Tropical weather analysis - October 13, 2010

Paula

Extremely tiny Hurricane Paula has weakened steadily throughout the day today, and is now only a Category 1 hurricane. Here is the latest information on this system as of the 11:00 PM CDT advisory from the National Hurricane Center:

Wind: 80 mph, with higher gusts
Movement: NE at 3 mph
Pressure: 993 mb
Location: 21.9°N 85.4°W
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

Analysis of infrared satellite animations suggest that Paula's circulation might be becoming somewhat exposed along the southwestern edge of the CDO. Indeed, high cloud motions observed on said imagery indicate that the hurricane is experiencing southwesterly vertical shear associated with a mid- to upper-level trough and associated cold front currently draped across the central Gulf of Mexico. CIMSS analysis indicates that this shear is prohibitively strong, at 30 kt.

Upper-level outflow is nonexistent to the southwest and quickly going in that direction on the western side as a consequence of the aforementioned shear.

Paula should continue to gradually spin down due to continued southwesterly then westerly vertical shear, and it would not surprise me at all to see Paula dissipate in as little as 36 hours if it manages to track directly over the mountainous terrain of Cuba. Since I suspect Paula will track just north of the Cuban coast after passing the hurricane warning area, I will not forecast such rapid dissipation at this time, but I do expect that Paula will have dissipated by 60 hours.

Analysis of water vapor imagery implies that Paula is already embedded within the mid-latitude southwesterly flow associated with the aforementioned trough. As such, the hurricane is now recurving, albeit at a painfully slow forward motion for the time being, as the approach of said trough has briefly weakened the steering currents surrounding the storm, as is usually the case just prior to and just after recurvature.

Based on various steering data I've analyzed, both real time and forecast, it appears that the trough responsible for Paula's current recurvature will not be strong enough to fully recurve Paula out to sea. All of the models, with the exception of the GFDL, which loses Paula north of Hispaniola in five days, suggest that that a severely weakened or dissipated Paula will eventually move southward back into the western Caribbean Sea underneath the northerly flow associated with the backside of the trough, which is forecast to eventually become a powerful Nor'easter.

Some, such as the NOGAPS, go even further and forecast Paula, or its remnants, to move NW into the southern Gulf of Mexico along the southwestern periphery of a building ridge across the Gulf of Mexico in about five days or so.

Needless to say, confidence in the forecast track beyond two days is not high.

Right now, I my forecast track is just a bit to the south (about 75-100 miles) of the 18z GFDL for the first 48 hours, and just north of NHC's current forecast track during that time.

After 48 hours, my forecast track agrees pretty strongly with that of the NHC, albeit a tad farther westward at the end of the forecast period.

Watches and warnings

A HURRICANE WARNING IS IN EFFECT FOR...
* THE CUBAN PROVINCE OF PINAR DEL RIO

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE CUBAN PROVINCES OF LA HABANA AND CUIDAD DE LA HABANA

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE FLORIDA KEYS FROM CRAIG KEY WESTWARD...INCLUDING THE DRY
TORTUGAS

Heavy rainfall in excess of 4 to 8 inches, with locally higher amounts, are possible across portions of western and central Cuba over the next couple of days, along with sustained hurricane force winds along the western and extreme west-central sections of the country, and residents in those areas should closely monitor the progress of Paula over the next couple days.

A storm surge in excess of 3 to 6 feet is possible across extreme western Cuba, which will be accompanied by large, destructive waves.

Elsewhere

Elsewhere in the tropics, most of the global models are indicating another tropical cyclone will develop in the Caribbean, this one north of Panama. The time frame is about a week, which, though still quite far out, is one where we need to start paying attention, especially given the model consensus with this.

The GFS suggests that an anticyclonic environment will develop across the southwest Caribbean at about that time, so this will need to be watched closely.