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Monthly Archives: November 2008

Hurricane Paloma has continued its rapid intensification this evening, and is now a major hurricane with Category 3 sustained winds of 115 mph as it passes Grand Cayman Island, approaches Cayman Brac and Little Cayman, and menaces Cuba.

Paloma’s right-front quadrant, where the strongest winds are located, is expected to make a direct hit on Cayman Brac and Little Cayman tomorrow morning. It is possible the storm will be even a little stronger by then. Storm Carib has coverage from a local perspective. See also Cayman Net News and the Cay Compass.

Here’s a look at the impressive storm on satellite:

You can also now just begin to see the storm’s eye on Cuban radar; see also here.

Paloma’s eventual impact on Cuba remains uncertain. Certainly, the storm will weaken before it reaches that island, as wind shear is expected to markedly increase shortly after Paloma passes the Caymans. By this time tomorrow, Paloma will definitely be less organized than it is now.

That said, the extent of pre-landfall weakening — if in fact there is a Cuba landfall — is a question mark, as is the storm’s track. The National Hurricane Center’s 10pm EST discussion explains the divergent track scenarios in the computer models:

AS HAS BEEN THE CASE FOR THE PAST 36 HOURS…THERE REMAINS A BIFURCATION IN THE NHC MODEL SUITE WITH THE UKMET…ECMWF…AND NOGAPS MODELS RAPIDLY WEAKENING PALOMA AND TURNING IT WESTWARD SOUTH OF CUBA BY 36 TO 48 HOURS…WHEREAS THE GFS…GFDL…AND HWRF MODELS MOVE A SOMEWHAT STRONGER CYCLONE ACROSS CUBA AND INTO THE CENTRAL BAHAMAS. BASED ON THE CURRENT SATELLITE TRENDS AND REPORT FROM RECON AIRCRAFT…THE OFFICIAL FORECAST TRACK LEANS TOWARD THE GFS…GFDL…AND HWRF SOLUTIONS…ALBEIT SOMEWHAT SLOWER.

In other words, the NHC is guessing that Paloma will hit Cuba early Sunday morning as a weakening hurricane (probably Category 1), but it’s really just that — a guess, albeit an educated one. Forecasters just aren’t sure what Paloma is going to do beyond the Caymans.

Paloma nears Caymans, approaches Cat. 2 status

November 7th, 2008 - 1:25 pm

Hurricane Paloma is continuing to strengthen as it approaches the Cayman Islands. Officially, the intensity is 90 mph as of 1:00 PM EST, and it’s possible we could see Paloma upgraded to Category 2 status at the next advisory, given what Dr. Jeff Masters writes:

Between 1 pm and 3 pm EST, an Air Force Hurricane Hunter aircraft dropped two sondes in the northwest eyewall of Paloma, and found winds of 90 and 97 mph at the surface form these sondes. The threshold of Category 2 strength is 96 mph.

Dr. Masters also notes that Paloma is showing some fascinating structural features, which could portend either imminent strengthening, an impending eyewall replacement cycle (which would tend to temporarily retard intensification), or perhaps both: a brief rapid-deepening phase, followed by an ERC. Masters writes:

The central pressure of Paloma is dropping at about 1-2 mb per hour. The Hurricane Hunters noted that Paloma appears to be forming a second eyewall concentric with the main eyewall, and there is also evidence of this on visible satellite loops. There was also a gap noted in the SSW side of the eyewall by the Hurricane Hunters, and the storm is undergoing some substantial structural changes. Formation of a secondary concentric eyewall will ordinarily slow down intensification of a hurricane, but is also spreads out the highest winds over a larger area. Recent infrared imagery shows that the eye has warmed, indicating strengthening. Some very impressive thunderstorms with high, cold tops are firing up at several points in the eyewall, also indicative of strengthening. These thunderstorms may be “hot towers”, which are often observed when a hurricane is embarking upon a major intensification phase. 

Although forecasters don’t have the ability to predict rapid intensification bursts or eyewall replacement cycles with any degree of precision, conditions are generally favorable for strengthening, and thus Paloma is expected to continue getting better organized for the next 24 hours or so. Officially, the storm is forecast to peak as a low-end Category 3 hurricane, with peak winds of 115 mph, tomorrow morning.

Then, wind shear is forecast to increase markedly, and thus Paloma will probably weaken back to a Cat. 1 before landfall in Cuba overnight Saturday night. After crossing Cuba, Paloma may “lose vertical coherence,” according to the 10am NHC discussion; in any event, it will continue to degrade rapidly, and will eventually become extratropical.

Meanwhile, weatherblogger Alan Sullivan is now aboard the cruise ship Noordam, preparing to sail in Paloma’s general direction. He writes:

There seems something apt about sailing into a hurricane on a luxurious cruise ship in such times. Paloma continues to strengthen steadily. In the stronger scenario we will experience tropical storm conditions at sea tomorrow, while the center of Paloma runs onto Cuba’s south coast. In the weaker scenario, we hit squally thunderstorms as upper energy shears northeast while Paloma fades in the Caribbean.

Paloma now a hurricane

November 6th, 2008 - 5:06 pm

Well, that was fast: barely 24 hours after being designated a tropical depression, Tropical Storm Paloma has officially become Hurricane Paloma as of 7:00 PM EST. Further rapid intensification is expected.

Details to come shortly.

UPDATE: From the 7pm NHC advisory:

…PALOMA RAPIDLY STRENGTHENS INTO A CATEGORY 1 HURRICANE…

. . . MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 75 MPH…120 KM/HR…WITH HIGHER GUSTS. PALOMA IS NOW A CATEGORY 1 HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE. PALOMA CONTINUES TO RAPIDLY ORGANIZE AND ADDITIONAL STRENGTHENING IS LIKELY. PALOMA IS EXPECTED TO BECOME A CATEGORY 2 HURRICANE ON FRIDAY.

Weatherblogger Alan Sullivan, who is scheduled to embark Friday for a cruise on Holland America’s Noordam, with scheduled stops in the Caribbean and the Bahamas, writes of Paloma:

The model projections fall into two distinct camps, as they often do. One group is weaker and slower. The storm is sheared apart before Cuban landfall, or it lingers dying in the Caribbean. They other group is faster and stronger. The storm accelerates with the upper flow, maintaining its integrity longer. This would mean real trouble for Noordam. It would also echo what happened with Omar last month. I deem it the more probable scenario.

We shall see. Dr. Jeff Masters has more.

Hello, Paloma

November 6th, 2008 - 8:40 am

Tropical Storm Paloma has formed, and is strengthening:

SATELLITE IMAGES SHOW AN ORGANIZING TROPICAL CYCLONE WITH A CENTRAL DENSE OVERCAST FEATURE DEVELOPING NEAR THE APPARENT CENTER. BANDING FEATURES ARE ALSO BECOMING MORE PROMINENT ESPECIALLY NORTH OF THE CENTER. THE INITIAL INTENSITY IS INCREASED TO [45 MPH] . . . AN AIR FORCE AIRCRAFT IS SCHEDULED TO BE IN THE AREA AROUND [1:00 PM EST] TO PROVIDE A BETTER ESTIMATE.

Further strengthening is forecast; Paloma is expected to be a hurricane by Friday evening, and a Category 2 hurricane by Saturday. It’s also possible the storm could get stronger than that, and/or could strengthen more quickly. Indeed, the National Hurricane Center estimates that the chances of rapid deepening (which is always very difficult to predict) are 3 to 4 times higher than the climatological average.

Dr. Jeff Masters says Paloma is “already starting to build an eyewall.” As for the forecast, Dr. Masters notes that wind shear is now expected to increase significantly on Saturday night, likely weakening Paloma before the expected landfall in Cuba on Sunday. The Caymans may still get hit by a Cat. 3 major hurricane, however.

A major late-season threat in the Caribbean

November 5th, 2008 - 11:33 pm

Just when you (and I) thought hurricane season was effectively over, Tropical Depression Seventeen has formed off the coast of Nicaragua — and it could be a major threat to the Cayman Islands and Cuba this weekend.

Although T.D. 17 currently has maximum sustained winds of just 35 mph, conditions are ripe for strengthening, with warm waters and extremely low wind shear. Tropical Depression 17 is expected to become Tropical Storm Paloma sometime Wednesday, and Hurricane Paloma within 48 hours. After that? Watch out:

[B]oth the GFDL and HWRF models … predict TD 17 will pass though the Cayman Islands on Saturday morning as a Category 2 hurricane, and strengthen to a Category 3 or 4 hurricane by landfall Sunday morning in central Cuba.

Other computer models, it should be noted, are less aggressive than the GFDL and HWRF, which is unsurprising; those models are not infrequently high-end outliers when it comes to intensity forecasts. Nevertheless, there is a real chance of a major November hurricane for the Caymans and Cuba (with some possible impacts on Jamaica). Dr. Jeff Masters writes, “I give TD 17 a 70% chance of becoming a hurricane, and a 40% chance of becoming a major hurricane.” 

Of course, even if that 40% comes to fruition, it is possible proto-Paloma could become a major hurricane, but then weaken before landfall. That seems to be what Alan Sullivan is tentatively anticipating.

Alternatively, it is also possible the storm might not be picked up at all by the trough of low pressure that’s expected to take it toward Cuba, in which case it could meander near land or over upwelled waters, potentially inhibiting its development. But that scenario gets less likely as TD 17 gets stronger, because the storm is more likely to “feel” the trough if it is better organized.

In any case, while it’s too early to make any definite predictions, this one definitely bears watching.