000 AXNT20 KNHC 281749 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU JUL 28 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 FEATURES... TROPICAL STORM DON IS CENTERED NEAR 24.6N 90.7W AT 28/1800 UTC OR 410 NM ESE OF CORPUS CHRISTI TEXAS OR ABOUT 370 NM E OF BROWNSVILLE TEXAS MOVING NW AT 13 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. DON IS LOCATED ON THE SOUTHERN PERIPHERY OF A MIDDLE TO UPPER LEVEL RIDGE WITH AXIS ALONG 90W ACROSS THE NORTH-CENTRAL GULF OF MEXICO THAT CONTINUES TO PROVIDE AMPLE UPPER LEVEL DIFFLUENCE AND ENHANCEMENT TO THE ONGOING SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120 NM OF THE SE QUADRANT AND WITHIN 150 NM OF THE SW QUADRANT. 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. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 11N17W TO 21N17W MOVING W AT 10-15 KT. EXAMINING RECENT HOVMOLLER DIAGRAM DATA AND THE UPPER AIR TIME SECTION ANALYSES INDICATES THE WAVE IS VERY NEAR TO PASSING DAKAR SENEGAL AS OF 28/1200 UTC. FURTHER INSPECTION OF DAKAR'S PAST TWO UPPER-AIR SOUNDINGS SHOW THE 850 MB WIND SHIFTING FROM NE AT 15 KT TO SE AT 20 KT...INDICATING PASSAGE ALOFT. AT THIS TIME...NO SIGNIFICANT CONVECTION IS NOTED ON SATELLITE IMAGERY AS THE WAVE MOVES OFF THE W AFRICA COAST. TROPICAL WAVE IS ANALYZED FROM 05N38W TO 14N33W MOVING W AT 15-20 KT. A BROAD LOW-LEVEL CYCLONIC CIRCULATION IS NOTED IN THE VICINITY OF THE WAVE AXIS FOCUSING ON A 1010 MB LOW CENTERED NEAR 07N38W. AN AREA OF INCREASED TOTAL PRECIPITABLE WATER ALSO COINCIDES WITH THE WAVE AXIS FROM 08N-15N BETWEEN 30W-38W. SCATTERED MODERATE CONVECTION IS OCCURRING FROM 09N-12N BETWEEN 33W-39W. TROPICAL WAVE IS ANALYZED FROM 13N68W TO 24N64W MOVING W-NW AT 15-20 KT. BOTH LOWER LEVEL STREAMLINE ANALYSIS AND NEAR 700 MB MODEL EVALUATION INDICATES THE WAVE REMAINS BROAD AS IT MOVES ACROSS THE EASTERN CARIBBEAN SEA. THIS IS CONFIRMED IN TOTAL PRECIPITABLE WATER IMAGERY AS VALUES OF LOW-LEVEL MOISTURE ARE MAXIMIZED FROM 10N-24N BETWEEN 57W-70W. ISOLATED MODERATE CONVECTION IS FROM 17N-19N BETWEEN 64W-71W INCLUDING PUERTO RICO AND THE US/UK VIRGIN ISLANDS. SCATTERED MODERATE CONVECTION IS ALSO OCCURRING TO THE SOUTH AND EAST FROM 12N-17N BETWEEN 60W-67W INCLUDING MANY OF THE LESSER ANTILLES. PRECIPITATION TOTALS OVER THE PAST 24 HOURS WITH THIS WAVE INCLUDE: GUADELOUPE...0.79 INCHES...SAN JUAN PUERTO RICO...1.57 INCHES...AND TRINIDAD...2.17 INCHES. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM NEAR THE AFRICAN COAST IN THE VICINITY OF 10N19W TO 10N35W THEN RESUMES NEAR 06N39W TO 04N45W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 04N45W TO 02N51W. ISOLATED MODERATE CONVECTION IS FROM 04N-07N BETWEEN 39W-46W. ...DISCUSSION... GULF OF MEXICO... TROPICAL STORM DON CONTINUES TO TRACK NW TOWARDS THE TEXAS COASTLINE REMAINING ON THE SOUTHERN PERIPHERY OF AN UPPER LEVEL RIDGE ACROSS MUCH OF THE NORTH-CENTRAL GULF BETWEEN 85W-95W. AT THE SURFACE...DON CONTINUES TO GENERATE A STRONG PRESSURE GRADIENT BETWEEN ITS CENTER AND A SURFACE RIDGE WITH AXIS EXTENDING ACROSS THE GULF COASTAL PLAIN FROM THE W ATLC ALONG 30N. STRONG SE WINDS AS CAPTURED BY A 28/1146 UTC WINDSAT PASS SHOW SPEEDS WITHIN THE 15 TO 25 KT RANGE OVER MUCH OF THE EASTERN GULF W OF 90W. MOSAIC DOPPLER RADAR IMAGERY AND LIGHTNING DATA INDICATE SCATTERED MODERATE CONVECTION N OF 26N BETWEEN 85W-91W...AND INLAND OVER THE FLORIDA PANHANDLE AND SOUTHERN ALABAMA AND MISSISSIPPI. AS DON TRACKS INLAND BY EARLY SATURDAY...THE SURFACE RIDGE AXIS WILL RE-ESTABLISH ITSELF ALONG 30N THROUGH THE REMAINDER OF THE UPCOMING WEEKEND. CARIBBEAN SEA... AS THE TROPICAL WAVE ALONG 67W TRACKS WESTWARD...WATER VAPOR IMAGERY INDICATES IT CONTINUES TO INTERACT WITH AN UPPER LEVEL TROUGH AXIS THAT EXTENDS FROM AN UPPER LEVEL LOW CENTERED IN THE CENTRAL ATLC NEAR 28N56W TO 18N65W THEN SOUTHWESTWARD TO AN UPPER LEVEL LOW NEAR 15N77W. LOW-LEVEL CONVERGENCE IN THE VICINITY OF THE WAVE AXIS AND UPPER LEVEL DIFFLUENCE LOCATED SOUTH AND EAST OF THE UPPER LEVEL TROUGH AXIS ARE GENERATING ISOLATED TO SCATTERED MODERATE CONVECTION OVER A LARGE PORTION OF THE EASTERN CARIBBEAN N OF 11N E OF 71W. MOST OF THE ONGOING INTENSE CONVECTION AND HEAVIER PRECIPITATION IS FOCUSED EAST OF THE WAVE AXIS OVER EASTERN PUERTO RICO AND WITHIN 120 NM EITHER SIDE OF THE LESSER ANTILLES ARCHIPELAGO. FARTHER WEST...THE UPPER LEVEL LOW CENTERED OVER THE WESTERN CARIBBEAN EXHIBITS MOSTLY AIR DRY N OF 12N BETWEEN 75W-82W...HOWEVER OVER THE NW CARIBBEAN LOW-LEVEL MOISTURE AND INSTABILITY ALONG WITH UPPER LEVEL DIFFLUENCE ARE GENERATING A LARGE AREA OF SCATTERED SHOWERS AND TSTMS N OF 15N BETWEEN 83W-89W...INCLUDING THE GULF OF HONDURAS AND INLAND PORTIONS OF BELIZE AND THE EASTERN YUCATAN PENINSULA. THIS AREA OF PRECIPITATION AND MOISTURE IS EXPECTED TO SHIFT WESTWARD OVER THE NEXT 24 HOURS WITH THE POTENTIAL FOR LOCALLY HEAVY RAINFALL AND POSSIBLE FLASH FLOODING ACROSS CENTRAL AMERICA N OF 15N. ATLANTIC OCEAN... A MAJORITY OF THE ATLC BASIN REMAINS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1029 MB HIGH CENTERED NEAR 36N35W. THE RIDGE AXIS EXTENDS SW FROM THE HIGH TO 32N48W THEN WESTWARD ALONG 30N TO THE FLORIDA PENINSULA. A TROPICAL WAVE IS LOCATED ALONG 65W...ON THE SOUTHWESTERN PERIPHERY OF THE RIDGE...AND MOST CONVECTIVE ACTIVITY REMAINS S OF 21N BETWEEN 59W-67W. OTHERWISE...NE TO E WINDS PREVAIL IN THE RANGE FROM 15 TO 25 KT ACROSS MUCH OF THE BASIN THIS AFTERNOON. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN