Hurricane season not over?

Is the hurricane season of 2007 over? An area of disturbed weather, designated Invest 94 by NHC, has developed about 400 miles east of Puerto Rico, and is moving west at 15-20 mph. The disturbance shows some modest organization on satellite imagery (Figure 1), with decent heavy thunderstorm activity, and an upper-level outflow channel to the north. Water temperatures in the region are about 26° C, which is right at the limit of what can support formation of a tropical storm. This evening's 8:12 pm EST QuikSCAT pass showed top winds of 30-35 mph, but no evidence of a surface circulation, and not much of a wind shift at the surface. Wind shear is 20-25 knots over the disturbance, which is too high to allow anything but slow development.


Figure 1. Latest satellite image of Invest 94.

Here's what NHC had to say about the disturbance:

1030 PM EST Sun Dec 9 2007

The area of disturbed weather associated with a broad area of low pressure centered about 425 miles east of Puerto Rico remains fairly well-organized...but satellite images and surface observations suggest that this system has not developed a closed circulation yet. This system is moving westward at 15 to 20 mph and is producing heavy squalls with gale force winds to the north of the shower activity. Environmental conditions appear to be favorable for some development and a tropical or subtropical storm could form during the next 24 hours. Interests in the northern Leeward Islands...the Virgin Islands...Puerto Rico...Hispaniola...and the eastern Bahamas should monitor the progress of this system.

None of the models develop the disturbance, but they do indicate that wind shear will remain near 20 knots through Monday night. This may allow 94L to stay organized enough to bring heavy rain and wind gusts up to 40 mph to Puerto Rico Monday night and on Tuesday morning to the eastern Dominican Republic. The disturbance is moving fast enough, about 20 mph, that the chances for serious flooding like Tropical Storm Noel brought to the region are low. By Tuesday, the models are showing an increase in wind shear to 30 knots, which should prevent further development. If there's anything left of 94L by Thursday, when it reaches the Western Caribbean, wind shear is expected to drop to 15 knots, and the system has a better chance of developing. I don't expect 94L will ever develop into a tropical storm, though.

I'll have a update Monday morning.

Jeff Masters