000 AXNT20 KNHC 161748 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE AUG 16 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURE... THE CENTER OF TROPICAL STORM GERT AT 16/1500 UTC IS NEAR 38.1N 57.5W...ABOUT 500 NM NE OF BERMUDA. GERT IS MOVING NE AT 23 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 50 KT WITH GUSTS TO 60 KT. PUBLIC ADVISORIES ON TROPICAL STORM GERT ARE ISSUED UNDER WMO HEADER WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2. FORECAST/ADVISORIES ON TROPICAL STORM GERT ARE ISSUED UNDER WMO HEADER WTNT22 KNHC AND UNDER AWIPS HEADER MIATCMAT2. THE STORM CENTER IS EXPECTED TO ACCELERATE NE BEFORE BECOMING EXTRATROPICAL. ISOLATED MODERATE CONVECTION IS FROM 37N-39N BETWEEN 56W-60W. ...TROPICAL WAVES... WELL DEFINED TROPICAL WAVE IS MOVING W THROUGH THE CAPE VERDE ISLANDS ALONG 17N24W TO 11N27W AT 15 KT. SATELLITE IMAGERY SHOWS DISTINGUISHABLE LOW-LEVEL CYCLONIC FLOW AROUND THE WAVE AXIS WHICH MAY BE FORMING A LOW CENTER ON THE WAVE AXIS. THIS CYCLONIC FLOW IS ALSO EVIDENT IN SCATTEROMETER DATA. THE WAVE IS EMBEDDED WITHIN A SURGE OF DEEP LAYER MOISTURE EXTENDING TO 21N. WHILE NO DEEP CONVECTION IS IN CLOSE VICINITY OF THE WAVE...A CLUSTER OF MODERATE/STRONG CONVECTION IS SW OF IT FROM 7N-10N BETWEEN 28W-34W. TROPICAL WAVE IS MOVING W ACROSS THE ERN CARIBBEAN ALONG 18N66W TO 11N65W AT 20 KT. A RECENT ASCAT SCATTEROMETER PASS INDICATES LOW-LEVEL CYCLONIC FLOW IS AROUND THE WAVE AXIS. VERY ENHANCED MOISTURE VALUES SURROUND THE WAVE ACROSS THE ERN CARIBBEAN E OF 71W. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM 15N-18N BETWEEN 61W-71W. ACCORDING TO THE SAN JUAN PUERTO RICO RADAR...MOST OF THE STRONGEST ACTIVITY IS S OF THE ISLANDS WITH MORE SCATTERED ACTIVITY OVER THE ISLAND. AN AREA OF AFRICAN DUST IS TO THE N OF THE ISLANDS WHICH MAY BE WHAT IS INHIBITING CONVECTION TO THE N. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W OF A TROPICAL WAVE NEAR THE CAPE VERDE ISLANDS ALONG 10N29W 10N43W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS JUST OFF THE AFRICAN COAST FROM 8N-12N BETWEEN 18W-25W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 5N-12N BETWEEN 40W-46W. ...DISCUSSION... THE GULF OF MEXICO... A LONGWAVE UPPER LEVEL TROUGH IS MOVING EWD WITH AXIS NOW OVER THE ERN SEABOARD. THE UPPER TROUGH CONTINUES TO SUPPORT A STATIONARY FRONT ACROSS THE NE GULF OF MEXICO FROM THE BIG BEND OF FLORIDA NEAR 29N83W TO SE LOUISIANA NEAR 29N90W. ISOLATED SHOWERS/THUNDERSTORMS ARE S OF THE FRONT WITHIN 300 NM BETWEEN 81W-86W OVER MUCH OF CENTRAL AND S FLORIDA. THE REMAINDER OF THE BASIN IS UNDER WEAK SURFACE RIDGING AROUND A 1015 MB HIGH IN THE NW GULF NEAR 27N92W. ALOFT...UPPER LEVEL RIDGING COVERS THE WRN GULF AROUND AN UPPER LEVEL HIGH CENTERED OVER SRN NEW MEXICO NEAR 32N107W. A FEW SHOWERS/POSSIBLE THUNDERSTORMS ARE IN THE FAR SW BAY OF CAMPECHE S OF 21N W OF 95W WHICH MAY BE REMNANTS OF A TROPICAL WAVE THAT DISSIPATED OVER MEXICO AT 16/0000 UTC. EXPECT WEAK RIDGING TO REMAIN OVER THE WRN HALF OF THE BASIN WITH THE STATIONARY FRONT CONTINUING TO SIT OVER THE NE GULF. THE CARIBBEAN SEA... ISOLATED SHOWERS/THUNDERSTORMS DOT THE NW CARIBBEAN FROM BELIZE TO CENTRAL CUBA ASSOCIATED WITH A SURFACE TROUGH ACROSS ERN CUBA AS WELL AS AN UPPER LEVEL TROUGH EXTENDING FROM HONDURAS TO WRN CUBA. WATER VAPOR IMAGERY INDICATES DRY AIR ALOFT COVERS THE CENTRAL CARIBBEAN WHICH IS HELPING TO MAINTAIN FAIR CONDITIONS. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN FROM 12N-16N BETWEEN 78W-85W...AND ACROSS PORTIONS OF PANAMA AND COSTA RICA INFLUENCED BY THE MONSOON TROUGH THAT EXTENDS FROM THE E PACIFIC ACROSS CENTRAL COSTA RICA TO NRN COLOMBIA. A TROPICAL WAVE IS IMPACTING THE ERN CARIBBEAN BRINGING STRONG SHOWERS/THUNDERSTORMS TO THE AREA FROM 15N-18N BETWEEN 61W-71W. A CLUSTER OF STORMS HAS ALSO JUST POPPED UP OVER ERN DOMINICAN REPUBLIC. WHILE MUCH OF THE ACTIVITY IS S OF THE ISLANDS...THERE IS STILL THE POTENTIAL FOR HEAVY ACTIVITY OVER THE N CENTRAL CARIBBEAN OVER THE NEXT 24 HOURS. SEE TROPICAL WAVE SECTION ABOVE FOR MORE DETAILS. ALOFT...MAINLY ELY FLOW ALOFT COVERS THE ERN CARIBBEAN WITH WEAK UPPER RIDGING CENTERED NEAR 15N80W. THE ATLANTIC OCEAN... SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS MUCH OF THE W ATLC N OF 26N W OF 71W ASSOCIATED WITH A DEEP LAYER TROUGH EXTENDING DOWN THE ERN SEABOARD. A PAIR OF WEAK UPPER RIDGES COVER THE SW N ATLC CENTERED N OF CUBA NEAR 23N76W...AND N OF PUERTO RICO NEAR 19N66W. A SURFACE TROUGH EXTENDS FROM THE CENTRAL BAHAMAS NEAR 24N74W TO ERN CUBA NEAR 20N78W SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS WITHIN 50 NM OF THE AXIS. THE REMAINDER OF THE CENTRAL AND ERN ATLC IS DOMINATED BY BROAD SURFACE RIDGING. ALOFT...AN UPPER LEVEL LOW IS CENTERED NEAR 24N53W. AN UPPER LEVEL RIDGE IT TO THE N CENTERED NEAR 39N52W. ANOTHER UPPER LEVEL RIDGE IS CENTERED OVER THE CANARY ISLANDS NEAR 29N18W. VISIBLE SATELLITE IMAGERY INDICATES TWO AREAS OF DUST. THE FIRST IS N OF A TROPICAL WAVE ACROSS THE CAPE VERDE ISLANDS N OF 20N E OF 30W. THE SECOND IS N OF 18N BETWEEN 45W-65W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON