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Atlantic Tropical Weather Update 9/12/08

[Update 12:00A MDT]:

Hurricane Ike is making landfall at Galveston.  The seawall there is expected to have been topped and the city flooded.  Hurricane Ike’s second spiral band is now passing through Houston, 50 miles to Galveston’s northwest.  A heavy burst of convection has recently generated to the north of Ike’s center as his bands begin to rapidly spiral toward the surface low.  Ike’s eye was measured at one point to be an astounding 49 miles across.  Beyond being numerically impressive, an eye that size presents a real hazard to Gulf coast residents.  After the leading edge passes over one point, it could be one to three hours before the other side passes over the same point with hurricane force winds.

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[Update 9:45P MDT]:

We’re down to the final few hours prior to Hurricane Ike’s landfall. There have been some important, last-hour changes to Ike that I’ll discuss below. Let’s start with his vitals tonight:

Center located at 28.6N, 94.4W; maximum sustained surface winds of 110mph (1mph less than Category 3 strength); moving NW @ 12mph; minimum surface pressure of 952mb (still very low for a Category 2 storm).

The center of Hurricane Ike is about 50 miles from shore at this time. As he has approached the coast, radar imagery has helped show that Ike’s eye is finally becoming more pronounced. Recent radar loops have shown small, mesoscale vortices traveling around the interior of Ike’s eye-wall. Seeing them on satellite is one thing; seeing them on radar is pretty impressive.

The NHC is also pointing out that winds above the surface are reaching Category 4 strength: at levels a few hundred feet above the surface, winds are screaming at 130mph. A few things should be noted here: Ike’s official category is based off surface wind speeds, surface winds are very typically slower than those found just a short distance further up due to friction, and those higher wind speeds aloft will cause a lot of damage to high-rises in the Houston area, which is already in the hurricane force wind region.

At this point, it looks like Ike’s center will pass directly over Galveston and just to the east of Houston proper. Ike’s wind field remains very, very impressive in scope. Most of Louisiana and a good portion of southeastern Texas is within Ike’s tropical storm force wind field. Areas between Freeport, TX and Lake Charles, LA are in the hurricane force wind field. A huge region to the center’s east and south are still experiencing hurricane and tropical storm force winds.

That wind field has already caused a 10 foot rise in water along the Gulf coast. One thing working against Galveston and Houston is high tide, which will occur at about 1A CDT, just as Ike is coming ashore. The total storm surge numbers will be impressive to note post-event.

One silver lining to this storm is the current relative lack of convection to the north of Ike’s center. A large convective band is located to the center’s south, but a distinct break between bands can be seen just north of the center. Whether that feature remains in place as Ike makes landfall will be seen. [Update 10:15P]: As I’ve updated this post, the lack of convection north of Ike’s center has slowly gone away as his eye continues to organize. The convective band forming where there was very little just an hour ago isn’t very intense yet, but it looks much more like a textbook hurricane eye-wall.

Ike should continue along his current trajectory until the center is located to Houston’s north, at which time he should begin curving around the strong ridge sitting over the eastern U.S. The upper-level trough that is currently moving across the central U.S. will weaken the ridge in the area of Ike’s path, which will help steer him in a more northerly direction. By the time Ike’s center passes east of Dallas, TX, he should begin moving northeasterly. By Sunday night, Ike should be located over Indiana, on his way to being absorbed and caught up in the westerlies.

Over 1 million people evacuated ahead of Ike’s landfall. Some few hundred thousand refused evacuation orders in the face of the NWS’s warning that they could face imminent death. Sen. Cornyn (R-TX) identified Hurricane Gustav’s relatively weak effects and storm complacency. I’ve got a different opinion: Republicans have spent years convincing Americans that government can’t work. Hurricane Katrina provided stark imagery of how dangerous it is when government doesn’t work. Now Sen. Cornyn expects Texans to acknowledge government authority and advice when the cities of his state face catastrophe? It’s Hurricane Gustav’s fault? How petty and immoral of you, Senator.

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Atlantic Tropical Weather Update 9/11/08

[Update 10P MDT]:

No major changes to Hurricane Ike throughout the day. His pressure remains very low for a Category 2 storm. Concentric wind maxima continue to battle for dominance within the storm, but the inner wall is starting to erode. Ike continues to close in on the Galveston area, with landfall likely to occur in just over 24 hours. Ike’s vitals:

Center located at 26.3N, 90.4W; maximum sustained winds of 100mph; moving WNW @ 12mph; minimum pressure of 950mb.

Hurricane Ike’s official path has been shifted slightly to the right of the previous track. This brings Ike a little closer to the Galveston Bay area Friday night and Saturday morning, but keeps him just to the south of Galveston as he comes roaring ashore. For the first time, Hurricane Ike’s intensity forecast keeps him as a strong Category 2 until landfall. This may not be a blessing for Texas residents as one of the reasons for his lack of intensification is the very wide wind field of hurricane force winds and the even wider field of tropical storm force winds. For instance, Houma, Louisiana is within an envelope experiencing tropical storm force winds and it is over 200 miles to the north of Ike’s center.

Thousands of residents have been evacuated from Galveston, TX and low-lying areas in and around Houston, TX. Refining facilities have been temporarily shut down and will likely remain so for about four days. At this point in time, Hurricane Ike’s cloud shield covers nearly all of the Gulf of Mexico, no small feat. If his center were further west, the shield would easily extend from Texas to Florida. And he’s only a Category 2 storm.

Elsewhere in the recently quiet Atlantic, there is an area 350 miles east of the southern Bahama Islands that the NHC is monitoring for development. This area includes a portion of the remnants of Tropical Storm Josephine, which was sheared apart in the eastern Atlantic. This disturbance has been identified as Invest-91.

I’ve seen two model runs that take the disturbance through the Bahamas and off the coast of Florida in a few days time. They also show the disturbance continuing to develop, but are unclear whether it would be organized enough to become a Tropical Depression. Model ensembles indicate the the disturbance is likely to move over Cuba within the next four days or so. At this time, convection is confined and there isn’t any indication of circulation around a central low. The disturbance is moving over waters that Hanna and Ike moved over in the past one to two weeks. As such, conditions aren’t very amenable right now for development.

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Atlantic Tropical Weather Update 9/10/08

[Update 5:30P MDT]:

There is an interesting change to Hurricane Ike’s intensity forecast.  As of this early evening’s information, Ike could intensify through the afternoon on Friday (2 days away), up to a Category 4 storm.  Now, that could mean the models are forecasting maximum sustained winds just over the Cat3/Cat4 threshold.  Looking at the text guidance from the NHC, this looks to be the case.  Whether Ike can attain that strength or how long it can be maintained if he does reach it is something that remains to be seen.  Hurricane Ike should reach major hurricane status, Category 3, tomorrow afternoon.

The NHC has been writing about the extent of hurricane force and tropical storm force winds from the center.  That extent is pretty large for a storm, so it won’t matter too much where Ike makes landfall.  Of more importance is the wide area around that location that will feel the effects of a major hurricane.

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[Update 12:15P MDT]:

Ike’s reintensification to a Category 2 storm occurred in less than 8 hours.  Since this morning, his sustained winds have increased by 15mph.  Further intensification is expected, though it could be non-continuous as eye-wall replacements continue.  Here are Ike’s vitals as of this afternoon:

Center located at 24.2N, 85.8W; maximum sustained winds of 100mph; moving NW @ 8mph; minimum pressure of 958mb.  Ike looks pretty good on satellite imagery.  There is some dry air to his west that he is ingesting, and that could have some small affect on his potential intensification over the next couple of days.  This afternoon’s official forecast calls for a Category 3 landing Saturday morning on the Texas coast.

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There hasn’t been much of a change to Hurricane Ike or his future overnight. Some numbers to update:

Center located at 23.9N, 85.3W; maximum sustained winds of 85mph (slightly stronger than last night); moving NW @ 8mph; minimum pressure of 959mb (lower than last night and still pretty low for a Category 1 storm). Given the decrease in pressure and the increase in wind speed that has already occurred, Ike should be a Category 2 storm (minimum wind speed 96mph) within the next 12-24 hours.

Ike should continue his path toward the northwest through the next three days, intensifying during the same period. Ike has a good chance of reintensifying to a strong Category 2 or weak Category 3 storm in the Gulf of Mexico. This morning’s official track forecast calls for a landfall near Corpus Christi, TX on Saturday morning. The model track envelope is narrowing down as we get closer to the event. After that, of course, there is a wide spread in how the models handle Ike over the U.S.


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Atlantic Tropical Weather Update 9/9/08

[Update 9:30P MDT]:

Hurricane Ike has strengthened a bit this evening since moving off the Cuban landmass. His vitals this evening:

Center located at 23.2N, 84.3W; maximum sustained winds of 80mph; moving WNW @ 9mph; minimum pressure still around 967mb. That low pressure, combined with warm Gulf waters and low vertical shear, should work to intensify Ike over the next couple of days.

Where is Ike headed? He’ll continue that WNW motion for about the next 24 hours, during which time, Ike should intensify to a Category 2 storm. After that, the ridge to his north will shift a little and strengthen also, which should force Ike a little more toward the west for the 1-2 day time period. Conducive environmental conditions should allow Ike to intensify further, to a Category 3 storm by Thursday morning.

By three days from now (Friday night), Ike should still be a major hurricane, and will be bearing down on the central Texas coast. Which means landfall is still expected late Friday night into early Saturday morning. The specific intensity at landfall will likely be somewhat weaker than Ike will be in the middle of the warm Gulf. Cooler and shallower waters closer to shore won’t be enough to keep Ike at maximum strength. Most of the model solutions indicate a landfall somewhat south of the official track. Two outliers are present tonight: the first (which so far is the most stable, correct model forecasting Ike’s track since before his initial Cuban landfall) shows a landfall northeast of Corpus Christi and southwest of Galveston. The second shows a Mexican landfall. That solution is the least likely at this stage, I think. It’s time to start thinking about impacts at landfall, which will include high surge, moderate-sized waves, heavy rainbands and the threat of tornadoes.

By Saturday evening, Tropical Storm Ike is expected to be located in central Texas. By Sunday evening, Tropical Depression Ike is forecasted to be in central Oklahoma.

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Atlantic Tropical Weather Update 9/8/08

[Update 9P MDT]:

Additional significant changes to Hurricane Ike’s future accompanied tonight’s National Hurricane Center update.  At this point, I’m not even convinced of a U.S. landfall this weekend.  Small changes in the early time periods are having huge impacts on the long-term track.  Ike is still a Category 1 storm, as his vitals attest:

Center located at 21.8N, 80.8W; maximum sustained winds of 80mph (still just barely hurricane strength); moving WNW @ 13mph; minimum pressure of 967mb.  So Ike still has very low pressure for a Category 1 storm, indicating the potential for reintensification when his center is no longer affected by land.

Hurricane Ike is expected to make his 2nd Cuban landfall tomorrow morning.  By late tomorrow afternoon or early evening, Ike will reemerge over the Gulf of Mexico.  Shortly after that happens, the intensity forecast calls for Ike to restrengthen to Category 2 status.  Ike is still forecasted to maintain his current trajectory until Wednesday night.  Starting Wednesday night, Ike is officially expected to turn back toward the WNW through the remainder of the forecast period.  This would bring Ike ashore along the Texas coast south of Corpus Christi Saturday afternoon as a Category 3 storm.

As I’ve noted all day, the models still collect themselves into two kinds of solutions.  Each set continues to move toward the south earlier in the forecast period.  There hasn’t been as much of a change in the forecast track of the most stable model.  It continues to show a landfall in the region either northeast or southwest of Corpus Christi.  So that’s about as good a forecast as can be generated right now.  All the other models have been inconsistent in one way or another throughout Ike’s lifetime.  With this latest update, one model solution puts Ike ashore on Mexico’s northeastern coast.  Another model brings Ike ashore on Texas’ far southern coast.  So at this point, a Mexican landfall cannot be ruled out.  About the only thing that hasn’t changed significantly is the intensity forecast.  We’ll see about that in the next few days too.

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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.

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[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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