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Atlantic Tropical Weather Update 9/4/08

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[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.

[Update 4:30P MDT]:

Some small updates to the storms currently in the Atlantic are available. Starting with T.S. Hanna:

Center located at 25.5N, 75.0W; maximum sustained winds of 65mph (might be a little generous); moving NW @ 14mph; minimum pressure of 988mb.

T.S. Hanna really got battered fighting off two upper level lows and mid-level dry air. She looks ragged on satellite imagery, with convection clearly displaced away from the “center” of the storm. Her official track forecast takes her northwest for the next 24-36 hours as a Tropical Storm, making landfall near the North Carolina/South Carolina border. As such, the NHC and NWS have issued Tropical Storm Warnings and Hurricane Watches along the North and South Carolina coasts. Tropical Storm Watches have been issued for Georgia and Virginia.

She could stay a little further inland than previously forecasted as she continues to make her way around the Atlantic ridge steering her. She is likely to affect the Carolinas and Virginia during the first half of Saturday, then turn more northeastward, moving across some Northeastern states on her way to Canada by Sunday afternoon. Surge and rain is her main threat, both of which should be confined to the western portion of the storm.

Hurricane Ike has weakened slightly during the day as the northeasterly shear has affected him. His vitals this afternoon:

Center located at 23.6N, 58.2W; maximum sustained winds of 135mph; moving WNW @ 14mph; minimum pressure of 945mb. So his winds have come down some and his pressure has risen, as expected.

Ike’s future over the next 24 hours is the biggest change. He is likely about as far north as he is going to get in the short term. He should make a gentle turn to a more due west track, then shift a little south of west by this time tomorrow. Due to the shear environment, his intensity should decrease some. The official intensity forecast calls for Ike to be a strong Category 2 in 24 hours. The same forecast calls for Ike to reintensify to Category 3 strength as Ike moves past the worst of the shear environment. Sunday, Ike is expected to stop moving WSW/SW and shift again more due west or north of west as a Category 3 storm. This time period should see Ike affecting the southeastern Bahamas Islands, then the central Bahamas Sunday night and Monday morning.

The official forecast keeps him as a Category 3 storm during this time period, but I’m willing to bet he could weaken again as he contends with Tropical Storm Hanna’s left-over upwelling. In any event, the ridge steering Ike should keep him moving toward the northwest through Monday and Tuesday. Unfortunately, the official track forecast now indicates that this course could put Ike on a collision course with southern Florida. Whether he is a Category 2 or 3 is fairly irrelevant. He will be a strong hurricane if he ends up making landfall over Florida. The only good news available given this scenario is Ike is a small storm right now. If he stays on the small side, the total area affected would obviously be limited.

Tropical Storm Josephine’s future remains largely unchanged, though she has weakened during the day also. Her vitals this afternoon include: center located at 14.6N, 33.2W; maximum sustained winds of 45mph; moving WNW @ 10mph.

T.S. Josephine should move at nearly the same speed in the same direction for the next 2-3 days. Sometime during Saturday or Sunday, her steering currents could help her pick up some speed. In contrast to earlier forecasts, T.S. Josephine’s official intensity forecast calls for her to remain a tropical storm, likely weak or moderate strength, through the 5-day period.

***

There haven’t been too many changes in the Atlantic basin since late last night. Probably for the last time, let’s start with Tropical Depression Gustav. He started moving northeast last night and is currently providing plenty of rain for Missouri, Iowa, Illinois, and even Michigan. He should continue being advected across the U.S. and into Canada as he is absorbed in the large-scale flow.

Moving on to Tropical Storm Hanna, which is quite a strange storm at this point. It actually looks like she has lost some tropical characteristics: she looks elongated and the rain bands are located a ways from the center of circulation. That being said, the NHC still classifies her as a tropical system, so let’s look at her vitals:

Center located at 24.5N, 73.5W; maximum sustained winds of 65mph; moving NW @ 12mph; minimum pressure of 989mb.

T.S. Hanna will continue moving NW around the edge of the ridge set up over the Atlantic. Starting tomorrow morning, Hanna should shift her trajectory slightly more towards the north. That shift will continue through the day tomorrow, giving Hanna a NNE trajectory late Friday night into early Saturday morning. During the night Friday, Hanna could intensify slightly to Cateory 1 hurricane status again.

Landfall could occur along the North Carolina coast early Saturday morning. After that landfall, T.S. Hanna is forecasted to continue moving around the ridge, which means a shift further east of north. Such a path would take her back over the Atlantic, next to coast from Virginia to Maine by Sunday morning. After that, Hanna should find herself on the northern edge of the ridge and will move ENE out over the open Atlantic.

Hurricane Ike continues to race across the Atlantic. Starting with his vitals:

Center located at 23.2N, 57.0W; maximum sustained winds of 140mph, making him a strong Category 4 storm; moving WNW @ 16mph; minimum pressure of 938mb, which is 10mb less than last night’s reading.

Hurricane Ike’s intensification is likely finished for now. Some northerly shear is starting to affect the storm. Given that, sometime starting tonight to early tomorrow morning, Ike could weaken back to a Category 3 storm. At that time, the ridge to Ike’s north should strengthen some and start pushing Ike back toward the WSW. There is expected to be little change in Ike’s makeup over the weekend, with Sunday dawning with another major hurricane bearing down on the south-eastern Bahamas. As I wrote last night, that’s when things could start changing for Ike.

First, Ike will continue moving along the edge of the Atlantic ridge. That means a more NW heading for the storm once Ike reaches the Bahamas. But remember, Hanna spent over 24 hours in basically the same spot that Ike is forecasted to move over starting Sunday. Further, he is forecasted to move over nearly the same path that Hanna is taking today. Even a tropical storm like Hanna dredges up colder water as they suck the heat out of the top of the ocean.

Early next week, things start to look a little scary for the east coast. Ike could take aim at any state as he continues to make his way around the Atlantic ridge. It is still too early to tell where, if anywhere, Ike could make landfall. It is similarly too early to tell how strong he might be if he does make landfall.

Tropical Storm Josephine continues on her westward trek across the basin. She hasn’t changed much since yesterday, weakening slightly according to the official NHC analysis. There isn’t much new in her future, either. Her vitals:

Center located at 14.5N, 32.2W; maximum sustained winds of 50mph; moving WNW @ 10mph (slower than yesterday); minimum pressure of 1000mb.

Josephine is forecasted to move slowly toward the WNW over the weekend. Early next week, Josephine should pick up some speed and maybe begin moving more towards the NW. Some slight further weakening is possible in the next three days, followed by a slight reintensification. T.S. Josephine isn’t currently expected to intensify to hurricane strength.

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