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Atlantic Tropical Weather Update 9/7/08

[Update 9:30P MDT]:

Hurricane Ike looks like he is about to make landfall on eastern Cuba’s north coast. As Brian points out however, Ike has wobbled a little bit on the approach to Cuba. A little movement to the northwest on satellite imagery was apparent earlier this afternoon. The NHC makes note of this, but doesn’t think it is a permanent change to his trajectory.

Ike has slightly weakened today, currently with sustained winds of 120mph, putting him in the middle of the Category 3 classification. Hurricane warnings are out for a number of the Bahamas still in Ike’s powerful northeastern quadrant, as well as for most of Cuba. Hurricane watches have been issued for western Cuba and the Florida Keys, which went under a mandatory evacuation order earlier today.

By tomorrow night, Ike should be about halfway across Cuba. By this time Tuesday night, Ike should be back over water, this time the Gulf of Mexico. The official intensity forecast calls for Ike to weaken to a Category 1 storm by this time Tuesday night. As Ike crosses over the warm Gulf waters and doesn’t have to fight off any shear he should reintensify on his way to the Gulf coast. The track forecast out tonight points toward a possible Texas landing. That’s based on an evaluation that the next synoptic-scale trough doesn’t reach far enough south to induce Ike to move in a more northerly direction.

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Atlantic Tropical Weather Update 9/6/08

[Update 10:45P MDT]:

Just a quick update tonight.  Hurricane Ike’s extended track continues to move further to the south and west and the large-scale flow develops.  Ike is now forecasted to cross over most of Florida from east to west, then emerge over the Gulf of Mexico on Tuesday afternoon as a much weaker hurricane.  Then, the official track takes Ike through the central Gulf.  Extrapolating the track takes Ike quite a bit further west than today’s earlier official forecasts.  This very dangerous storm is going to cause a lot of damage over Cuba for nearly three days, then is likely to threaten some portion of the northern Gulf coast.

***

[Update 3P MDT]:

Tropical Storm Hanna is racing across the eastern seaboard, Hurricane Ike has reintensified and is threatening the Bahamas and Cuba, and Tropical Depression Josephine has disorganized to a mere disturbance.

Tropical Storm Hanna’s center is located at 38.5N, 75.8W; has maximum sustained winds of 50mph; is moving quickly towards the NE @ 27mph!; and has a minimum pressure of 994mb. Lots of rain and those strong winds have affected the Carolinas, Virginia this morning and now is impacting Maryland, Pennsylvania and New Jersey. Later tonight and tomorrow morning, New York and the other northeastern states will see Hanna race through. Hanna looks likely to move back off into the Atlantic tomorrow before striking some Canadian provinces through Monday morning. As has been predicted for some time, Hanna will continue racing off towards the east across the Atlantic. By Thursday, Hanna should be between Ireland and Iceland in the north Atlantic. Her tropical characteristics should have been long exhausted by then and will resemble another mid-latitude storm like Gustav did after getting caught up in the westerlies.

Hurricane Ike has reintensified today as the shear affecting him the past day or so has finally been left behind as he moves toward the west across the Atlantic. His center is currently located at 21.4N, 69.7W; has maximum sustained winds back up to 135mph (making Ike a Category 4 storm again); is moving WSW @ 14mph; and his central pressure is back down to 949mb. Ike is currently moving south of the region where Hanna stalled, and thus could avoid the cooler waters she left behind. The WSW motion should continue over the next 24-36 hours as the ridge to Ike’s north continues to direct him.

Which brings us to Monday morning. Hurricane Ike is now forecasted to make landfall along Cuba’s north coast as a Category 4 storm. If this comes to pass, and Ike moves across Cuba as the most recent official forecast indicates, Hurricane Cuba will weaken back to a Category 1 storm before reemerging over the Gulf of Mexico sometime Tuesday afternoon. The majority of the model solutions keep Ike on the northern half of Cuba during his transit. One outlier moves Ike directly across southern Cuba and places Ike in the northern Caribbean Sea in 36 hours. That outlier has done a pretty good job in recent days in correctly forecasting Ike’s continued WSW motion. So it’s not out of the question that Ike could indeed take this path.

The official track forecast places Ike on a direct path toward the northern Gulf coast between Tuesday afternoon and Thursday afternoon. The official intensity forecast calls for Ike to restrengthen to Category 3 strength by Thursday afternoon. The Gulf is still plenty warm and shear isn’t expected to be much of a problem during the forecast period. If the official forecast ends up being correct, extrapolating Ike’s motion from Thursday afternoon places it at the Gulf coast next Saturday. Ike’s potential landfall point is way too far out in the future to identify at this time, so Gulf coast residents need to keep appraised of Ike’s progress. Many residents could unfortunately be required to evacuate again. I hope Gustav’s relative lack of impact (compared to the 2005 storms) on the Gulf coast hasn’t placed too strong a sense of invincibility on the parts of Gulf coast residents. While we don’t know where Ike will land yet, he hold too much potential for destruction to ignore.

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Atlantic Tropical Weather Update 9/5/08

[Update 12P MDT]:

For informational purposes: Tropical Storm Hanna is approaching Category 1 hurricane strength.  It means little except for official designations and statistics.  The reality is Hanna’s sustained wind speed have increased by 5mph to 70mph.  The difference at landfall between a strong tropical storm and a weak Category 1 hurricane is negligible.  The outer rain band of Hanna is now making its way across the Carolinas.

New model runs that started this morning became available.  I’m not sure if it’s good or bad news for the U.S.  Instead of making landfall along the southern Florida coast, Hurricane Ike’s projected path has flattened out somewhat and it now appears more likely that he will brush by either Cuba or Florida Tuesday on his way into the Gulf of Mexico.  The official track forecast splits the difference and moves Ike through the Florida Strait as a Category 4 storm.  Once in the Gulf, Ike could weaken to a Category 3 storm as he contends with cooler waters.  If the ridge guiding Ike’s motion remains strong through the weekend and into early next week, Ike could wait to turn towards the northwest and north until he’s in the eastern Gulf.

***

A couple of important changes are available to discuss this morning with regard to the storms currently in the Atlantic.

The first storm to talk about is Tropical Storm Hanna. Her vitals as of this morning:

Center located at 28.2N, 78.2W; maximum sustained winds of 65mph; moving NW @ 18mph; minimum pressure of 980mb. So T.S. Hanna’s pressure has dropped slightly overnight. It won’t be enough to cause the storm to intensify to hurricane status, due to the dry air Hanna continues to entrain. Her track forecast has shifted overnight. Instead of making landfall over the coast of North Carolina, Hanna is now expected to come ashore over near the North Carolina/South Carolina border again either very late tonight or very early tomorrow morning as a tropical storm.

As a result, the official track forecast moves Hanna a little to the left of the official track presented yesterday. She should pass south of Washington D.C., but is also likely to impact New York City and Boston by Sunday morning, albeit as a weaker and very fast moving system. Surge impacts will remain as a threat to coastal areas. Up to 5″ of rain is expected over a wide area of coastal locations from South Carolina to Massachusetts.

Hurricane Ike has weakened slightly overnight, as was expected. Here are his vitals this morning:

Center located at 23.7N, 61.0W; maximum sustained winds of 125mph; moving W @ 14mph; minimum pressure of 945mb.

Ike’s northwestward motion, again as correctly forecasted, has shifted to a more due westerly motion. The 125mph winds mean Hurricane Ike is again a Category 3 storm. In the next 24 hours, Ike should begin moving more toward the WSW or SW as the ridge to his north strengthens. By this time tomorrow, Ike is officially forecasted to weaken to a Category 2 storm until he finally leaves the northeasterly shear behind. During the day on Saturday, however, Ike is forecasted to regain his Category 3 status due to 29C sea surface temperatures and a weak shear environment.

Ike’s motion after Saturday night remain pretty uncertain. A lot depends on how strong the ridge to his north is and where it sets up. By Sunday morning, Ike is still expected to be bearing down on the southeastern Bahamas. Sometime during Sunday afternoon or night, Ike’s official forecast indicates a curve back to the west, then the west-northwest. Further intensification is identified during this time period, and by Monday morning, Ike could again be a Category 4 storm racing through the central Bahamas. The curvature to his track could very slowly increase toward the north in the 4-5 day range. Ike is currently forecasted to finish moving through the Bahamas by Tuesday morning and could threaten south Florida Tuesday night or very early Wednesday morning. Compared to last nights model runs, Ike’s track has shifted southward across Florida. Last night, Miami looked like it was going to be the site of landfall. This morning, it looks like the southern tip of Florida could be that site, which would unfortunately put Miami on the right (more powerful) side of a major hurricane.

I’ll say again that the exact location of the storm in the 4-5 day range is incredibly questionable. But two consecutive model envelopes have put Florida in Ike’s path at the end of the period. However, Ike could just as easily make landfall over Cuba, as two models are showing, or could turn toward the north before striking Florida, as another model shows. As we go through the weekend, Ike’s potential U.S. impacts will become more clear.

Tropical Storm Josephine has battled some southerly shear overnight and it shows this morning.  Her convection is now displaced from the center and she has weakened.  Her vitals:

Center located at 15.8N, 34.8W; maximum sustained winds of 45mph; moving WNW @ 8mph.

T.S. Josephine will continue moving generally toward the NW over the 5 day forecast period.  The next two days will prove critical for Josephine’s existence.  If she can survive the shear currently present, she could stay alive.  If she doesn’t, she will be reduced to a disturbance that will have to wait to move further west before potential redevelopment.


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Atlantic Tropical Weather Update 9/4/08

[Update 10:30P MDT]:

There was nothing terribly critical with the NHC’s 11P update.

Tropcial Storm Hanna looks more and more certain to make landfall along the North Carolina coast as a Tropical Storm overnight Friday into Saturday.

The last part of Hurricane Ike‘s forecast (Tuesday night) hints at a possible southern Florida landfall, possibly as a major hurricane.  I don’t think the intensity models have properly accounted for these conditions.  Ike should pass over these cooler waters after he stops battling the northeasterly wind shear he’s currently facing.  As time has gone by, Ike’s official track at the end of the period hasn’t curved back toward the NW or N.  This means there is the possibility that Ike could roll over Florida and re-emerge over the Gulf of Mexico after Tuesday.  The suite of model track solutions still shows large variability by the third day.  One model continues to show a glancing landfall off Cuba’s north coast.  One shows Ike moving through the Florida Strait after running over the Bahamas.  Three keep Ike out in the Atlantic.  And one shows Ike moving nearly due west over the next five days.  Some fairly substantial discrepancies will have to be ironed out, and this should happen in the next day or two.

Tropical Storm Josephine has slowly started moving slightly north of due west, with no chance of affecting any kind of land within the next week.  Here are all the storms’ vitals:

Tropical Strom Hanna’s center is located at 26.5N, 76.3W; has maximum sustained winds of 65mph; is moving NW @ 14mph; and has a minimum pressure of 987mb.

Hurricane Ike’s center is located at 23.6N, 59.5W; still has maximum sustained winds of 135mph; is moving W @ 14mph; and has a minimum pressure of 945mb.

Tropical Storm Josephine’s center is located at 15.1N, 33.8W; has maximum sustained winds of 45mph; is moving WNW @ 10mph; and has a minimum pressure of 1002mb.

***

Earlier update and original post below the fold.

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Atlantic Tropical Weather Update 9/3/08

[Update 9:30P MDT]:

One major update among the range of updated information is available tonight. Forecasts are notoriously difficult for hurricanes. Ike exploded in the past eight hours. More details on him below. As usual, the updates are alphabetical.

Tropical Depression Gustav remains stuck over eastern Oklahoma/western Arkansas. There hasn’t been any change to his future.

Tropical Storm Hanna has maintained herself quite nicely in the face of very unfavorable environmental conditions. Her vitals include: center located at 23.2N, 72.1W; maximum sustained winds of 65mph; moving NNW @ 12mph; minimum pressure of 989mb. So Hanna has begun moving just west of north. Her path should move a little more west in the next day and continue thereafter.

There is some distance between Hanna and the Bahama Islands. They’re not experiencing drenching rains so much as they’re seeing winds just under tropical storm strength that get gusty at times and the surf is getting kicked up a bit. The official intensity forecast calls for Hanna to reintensify to hurricane strength by Friday morning. As you’ll read below, her intensity could jump up unexpectedly as she moves over warmer, but shallower, waters on her way toward the U.S. By Friday night, Hanna should be located off the coast of South Carolina. The next day’s worth of motion and investigation will really affect her exact path and potential landfall sites.

Somewhere near this same time, she should once again shift her trajectory back toward the north, then the northeast. This could keep her from making landfall over South Carolina and instead do so over eastern North Carolina. The official track forecast still keeps Hanna close to either the ocean or the shore, depending upon the eventual track. Regardless, she looks likely to affect a lot of square miles as she makes her way northeast from North Carolina, possibly getting up toward New Jersey by Saturday night as a Tropical Storm.

Hanna should continue to make her way around the periphery of the high pressure system responsible for her steering. She could affect the remainder of the New England region and southeastern Canada before she moves away from land around 50N by next Monday.

Okay – the big news of the day. Tropical Storm Ike became Hurricane Ike earlier this afternoon. Since then, his intensity has simply exploded. Hurricane Ike is now the third major hurricane of the 2008 Atlantic season. In fact, Ike blew through Categories 2 and 3. He is now a Category 4 storm! Here are his vitals as of tonight:

Center located at 22.1N, 54.1W; maximum sustained winds of 135mph!; moving WNW @ 17mph; minimum pressure of 948mb!! I’ll look for the official measurement, but it seems to me like Ike’s pressure dropped 36mb in about 6 hours. That is incredible intensification and is indicative of the massive heat content available in the Atlantic Ocean. Beneficial environmental conditions haven’t hurt him any, obviously. Ike still has a very small, tight eye on satellite imagery. Additional intensification is possible in the next 12 hours, but any further changes will be dependent on eye-wall replacement cycles.

In between 12 and 72 hours (.5 – 3 days), Hurricane Ike will experience northeasterly shear as the upper level low that was affecting Hanna makes its way eastward across the Atlantic. The official intensity forecast calls for slight weakening during that time period. Ike’s official track forecast calls for him to continue his general northwestward motion over the next 24-36 hours. Starting Friday morning, Ike should curve back toward the southwest as a ridge restrengthens after the low passes through the region. Ike should pass well north of Puerto Rico Friday night through Saturday morning. Saturday night could see Ike north of the Dominican Republic, again at a good distance.

The ridge that should push Ike southward in the 2-4 day time period should shift around late day 4 and then in day 5 as well. Similar to Hanna’s track around the ridge, Ike should move around the southwestern periphery of the same feature. That means Ike could move through the southern portion of the Bahamas (not much change from earlier) on his way through the central Islands by the time Monday night rolls around. During the 4-5 day time period, the official forecast calls for Ike to reintensify back to a Category 4 storm.

So starting at the beginning of next week, things are going to get exciting for the U.S. Will Ike make landfall over Cuba? Will he make landfall over the U.S.? Will he move through the Florida strait into the Gulf of Mexico? If he makes landfall over the U.S., where will that occur? Will he follow Hanna’s path around the edge of the ridge and possibly miss land altogether? Also of importance: Hanna has stirred up the Atlantic around the Bahamas for quite some time now. Ike could encounter much cooler surface waters than Hanna had available to her. Will that work to weaken Ike somewhat or quite a bit? There are lots of questions. We’ll just have to keep watching.

Tropical Storm Josephine’s future hasn’t changed since this afternoon. Let’s start with her current vitals: center located at 13.9N, 30.7W; maximum sustained winds of 50mph; moving W @ 12mph; minimum pressure of 1000mb. Josephine is still forecasted to begin moving more north of west in the next couple of days, albeit a little more slowly than her current speed. She is still forecasted to weaken to Tropical Depression status by Saturday, if not sooner.

***

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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.

***

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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