000 AXNT20 KNHC 111049 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SAT JUL 11 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 18N33W TO 10N36W TO 6N36W MOVING W 15-20 KT. THIS WAVE COINCIDES WITH A WELL-DEFINED MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITHIN A BROAD AREA OF LOW/MID-LEVEL CYCLONIC TURNING...WITH SATELLITE-DERIVED WINDS INDICATING CYCLONIC CURVATURE IN THE FLOW WITHIN THE 600-800 MB LAYER. DEEP CONVECTION IS ABSENT NEAR THE WAVE SUPPRESSED BY LOW/MID-LEVEL DRY SAHARAN AIR. A TROPICAL WAVE EXTENDS FROM 20N67W TO 14N70W TO 9N70W MOVING W 20-25 KT. A LOW-LEVEL EASTERLY JET...DRIVEN BY THE STRONG HEIGHT GRADIENT SW OF A RIDGE OVER THE CENTRAL NORTH ATLC...HAS FORCED THE THIS WAVE TO ACCELERATE QUICKLY ENOUGH WESTWARD TO BECOME DISCONNECTED FROM A LAGGING VORTICITY MAXIMUM FARTHER TO THE NORTH. THIS IS GIVING THE WAVE...WHICH WAS PREVIOUSLY MORE AMPLIFIED...A FRACTURED-LIKE APPEARANCE. THE NORTHERN VORTICITY MAXIMUM IS BEING ANALYZED AS A SURFACE TROUGH EXTENDING FROM 24N62W TO 21N64W. ACROSS THE ABC ISLANDS...NE WINDS ARE NOTED AHEAD OF THE WAVE...WITH SE WINDS BEHIND THE WAVE. SCATTERED MODERATE CONVECTION IS FROM 16N-18N BETWEEN 67W-71W INCLUDING S PORTIONS OF HISPANIOLA. THIS CONVECTION IS BEING ENHANCED BY A MAXIMUM DEEP LAYER MOISTURE JUXTAPOSED WITH DIFFLUENT SOUTHERLY FLOW ALOFT. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 9N13W 9N25W 10N34W 6N46W 6N59W. SCATTERED MODERATE CONVECTION IS FROM 6N-11N E OF 22W. ...DISCUSSION... GULF OF MEXICO... A LARGE UPPER HIGH OVER THE S CENTRAL PLAINS IS PROVIDING NLY FLOW AND ADVECTING DRY AIR SOUTHWARD...HELPING TO SUSTAIN A SURFACE RIDGE ALONG 28N. THE SOUTHERN END OF AN UPPER TROUGH HAS BEEN PINCHED OFF...YIELDING AN UPPER LOW OVER W CUBA NEAR 22N85W. INSTABILITY NEAR AND E OF THE UPPER LOW IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS S OF 25N E OF 85W...AS REVEALED BY DOPPLER RADAR AND LIGHTNING DATA. SCATTERED SHOWERS AND TSTMS ARE ALSO OCCURRING OVER THE SW BAY OF CAMPECHE ASSOCIATED WITH UPPER DIFFLUENCE AND LOW-LEVEL CONVERGENCE ALONG THE COAST OF MEXICO. SFC RIDGING IS EXPECTED TO SHIFT NWD TODAY AND SUN CAUSING LIGHT AND VARIABLE FLOW OVER THE N WATERS AND MODERATE ELY WINDS OVER THE S WATERS. CARIBBEAN SEA... FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF COLOMBIA. AN EARLIER QUIKSCAT PASS CONFIRMED THE STRONG WINDS NEAR THE COAST OF COLOMBIA AND ENHANCED NE FLOW IN THE WINDWARD PASSAGE. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL DAYS AS THE SUBTROPICAL RIDGE STRENGTHENS. ALOFT...AN UPPER LEVEL TROUGH IS OVER THE W CARIBBEAN AND IS ASSOCIATED WITH AN UPPER LEVEL LOW OVER W CUBA NEAR 22N85W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER LOW AND UPPER TROUGH IS RESULTING IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE NW CARIBBEAN N OF 19N W OF 80W. UPPER LEVEL DIFFLUENCE S OF THE TROUGH IS INTERACTING WITH DEEP LAYER MOISTURE OVER THE SW CARIBBEAN TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS S OF 15N W OF 78W...INCLUDING ADJACENT AREAS OF CENTRAL AMERICA. ATLANTIC OCEAN... THE ATLANTIC DISCUSSION ZONE REMAINS RATHER QUIET WITH ONLY A FEW AREAS OF UNSETTLED WEATHER TO MENTION. AN UPPER LEVEL TROUGH OVER THE SW NORTH ATLC IS ASSOCIATED WITH A DISSIPATING COLD FRONT EXTENDING FROM 28N75W TO 31N71W...WITH SCATTERED SHOWERS AND THUNDERSTORMS FROM 23N-26N W OF 76W. FARTHER E...AN UPPER LOW NEAR 29N57W AND A W-NW MOVING SFC TROUGH FROM 27N68W TO 21N75W ARE PRODUCING SCATTERED SHOWERS AND TSTMS WITHIN 120 NM OF THE SFC TROUGH AXIS. THE REMAINDER OF THE BASIN IS RELATIVELY INACTIVE SUPPRESSED BY DEEP LAYER RIDGING AND ASSOCIATED STABLE AIR. THE SUBTROPICAL RIDGE IS EXPECTED TO STRENGTHEN SLIGHTLY OVER THE NEXT FEW DAYS INCREASING TRADES OVER THE TROPICS. $$ COHEN/CANGIALOSI