[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU OCT 20 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 1735 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM NEAR 17N38W TO 8N48W MOVING W AT
5-8 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. A MID LEVEL CYCLONIC
CIRCULATION IS OBSERVED OVER THE SRN EXTENSION OF THE WAVE
AXIS...AND SHORT RANGE COMPUTER MODELS SUGGEST THIS MID LEVEL
CIRCULATION COULD REACH SURFACE LEVEL OVER THE NEXT 6-12
HOURS...WITH NO CHANCES OF FURTHER DEVELOPMENT. CLUSTERS OF
SCATTERED MODERATE TO STRONG CONVECTION ARE WITHIN 150-190 NM ON
EITHER SIDE OF THE WAVE AXIS.

THE TROPICAL WAVE THAT WAS MOVING ACROSS THE NE WATERS OF SOUTH
AMERICA OVER THE PAST FEW DAYS HAS LOST SOME OF ITS WAVE
QUALITIES AND STRUCTURE...WITH VERY LITTLE WESTWARD PROGRESSION.
THEREFORE...A TROUGH AXIS HAS REPLACED THE WAVE...ANALYZED FORM
13N54W TO 6N55W. DESPITE THE DOWNGRADE OF THIS WAVE...SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ARE WITHIN 130 NM ON EITHER
SIDE OF THE AXIS.

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

THE MONSOON TROUGH EXTENDS SW TO 9N20W TO 5N28W. SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION FROM 2N-11N BETWEEN
15N-30W. THE ITCZ IS DISRUPTED BY THE PRESENCE OF A TROPICAL
WAVE AND SURFACE TROUGH DISCUSSED ABOVE.

...DISCUSSION...

THE GULF OF MEXICO...
A COOL AND DRY AIRMASS IS IN PLACE ACROSS THE GULF THIS
AFTERNOON...AS SURFACE OBS SHOW N TO NW FLOW 10-15 KT ACROSS THE
DISCUSSION AREA. AS THIS AIRMASS MOVES OVER THE WARM WATERS OF
THE GULF...SATELLITE VISIBLE IMAGERY SHOWS STRATOCUMULUS CLOUDS
FORMING E OF A LINE FROM 30N85W TO 19N96W. CLEAR SKIES ARE TO
THE OTHER SIDE OF THE LINE. STRONG SUBSIDENCE ALOFT COVERS THE
GULF AS WELL...SUPPORTING THE FAIR WEATHER ENVIRONMENT ACROSS
THE AREA. CONDITIONS ARE EXPECTED TO REMAIN CONSTANT OVER THE
NEXT 24 HOURS.

THE CARIBBEAN SEA...
CLUSTERS OF HEAVY SHOWERS AND THUNDERSTORMS CONTINUE TO AFFECT
THE NW AND SW BASINS W OF 73W...ASSOCIATED TO THE COLD FRONT
MENTIONED IN THE ATLC DISCUSSION. THE SOUTHERN EXTENSION OF THE
COLD FRONT MOVES ACROSS ERN CUBA...AND EXTENDS SW TO N CENTRAL
JAMAICA. N-NW WINDS BEHIND THE FRONT IN COMBINATION WITH ESE
TRADE WINDS AHEAD OF IT ARE GENERATING AN AREA OF BROAD CYCLONIC
LOW LEVEL CIRCULATION OVER THE SW CARIBBEAN. A SURFACE TROUGH IS
ANALYZED IN THIS REGION FROM 18N80W TO 10N80W. THE CONVECTION
ASSOCIATED TO THIS TROUGH IS CONCENTRATED OVER THE SRN HALF OF
THE AXIS COVERING S OF 14N W OF 73W. SHORT RANGE COMPUTER MODELS
SUGGEST THE CONVECTION IN THIS REGION WILL LINGER OVER THE NEXT
24 HOURS. OTHERWISE...FAIR WEATHER CONDITIONS PREVAIL ELSEWHERE
ACROSS THE AREA...AS A BROAD UPPER ANTICYCLONE DRAWS DRY AND
SUBSIDENT AIR ALOFT SUPPRESSING DEEP CONVECTION ACROSS THE AREA.

THE ATLANTIC OCEAN...
A DEEP LAYER TROUGH/CUT OFF LOW SWINGS ACROSS THE N-ERN CONUS
SUPPORTING A COLD FRONT MOVING ACROSS THE WRN ATLC ANALYZED
ALONG 32N70W TO ACROSS THE CENTRAL BAHAMAS NEAR 24N76W TO INTO
THE CARIBBEAN ACROSS ERN CUBA ALONG 21N77W. SCATTERED MODERATE
TO HEAVY SHOWERS AND THUNDERSTORMS ARE WITHIN 60 NM ON EITHER
SIDE OF THE BOUNDARY. THE FRONT AND ASSOCIATED CONVECTION IS
EXPECTED TO CONTINUE TO PROGRESS ENE DURING THE NEXT 24 HOURS.
AN UPPER LEVEL CYCLONIC CIRCULATION IS CENTERED 23N50W. THIS
CIRCULATION IS MOVING W-SW WITH WIDELY SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS FROM 17N-30N BETWEEN 47W-57W. EXCEPT FOR
THE CONVECTION ASSOCIATED TO A TROPICAL WAVE...FAIR WEATHER
CONDITIONS ARE ELSEWHERE ACROSS THE AREA PROVIDED BY A BROAD
UPPER ANTICYCLONE COVERING THE WRN ATLC AHEAD OF THE FRONTAL
CONVECTION...AND A BROAD SURFACE RIDGE OF HIGH PRESSURE ANCHORED
N OF THE DISCUSSION AREA.

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

$$

GARCIA




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