000 AXNT20 KNHC 311046 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT MON JUL 30 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1030 UTC. ...SPECIAL FEATURES... TROPICAL DEPRESSION THREE CENTERED NEAR 37.8N 64.9W AT 31/0900 UTC OR 330 NM NORTH OF BERMUDA AND ABOUT 330 NM SOUTHEAST OF CHATHAM MASSACHUSETTS MOVING NNE 18 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WINDS ARE 30 KT WITH GUSTS TO 40 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR ADDITIONAL DETAILS. THE SYSTEM REMAINS IN A SHEARED ENVIRONMENT WITH THE DEEP CONVECTION CONFINED TO WITHIN 120-150 NM NORTHEAST OF THE PARTIALLY EXPOSED LOW LEVEL CENTER. ALTHOUGH THE SYSTEM IS EXPECTED TO REMAIN IN THIS ENVIRONMENT UNTIL IT TRANSITIONS TO AN EXTRATROPICAL SYSTEM WITHIN 24 HOURS...THERE IS THE POTENTIAL FOR THE DEPRESSION TO REACH STORM STRENGTH WITHIN THAT TIME. 1010 MB LOW NEAR 10N50W POSSIBLY SPAWNED BY THE RE-LOCATED TROPICAL WAVE ALONG 58W WAS LOCATED ABOUT 650 NM E OF THE WINDWARD ISLANDS IS FAIRLY WELL ORGANIZED WITH A BAND OF SCATTERED MODERATE TO STRONG CONVECTION DEVELOPING WITHIN 120-150 NM OF THE WELL DEFINED LOW LEVEL CENTER. THIS SYSTEM IS IN A FAVORABLE ENVIRONMENTAL FOR DEVELOPMENT AND COULD BECOME A TROPICAL DEPRESSION OVER THE NEXT COUPLE OF DAYS. ...TROPICAL WAVES... TROPICAL WAVE RE-LOCATED TO ALONG 34W/35W S OF 20N WITH A TRAILING 1010 MB LOW NEAR 12N29W. THE WAVE WAS MOVING W AT 10-15 KT WHILE THE LOW WAS DRIFTING WWD. BROAD CYCLONIC TURNING IN THE STRATOCUMULUS FIELD WAS NOTED ALONG THE WAVE AXIS WITH ADDITIONAL TURNING NOTED IN THE VICINITY OF THE TRAILING LOW. A FEW EMBEDDED SHOWERS WERE NOTED IN THE W SEMICIRCLE OF THE LOW. SCATTERED MODERATE THUNDERSTORMS WERE NOTED MAINLY WITHIN 90 NM OF THE INTERSECTION OF THE WAVE AND ITCZ BETWEEN 29W AND 38W. RE-LOCATED TROPICAL WAVE ALONG 58W S OF 18N WAS MOVING W 15 KT. THE WAVE WAS RELOCATED BASED ON SSMI DERIVED TOTAL PRECIPITABLE WATER (TPW) IMAGERY WHICH CLEARLY SHOWED THE AXIS OF THE WAVE FURTHER W AND SEPARATING FROM THE LOW PRESSURE AREA NEAR 10N50W. BROKEN TO OVERCAST MULTILAYERED CLOUDS WITH WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WERE SPREADING WWD OVER THE WINDWARD ISLANDS. TROPICAL WAVE IN THE E-CENTRAL CARIBBEAN AND SW N ATLANTIC IS TILTED FROM 23N67W THROUGH 15N69W TO INLAND OVER SOUTH AMERICA NEAR 5N69W MOVING W 10-15 KT. BROAD LOW LEVEL INVERTED-V SIGNATURE NOTED IN TRADE WIND CUMULUS FIELD GENERALLY IN THE ARE BETWEEN 66W-76W. WIDELY SCATTERED THUNDERSTORMS WERE OCCURRING AT THE NORTHERN END OF THE WAVE AXIS JUST NORTH OF PUERTO RICO AND HISPANIOLA. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N16W 13N23W 8N34W 11N44W 9N55W 8N60W. EXCEPT AS NOTED ABOVE...SCATTERED MODERATE/STRONG CONVECTION IS MOVING OFF W AFRICA WITHIN 120 NM OF THE COAST FROM 9N-16N. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 90 NM OF THE COAST OF SOUTH AMERICA BETWEEN 54W AND 59W. ...DISCUSSION... GULF OF MEXICO... LARGE MID TO UPPER LEVEL ANTICYCLONE WITH CENTERS OVER THE TEXAS BIG BEND AND E-CENTRAL TEXAS APPEARS TO BE RETROGRADING TO THE W WITH THE ASSOCIATED RIDGE EXTENDED ESEWD ACROSS THE NE GULF TO CENTRAL FLORIDA. AS A RESULT ANTICYCLONIC FLOW ALOFT PREVAILED OVER MOST OF THE GULF OF MEXICO. A SMALL CYCLONIC CIRCULATION NEAR 24N99W WAS UNDERCUTTING THE RIDGE AS IT MOVED INTO NE MEXICO. MODERATE BUT SOMEWHAT DIFLUENT NELY UPPER LEVEL FLOW WAS ADVECTING HIGH LEVEL CLOUD DEBRIS ACROSS THE ERN HALF OF THE GULF AND ALSO MAINTAINING WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN THE AREA. A MORE SUBSTANTIAL LINE OF THUNDERSTORMS WAS NOTED OFF THE ALABAMA...MISSISSIPPI AND LOUISIANA COASTS. AT THE SURFACE...WEAK RIDGE EXTENDS FROM THE W ATLC ACROSS THE STRAITS OF FLORIDA TO A 1015 MB HIGH OVER THE CENTRAL GULF NEAR 26N90W. THIS OVERALL PATTERN IS EXPECTED TO REMAIN IN PLACE FOR THE NEXT SEVERAL DAYS OR SO. THE PRESENCE OF DIFLUENT FLOW SE OF THE ANTICYCLONE AND AN APPROACHING UPPER LEVEL TROUGH/ASSOCIATED FRONTAL SYSTEM OVER THE DEEP SOUTH HOLDS THE POTENTIAL FOR ADDITIONAL SCATTERED THUNDERSTORMS OVER THE NE GULF AND NORTH FLORIDA LATER TODAY. CARIBBEAN... AN UPPER RIDGE EXTENDS FROM NW COLOMBIA NEAR 9N78W NW TO THE YUCATAN PENINSULA NEAR BELIZE. WEAK UPPER LEVEL INVERTED TROUGH COUPLED WITH DRY STABLE AIR DOMINATES THE REMAINDER OF THE CARIBBEAN W OF 67W. WIDELY SCATTERED TRADE WIND SHOWERS AND A FEW THUNDERSTORMS WERE NOTED IN THE EASTERN CARIBBEAN PER SAN JUAN WSR-88D DATA...AND ALSO MOVING INTO THE CENTRAL WINDWARD ISLANDS IN ADVANCE OF THE TROPICAL WAVE ALONG 58W. ATLANTIC... SEE SPECIAL FEATURES FOR TROPICAL DEPRESSION THREE. VERY AMPLIFIED PATTERN IN PLACE OVER THE N ATLANTIC WITH SHORT TERM IMPLICATIONS FOR THE TROPICAL DEPRESSION. BROAD TROUGH COMPLEX OVER THE NW ATLANTIC WITH FIRST NEGATIVELY TILTED SHORTWAVE EXTENDING FROM NEW ENGLAND SEWD THROUGH 38N67W TO 35N64W. UPPER LEVEL DIFFLUENCE E OF THE TROUGH AXIS IS ALLOWING DEEP CONVECTION TO PERSIST IN THE VICINITY OF THE LOW LEVEL CENTER OF THE DEPRESSION. A SECOND POTENT SHORTWAVE TROUGH SWINGING IN FROM THE NW AND CUTTING ACROSS THE MID-ATLANTIC STATES INTO THE CAROLINAS HAS ALLOWED SCATTERED STRONG THUNDERSTORMS TO PERSIST AHEAD OF ANOTHER AREA OF LOW PRESSURE NEAR 32N76W AND A SURFACE TROUGH EXTENDING SWD TO NEAR 29N79W. THE FLOW IS STRONGLY DIFLUENT AS WELL IN THIS AREA AND SHOULD CONTRIBUTE TO OVERALL INTENSIFICATION OF THIS AREA OF LOW PRESSURE OVER THE NEXT 24 HOURS. FURTHER S...AN ELONGATED RIDGE AXIS FROM 31N57W SWWD TO THE WRN BAHAMAS WITH SOME MODERATE SUBSIDENCE NOTED S OF THE RIDGE. CYCLONIC CIRCULATION NEAR 30N51W MOVING WWD 10 KT HAS ASSOCIATED SHEAR AXIS EXTENDING SWWD TO A SMALL CYCLONIC CIRCULATION NEAR 20N65W. ANTICYCLONES NEAR 16N48W AND 26N27W AND ASSOCIATED FLOW PREVAIL OVER THE REMAINDER OF THE ATLANTIC WITH DEEP EASTERLY FLOW IN PLACE OVER THE AREA. UW CIMSS SAL ANALYSIS INDICATES SAHARAN DUST CONTINUES OVER THE ATLANTIC E OF 45W THOUGH THE COVERAGE IS NOT AS EXTENSIVE AS PREVIOUS DAYS. AT THE SURFACE...DRY STABLE AIR E OF 60W AND A SURFACE RIDGE ANCHORED BY A 1027 MB HIGH WELL N OF THE REGION NEAR 41N41W DOMINATE THE ATLC GIVING THE AREA FAIR CONDITIONS TONIGHT. $$ COBB