Caribbean disturbance develops a spin

The tropical disturbance in the central Caribbean sea, south of Jamiaca, is still small and has limited deep convection, but now has a well-defined circulation visible on satellite imagery. Winds measured at NOAA buoy 42058 located at 15N 85W also showed this circulation, as the winds at the buoy switched from east to west this morning when the disturbance passed by. Surface pressures did not falling significantly at the buoy when the disturbance passed by, so this is still a very weak low pressure area. Wind shear over the disturbance has fallen to the 5 - 10 knot range, which is in the slightly to moderately favorable range for tropical storm development. An upper-level anti-cyclone appears to be developing on top of the disturbance, which should greatly aid the upper-level outflow needed to take away all the air lifted to the upper atmosphere by the deep convection near the storm's center.

The disturbance has slowed its forward motion to about 10 mph to the west-northwest. This motion is forecast to slow down even further over the next three days, which will keep the system in the western Caribbean through Friday, and favor development. The reconnaissance airplane scheduled to visit the area today was cancelled, and has been rescheduled for Wednesday.

The upper-level wind shear is forecast to relax further during the next two days, and I expect this system to become Tropical Depression 19 on Wednesday--Thursday at the latest. The global computer models do not develop this system into a tropical storm, and are not much help in forecasting what will happen. The latest 12Z (8am EDT) run of the GFS model predicts that the system will move to a point just south of the western tip of Cuba on Friday, but dissipates the system after that.


Figure 1. Early run of the BAMM model takes the Caribbean disturbance into the Yucatan Peninsula.

Africa westward
The ITCZ is active in the region extending from the African coast westwards for 1000 miles. Some of the global computer models are forecasting that a tropical storm will develop along this area later this week. There are currently no suspect areas to focus on, though.

Gulf of Mexico
A cluster of thunderstorms associated with the tail end of the cold front that pulled Rita northeast across the U.S. is over the northern Gulf of Mexico. Strong upper levels winds are producing 30 knots of shear over this region and should prevent any development.

Alaska and Hawaii
We don't talk much about these states in my tropical blog, but Nome, Alaska had a huge mid-latitude cyclone hit them Friday. The storm brought sustained tropical storm force winds gusting to 52 mph, a 10-foot storm surge, and a pressure of 972 mb! This was in essence a Category 1 hurricane, as far as the storm surge and pressure go. Thanks to wunderphotographer Destiny, who brought this newspaper article to my attention.

Hawaii has its second tropical system of the season to be concerned with. Hawaii dodged major Hurricane Jova last week, andTropical Storm Kenneth is expected to pass within 100 miles of the Islands by the end of the week. Kenneth should only be a tropical depression by then, and bring a few extra rain showers to the islands.

Jeff Masters