[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT SEP 24 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 17.9N 57.4W AT 24/2100
UTC OR ABOUT 295 MI...475 KM E OF THE LESSER ANTILLES MOVING WNW
AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM
SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. PLEASE SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. NUMEROUS MODERATE TO
STRONG CONVECTION IS FROM 15N-21N BETWEEN 51W-59W. SHEAR IS
EXPECTED TO GRADUALLY INCREASE OVER THE NEXT 72 HOURS...WHICH
SHOULD INDUCE GRADUAL WEAKENING.

TROPICAL DEPRESSION SEVENTEEN BECAME T.S. PHILIPPE AT 24/2100
UTC CENTERED NEAR 11.2N 27.9W...OR ABOUT 345 MI...550 KM SW OF
THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING WNW AT ABOUT 12 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED
WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. PLEASE SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. SCATTERED MODERATE/STRONG CONVECTION IS AROUND
THE S-WRN SEMI-CIRCLE FROM 8N-12N BETWEEN 27W-31W. PHILIPPE IS
EXPECTED TO MOVE WEST-NORTHWESTWARD AROUND THE SOUTHERN
PERIPHERY OF A STRONG SUBTROPICAL RIDGE LOCATED TO THE NORTH OF
THE CYCLONE.

...TROPICAL WAVES...

TROPICAL WAVE IS IN THE CENTRAL ATLC ANALYZED FROM 18N39W TO
11N40W MOVING W 10-15 KT. LOW LEVEL SATELLITE DERIVED WINDS
INDICATE WEAK CYCLONIC TURNING AROUND THE WAVE AXIS. THE WAVE IS
BETTER DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY SHOWING A
SURGE OF DEEP LAYER MOISTURE IN THE VICINITY OF THE WAVE AXIS.
CURRENTLY NO DEEP CONVECTION ACCOMPANIES THE WAVE.

...ITCZ/MONSOON TROUGH...

DUE TO THE LARGE SCALE CIRCULATION OF NEWLY FORMED T.S. PHILIPPE
...THE CENTRAL ATLC TROPICAL WAVE AND T.S. OPHELIA...THE OCEANIC
MONSOON TROUGH AND THE ITCZ ARE NOT PRESENT. AS PHILIPPE MOVES
TOWARDS THE WNW...THE MONSOON TROUGH WILL SLOWLY BUILD BACK IN
BEHIND IT.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY SHOWS A BROAD UPPER TROUGH/CUT-OFF LOW
CENTERED OVER THE STATE OF ILLINOIS. THE CYCLONIC FLOW
ASSOCIATED TO THIS FEATURE COVERS MOST OF THE ERN CONUS AND
PUSHES A LONGWAVE THAT SWINGS OVER THE NE GULF...SUPPORTING A
WEAK STATIONARY FRONT EXTENDING ACROSS THE NRN GULF FROM 30N83W
TO 28N91W. THIS FRONT RELATES VERY WELL WITH FAIRLY DRY DEW
POINTS TO THE N OF ITS AXIS...WITH NO SIGNIFICANT CONVECTION
OCCURRING IN ITS VICINITY. THE SAME UPPER LEVEL CONDITIONS APPLY
TO A WEAK SURFACE TROUGH ANALYZED FROM 26N85W TO 23N90W.
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE DEVELOPING
WITHIN 30-90 NM ON EITHER SIDE OF THE TROUGH AXIS. FAIR WEATHER
CONDITIONS ARE OBSERVED ELSEWHERE ACROSS THE BASIN THIS EVENING.
EXPECT THE STATIONARY FRONT CONTINUE TO WEAKEN OVER THE NEXT
12-24 HOURS. THE UPPER LEVEL TROUGH WILL ALSO REMAIN SOMEWHAT
STATIONARY ACROSS THE ERN CONUS KEEPING DRY AIR ACROSS THE NW
GULF WHICH WILL FURTHER SUPPORT FAIR CONDITIONS.

CARIBBEAN SEA...
MOSTLY FAIR WEATHER CONDITIONS WITH 15-20 KT ELY TRADEWIND FLOW
ARE OBSERVED OVER MOST OF THE CARIBBEAN SEA THIS EVENING AS
A DRY AIRMASS MOVES ACROSS THE ERN AND CENTRAL CARIBBEAN. THE
ONLY AREA OF CONVECTION IS OBSERVED IN THE FAR SW BASIN. LAST
SATELLITE VISIBLE PICTURES OF THE DAY SHOWED CLUSTERS OF
MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS S OF 17N W OF
80W...ASSOCIATED TO THE MONSOON TROUGH EXTENDING ACROSS
NICARAGUA INTO NRN COLOMBIA. COMPUTER MODELS SUGGEST THIS
FEATURE WILL REMAIN NEARLY STATIONARY OVER THE NEXT 24 HOURS.
TROPICAL STORM OPHELIA IS CURRENTLY E OF THE LESSER ANTILLES AND
SOME OF THE OUTER BANDS WILL PASS OVER THIS GROUP OF ISLANDS AND
ADJACENT WATERS N OF MARTINIQUE TONIGHT.

ATLANTIC OCEAN...
AN ELONGATED 1012 MB LOW IS 130 NM E OF DAYTONA BEACH FLORIDA
PRODUCING A LARGE AREA OF SHOWERS AND THUNDERSTORMS ACROSS THE
SW NORTH ATLC INCLUDING MUCH OF THE BAHAMAS W OF 74W. THIS
SYSTEM IS SUPPORTED ALOFT BY A BROAD UPPER LEVEL LONGWAVE MOVING
OFF THE SE CONUS SEABOARD. THIS DISTURBANCE HAS NOT BECOME ANY
BETTER ORGANIZED DURING THE PAST 6 HOURS...AND THE POTENTIAL FOR
DEVELOPMENT HAS DIMINISHED. AN UPPER RIDGE IS AHEAD OF THIS AREA
OF CONVECTION SUPPORTING A 1024 MB HIGH NEAR 34N64W. A WEAK
UPPER LOW IS N OF HISPANIOLA AND CONTINUES TO SHEAR T.S.
OPHELIA. A BROAD UPPER TROUGH COVERS THE ERN NORTH ATLC
SUPPORTING A WEAK COLD FRONT THAT CLIPS THE AREA ALONG 32N31W TO
29N37W GENERATING ISOLATED SHOWERS WITHIN 50 NM OF THE AXIS. A
WEAK 1020 MB HIGH IS E OF THE FRONT NEAR THE MADEIRA ISLANDS
PROVIDING FAIR WEATHER ACROSS THE SE ATLC.

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

$$

GARCIA




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