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August 2012
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Ernesto to Remain Weak for Now, then Strengthen Later; Long-term Track Still Uncertain

   Posted by Levi at 6:18pm on August 3, 2012

Ernesto has formed, and is now moving into the eastern Caribbean after passing the Antilles Islands last night. Overall organization of the system has not changed, with limited thunderstorm coverage over a tight but weak circulation. Dry air being entrained from the west is inhibiting Ernesto, and the storm is also now embedded in a fast 20mph+ trade wind flow that is unfavorable for the intensification of the circulation. This will likely limit Ernesto to weak-moderate tropical storm intensity until it makes it to the longitude of Jamaica, at which point the trade winds slow down, and upper-level ridging will likely make the environment quite conducive for intensification. Ernesto may even open up into an open wave without westerlies on the southern side for a time before then, but should remain robust and redevelop a closed circulation in the western Caribbean if it does.

The future track of Ernesto largely depends on his intensity in the western Caribbean, as the weakness in the ridge over the Gulf of Mexico will not be strong enough to pick up a weakling system, but would likely pick up a hurricane and bring it north of 25N. While Ernesto should start strengthening once to 75W, if he starts off very weak then he may not have the time to strengthen enough to move into the weakness and encroach upon the northwest Gulf of Mexico, but instead could get re-caught by the Texas ridge and move WNW across the Yucatan and then into the northern half of Mexico in the western gulf. This is the solution adopted by the ECMWF over the last couple days, and more recently the latest GFS and CMC runs. The other models still go to the north with a stronger system, along with the NHC. It is starting to seem a bit more likely that Ernesto hits the Yucatan and then moves into the Bay of Campeche, given that the environment doesn’t seem to support strengthening until west of Jamaica. The NHC shows Ernesto strengthening into a hurricane near Jamaica, a solution I find less likely given the strong trade winds and dry air ahead of Ernesto right now.

Overall, Ernesto’s intensity in the western Caribbean will largely determine whether he becomes a problem for the United States down the road. The favorable conditions in the western Caribbean mean that Ernesto will likely become a significant problem for central America even if the shorter, southerly route is taken with less time over water. These possibilities are still 5-8 days out so nothing can be guaranteed yet, and interests in the western Caribbean and along the gulf coast should monitor Ernesto over the coming days.

We shall see what happens!