000 AXNT20 KNHC 121143 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... HURRICANE HUMBERTO IS CENTERED NEAR 20.5N 28.7W AT 12/0900 UTC OR ABOUT 382 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. 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. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION COVER THE AREA FROM 19N-24N BETWEEN 26W-30W. TROPICAL DEPRESSION GABRIELLE IS CENTERED NEAR 33.5N 67.7W AT 12/0900 UTC OR ABOUT 165 NM W-NW OF BERMUDA AND ABOUT 480 NM S- SE OF NANTUCKET MASSACHUSETTS MOVING NW AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1010 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. 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. SCATTERED MODERATE/ISOLATED STRONG CONVECTION REDEVELOPED CLOSE TO THE CENTER OVER THE PAST FEW HOURS FROM 32N-35W BETWEEN 64W-67W. A BROAD AREA OF LOW PRESSURE OVER THE YUCATAN PENINSULA AND THE BAY OF CAMPECHE IS ANALYZED AS A SURFACE TROUGH THAT AT 12/0900 UTC EXTENDS FROM THE GULF OF MEXICO NEAR 25N90W ALONG 21N91W TO A 1005 MB LOW IN THE BAY OF CAMPECHE NEAR 19N92W. IT APPEARS THE LOW HAS REDEVELOPED W OF WHERE IT WAS LOCATED PREVIOUSLY. THE SHOWERS/THUNDERSTORMS HAVE INCREASED DURING THE PAST FEW HOURS AS SURFACE PRESSURES CONTINUE TO FALL. AN UPPER TROUGH OVER THE GULF OF MEXICO AND AN UPPER RIDGE OVER THE CARIBBEAN ARE CREATING A BROAD AREA OF INSTABILITY WITH SCATTERED/HEAVY SHOWERS AND SCATTERED THUNDERSTORMS S OF 21N ACROSS THE BAY OF CAMPECHE. CLUSTERS OF SCATTERED TO HEAVY SHOWERS WITH EMBEDDED THUNDERSTORMS COVER THE AREA S OF 25N BETWEEN 80W-91W INCLUDING PORTIONS OF W CUBA...YUCATAN PENINSULA...CENTRAL AMERICA...AND THE SW CARIBBEAN. ENVIRONMENTAL CONDITIONS APPEAR TO BE FAVORABLE FOR DEVELOPMENT AND THIS DISTURBANCE HAS A HIGH CHANCE...60 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 12N16W TO 11N21W THEN RESUMES SW OF HURRICANE HUMBERTO NEAR 15N34W TO 11N48W WHERE THE ITCZ BEGINS AND CONTINUES INTO SOUTH AMERICA NEAR 9N61W. THE MONSOON TROUGH CONTINUES TO BE DISRUPTED BY HURRICANE HUMBERTO. CLUSTERS OF SCATTERED MODERATE/ ISOLATED STRONG CONVECTION ARE FROM 6N-12N E OF 22W TO THE COAST OF W AFRICA. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 10N-17N BETWEEN 26W-30W AND FROM 6N-10N BETWEEN 34W-50W. A 1007 MB LOW IS CENTERED NEAR 16N53W WITH SCATTERED MODERATE/STRONG CONVECTION WITHIN 90 NM E OF THE CENTER. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH EXTENDS OVER THE W GULF FROM AN UPPER LOW ALONG THE COAST OF TEXAS NEAR GALVESTON ALONG 25N94W TO OVER THE W BAY OF CAMPECHE NEAR TUXPAN. AN UPPER LOW IS ALONG THE COAST OF GEORGIA AND EXTENDS AN UPPER TROUGH ACROSS THE NE GULF N OF 27N E OF 87W. A SURFACE TROUGH EXTENDS FROM THE W ATLC ALONG THE BASE OF THE UPPER LOW ACROSS FLORIDA BETWEEN WEST PALM BEACH TO JUST S OF FORT MYERS THEN INTO THE GULF TO 26N85W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 150 NM S OF THE SURFACE TROUGH E OF 85W ACROSS FLORIDA AND THROUGH THE STRAITS OF FLORIDA. SIMILAR ACTIVITY IS N OF THE SURFACE TROUGH WITHIN 30 NM OF LINE FROM FORT MYERS TO 29N85W. AN UPPER RIDGE ANCHORED OVER THE W CARIBBEAN COVERS THE REMAINDER OF THE SE GULF. THIS IS CREATING A VERY DIFFLUENT ENVIRONMENT MAINLY FOR THE S GULF. THE SURFACE TROUGH AND LOW IN THE CENTRAL GULF AND BAY OF CAMPECHE WITH THE ASSOCIATED WEATHER ARE DISCUSSED IN THE SPECIAL FEATURES ABOVE. A SURFACE RIDGE EXTENDS OVER THE N GULF ANCHORED BY A SERIES OF WEAK HIGHS OVER THE SE CONUS. SURFACE RIDGE WILL PERSIST THROUGH TONIGHT. THE SURFACE TROUGH/LOW IN THE SPECIAL FEATURES ABOVE IS FORECAST TO MOVE VERY SLOWLY W-NW AND POSSIBLY DEVELOP INTO A TROPICAL CYCLONE. CARIBBEAN SEA... SEE THE SPECIAL FEATURES ABOVE FOR THE ACTIVITY OVER THE W CARIBBEAN ASSOCIATED WITH THE SURFACE TROUGH/LOW IN THE BAY OF CAMPECHE. AN UPPER RIDGE IS ANCHORED OVER THE NW CARIBBEAN IN THE GULF OF HONDURAS COVERING THE AREA W OF 78W ACROSS CUBA INTO THE SE GULF OF MEXICO. AN UPPER LOW DOMINATES THE REMAINDER OF THE CARIBBEAN CENTERED NEAR 16N73W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 14N TO INLAND OVER COLOMBIA BETWEEN 70W- 76W. A SURFACE TROUGH IS APPROACHING THE LEEWARD ISLANDS AND IS DISCUSSED IN THE ATLC SECTION BELOW. 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... HISPANIOLA IS UNDER MOSTLY CLEAR SKIES THIS MORNING. HOWEVER... ISOLATED SHOWERS COULD STILL FORM ESPECIALLY OVER THE S PORTION OF THE DOMINICAN REPUBLIC. THE UPPER TROUGH CURRENTLY COVERING THE CARIBBEAN WILL SHIFT W. SOUTHERLY SURFACE FLOW WILL THEN DOMINATE THE ISLAND BY FRI MORNING. THE WEAK SURFACE TROUGH CURRENTLY E OF THE LEEWARD ISLANDS WILL CONTINUE W CROSSING THE ISLAND ON SAT. THIS COULD INCREASE THE CHANCES OF HEAVIER SHOWERS AND THUNDERSTORMS TO HISPANIOLA LATE FRI INTO SAT. AFTERNOON HEATING COULD STILL BRING POTENTIAL SCATTERED THUNDERSTORMS THROUGH THE REMAINDER OF THE WEEKEND. ATLANTIC OCEAN... THE PRIMARY CONCERNS FOR THE ATLC BASIN THIS MORNING ARE TROPICAL DEPRESSION GABRIELLE IN THE W ATLC AND HURRICANE HUMBERTO IN THE E ATLC. SEE SPECIAL FEATURES ABOVE. AN UPPER LOW IS CENTERED ALONG THE COAST OF GEORGIA WITH AN UPPER TROUGH COVERING THE W ATLC N OF 27N W OF 75W. A SURFACE TROUGH IS ALONG THE S PERIPHERY OF THE UPPER TROUGH FROM 32N75W 28N77W ACROSS FLORIDA INTO THE GULF OF MEXICO NEAR WEST PALM BEACH. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 90 NM OF LINE FROM OVER FLORIDA NEAR FORT LAUDERDALE CROSSING THE SURFACE TROUGH NEAR 28N77W TO BEYOND 32N76W. CLUSTERS OF SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS DOT THE AREA FROM 27N-30N BETWEEN 64W- 70W. A SHORTWAVE UPPER TROUGH IS DEVELOPING OVER THE LEEWARD ISLANDS FROM 19N64W TO 11N59W SUPPORTING A SURFACE TROUGH THAT IS APPROACHING THE LEEWARD ISLANDS EXTENDING FROM 24N65W 18N62W TO 15N54W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 13N- 16N BETWEEN 53W-62W INCLUDING THE ISLANDS BETWEEN DOMINICA AND SAINT LUCIA. ISOLATED SHOWERS ARE WITHIN 90/120 NM EITHER SIDE OF THE TROUGH INCLUDING THE LEEWARD AND VIRGIN ISLANDS. A WEAK PRESSURE PATTERN WILL PREVAIL ACROSS THE MOST OF THE ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW/NR