000 AXNT20 KNHC 212356 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT AUG 21 2010 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURES... TROPICAL DEPRESSION SIX IS CENTERED NEAR 11.0N 32.1W AT 21/2100 UTC OR 500 NM WSW OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING W-NW AT 08 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO 35 KT. STRENGTHENING IS FORECAST OVER THE NEXT FEW DAYS AS THE CYCLONE RESIDES ON THE SOUTHWESTERN PERIPHERY OF AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 21N20W WITH AN UPPER LEVEL RIDGE AXIS EXTENDING SW FROM THE CENTER TO 15N39W. THIS IS EXPECTED TO PROVIDE AN OVERALL FAVORABLE UPPER LEVEL DIFFLUENT ENVIRONMENT FOR THE SYSTEM TO MAINTAIN ORGANIZED CONVECTION AND PROVIDE FOR MINIMAL WIND SHEAR. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION COVERS A BROAD AREA FROM 06N-16N BETWEEN 25W-41W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 12N46W TO 18N50W TO 25N49W MOVING W AT 15-20 KT. SATELLITE IMAGERY INDICATES CYCLONIC FLOW IN THE LOW-LEVEL CLOUD FIELD ALONG THE WAVE AXIS. AN AREA OF MAXIMUM DEEP LAYER MOISTURE IS OBSERVED ON THE TPW IMAGERY FROM 10N-25N BETWEEN 44W-53W...HOWEVER MUCH OF THE MOISTURE TO THE EAST OF THE WAVE IS POSITIONED BENEATH A STABLE SAHARAN AIR LAYER THAT COVERS MUCH OF THE CENTRAL ATLC N OF 15N BETWEEN 30W-45W. NO SIGNIFICANT DEEP ORGANIZED CONVECTION ACCOMPANIES THE WAVE... HOWEVER ISOLATED SHOWERS ARE FROM 10N-15N BETWEEN 46W-50W...AND FROM 18N-24N BETWEEN 46W-52W. TROPICAL WAVE EXTENDS FROM 14N69W TO 24N66W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH A MID-LEVEL TROUGH OVER THE W ATLC BETWEEN 65W-74W. MAXIMUM TOTAL PRECIPITABLE WATER VALUES ARE HIGHEST N OF 20N BETWEEN 60W-68W AS THIS MOISTURE CONTINUES TO ADVECT NORTHWARD DUE TO A WEAKNESS IN THE SUBTROPICAL RIDGE BETWEEN 70W-80W. ISOLATED MODERATE CONVECTION AND WIDELY SCATTERED SHOWERS ARE OCCURRING FROM 18N-28N BETWEEN 62W-70W. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 11N48W 11N57W THEN RESUMES OVER THE SOUTH-CENTRAL CARIBBEAN SEA NEAR 12N71W 11N80W 14N90W. ASIDE FROM THE CONVECTION ASSOCIATED WITH T.D. SIX...ISOLATED MODERATE CONVECTION IS FROM 04N-09N BETWEEN 41W-53W. FARTHER EAST OVER THE TROPICAL EASTERN ATLC...THE GRADUAL DISSIPATION OF THE MONSOON TROUGH THAT HAS PERSISTED OVER THE PAST SEVERAL DAYS IS ANALYZED AS A SURFACE TROUGH FROM NE OF T.D. SIX NEAR 15N26W TO 17N18W. CONVECTION IS MOSTLY ASSOCIATED WITH THE ONGOING TROPICAL CYCLONE LOCATED W OF 25W. ELSEWHERE...SCATTERED MODERATE TO STRONG CONVECTION IS MOVING OFF THE W AFRICA COAST FROM 04N-14N E OF 18W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER SOUTHERN NEW MEXICO NEAR 32N107W AND EXTENDS AN UPPER LEVEL RIDGE AXIS EASTWARD TO THE NE GULF NEAR 30N87W. THIS UPPER LEVEL FEATURE IS PROVIDING EASTERLY FLOW ALOFT OVER MUCH OF THE GULF N OF 22N. LOW TO MID-LEVEL INSTABILITY AND UPPER LEVEL DIFFLUENCE PROVIDED BY THE UPPER LEVEL RIDGE IS GENERATING SCATTERED SHOWERS AND TSTMS OVER THE EASTERN GULF AND FLORIDA PENINSULA NE OF A LINE FROM 29N90W TO WESTERN CUBA NEAR 23N83W. A FEW ISOLATED SHOWERS OVER WESTERN CUBA W OF 83W HAVE MOVED WESTWARD AND EXTEND OVER THE YUCATAN CHANNEL FROM 21N-23N BETWEEN 83W-88W. OVER THE SW GULF...AN UPPER LEVEL LOW IS NOTED ON WATER VAPOR IMAGERY NEAR 20N94W THAT IS SUPPORTING THE REMNANTS OF A TROPICAL WAVE ANALYZED AS A SURFACE TROUGH FROM 20N98W TO 17N93W OVER INTERIOR SOUTHERN MEXICO. SCATTERED SHOWERS AND TSTMS ARE FOCUSED ALONG THE SURFACE TROUGH AND ARE LOCATED WITHIN 90 NM EITHER SIDE OF A BOUNDARY. THE REMAINDER OF THE GULF IS UNDER THE INFLUENCE OF THE EASTERN FLOW ALOFT MENTIONED ABOVE AND THIS SUPPORTS A 1019 MB SURFACE HIGH CENTERED OVER THE CENTRAL GULF NEAR 26N89W. CLEAR SKIES ARE NOTED ON SATELLITE IMAGERY N OF 20N W OF 90W UNDER LIGHT ANTICYCLONIC WINDS. CARIBBEAN SEA... CONVERGENT LOW-LEVEL SOUTHEASTERLY FLOW DOMINATES ACROSS THE WESTERN CARIBBEAN W OF 78W AND PORTIONS OF CENTRAL AMERICA THIS EVENING. AN UPPER LEVEL TROUGH AXIS EXTENDS FROM AN UPPER LOW CENTERED OVER THE WINDWARD PASSAGE NEAR 20N74W WESTWARD TO THE NORTHERN YUCATAN PENINSULA NEAR 20N89W. THESE TWO FACTORS ALONG WITH ABUNDANT MOISTURE AND INSTABILITY ARE GENERATING SCATTERED SHOWERS AND TSTMS FROM 11N-18N BETWEEN 77W-87W. THE ITCZ AXIS EXTENDS ACROSS THE SW CARIBBEAN ALONG 11N AND IS ALSO PROVIDING LOW-LEVEL FOCUS FOR SCATTERED SHOWERS AND ISOLATED TSTMS OVER PORTIONS OF COSTA RICA AND PANAMA THIS EVENING. FARTHER EAST... THE UPPER LEVEL LOW CENTERED OVER THE WINDWARD PASSAGE IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER HISPANIOLA AND THE NEARBY ADJACENT COASTAL WATERS FROM 16N-21N BETWEEN 68W-75W. THE APPROACH OF A TROPICAL WAVE ALONG 68W WILL CONTINUE TO PROVIDE SCATTERED SHOWER ACTIVITY OVER THE NEXT 12-24 HOURS AS THE WAVE MOVES WESTWARD OVER HISPANIOLA AND THE NORTH-CENTRAL CARIBBEAN SEA. LASTLY...WHILE MUCH OF THE EASTERN CARIBBEAN BETWEEN 63W-68W IS UNDER RELATIVELY CLEAR SKIES...THE APPROACH OF A SURFACE TROUGH FROM 10N-16N ALONG 59W IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 09N-18N BETWEEN 57W-62W. INCREASED CLOUDINESS AND PRECIPITATION IS EXPECTED ACROSS THE LESSER ANTILLES OVER THE NEXT 12-24 HOURS. ATLANTIC OCEAN... AN ANTICYCLONIC CIRCULATION CENTERED OVER THE SE CONUS NEAR 31N86W IS PROVIDING MOST OF THE W ATLC WITH NE UPPER LEVEL FLOW N OF 22N W OF 72W. AN UPPER LEVEL LOW IS CENTERED OVER THE WINDWARD PASSAGE NEAR 20N74W AND EXTENDS AN UPPER LEVEL TROUGH AXIS NORTHWARD TO 30N70W. BETWEEN THESE TWO UPPER LEVEL FEATURES...UPPER LEVEL DIFFLUENCE ALONG WITH LOW-LEVEL MOISTURE AND DAYTIME INSTABILITY ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 21N-31N W OF 72W. A TROPICAL WAVE ALONG 68W IS EMBEDDED WITHIN IN THE NORTHERLY UPPER LEVEL FLOW EAST OF THE UPPER LOW AND IS ADVECTING MOISTURE...WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS N-NW FROM 18N-28N BETWEEN 62W-70W. ELSEWHERE ACROSS THE REMAINDER OF THE CENTRAL AND EASTERN ATLC...SURFACE RIDGING DOMINATES N OF 25N ANCHORED BY A 1024 MB HIGH CENTERED NEAR 31N33W MAINTAINING GENERALLY FAIR WEATHER E OF 62W. THE RIDGE AXIS EXTENDS FROM THE HIGH CENTER ALONG 30N TO 50W THEN SW TO 22N60W. ALOFT...AN UPPER LEVEL ANTICYCLONE COVERS THE CENTRAL ATLC CENTERED NEAR 31N44W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN