[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 092337
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU MAY 09 2013

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
2245 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE COAST OF SENEGAL NEAR 14N17W
TO 6N24W. THE ITCZ BEGINS NEAR 6N24 AND CONTINUES ALONG EQ36W
EQ47W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 1N-6N
BETWEEN 10W-20W.

...DISCUSSION...

GULF OF MEXICO...
SURFACE RIDGING CONTINUES ACROSS THE GULF OF MEXICO CENTERED IN
THE NE GULF AROUND A 1023 MB HIGH NEAR 29N85W. WINDS ARE LIGHT
AND ANTI-CYCLONIC NEAR THE HIGH CENTER BUT INCREASE UP TO 15 KT
ACROSS THE WESTERN GULF WHERE SOUTHEASTERLY RETURN FLOW IS
BUILDING. MOSTLY CLEAR SKIES ARE PRESENT THROUGHOUT THE AREA
EXCEPT FOR SOME CLOUD COVER ALONG THE TEXAS AND LOUISIANA COASTS
ASSOCIATED WITH MOISTURE FLOWING OVER THE AREA. ALOFT...AN UPPER
LEVEL RIDGE COVERS THE WESTERN GULF WITH AXIS NEAR 93W. UPPER
LEVEL TROUGHING IS STILL ACROSS THE EASTERN GULF WITH AXIS NEAR
78W. A FEW STRONG CLUSTERS OF SHOWERS AND THUNDERSTORMS HAVE
FORMED OVER SOUTHEAST FLORIDA ASSOCIATED WITH A SEABREEZE
TROUGH. THE SURFACE RIDGE IS EXPECTED TO CONTINUE MOVING
EASTWARD UNTIL A FRONTAL BOUNDARY SKIMS THE NORTHERN GULF EARLY
SATURDAY. SHOWERS AND THUNDERSTORMS WILL BE LIKELY ACROSS THE
NORTHERN GULF AS THE FRONT PASSES.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH DOMINATES THE UPPER LEVELS OVER THE
CARIBBEAN ALONG 78W PROVIDING DRY AIR ALOFT ACROSS THE FAR
WESTERN CARIBBEAN...BUT MOIST DIFFLUENCE ALOFT ACROSS THE
EASTERN HALF. THIS PATTERN IS PROVIDING FAIR CONDITIONS ACROSS
THE NW CORNER OF THE BASIN AS WELL AS THE SE PORTION. THE UPPER
TROUGH SUPPORTS A SURFACE TROUGH EXTENDING FROM 18N79W TO A 1010
MB SURFACE LOW OVER COLOMBIA AT 9N76W. TWO AREAS OF HEAVY
SHOWERS AND THUNDERSTORMS ARE NOTED DUE TO THE BROAD SURFACE
TROUGHING AND DIFFLUENCE ALOFT. THE FIRST IS ACROSS CENTRAL
AMERICA INCLUDING COSTA RICA...PANAMA...AND NORTHERN COLOMBIA.
ACTIVITY IS SOUTH OF 12N BETWEEN 72W-85W. THE SECOND AREA OF
ACTIVITY IS ACROSS CUBA AND HISPANIOLA. LIGHTNING DATA INDICATES
HEAVY SHOWERS AND THUNDERSTORMS ARE ACROSS CUBA FROM 21N-23N
BETWEEN 77W-82W. SCATTERED SHOWERS CONTINUE TO THE EAST...NORTH
OF 17N BETWEEN 69W-77W INCLUDING MUCH OF HISPANIOLA. ISOLATED
SHOWERS AND THUNDERSTORMS ARE ALSO ACROSS THE NORTHERN LEEWARDS
ISLANDS AND PUERTO RICO ASSOCIATED WITH A SHEAR AXIS IMMEDIATELY
TO THE NORTH. TRADEWIND FLOW OF 15-20 KT IS PRESENT THROUGHOUT
MUCH OF THE AREA TURNING CYCLONICALLY AROUND THE TROUGH. THE
SURFACE TROUGH IS EXPECTED TO CONTINUE MOVING WEST...WHICH
SHOULD SHIFT SOME OF THE MOISTURE AWAY FROM CUBA AND HISPANIOLA.
MOISTURE WITH THE SHEAR AXIS MAY SHIFT SOUTH AND PROVIDE SHOWERS
OVER THE FAR EASTERN CARIBBEAN.

ATLANTIC OCEAN...
BROAD LOW PRESSURE COVERS THE FAR WEST ATLC ASSOCIATED WITH AN
UPPER LEVEL TROUGH ALONG 78W. A SURFACE TROUGH EXTENDS ALONG
27N71W TO 19N74W. THE COMBINATION OF SURFACE CONVERGENCE AND
UPPER LEVEL DIFFLUENCE IS PRODUCING A LARGE AREA OF SHOWERS AND
THUNDERSTORMS ACROSS THE BAHAMAS FROM 20N-30N BETWEEN 65W-76W.
BROAD SURFACE RIDGING COVERS THE REMAINDER OF THE WESTERN AND
CENTRAL ATLC SUPPORTED BY AN UPPER LEVEL RIDGE ALONG 60W.
SCATTERED SHOWERS CONTINUE NORTH OF THE LEEWARD ISLANDS AND INTO
THE CENTRAL ATLC NEAR A SHEAR AXIS THAT EXTENDS FROM FARTHER
EAST NEAR 23N27W TO ALONG 16N47W 14N56W 18N62W 19N67W. SCATTERED
SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THE AXIS WEST OF 37W.
BROAD UPPER TROUGHING COVERS THE EASTERN ATLC WITH AXIS NEAR
35W. THE UPPER TROUGH SUPPORTS A WEAK 1016 MB SURFACE LOW NEAR
30N30W. A SURFACE TROUGH EXTENDS FROM THE LOW CENTER TO NEAR
26N36W. NO SHOWER ACTIVITY IS NEAR THE TROUGH. A SECOND SURFACE
TROUGH EXTENDS ALONG 31N21W TO 23N27W AND CONNECTS TO THE SHEAR
AXIS THAT CONTINUES TOWARDS THE NE CARIBBEAN. ISOLATED SHOWERS
ARE WITHIN 90 NM EAST OF THE AXIS. THE AREA OF MOISTURE IN THE
WEST ATLC IS EXPECTED TO GRADUALLY DRIFT EAST AND WILL MERGE
WITH THE MOISTURE NEAR THE SHEAR AXIS.

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

AT THE REQUEST OF METEO-FRANCE AND THE METEOROLOGICAL SERVICES OF
HAITI AND THE DOMINICAN REPUBLIC...THE TROPICAL ANALYSIS AND
FORECAST BRANCH (TAFB) WILL BEGIN PROVIDING...ON A TEMPORARY
BASIS...A SEPARATE DETAILED SECTION WITHIN THE ATLANTIC TROPICAL
WEATHER DISCUSSION (TWDAT). IT WILL COVER BOTH HAITI AND THE
DOMINICAN REPUBLIC DUE TO THE SHARED GEOGRAPHY OF BOTH COUNTRIES
ON THE ISLAND OF HISPANIOLA.

THE SECTION BEGINS ON MAY 15 2013 AT 1800 UTC...2 PM EDT. IT
WILL PROVIDE GUIDANCE FOR SIGNIFICANT WEATHER EVENTS THAT ARE
EXPECTED TO IMPACT THE REGION THROUGH 48 HOURS...WITH THE FOCUS
ON ASSESSING THE POTENTIAL FOR HEAVY RAINFALL.

$$
WALTON

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