000 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