[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231149
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI SEP 23 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 14.5N 51.0W AT 23/0900
UTC OR 640 NM E-SE OF THE LEEWARD ISLANDS MOVING W-NW AT 11 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SCATTERED MODERATE
CONVECTION IS FROM 12N-19N BETWEEN 45W-49W AND FROM 08N-12N
BETWEEN 47W-55W LOCATED MAINLY EAST AND SOUTHEAST OF THE
LOW-LEVEL CIRCULATION. A SURFACE TROUGH TRAILS TO THE SOUTHWEST
ANALYZED FROM 11N50W TO 06N56W. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 11N33W TO 21N31W MOVING W AT
10-15 KT. INFRARED SHORTWAVE SATELLITE IMAGERY AND LOW-LEVEL
STREAMLINE ANALYSIS INDICATES BROAD CYCLONIC FLOW IN THE
VICINITY OF THE WAVE AXIS BETWEEN 30W-37W. TOTAL PRECIPITABLE
WATER IMAGERY INDICATES THAT ENHANCED DEEP LAYER MOISTURE
ACCOMPANIES THE WAVE FROM 08N-22N BETWEEN 28W-36W. NO
SIGNIFICANT DEEP CONVECTION IS NOTED WITH THE WAVE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N17W
ALONG 07N23W TO 09N31W. SCATTERED MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 07N-13N BETWEEN 19W-25W...AND SCATTERED
MODERATE CONVECTION IS FROM 04N-07N BETWEEN 21W-29W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LONGWAVE TROUGH WITH AXIS MOVING ACROSS THE
CENTRAL CONUS IS IMPACTING THE WEATHER IN THE EASTERN GULF THIS
MORNING. MIDDLE TO UPPER LEVEL DIFFLUENCE AROUND THE EASTERN
PERIPHERY OF THE UPPER LEVEL TROUGHING IS SUPPORTING AN AREA OF
ISOLATED SHOWERS AND TSTMS FOCUSED WITHIN 120 NM EITHER SIDE OF
A SURFACE TROUGH ANALYZED ALONG 29N85W TO 27N87W TO 23N88W. THE
UPPER LEVEL TROUGH IS ALSO SUPPORTING A COLD FRONT EXTENDING
FROM SW LOUISIANA NEAR 30N93W TO 28N97W...HOWEVER...THE FRONT
REMAINS DRY WITH NO PRECIPITATION RETURNS ON MOSAIC DOPPLER
RADAR IMAGERY. THEREFORE...THE REMAINDER OF THE GULF W OF THE
SURFACE TROUGH IS UNDER MOSTLY CLEAR SKIES AND FAIR CONDITIONS
DUE TO DRY AIR ALOFT. THE SURFACE TROUGH IS FORECAST TO REMAIN
STATIONARY BEFORE BEING ABSORBED BY THE COLD FRONT BY LATE
FRIDAY. BEYOND LATE FRIDAY...THE FRONT IS EXPECTED TO GRADUALLY
WEAKEN OVER THE NORTH-CENTRAL AND NE GULF THROUGH LATE SATURDAY.

CARIBBEAN SEA...
RATHER BENIGN CONDITIONS AND WEAK DYNAMICS IN THE MIDDLE AND
UPPER LEVELS ACROSS THE WESTERN CARIBBEAN ARE LEADING TO MOSTLY
FAIR CONDITIONS WITH TRADES REMAINING IN THE 10 TO 15 KT
RANGE...AND STRONGER NEAR THE COAST OF COLOMBIA THIS MORNING.
LOW-LEVEL MOISTURE CONTINUES TO CONVERGE OVER THE WESTERN
CARIBBEAN DUE TO THESE TRADES AND ISOLATED SHOWERS AND TSTMS ARE
OCCURRING W OF A LINE FROM 20N87W TO 11N74W. A WEAK UPPER LEVEL
TROUGH WITH AXIS ALONG 85W S OF 18N IS PROGRESSING WESTWARD
ACROSS NICARAGUA AND HONDURAS AND IS LIKELY ENHANCING THE
CONVECTION LOCATED OVER THE SW CARIBBEAN. FARTHER EAST ACROSS
THE CENTRAL CARIBBEAN...AN AREA OF LOW TO MIDDLE LEVEL MOISTURE
IS GENERATING ISOLATED SHOWERS AND TSTMS N OF 12N BETWEEN
67W-74W AND IS EXPECTED TO CONTINUE PROPAGATING WESTWARD ACROSS
PORTIONS OF HISPANIOLA...THE WINDWARD PASSAGE REGION...AND
JAMAICA THROUGH LATE FRIDAY. E OF 67W...MOSTLY CLEAR SKIES AND
FAIR CONDITIONS ARE FORECAST TO REMAIN IN PLACE TODAY AS OPHELIA
IS EXPECTED TO TRACK TO THE NE OF THE NORTHERN LEEWARD ISLANDS
BY EARLY NEXT WEEK. LASTLY...LOW-LEVEL MOISTURE CONVERGENCE
ACROSS THE SE CARIBBEAN IS GENERATING ISOLATED SHOWERS S OF 12N
BETWEEN 59W-65W...INCLUDING TRINIDAD AND TOBAGO.

ATLANTIC OCEAN...
A LARGE AREA OF LOW TO MIDDLE LEVEL MOISTURE RESIDES ON THE
SOUTHERN PERIPHERY OF AN UPPER LEVEL ANTICYCLONIC CIRCULATION
CENTERED OVER THE SW NORTH ATLC WATERS NEAR 32N71W. A SURFACE
TROUGH IS ANALYZED FROM 27N73W TO 23N78W OVER THE CENTRAL
BAHAMAS WITH LOW-LEVEL CONVERGENT SE WINDS GENERATING WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 22N-28N BETWEEN
64W-77W. ON THE WESTERN PERIPHERY OF THE UPPER LEVEL RIDGE...
MOISTURE STREAMING NORTHEASTWARD FROM THE EASTERN GULF OF MEXICO
ACROSS THE FLORIDA PENINSULA IS GENERATING SCATTERED SHOWERS AND
ISOLATED TSTMS N OF 29N BETWEEN 77W-81W. THE REMAINDER OF THE
CENTRAL AND EASTERN ATLC N OF 20N IS UNDER THE INFLUENCE OF A
SURFACE RIDGE ANCHORED BY A 1027 MB HIGH CENTERED NEAR 36N56W
AND A 1022 MB HIGH CENTERED NEAR 35N20W. A COLD FRONT AND
ASSOCIATED LOW-LEVEL MOISTURE IS LOCATED MOSTLY NORTH OF THE
DISCUSSION AREA BETWEEN THE TWO SURFACE HIGHS WITH THE COLD
FRONT ANALYZED FROM THE AZORES NEAR 38N28W TO 30N43W. ISOLATED
SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE BOUNDARY.
A WEAK PRE-FRONTAL TROUGH IS ALSO ANALYZED FROM 33N31W TO
28N34W. OTHERWISE...TROPICAL STORM OPHELIA IS IMPACTING THE
CENTRAL TROPICAL ATLC AND IS FORECAST TO TRACK W-NW OVER THE
NEXT FEW DAYS TO NEAR 23N64.5W BY EARLY TUESDAY.

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

$$
HUFFMAN




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