrading to a Tropical Depression again. Her weakening won’t reduce her potential lethality as torrential rains will be the main characteristic of the storm as she moves across Mexico. The extended track is very uncertain: some model solutions show her moving across all of Mexico, while one turns her northwestward and over western Texas and southeastern New Mexico in five plus days.

Aesthetically, Dolly looks good on satellite imagery. A clear eye is forming, and has been measured to be about 20nm across, which is pretty big. Concentric rings of convective clouds are swirling into the middle of the storm.

[Update 3:20P MDT]:

Dolly has strengthened to a Category 1 hurricane. Hurricane hunter aircraft data measured winds at flight level than when extrapolated to the surface, pass the threshold for hurricane strength. Additionally, Dvorak estimates confirm Dolly’s strength. Her updated vitals:

24.6N, 95.3W; maximum surface winds of 75mph; minimum surface pressure of 985.0mb.

Some further strengthening is expected before Dolly makes official landfall, probably as a strong Category 1 storm. That landfall is still expected to occur somewhere near the Texas-Mexico border, near Brownsville, TX sometime Wednesday afternoon. Thereafter, weakening back to Tropical Storm status should occur ~24 hours after landfall and to Tropical Depression statues ~24 hours after that. Heavy rains and strong winds will be the main problems associated with this storm.

More after the fold.

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