000 AXNT20 KNHC 121803 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU SEP 12 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... HURRICANE HUMBERTO IS CENTERED NEAR 21.8N 29.0W AT 12/1500 UTC OR ABOUT 448 NM NW OF THE CAPE VERDE ISLANDS MOVING N AT 12 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 982 MB. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90 KT. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION COVER THE AREA FROM 20N-26N BETWEEN 22W-30W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. GABRIELLE REGAINED TROPICAL STORM STRENGTH AND AS OF 12/1500 UTC IS CENTERED NEAR 33.9N 67.7W OR 175 NM NW OF BERMUDA. ITS PRESENT MOVEMENT IS N AT 7 KT AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 40 KT. A CLUSTER OF MODERATE CONVECTION IS E OF THE CENTER FROM 32N-35N BETWEEN 65W-67W WITH SCATTERED MODERATE TRAILING CONVECTION FROM 28N-32N BETWEEN 64W-68W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. A BROAD AREA OF LOW PRESSURE IS OVER THE WESTERN GULF AND IS ANALYZED AS A SURFACE TROUGH THAT AT 12/1500 UTC EXTENDS FROM 25N93W TO A 1005 MB LOW IN THE BAY OF CAMPECHE NEAR 19N92W. A CLUSTER OF MODERATE/ISOLATED STRONG CONVECTION IS FROM 17N-22N BETWEEN 89W-94W. SCATTERED MODERATE CONVECTION AND TSTMS ARE ELSEWHERE IN THE GULF S OF 26N W OF 88W. SATELLITE AND SURFACE OBSERVATIONS INDICATE THAT A TROPICAL DEPRESSION COULD BE FORMING IN THE SOUTH-CENTRAL BAY OF CAMPECHE...AND IF THIS TREND CONTINUES...ADVISORIES WILL BE INITIATED LATER TODAY OR TONIGHT. ENVIRONMENTAL CONDITIONS CONTINUE TO APPEAR FAVORABLE FOR DEVELOPMENT GIVING THIS DISTURBANCE A HIGH CHANCE...80 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS SYSTEM IS FORECAST TO MOVE VERY SLOWLY ACROSS THE SOUTHERN GULF OF MEXICO PRODUCING LOCALLY HEAVY RAINS OVER A LARGE PART OF EASTERN MEXICO DURING THE NEXT SEVERAL DAYS. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. ...TROPICAL WAVES... NONE. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC NEAR 11N15W TO 08N24W THEN RESUMES SW OF HURRICANE HUMBERTO NEAR 11N32W TO 09N55W WHERE THE ITCZ BEGINS AND CONTINUES INTO SOUTH AMERICA NEAR 10N60W. THE MONSOON TROUGH CONTINUES TO BE DISRUPTED BY HURRICANE HUMBERTO. SCATTERED MODERATE CONVECTION IS FROM 06N-12N BETWEEN 18W-30W. SCATTERED SHOWERS ARE FROM 08N- 10N BETWEEN 37W-45W. ...DISCUSSION... GULF OF MEXICO... A MIDDLE-LEVEL LOW CENTERED IN THE BAY OF CAMPECHE NEAR 19N92W SUPPORTS THE BROAD AREA OF LOW PRESSURE DISCUSSED IN THE SPECIAL FEATURES. AN ELONGATED UPPER-LEVEL LOW IS CENTERED IN THE NW GULF NEAR 27N95W. ANOTHER ELONGATED UPPER LOW IS CENTERED E OF GEORGIA EXTENDING ACROSS FLORIDA AND THE E GULF E OF 86W WHILE A BROAD RIDGE COVERS THE SE GULF. THIS UPPER-LEVEL PATTERN IS GENERATING DIFFLUENCE TO SUPPORT THE CONVECTION IN THE EASTERN GULF S OF 26N...INCLUDING SOUTH FLORIDA...THE STRAITS AND THE YUCATAN CHANNEL. SURFACE RIDGING DOMINATES THE NE GULF N OF 27N WHERE LOWER TO MIDDLE LEVEL DRY AIR SUPPORTS FAIR WEATHER THIS AFTERNOON. THE SURFACE TROUGH/LOW IN THE SPECIAL FEATURES ABOVE IS FORECAST TO STAY NEARLY STATIONARY WITHIN THE NEXT 48 HOURS AND POSSIBLY DEVELOP INTO A TROPICAL CYCLONE. CARIBBEAN SEA... SCATTERED MODERATE CONVECTION AND TSTMS TRAILING THE DISTURBANCE IN THE BAY OF CAMPECHE COVERS THE NW CARIBBEAN SEA N OF 17N W OF 81W. SIMILAR CONVECTION IS OVER THE SOUTHERN BASIN S OF 14N BETWEEN 77W-83W BEING SUPPORTED BY MIDDLE-LEVEL DIFFLUENCE AND THE MONSOON TROUGH. AN ELONGATED UPPER-LEVEL LOW IS CENTERED OVER THE CENTRAL CARIBBEAN NEAR 15N73W TO SUPPORT NUMEROUS MODERATE CONVECTION S OF 17N TO INLAND VENEZUELA AND COLOMBIA BETWEEN 70W-74W. AN ELONGATED RIDGE EXTENDS OVER THE WESTERN N ATLC TO THE E CARIBBEAN GENERATING DIFFLUENT FLOW ALOFT TO SUPPORT THE CONVECTION ASSOCIATED WITH A SURFACE TROUGH MOVING ACROSS PUERTO RICO SE TO THE WINDWARD ISLANDS. THE AXIS OF THIS SURFACE TROUGH EXTENDS FROM 23N68W IN THE ATLC TO 18N66W TO 14N62W TO 12N58W. RAINSHOWERS AND TSTMS ARE OVER CENTRAL AND WESTERN PUERTO RICO. A LARGE AREA OF SCATTERED MODERATE CONVECTION AND TSTMS IS FROM 12N-15N BETWEEN 57W-65W...INCLUDING THE LEEWARD ISLANDS. THE SURFACE TROUGH IS EXPECTED TO DRIFT W- SW AND ENTER THE DOMINICAN REPUBLIC TONIGHT. RAINSHOWERS ASSOCIATED WITH THE NOW DISTURBANCE IN THE SW GULF WILL CONTINUE TO AFFECT THE WESTERN BASIN THROUGH SAT AFTERNOON AND POSSIBLY BEYOND THAT TIME FRAME. MODERATE TO FRESH TRADE WINDS WILL CONTINUE ACROSS THE CENTRAL AND E CARIBBEAN THROUGH TODAY WHILE MODERATE SE WINDS WILL PREVAIL ACROSS THE W CARIBBEAN. HISPANIOLA... ISOLATED SHOWERS AND ISOLATED TSTMS ARE OVER THE ISLAND BEING ENHANCED BY AN ELONGATED UPPER-LEVEL LOW CENTERED OVER THE CARIBBEAN SEA. HOWEVER...HEAVIER PRECIPITATION CAN START AS SOON AS THIS EVENING ASSOCIATED WITH THE SURFACE TROUGH MOVING ACROSS PUERTO RICO AND THE WINDWARD ISLAND. THE TROUGH IS EXPECTED TO CONTINUE TO MOVE W-SW AND ENTER THE DOMINICAN REPUBLIC TONIGHT. THE TROUGH SHOULD HAVE EXIT HAITI BY EARLY FRIDAY BUT RAINSHOWERS CAN PERSIST THROUGH VERY EARLY SATURDAY. ATLANTIC OCEAN... THE PRIMARY CONCERNS FOR THE ATLC BASIN THIS AFTERNOON ARE TROPICAL STORM GABRIELLE IN THE W ATLC AND HURRICANE HUMBERTO IN THE E ATLC. SEE SPECIAL FEATURES ABOVE. AN UPPER-LEVEL LOW CENTERED E OF GEORGIA IS ENHANCING SCATTERED SHOWERS AND TSTMS FROM 25N-35N W OF 74W...INCLUDING THE NORTHERN BAHAMAS. TRAILING RAINSHOWERS FROM TROPICAL STORM GABRIELLE ARE FURTHER E N OF 27N BETWEEN 64W-69W. AN UPPER-LEVEL LOW OVER THE CENTRAL BASIN EXTENDS A TROUGH AXIS SW TOWARDS E OF THE WINDWARD ISLANDS. THIS TROUGHINESS SUPPORTS A 1007 MB SURFACE LOW PRESSURE CENTER NEAR 16N53W. THIS LOW WAS PREVIOUSLY ATTACHED TO THE SURFACE TROUGH THAT NOW MOVES ACROSS PUERTO RICO AND THE WINDWARD ISLANDS. SEE THE CARIBBEAN SECTION FOR MORE INFORMATION ABOUT THE TROUGH. A WEAK PRESSURE PATTERN WILL PREVAIL ACROSS THE MOST OF THE ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ RAMOS