Paloma forms and steadily intensifies
Tropical Storm Paloma formed last night, and is steadily strengthening. Visible satellite images show a significant increase in organization of the storm is occurring, with low level spiral bands beginning to wrap around the center and upper level outflow expanding on all sides except to the south. Recent microwave images (Figure 1) indicate that Paloma is already starting to build an eyewall.
Figure 1. Microwave image of Paloma at 7:15 am EST Thursday November 6, 2008. A partial eyewall is evident on the southeast side of the center. Image credit: Navy Research Lab, Monterey.
The intensity forecast
Wind shear has dropped to a very low 0-5 knots, and is expected to remain very low, 0-5 knots, over the next day. Wind shear will increase to 10-15 knots Friday and Saturday, as the storm heads north, but I don't expect Paloma will stop intensifying until it crosses 20° North Latitude (between the Cayman Islands and Cuba) Saturday night, when the shear will increase to 30-50 knots. Water temperatures are warm, 29°C, and this warm water extends to great depth. These are very favorable conditions for intensification, and Paloma should be a hurricane by Friday. I expect Paloma will be a Category 2 or 3 hurricane when it passes through the Cayman Islands on Saturday. The latest (6Z, 1am EST) of the HWRF model predicts Paloma will pass though the Cayman Islands on Saturday morning as a Category 3 hurricane. The GFDL and SHIPS intensity models are less aggressive, predicting a Category 1 hurricane. I believe a Category 3 hurricane is more likely than a Category 1 hurricane for the Cayman Islands, and Paloma has the potential to imitate Hurricane Michelle of 2001. Michelle formed in the same region at the same time of year, and took just three days to intensify from a tropical depression to a Category 4 hurricane. Michelle made landfall in central Cuba as a Category 4 hurricane, then weakened to a Category 1 hurricane as it passed through the Bahamas. Paloma will likely be a Category 1 or 2 hurricane at landfall in Cuba, and a strong tropical storm with 60-70 mph winds in the Bahamas.
The track forecast
A strong trough of low pressure approaching the U.S. East Coast is pulling Paloma to the north, and this trough should continue to pull the storm northwards and then turn it northeastward by Saturday. Several major models--the NOGAPS, GFS, and ECMWF--predict that Paloma will be torn in two by the wind shear just south of Cuba, with the low level remnants getting forced westward towards the Yucatan Peninsula. This solution seems unlikely, given the fact that Paloma is likely to grow much stronger and more resistant to wind shear than these models are predicting. I expect Paloma will follow the track of the GFDL, HWRF, and GFS models, which show the storm may pass very close to Grand Cayman Island on Saturday, then make landfall in southern Cuba on Sunday and continue on through the central Bahamas.
Links to follow
Wundermap for 16N 83W
I'll have an update this afternoon. A new Hurricane Hunter plane is on its way to Paloma, and should arrive at the center around 1 pm EST.