New disturbance 90L entering the Caribbean; Hawaii needs to watch 97C

A small area of disturbed weather with heavy thunderstorm activity and an apparent surface circulation (90L) is centered near the island of Barbados this morning. A buoy about 150 miles northeast of the center of 90L recorded sustained winds of 35 mph with higher gusts last night. Winds from the QuikSCAT satellite pass from 5:45am EDT this morning showed winds as high as 30 mph. QuikSCAT also showed what may be a closed circulation at the surface. Winds at Barbados shifted to westerly this morning at 8am AST, confirming that 90L probably has a surface circulation. Martinique radar shows little thunderstorm activity so far, but this should increase this afternoon as 90L moves through the Lesser Antilles Islands and the heavier showers come in range of the radar. Winds so far today in Martinique have been below 10 mph.

In the disturbance's favor are a moist environment, low wind shear of 5-10 knots, and warm water temperatures of 83 degrees F. The main inhibiting factor is probably 90L's very small size. Disturbances this small have trouble developing into tropical storms, since they are very fragile and require near-perfect environmental conditions. The storm does not have a perfect environment; visible satellite loops from this morning show a competing circulation a few hundred miles to the east of Barbados interfering with 90L's organization. Still, 90L does have a chance to develop, since wind shear is forecast to remain below 10 knots for the next three days over the Caribbean. However, wind shear increases dramatically just north of the Caribbean, so if 90L moves north of Puerto Rico, it will likely be quickly destroyed. Most of the models forecast a west-northwest track for 90L over the next few days. Puerto Rico and the Dominican Republic should expect to feel 90L's rain and winds on Friday and Saturday. It's possible 90L could develop into a 50 mph tropical storm by that time. It is very unlikely 90L will intensify into a hurricane. The most likely scenario is for 90L to remain a tropical disturbance, or become a tropical depression that never organizes into a tropical storm.


Figure 1. Preliminary model tracks for disturbance "90L".

Hawaii
Residents of Hawaii should to continue watch an area of disturbed weather (now called 97C) near 8N, 167W, about 900 miles southwest of the Hawaiian Islands. A QuikSCAT satellite pass from 1:23am EDT this morning showed a closed surface circulation, and some wind barbs of 40-45 mph to the south of the center. The thunderstorm activity has gotten more intense over the past day, but is still very disorganized. The system is currently under about 10 knots of winds shear, and is underneath an upper-level anticyclone. Sea Surface Temperatures (SSTs) are about 29C, and there is a very deep pool of warm water underneath to fuel intensification. These are all very favorable conditions for development. SSTs stay above 26C all the way to Hawaii, and a landfalling hurricane in the islands is a possibility a week or so from now. The 6Z (2am EDT) run of the GFDL model intensified 97C into a hurricane by Sunday. However, the more recent 12Z (8am) run did not develop 97C at all.


Figure 2. Preliminary model tracks for disturbance "97C".

Elsewhere in the tropics
The models continue to show the possibility of a low pressure system forming in the Gulf of Mexico near the Texas coast early next week. This low will probably be non-tropical, though. The models are now less enthused about a new hurricane developing along the Pacific coast of Mexico and threatening Baja next week. Baja does not have to worry about Tropical Storm Norman, which dissipated last night, nor Tropical Depression Olivia, which is expected to dissipate Friday before reaching Baja.

I'll have an update later today if 90L or 97C show significant change.

Jeff Masters