Ernesto is very poorly organized

ERNESTO

A disorganized Tropical Storm Ernesto continues to speed westward at 23 mph across the Caribbean. Ernesto has brought sporadic heavy rains to Jamaica today, and Kingston has picked up 0.51" of rain as of noon, and recorded top sustained winds of 22 mph. Ernesto looks very unhealthy on visible satellite loops, with its low-level circulation center a naked swirl exposed to view with almost no heavy thunderstorm activity near the center. However, the storm does have some rather far-flung spiral bands, and these bands are bringing occasional heavy downpours to Haiti, western Cuba, Jamaica, and the southwest Dominican Republic. This morning's flight by the Hurricane Hunters found that Ernesto had a very high central pressure of 1006 mb and top winds near 50 mph. The latest wind shear analysis from the SHIPS model shows moderate shear of 10 - 15 knots affecting the storm, but there must be some wind shear the satellites are not able to detect affecting Ernesto, given its disorganized appearance. Water vapor satellite loops show a large area of dry air to the west, and this dry air is also interfering with Ernesto's organization

Ernesto's rapid forward speed of 23 mph has been part of the reason for its lack of intensification, but the storm is expected to slow down Monday and Tuesday in response to a trough of low pressure passing to the north. This slowing, in combination with low wind shear, a moister environment, and increasing heat energy in the ocean, may allow Ernesto to strengthen some before making landfall in Belize or Mexico's Yucatan Peninsula on Tuesday night. However, the storm will be passing very close to the north coast of Honduras, putting a portion of its circulation over land and limiting intensification potential. It is unlikely Ernesto will become a hurricane in the Caribbean; NHC is giving just a 19% chance that this will occur. The main threat from Ernesto will be heavy rains over Honduras, Belize, Mexico, and Jamaica. The track forecast for Ernesto has become a bit easier, since the storm's current disorganization and more southerly path make will make it more difficult for the storm to make a northwesterly turn into the Gulf of Mexico like the UKMET and GFDL models are predicting. A stronger Ernesto would have been more likely to turn northwest under the influence of a trough of low pressure passing to the north. If Ernesto survives its crossing of the Yucatan Peninsula, the potential exists for it to re-strengthen over the Bay of Campeche, and make a second landfall on Mexico's coast on Friday, between Tampico and Veracruz. It's pretty unlikely that Ernesto will hit the U.S.-- though Brownsville, Texas could see some rain from Ernesto's outer spiral bands on Friday, if the storm survives that long

FLORENCE

Tropical Storm Florence continues to plow westward at 14 mph over the Eastern Atlantic, and is not a threat to any land areas for next five days. The SHIPS model is predicting a moderate 5 - 15 knots of wind shear for Florence Sunday and Monday, but the shear will increase to the high range as Florence encounters an upper-level trough of low pressure on Tuesday. The latest Saharan Air Layer Analysis shows that a large area of dry air lies to the north and west of Florence, and this dry air will likely cause problems for the storm. Ocean temperature are near 26 - 26.5°C, which is right at the threshold for where a tropical storm can typically exist. It is possible that Florence could pose a threat to Bermuda next weekend, if the storm survives that long. Both the GFS and ECMWF models dissipate Florence before then.

~ Jeff Masters, Weather Underground