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A sleeping giant: 94L

By: Dr. Jeff Masters, 1:00 PM GMT on October 10, 2007

A large low pressure system (94L) has moved inland over Mexico's Yucatan Peninsula, and is bringing heavy rain to Mexico, Belize, and Guatemala. These heavy rains can be viewed on Cancun radar. Satellite loops and the steering flow product from the University of Wisconsin CIMSS group (Figure 1) show the large size of this circulation nicely. This is an unusually large and deep low pressure system, and it will take several days for it to spin down. Most of the computer models are indicating that the center will remain over land and 94L will eventually die. However, the GFDL model continues to show the possibility that the center of 94L will drift back into the Western Caribbean, or into the Southern Gulf of Mexico, allowing 94L to intensify into a tropical storm. Considering the huge amount of atmosphere 94L has put into motion, it would not be a surprise to see some of that spin still remaining 3-4 days from now, and we will have to watch this system until that spin is gone. Wind shear is about 10 knots, and is expected to remain 10 knots or below for the next 2-3 days over the Yucatan.

Figure 1. Average steering flow at low levels in the atmosphere (between 700 mb and 850 mb) as computed by University of Wisconsin's CIMSS group. The arrows show the counter-clockwise flow of air around the low pressure system 94L over Mexico's Yucatan Peninsula.

Elsewhere in the tropics
Most of the computer models are forecasting that a low pressure system will develop in the Bahamas along an old cold front on Thursday or Friday, then move rapidly northeastward to Bermuda. This is likely to be an extratropical storm, but could bring wind gusts of 40 mph and heavy rain to Bermuda on Friday or Saturday.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.