000 AXNT20 KNHC 211755 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE JUL 21 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 TROPICAL WAVE IS ALONG 38W S OF 13N MOVING W NEAR 23 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN LOW LEVEL CYCLONIC CIRCULATION BASED ON THE CIMSS WAVETRAK PRODUCT AND 600-950 MB CLOUD DRIFT WINDS. DEEP CONVECTION IS LIMITED NEAR THE WAVE AS A LARGE AREA OF SAHARAN AIR IS OBSERVED ON VISIBLE SATELLITE IMAGERY E OF 60W. HOWEVER...SCATTERED SHOWERS ARE OCCURRING FROM 5N-10N BETWEEN 36W-39W. A TROPICAL WAVE IS ALONG 57W S OF 20N MOVING W NEAR 25 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THIS WAVE IS FOLLOWED BY ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR...WHICH IS LIMITING THE AREAL COVERAGE OF DEEP CONVECTION IN THE VICINITY OF THE WAVE. HOWEVER...SCATTERED SHOWERS ARE FROM 14N-17N BETWEEN 54W-60W. A TROPICAL WAVE IS ALONG 69W S OF 22N MOVING W NEAR 25 KT. THIS WAVE COINCIDES WITH A LARGE AREA OF MAXIMUM TOTAL PRECIPITABLE WATER ACROSS MUCH OF THE CARIBBEAN BASIN WITH A MAXIMUM IN LOW-LEVEL CYCLONIC CURVATURE ALONG THE WAVE AXIS. VISIBLE SATELLITE AND SAN JUAN DOPPLER RADAR DATA DEPICT NUMEROUS SHOWERS AND SCATTERED TSTMS FROM 14N-19N BETWEEN 63W-69W. A TROPICAL WAVE IS ALONG 85W S OF 23N MOVING W NEAR 20 KT. THIS WAVE CONTINUES TRACKING WWD ACROSS THE NW CARIBBEAN AND SRN PORTIONS OF CENTRAL AMERICA WHILE UNDER AN ANTICYCLONIC CIRCULATION ALOFT CENTERED NEAR 15N80W. SCATTERED MODERATE/ ISOLATED STRONG CONVECTION IS FROM 8N-16N BETWEEN 80W-85W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 15N17W 8N36W 6N40W 6N55W AND ACROSS NRN VENEZUELA. SCATTERED MODERATE CONVECTION IS FROM 10N-19N BETWEEN 15W-20W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-8N BETWEEN 42W-54W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH AXIS EXTENDS ALONG THE ERN U.S. SEABOARD ACROSS FLORIDA AND INTO THE SE GULF AND STRAITS OF FLORIDA. AS OF 1500 UTC...THIS UPPER TROUGH SUPPORTS A WEAK SURFACE TROUGH THAT EXTENDS FROM A 1016 MB LOW NEAR SAVANNAH GEORGIA THROUGH THE FLORIDA BIG BEND REGION ALONG 29N83W 25N85W. DRY AIR IN THE BASE OF THE UPPER LEVEL TROUGH IS INHIBITING DEEP CONVECTION NEAR THE SURFACE TROUGH...AS WELL AS ACROSS THE SRN GULF S OF 25N. HOWEVER...TO THE SE OF THE BOUNDARY ACROSS S FLORIDA AND THE FLORIDA KEYS...LOW LEVEL CONVERGENCE IS INTERACTING WITH DEEP LAYER MOISTURE TO RESULT IN ISOLATED SHOWERS AND TSTMS S OF 26N E OF 83W. ACROSS THE W GULF...A UPPER LEVEL RIDGE AXIS EXTENDS FROM BROWNSVILLE TEXAS TO NEAR 25N90W AND IS PROVIDING SUBSIDENCE IN NLY FLOW ALOFT THAT CONTINUES TO SUPPORT GENERALLY FAIR WEATHER. HOWEVER...HIGH LEVEL DEBRIS CLOUDS FROM SHOWER AND TSTM ACTIVITY OVER TEXAS AND LOUISIANA ARE BEING ADVECTED SWD ACROSS THE NW GULF. CARIBBEAN SEA... A BROAD UPPER LEVEL RIDGE IS ACROSS MUCH OF THE CARIBBEAN... WHICH IS ANCHORED BY AN UPPER LEVEL HIGH NEAR 15N80W. UPPER LEVEL DIVERGENCE ACROSS THE NRN PERIPHERY OF THIS RIDGE IS INTERACTING WITH ATMOSPHERIC INSTABILITY TO RESULT IN THE NUMEROUS SHOWERS AND SCATTERED TSTMS ASSOCIATED WITH THE TROPICAL WAVE ALONG 69W THAT IS IMPACTING PUERTO RICO...THE US/UK VIRGIN ISLANDS AND NEARBY COASTAL WATERS. MORE WIDELY SCATTERED SHOWERS ARE ALSO NOTED OVER THE LESSER ANTILLES AS THE TROPICAL WAVE HAS ALREADY PASSED TO THE W...WHILE AN INCREASE IN SHOWER AND TSTM ACTIVITY IS FORECAST FOR HISPANIOLA AND THE N/CENTRAL CARIBBEAN WATERS THROUGH TONIGHT INTO WEDNESDAY. THIS TROPICAL WAVE IS INTERACTING WITH A SURFACE RIDGE N OF THE CARIBBEAN LOCATED IN THE SW NORTH ATLC RESULTING IN FRESH TO STRONG WINDS ACROSS THE ERN CARIBBEAN AND THESE WINDS ARE FORECAST TO CONTINUE THROUGH THE REMAINDER OF THE WEEK. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH AXIS IS ALONG THE ERN U.S. SEABOARD DIPPING S OVER THE FLORIDA PENINSULA TO WRN CUBA. THIS UPPER LEVEL TROUGH SUPPORTS A LARGE AREA OF MOIST LOW-LEVEL SLY FLOW AND CONVERGENCE FOCUSED ALONG A SURFACE TROUGH THAT EXTENDS FROM 23N78W ACROSS THE NW BAHAMAS TO 28N77W. SCATTERED SHOWERS AND TSTMS COVER A LARGE PORTION OF THE SW NORTH ATLC FROM 22N-32N FROM 69W-80W. TO THE SE...DEEP LAYER MOISTURE ASSOCIATED WITH THE TROPICAL WAVE ALONG 69W IS INTERACTING WITH UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE TO RESULT IN SCATTERED SHOWERS AND TSTMS S OF 22N BETWEEN 63W-72W. FARTHER TO THE E...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE IS RESULTING IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL AND E ATLC. THIS SURFACE RIDGE IS ASSOCIATED WITH A 1030 MB SURFACE HIGH NEAR 37N58W. ACROSS THE TROPICAL ATLC...A DISSIPATING 1016 MB LOW IS CENTERED NEAR 22N20W WITH A SURFACE TROUGH EXTENDING NE TO 25N16W AND ANOTHER SURFACE TROUGH EXTENDING FROM THE LOW S TO NEAR 18N23W. SCATTERED SHOWERS ARE WITHIN 90/120 NM EITHER SIDE OF THE SURFACE TROUGHS. $$ HUFFMAN