000 AXNT20 KNHC 021731 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU JUL 02 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 LARGE TROPICAL WAVE IS ALONG 28W/29W S OF 17N MOVING W NEAR 20 KT. THIS WAVE IS VERY BROAD WITH VISIBLE SATELLITE IMAGES INDICATING AN AREA OF CYCLONIC TURNING COVERING NEARLY A 1000 NM AREA. THE AXIS IS PLACED ROUGHLY IN THE CENTER OF THE CYCLONIC ENVELOPE WHERE CLOUD DRIFT WINDS SUGGEST A VORTICITY MAXIMUM NEAR 10N29W. SYNOPTIC PRESSURE OBSERVATIONS FROM THE CAPE VERDE ISLANDS SHOW A 3 MB PRESSURE INCREASE OVER THE PAST 24 HOURS...INDICATIVE OF THE WAVE PASSAGE. QUIKSCAT DATA REVEALS NE 20-25 KT WINDS W OF THE AXIS N OF 14N DUE TO THE TIGHTENED PRESSURE GRADIENT BETWEEN THE WAVE AND THE SUBTROPICAL RIDGE. CONVECTION IS FAIRLY LIMITED AND CONFINED TO THE INTERSECTION OF THE ITCZ. A TROPICAL WAVE HAS BEEN ADJUSTED W TO ALONG 47W/48W S OF 16N MOVING W 15-20 KT. THE ADJUSTMENT IN POSITION WAS BASED ON AN INVERTED V-SHAPE IN THE LOW-LEVEL CLOUD FIELD WHICH AGREES WITH A MAXIMUM IN TOTAL PRECIPITABLE WATER. THE INTERACTION WITH AN UPPER LOW TO ITS W IS FUELING SCATTERED MODERATE CONVECTION FROM 9N-11N BETWEEN 49W-52W. A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 70W/71W S OF 17N MOVING W 15-20 KT. VISIBLE IMAGES SHOW SLIGHT CYCLONIC TURNING IN THE LOW-LEVEL CLOUDS. ONE SMALL PATCH OF ENHANCED CLOUDINESS IS APPARENT NEAR THE N PORTION OF THE WAVE FROM 16N-17N BETWEEN 70W-72W...ENHANCED BY INSTABILITY ALONG AN E-W UPPER TROUGH AXIS. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N16W 9N27W 7N38W 6N46W 7N59W. SCATTERED MODERATE CONVECTION IS FROM 4N-11N BETWEEN 24W-37W. SCATTERED MODERATE CONVECTION IS FROM 3N-7N BETWEEN 49W-54W. ...DISCUSSION... GULF OF MEXICO... A DEEP LAYER TROUGH IS OVER THE EASTERN U.S. EXTENDING INTO THE N GULF. DEEP LAYER SW-W FLOW IS SUPPORTING SCATTERED SHOWERS AND TSTMS FROM 26N-28N E OF 94W. UPPER DIFFLUENCE BETWEEN A HIGH OVER W MEXICO AND AN UPPER LOW IN THE CARIBBEAN IS ENHANCING SCATTERED MODERATE CONVECTION OVER THE SRN BAY OF CAMPECHE. GENERALLY LIGHT S-SW SFC WINDS EXIST ACROSS THE AREA BETWEEN THE ATLC SUBTROPICAL RIDGE AND A FRONT OVER THE SE U.S. THIS FRONT IS EXPECTED TO GRADUALLY WEAKEN OVER THE NEXT COUPLE OF DAYS AS THE LOW MOVES NE ALLOWING SFC RIDGING TO BUILD W ACROSS THE GULF. CARIBBEAN SEA... ACROSS THE W CARIBBEAN...AN UPPER LEVEL LOW IS CENTERED NE OF HONDURAS NEAR 15N83W WITH AN ASSOCIATED UPPER LEVEL TROUGH EXTENDING SOUTHWARD TO COSTA RICA. ASSOCIATED ATMOSPHERIC INSTABILITY IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE SW CARIBBEAN S OF 12N W OF 77W INCLUDING PORTIONS OF COSTA RICA AND PANAMA. ACROSS THE NW CARIBBEAN...DEEP LAYER DRY AIR AND SUBSIDENCE IN NORTHERLY FLOW ALOFT W OF THE UPPER LOW IS SUPPORTING GENERALLY FAIR WEATHER. ACROSS THE E CARIBBEAN...A BROAD UPPER LEVEL RIDGE IS PRESENT. DEEP LAYER DRY AIR AND ATMOSPHERIC STABILITY ASSOCIATED WITH THIS UPPER LEVEL HIGH IS RESULTING IN GENERALLY FAIR WEATHER ACROSS THE E CARIBBEAN. THE SURFACE PRESSURE GRADIENT S OF A SURFACE RIDGE OVER THE CENTRAL AND E ATLC IS SUPPORTING NE TO E WINDS OF 20 TO 30 KT...HIGHEST 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 WITHIN 90 NM EITHER SIDE OF A LINE FROM 32N73W TO 27N80W 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 27N BETWEEN 43W-52W. 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 27N58W AND A 1026 MB SURFACE HIGH NEAR 31N27W. HOWEVER...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM AN UPPER LEVEL LOW NEAR 31N37W TO 22N42W. 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. ALSO...AN UPPER LEVEL HIGH OVER THE TROPICAL ATLC CENTERED NEAR 10N36W IS ENHANCING CONVECTION NEAR THE ITCZ. $$ COHEN/CANGIALOSI