Watching Late-Season Invest 99L

Update - Monday, November 21, 8:15AM EST
The weak center of Invest 99L continues to swirl in the central Atlantic near 26N 53W at 21/12Z with all of the convection displaced about 150 miles to the northeast by 50 knots of southwesterly windshear. NHC has raised the odds of subtropical or tropical development within 48 hours to 60%, i.e., the 'generosity level' has increased. Strong southwesterly shear will slowly relax by Wednesday morning so any chance for additional development will likely extend beyond the current 48 hour period. Upper level conditions become more favorable Wednesday and Thursday so some eventual development is possible IF the weak center can remain intact. The center is slowly drifting south in what appears to be an anticyclonic loop - future movement should be to the northeast.
ED

Original Post - Sunday, November 20, 10:44AM EST
Invest 99L, with little current movement, located well to the northeast of the northern Leeward Islands near 22N 54W at 19/12Z. 99L is a upper level low with a weak surface reflection (1010MB) that has been drifting to the southwest for most of last week. Southwesterly shear has displaced convective activity to the northeast of the surface low. NHC currently gives the system a 50/50 chance for subtropical development in the next couple of days, but to quote a line that NHC often uses, 'that might be generous'. Strong southwesterly shear over the system should continue into the middle of the week. SSTs are about 27C. If the system eventually become subtropical, it should remain at sea.
ED

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Edited by Ed Dunham (Mon Nov 21 2011 08:17 AM)

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