000 AXNT20 KNHC 011747 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED JUL 01 2009 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... A NEW TROPICAL WAVE HAS MOVED OFF THE W AFRICAN COAST AND IS APPROXIMATELY ALONG 20W S OF 13N. RECENT VISIBLE SATELLITE IMAGERY IN THIS AREA SHOWS THIS WELL-DEFINED FEATURE MOVING W NEAR 15 KT IN THE WAKE OF A LARGE MESOSCALE CONVECTIVE SYSTEM THAT RECENTLY MOVED OFF THE W AFRICAN COAST. ALSO...CYCLONIC MOTION OF LOW LEVEL CLOUDS IS EVIDENT NEAR THIS FEATURE. TIME-HEIGHT ANALYSES FROM DAKAR SENEGAL INDICATE AN ABRUPT SHIFT OF ANOMALOUS FLOW BELOW THE 600 MB LEVEL FROM NORTHEASTERLY TO SOUTHEASTERLY AROUND 01/0900 UTC...INDICATING THAT WAVE PASSAGE LIKELY OCCURRED AT DAKAR AROUND THAT TIME. THIS FEATURE COINCIDES WITH A DISTINCT MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THUS...A TROPICAL WAVE WILL BE ADDED TO THE 01/1800 UTC SURFACE ANALYSIS OVER THE TROPICAL E ATLC. CONSIDERABLE LOW/MID-LEVEL DRY SAHARAN AIR IS LIMITING THE AREAL COVERAGE OF DEEP CONVECTION NEAR THIS WAVE...HOWEVER SCATTERED MODERATE CONVECTION IS FROM 6N-10N BETWEEN 13W-22W. A TROPICAL WAVE IS ALONG 34W S OF 14N MOVING W 15-20 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. RECENT VISIBLE SATELLITE IMAGERY INDICATES THAT THE WAVE COINCIDES WITH AN INVERTED-V PATTERN IN THE COVERAGE OF LOW LEVEL CLOUDS. SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE. SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN 34W-37W. A TROPICAL WAVE EXTENDS ACROSS THE FAR E CARIBBEAN FROM 15N60W TO THE COAST OF VENEZUELA NEAR 10N63W TO 2N65W MOVING W 15-20 KT. THIS WAVE HAS BEEN ADJUSTED WESTWARD BASED ON RECENT SURFACE OBSERVATIONS...SCATTEROMETER DATA...AND TOTAL PRECIPITABLE WATER DATA. IN PARTICULAR...SURFACE OBSERVATIONS ACROSS THE WINDWARD ISLANDS...ALONG WITH THE QUIKSCAT PASS AROUND 01/0945 UTC... INDICATE CYCLONIC CURVATURE IN THE LOW LEVEL FLOW ACROSS THE WAVE. SURFACE PRESSURE RISES HAVE RECENTLY BEEN NOTED ACROSS THE WINDWARD ISLANDS FOLLOWING WAVE PASSAGE. ADDITIONALLY...RECENT VISIBLE SATELLITE IMAGERY INDICATES THAT THE WAVE CORRESPONDS WITH AN INVERTED-V PATTERN IN THE COVERAGE OF LOW LEVEL CLOUDS. THIS WAVE ALSO COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE CONVECTION IS FROM 12N-14N BETWEEN 62W-65W. A TROPICAL WAVE IS ALONG 97W/98W S OF 17N MOVING W NEAR 15 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. WHILE THIS WAVE IS PRIMARILY IN THE E PACIFIC REGION...IT IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 16N-19N BETWEEN 92W-97W INCLUDING PORTIONS OF S MEXICO AND THE ADJACENT WATERS OF THE SW GULF OF MEXICO. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 11N15W 7N23W 7N36W 5N48W 6N59W. SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 23W-27W. SCATTERED MODERATE CONVECTION IS ALSO FROM 3N-6N BETWEEN 38W-44W AND FROM 6N-9N BETWEEN 51W-59W. ...DISCUSSION... GULF OF MEXICO... A DEEP LAYER TROUGH OVER THE E UNITED STATES EXTENDS INTO THE NE GULF. ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT E OF THE TROUGH AXIS IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 25N E OF 90W INCLUDING PORTIONS OF THE W FLORIDA PENINSULA. THIS ACTIVITY IS BEING ENHANCED BY ABUNDANT DEEP LAYER MOISTURE OVER THE NE GULF AND FLORIDA PENINSULA. ALSO...AN UPPER LEVEL HIGH OVER THE SW GULF IS CENTERED NEAR 22N96W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THIS HIGH IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 24N W OF 95W. THIS ACTIVITY IS ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE NEAR THE TROPICAL WAVE ALONG 97W/98W S OF 17N DISCUSSED IN THE TROPICAL WAVES SECTION ABOVE. ACROSS THE S CENTRAL AND SE GULF...DEEP LAYER DRY AIR IS SUPPORTING GENERALLY FAIR WEATHER...WHERE SUBSIDENCE IS OCCURRING IN THE VICINITY OF A SURFACE RIDGE. THE PRESSURE GRADIENT AROUND THIS SURFACE RIDGE IS RESULTING IN E TO SE WINDS OF 10 TO 15 KT ACROSS PORTIONS OF THE SW GULF. CARIBBEAN SEA... ACROSS THE W CARIBBEAN...AN UPPER LEVEL LOW IS CENTERED NEAR 15N78W WITH ASSOCIATED ATMOSPHERIC INSTABILITY SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE SW CARIBBEAN S OF 13N W OF 76W INCLUDING PORTIONS OF COSTA RICA AND PANAMA. ACROSS THE NW CARIBBEAN...DEEP LAYER DRY AIR AND SUBSIDENCE IN NORTHEASTERLY FLOW ALOFT W OF THE UPPER LOW IS SUPPORTING GENERALLY FAIR WEATHER. ACROSS THE E CARIBBEAN...A BROAD UPPER LEVEL RIDGE IS PRESENT WITH AN UPPER LEVEL HIGH NEAR 13N67W. ATMOSPHERIC STABILITY ASSOCIATED WITH THIS UPPER LEVEL HIGH IS RESULTING IN GENERALLY FAIR WEATHER ACROSS THE E CARIBBEAN. HOWEVER...CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ACROSS THE FAR E CARIBBEAN IS BEING SUPPORTED BY UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL HIGH...AND THIS TROPICAL WAVE IS DISCUSSED IN THE TROPICAL WAVES SECTION ABOVE. THE SURFACE PRESSURE GRADIENT S OF A SURFACE RIDGE OVER THE CENTRAL AND E ATLC IS SUPPORTING E TO SE WINDS OF 20 TO 25 KT ACROSS MUCH OF THE CARIBBEAN...EXCEPT TO 30 KT NEAR THE COAST OF COLOMBIA. ATLANTIC OCEAN... ACROSS THE SW NORTH ATLC...ATMOSPHERIC LIFT IN SOUTHWESTERLY ALOFT IS INTERACTING WITH DEEP LAYER MOISTURE TO SUPPORT SCATTERED SHOWERS AND THUNDERSTORMS N OF 28N BETWEEN 70W-79W... AS WELL AS FROM 24N-27N BETWEEN 76W-79W INCLUDING THE NW BAHAMAS. TO THE E...DEEP LAYER MOISTURE STREAMING AROUND AN UPPER LEVEL HIGH CENTERED NEAR 27N70W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 29N BETWEEN 46W-55W. FARTHER TO THE E...GENERALLY FAIR WEATHER IS PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC...WHERE SUBSIDENCE IS OCCURRING NEAR A BROAD SURFACE RIDGE. THIS SURFACE RIDGE IS ASSOCIATED WITH A 1025 MB SURFACE HIGH NEAR 28N30W. HOWEVER...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM AN UPPER LEVEL LOW NEAR 31N37W TO 22N42W. DIFFLUENCE IN MOIST SOUTHWESTERLY FLOW ALOFT E OF THE TROUGH AXIS IS SUPPORTING SCATTERED SHOWERS N OF 27N BETWEEN 33W-38W. A BROAD AREA OF LOW/MID-LEVEL DRY SAHARAN AIR COVERS THE E ATLC S OF 25N TO THE ITCZ E OF 55W AND IS LIMITING THE AREAL COVERAGE OF DEEP CONVECTION IN THIS AREA. $$ COHEN