[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231743
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 14.6N 52.6W AT 23/1500
UTC OR 550 NM...1020 KM E-SE OF THE LEEWARD ISLANDS MOVING W
AT 14 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. A BURST OF
SCATTED TO NUMEROUS STRONG CONVECTION HAS DEVELOPED WITHIN 90-120
NM IN THE N SEMICIRCLE OF OPHELIA. SCATTERED MODERATE ISOLATED
STRONG IS OCCURRING ELSEWHERE IN AN ARC FROM 10N TO 19N BETWEEN
46W AND 52W...MAINLY EAST AND SOUTHEAST OF THE LOW-LEVEL
CIRCULATION. A SURFACE TROUGH TRAILS TO THE SOUTHWEST ANALYZED
FROM 11N52W TO 06N58W. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

LOW PRESSURE 1012 MB WAS LOCATED ALONG THE MONSOON TROUGH NEAR
9N20W. SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED WITHIN
180 NM OF THE LOW MAINLY IN THE W SEMICIRCLE. SCATTERED MODERATE
ISOLATED STRONG CONVECTION WAS INDICATED ELSEWHERE FROM 5N TO
12N BETWEEN 24W AND 29W.

TROPICAL WAVE IS ANALYZED FROM 11N36W TO 21N33W MOVING W AT 10
KT. VISIBLE SATELLITE IMAGERY AND LOW-LEVEL STREAMLINE ANALYSIS
INDICATES BROAD CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS
BETWEEN 31W-38W. 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
TO LOW PRESSURE NOTED ABOVE NEAR 9N20W. CONVECTION IS DESCRIBED
ABOVE IN REFERENCE TO THE LOW PRESSURE NEAR 9N20W.

...DISCUSSION...

GULF OF MEXICO...
A SHARP MID TO UPPER LEVEL LONGWAVE TROUGH WITH AXIS MOVING
ACROSS THE MISSISSIPPI RIVER VALLEY IS IMPACTING THE WEATHER IN
THE GULF. MIDDLE TO UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH
AXIS COMBINED WITH RESIDUAL LOW AND MID LEVEL MOISTURE IS
SUPPORTING AN AREA OF ISOLATED SHOWERS AND TSTMS FOCUSED WITHIN
120 NM EAST OF A SURFACE TROUGH ANALYZED ALONG 28N86W TO THE
MIDDLE OF THE YUCATAN PENINSULA. THE UPPER LEVEL TROUGH IS ALSO
SUPPORTING A COLD FRONT THAT HAS MOVED INTO THE GULF OF MEXICO
EXTENDING FROM NEAR LAFAYETTE LOUISIANA TO THE MIDDLE TEXAS
COAST. DEEP LAYERED SUBSIDENCE NOTED ON WATER VAPOR IMAGERY HAS
PRECLUDED ANY PRECIPITATION ASSOCIATED WITH THE FRONT WITH
VISIBLE SATELLITE IMAGERY INDICATING ONLY PATCHES OF LOW CLOUDS
IN INCREASING LOW LEVEL NORTHERLY FLOW AMIDST AREAS OF CLEAR
SKIES. THE SURFACE TROUGH IS FORECAST TO REMAIN STATIONARY
BEFORE BEING ABSORBED BY THE COLD FRONT BY THIS EVENING.
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 AFTERNOON.
LOW-LEVEL MOISTURE CONTINUES TO CONVERGE OVER THE WESTERN
CARIBBEAN DUE TO THESE TRADES WITH SCATTERED SHOWERS AND TSTMS
OCCURRING FROM THE HONDURAN-NICARAGUAN BORDER ALONG THE COAST OF
NICARAGUA...COSTA RICA AND PANAMA AND ELSEWHERE S OF 15N W OF
80W. A WEAK INVERTED UPPER LEVEL TROUGH WITH AXIS ALONG 86W 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 68W-74W AND IS EXPECTED TO CONTINUE PROPAGATING
WESTWARD ACROSS PORTIONS OF HISPANIOLA...THE WINDWARD PASSAGE
REGION...AND JAMAICA THROUGH TONIGHT. 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 SUNDAY AND MONDAY. 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 A LARGE MID TO UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED OVER THE SW NORTH ATLC WATERS NEAR 33N68W.
A SURFACE TROUGH IS ANALYZED FROM 28N74W TO 23N78W OVER THE
CENTRAL BAHAMAS WITH LOW-LEVEL CONVERGENT SE WINDS GENERATING
WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS FROM 22N-28N BETWEEN
70W-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 WIDELY SCATTERED
SHOWERS AND ISOLATED TSTMS OVER THE FLORIDA PENINSULA NEAR FORT
MYERS. 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 35N61W AND A 1026 MB HIGH CENTERED NEAR
35N46W. THE TAIL END OF A COLD FRONT AND ASSOCIATED LOW-LEVEL
MOISTURE IS LOCATED MOSTLY NORTH OF THE DISCUSSION AREA BETWEEN
35W AND 45W WITH THE COLD FRONT ANALYZED FROM THE AZORES NEAR
38N28W TO 30N40W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM
EITHER SIDE OF THE BOUNDARY. WEAK 1019 MB HIGH PRESSURE WAS
SITUATED WELL EAST OF THE FRONT NEAR 35N20W AND GOVERNED THE
WEATHER OVER THE FAR EAST ATLANTIC. OTHERWISE...TROPICAL STORM
OPHELIA IS IMPACTING THE WESTERN TROPICAL ATLC AND IS FORECAST
TO TRACK WNW OVER THE NEXT FEW DAYS PASSING NORTHEAST OF THE
LEEWARD ISLANDS SUNDAY AND MONDAY.

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

$$
COBB





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