[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 17 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURE...

A BROAD AREA OF LOW PRESSURE COVERS THE FAR NW CARIBBEAN AND THE
SE GULF OF MEXICO CENTERED AROUND A 1004 MB LOW JUST N OF THE
YUCATAN PENINSULA NEAR 22N89W. THE CIRCULATION AROUND THIS
SYSTEM COVERS A GREAT PORTION OF THE BASIN...RAGING FROM 15 KT
TO NEAR GALE FORCE CRITERIA S OF 28N E OF 91W. THIS SYSTEM IS
INTERACTING WITH AN UPPER LEVEL SHORTWAVE/TROUGH THAT IS
SHEARING THE CONVECTION TO THE EAST OF THE LOW LEVEL CIRCULATION
E OF 89W FROM 20N-27N. SCATTERED HEAVY SHOWERS AND THUNDERSTORMS
ARE IN THIS REGION...WITH THE POSSIBILITY OF STRONG GUSTY OUT
FLOW BOUNDARIES AND WATER SPOUTS. DUE TO THE COMPLEX SCENARIO
INVOLVING THE ENVIRONMENT AROUND THE SYSTEM...IT IS IMPORTANT TO
MENTION THAT THE SYSTEM HAS GENERATED MULTIPLE LOW LEVEL CENTERS
SEEN ON VISIBLE SATELLITE IMAGERY OVER THE PAST 6 HOURS...AND
CURRENT LOCATION OF THE MAIN CIRCULATION IS SOMEWHAT DIFFICULT
TO PIN DOWN. CONDITIONS ARE EXPECTED TO BECOME LESS FAVORABLE
FOR TROPICAL CYCLONE DEVELOPMENT WITHIN THE NEXT DAY OR TWO...
AND NOW THERE IS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY NORTHWARD AT 4-9
KT. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL AND GUSTY
WINDS ARE EXPECTED OVER WESTERN CUBA...THE FLORIDA KEYS...AND
SOUTH FLORIDA DURING THE NEXT DAY OR SO.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM CAPE VERDE ISLANDS NEAR 16N23W TO
7N28W W AT 10-15 KT. WAVE IS WELL DEFINED IN THE LOW LEVEL CLOUD
FIELD AND IS EMBEDDED WITHIN A DEEP SURGE OF MOISTURE DEPICTED
ON THE TOTAL PRECIPITABLE WATER IMAGERY. CLUSTERS OF SCATTERED
MODERATE TO STRONG CONVECTION ARE FROM 6N-15N BETWEEN 22W-30W.

TROPICAL WAVE IS ANALYZED IN THE CENTRAL TROPICAL ATLC FROM
14N41W TO 6N45W MOVING W 10-15 KT. WAVE IS MOVING THROUGH A
REGION OF UNFAVORABLE GROWTH AND HAS BECOME LEES DEFINED ON
SATELLITE IMAGERY. NO SIGNIFICANT CONVECTION IS AROUND THIS
SYSTEM.

TROPICAL WAVE IS ANALYZED OVER THE ERN CARIBBEAN FROM 17N64W TO
10N66W MOVING 10-15 KT. WAVE IS BEING SUPPRESSED BY A DRY AND
SUBSIDENT AIRMASS ALOFT INTRUDING ACROSS THE ERN AND N CENTRAL
BASIN ON WATER VAPOR IMAGERY. WEAK CYCLONIC TURNING IS OBSERVED
ON THE LOW LEVEL CLOUD FIELD ALONG THE WAVE AXIS. NO SIGNIFICANT
CONVECTION IS AROUND THIS SYSTEM.

...THE ITCZ/THE MONSOON TROUGH...

DUE TO THE LARGE CYCLONIC WIND FIELD ASSOCIATED TO THE TROPICAL
WAVES...THE OCEANIC MONSOON TROUGH REMAINS INLAND OVER NRN
AFRICA. CONSEQUENTLY...THE ITCZ IS DISRUPTED BY THE PRESENCE OF
THESE TROPICAL WAVES. NEVERTHELESS...A WEAK 1011 MB LOW IS
ANALYZED NEAR 10N40W. SCATTERED WEAK CONVECTION SURROUNDS THE
LOW CENTER FROM 6N-14N BETWEEN 36W-42W.

...DISCUSSION...

GULF OF MEXICO...
THE MAIN AREA OF ACTIVE WEATHER CONTINUES TO FOCUS AROUND THE
SPECIAL FEATURE LOW IMPACTING THE SE GULF. REFER TO THE SPECIAL
FEATURE SECTION ABOVE FOR MORE DETAILS. FAIR WEATHER CONDITIONS
ARE ELSEWHERE OUTSIDE THE CONVECTION ASSOCIATED TO THIS SYSTEM.
THE FAIR WEATHER AND CLEARING SKIES TO THE NW OF THE SYSTEM ARE
WELL ASSOCIATED TO STRONG SUBSIDENCE AND DRY AIR IN THE MID AND
UPPER LEVELS OF THE ATMOSPHERE NOTICED ON WATER VAPOR IMAGERY...
AS WELL AS WEAK SURFACE RIDGE OF HIGH PRESSURE ANCHORED OVER S
CENTRAL GEORGIA.

CARIBBEAN SEA...
MOST OF THE CARIBBEAN BASIN IS EXPERIENCING FAIR WEATHER
CONDITIONS THIS AFTERNOON...EXCEPT FOR THE FAR NW BASIN
INCLUDING THE YUCATAN CHANNEL...AND THE FAR SW BASIN N OF
PANAMA. THE BENIGN WEATHER IS OBSERVED AS A DRY AND SUBSIDENT
AIRMASS ALOFT INTRUDES ACROSS THE ERN AND N CENTRAL BASIN ON
WATER VAPOR IMAGERY. WHILE THE CONVECTION OVER THE FAR NW BASIN
IS ATTACHED TO THE SPECIAL FEATURE LOW...THE CONVECTION OVER THE
SW BASIN IS RELATED TO MONSOONAL FLOW ACROSS THIS AREA
GENERATING SCATTERED HEAVY SHOWERS AND ISOLATED THUNDERSTORMS S
OF 11N BETWEEN 75W-83W. OTHERWISE...LIGHT EASTERLY TRADE FLOW
PREDOMINATES ACROSS THE AREA...BECOMING SSE IN RESPONSE OF THE
LOWER PRESSURES RELATED TO THE SPECIAL FEATURE LOW. A TROPICAL
WAVE MOVES ACROSS THE ERN BASIN WITHOUT ANY SIGNIFICANT
CONVECTION...SEE ABOVE FOR MORE DETAILS.

ATLANTIC OCEAN...
A BROAD UPPER TROUGH COVERS THE NW ATLC N OF THE DISCUSSION AREA
AND SUPPORTING A FRONTAL BOUNDARY THAT ENTERS THE REGION NEAR
32N64W AS A SURFACE TROUGH EXTENDING SW TO THE BAHAMA ISLANDS
NEAR ELEUTHERA ISLAND. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE WITHIN 80 NM ON EITHER SIDE OF THE TROUGH
AXIS. AN ELONGATED UPPER LEVEL CIRCULATION CENTERED NEAR 20N54W
IS WRAPPED IN DRY AIR ALOFT. THE FLOW ASSOCIATED TO THIS
CIRCULATION IS DRAWING THE UPPER DRY AIRMASS IN TO THE ERN AND N
CENTRAL CARIBBEAN. TO THE E OF THIS CIRCULATION...A SUBTROPICAL
JET STREAK IS DEPICTED ON MODEL DATA SUPPORTING AN UPPER LEVEL
CIRCULATION AND ITS SURFACE REFLECTION CENTERED NEAR 32N34W. THE
CONVECTION ASSOCIATED TO THIS SYSTEM IS WELL REMOVED TO THE E OF
IT...N OF 27N BETWEEN 24W-40W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GARCIA




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