TROPICAL DISTURBANCE INVEST 95L SYNOPSIS…OCT. 17, 2011…ISSUED 9:10 A.M. EDT

UPDATE…OCT. 17, 2011…2:20 P.M.:

Satellite loop imagery indicates thunderstorm and shower activity have become less concentrated near the center of 95L, and have been sheared off toward the east.  RGB and Visible imagery indicate still, a broad circulation, with a notable vortex moving SSW of the convective activity.  Based on analysis of the current steering layer map, I will not rule out a partial cyclonic loop of the center, prior to 95L beginning to be picked up by the trof that is currently moving eastward.
95L RGB SATELLITE LOOP IMAGE

Albeit the NHC has downgraded the probability of cyclone development during the next 48 hours to MEDIUM (40%), the recent update of the GFS wind shear forecast map still indicates the upper level anticyclone now over the Yucatan Peninsula, should slide northward, with shear relaxing for a short window, which may allow for some further, slow organization, possibly enough for the system to become named.  The window of opportunity however, is short, and in about another 24-30 hours, upper level winds are forecast to become less favorable for tropical development.

NHC TROPICAL WEATHER OUTLOOK

GFS WIND SHEAR FORECAST

Regardless of development, tropical storm force conditions may still be experienced over the west central Florida coast, southward by afternoon tomorrow.  The current 12Z run of the ATCF model suite is pretty much in agreement from earlier this morning and the system could cross over the Tampa area, possibly a little further north.

12Z ATCF MODEL SUITE

I will include in tomorrows forecast, what affects this may have along the eastern seaboard over the next 3-4 days.  I will try to update again later this eve if warranted.

“Storm”

Good morning everyone!

Tropical Disturbance INVEST 95L has become a little better defined this morning.  Convection has become better organized and concentrated just NNE of the Yucatan channel.  The 2:00 a.m. EDT information suggests that the “center” was located near 22.0N;86.7W.  However, based on vorticity, various satellite loop imagery, and low level winds, I believe the broad center to be a little further west, just at the very edge of the convective cloud pattern, and north of the Yucatan Peninsula.

GLOBAL TRACKS 7 INVEST 95L TRACKING MAP

INVEST 95L SATELLITE INFRARED LOOP IMAGERY

 INVEST 95L SHORTWAVE SATELLITE LOOP IMAGERY

Currently, satellite motion and current steering suggests a north, to just west of north movement at 5 mph.  I expect this motion to continue through today, with a turn more toward the NNE by possibly tonight, into very early tomorrow morning.  Thereafter, in about 30-36 hours, I expect a NE motion as a deep layer trof moves eastward, based on the current run of the steering layers forecast maps.  Based on this, I agree with the 06Z Dynamic Model Guidance, and prefer a track blend of the TVCA/TVCN consensus.

06Z DYNAMIC MODEL GUIDANCE

The current wind shear map from CIMSS indicates upper level winds are marginal at the moment, with an upper level anticyclone over the eastern Yucatan Peninsula.  Albeit there is good outflow in all quads, the position of this feature is producing somewhat of a sheared environment, which is allowing for the “center” to be partially exposed to the west.  However, any relaxation of this shear would allow for some further organization, and could possibly allow for 95L to attain tropical storm status.  The most recent upper level wind depiction tends to indicate winds may be relaxing over the center even as I type this update.  This could be possible, as the current zonal shear forecast indicates this upper level anticyclone to shift northward to just south of the center, albeit 95L will have a short window of opportunity to pull off tropical storm status before SW wind shear increases in about 30 hours.  Given the excellent divergence aloft, and the strongest divergence being over the convective area, it would not surprise me to see a center “reformation” just under the convection.  The NHC has indicated the probability of 95L becoming a tropical cyclone within the next 48 hours to be HIGH (60%).

CURRENT WIND SHEAR MAP CIMSS

UPPER LEVEL WIND FLOW

UPPER LEVEL DIVERGENCE

NHC GRAPHICAL TROPICAL WEATHER OUTLOOK

Based on all of these parameters, the possibility does exist that tropical storm watches or warnings COULD be issued on short notice for the FL. west coast and south FL.  Regardless of development, given the proposed forecast track, residents of the Florida west coast from central Florida, southward could receive rainfall amounts on the order of 2-4 inches, and winds of up to tropical storm force, with higher gusts beginning as early as late tomorrow/early Wed.

I will continue to monitor 95L throughout the day, and will be updating as conditions warrant.

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST/TROPICAL FORECASTER
MEMBER WEST CENTRAL FL AMS (webmaster)
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)