Weather Nerd

Curtains for Gustav; Hanna weakens; proto-Josephine forms

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At 5:00 AM EDT, the National Hurricane Center issued its final advisory on Gustav, now a tropical depression over northwestern Louisiana. The storm’s remnant is expected to slowly spin itself out over Louisiana, Texas, Oklahoma and Arkansas, potentially causing flooding rains over the next 5 days.

Now the damage assessment and cleanup begins. The New Orleans Times-Picayune reports this morning that “Gustav spares New Orleans area, but reveals vulnerability.” Meanwhile, Baton Rouge, some 60 miles inland, saw a surprising amount of damage, and things were even rougher closer to the landfall location:

The bullet that missed New Orleans did its damage elsewhere in Louisiana on Monday as Gustav’s hurricane-speed winds caused extensive damage to homes and businesses from Grand Isle to Lafayette and shut off power to close to a million utility customers statewide. … Morgan City and Houma were the hardest hit towns while Lafourche and Terrebonne were the most impacted parishes, [Governor Bobby] Jindal said. … Power in many areas may not be restored for two weeks[.]

Craig at New Orleans Metblogs wrote last night:

While the national media oversensationalized the levee topping and too many televised reporters tried to make a run-of-the-mill event [in New Orleans] into Katrina II, I can tell you the best story most of the nation will never see. It’s what is happening this evening to the folks in Lafitte and other small communities directly south of New Orleans and to the southwest. Some are heavily flooded for the second time in three years — with many just-rebuilt lives, homes and businesses again in tatters. The problem is they are too few in number for most folks to care. And they’re still assessing damage in Lafourche and Terrebonne Parishes. God bless those folks tonight, as well as others still facing what’s left of this weather system. Those of us who stayed in New Orleans know how creepily lucky we are this time around.

There’s much more on Gustav’s impact on Louisiana at the Times-Picayune Hurricane Center. See also the various links at right.

Meanwhile, even as Gustav died this morning, Josephine was born. Or, to be more precise about it, Tropical Depression Ten, which will almost certainly earn the name Josephine, was born. Proto-Josephine is way out over the far eastern Atlantic, and is expected to steadily strengthen — into a tropical storm today, into a hurricane by Saturday — as it chugs west-northwestward. Any potential impact on the U.S. would be a very long way off: late next week at the earliest. We have plenty of time to watch this one. No need to send Geraldo anywhere just yet! (Actually, there’s probably never a need to do that, but I digress.)

In between Gustav and proto-Josephine are two other systems: Hanna, in the Bahamas, and Ike, midway between Africa and the Lesser Antilles. These will be the “headline” storms of the next week.

Hanna, which has been remarkably resilient despite heavy wind shear, suffered a setback this morning, weakening to a tropical storm after attaining hurricane status yesterday. Alan Sullivan, the hype-averse South Florida weatherblogger who has been unusually bullish about Hanna’s prospects for intensification (he wrote last night, “a category four landfall is quite conceivable”), explains this morning:

Hanna is hitting NW Haiti. This was not modelled. Flooding rains and much loss of life could occur. Southward motion continues, according to the satellite imagery, or else the storm is becoming vertically displaced. … The upper flow is too strong. We will have to totally rethink Hanna’s future. Weakening has already commenced. Pressure 987 mb. Winds 70 mph.

The Hurricane Center says Hanna “could regain hurricane strength later today or tomorrow, and the official forecast track continues to suggest a strike Friday or Saturday somewhere on the East Coast. But I think it’s fair to say that forecasters really have no idea what will happen. The 11am NHC discussion will be interesting. But this is a wait-and-see situation for sure. Haiti may be the death of Hanna. Or not. Stay tuned.

Ike is less complex, at least at present. As with proto-Josephine, steady strengthening is expected, and the forecast track is pretty straightforward: go west, young storm. It seems pretty likely that both Ike and Josephine will turn into powerful Cape Verde hurricanes in due course. We can only hope something comes along to weaken them, or better yet, recurve them out to sea. The latter seems somewhat more likely in Josephine’s case than in Ike’s, if the current forecast tracks are to be believed. But any approach to the U.S. coast is still a good long way off, and a lot can change between now and then.

I’ll be updating my sidebar soon — probably later today — to remove some of the Gustav-specific links, and add links related to the three storms that will be dominating this blog’s attention for the next couple of weeks.

UPDATE: T.D. 10 is officially Josephine, as of 11am EDT.

Meanwhile, on Hanna, the 11am discussion states:

HANNA HAS FINALLY SUCCUMBED TO THE STRONG VERTICAL SHEAR . . . THE INITIAL INTENSITY IS SET AT [70 MPH]…BUT GIVEN THE CURRENT SATELLITE PRESENTATION…THIS MIGHT BE A BIT GENEROUS. AN AIR FORCE RECONNAISSANCE AIRCRAFT WILL INVESTIGATE HANNA THIS AFTERNOON AND PROVIDE A BETTER INTENSITY ESTIMATE. . . . [IT APPEARS THAT] THE SHEAR WILL PERSIST IN THE SHORT-TERM…AND SOME ADDITIONAL WEAKENING IS POSSIBLE TODAY AND TONIGHT. IN ABOUT 24 HOURS…GLOBAL MODELS SHOW THE SHEAR WEAKENING AND THIS COULD ALLOW HANNA TO RESTRENGTHEN. HOWEVER…GIVEN THE PRESENT LACK OF ORGANIZATION…IT IS DIFFICULT TO KNOW HOW MUCH STRENGTHENING IS POSSIBLE. THE NEW OFFICIAL FORECAST IS LOWER THAN THE PREVIOUS ADVISORY BUT SHOWS HANNA BECOMING A CATEGORY ONE HURRICANE IN ABOUT 36 HOURS. IT SHOULD BE NOTED THAT THIS IS A LOW CONFIDENCE FORECAST. IN FACT…IF ONE CONSULTS THE WIND SPEED PROBABILITY
PRODUCT INCLUDED IN THIS PACKAGE…IT CAN BE SEEN THAT THERE IS NEARLY AN EQUAL PROBABILITY OF HANNA BEING A TROPICAL STORM OR HURRICANE AT DAY 3.

As for Hannah’s track:

DYNAMICAL TRACK MODELS HAVE SHIFTED A LITTLE TO THE WEST AND THE NEW OFFICIAL FORECAST FOLLOWS SUIT. ON THE FORECAST TRACK…HANNA IS EXPECTED TO APPROACH THE EAST COAST OF FLORIDA… GEORGIA…OR SOUTH CAROLINA IN 2 TO 3 DAYS. IT SHOULD BE STRESSED THAT THE EXPECTED ANGLE OF APPROACH AND TRACK UNCERTAINTY MAKE IT IMPOSSIBLE TO NARROW DOWN THE POTENTIAL IMPACT AREA.

Like I said: they have no idea what’s going to happen:

Contrast that with Ike, about which the NHC says:

MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT REGARDING THE TRACK OF IKE. MOST MODELS…EXCEPT FOR THE GFDN…ARE TIGHTLY CLUSTERED WITHIN THE FIRST 48 HOURS THEN ONLY SLIGHTLY DIVERGE BEYOND THAT TO DAY 5. IN FACT…WITH A LATITUDINAL SPREAD OF ONLY 5 DEGREES AT DAY 5…WE COULDN’T HAVE ASKED FOR BETTER AGREEMENT IN THE GUIDANCE.

Ike must be a welcome relief for forecasters, after all these recent complex steering patterns. (Though, to the NHC’s great credit, they really nailed the Gustav track forecast.)

Beyond “Day 5,” though, where will Ike go? This is the realm of unbridled speculation, of course. But, for what it’s worth, Alan Sullivan links to a post by meteorologist Brian Neudorff (a friend of mine) about Ike’s prospects according to history, and then Sullivan adds:

It seems that very few storms forming so far east and crossing the Atlantic at Ike’s latitude have ever made it into the Gulf — especially the western Gulf. Sooner or later these systems curl poleward. Normally Ike would be a candidate for troubling the East Coast, not the Gulf. But there is a big upper anticyclone crossing in tandem with Ike, to its north, and blocking any recurvature. I think Ike is all too likely to gain the longitude of Florida, but it may never pass the longitude of Mobile, AL. If you get my drift…