000 AXNT20 KNHC 202341 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON JUL 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 16N29W TO 10N31W TO 5N31W MOVING W 15-20 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN LOW LEVEL CYCLONIC CIRCULATION BASED ON THE CIMSS WAVETRAK PRODUCT. UPPER AIR DATA INDICATE THAT THIS WAVE LIKELY PASSED DAKAR SENEGAL PRIOR TO 19/1200 UTC. UPPER LEVEL CONFLUENCE IS INHIBITING DEEP CONVECTION NEAR THE WAVE. HOWEVER...SCATTERED SHOWERS ARE OCCURRING FROM 6N-9N BETWEEN 27W-30W. A TROPICAL WAVE EXTENDS FROM 17N47W TO 10N49W TO 4N49W MOVING W 15-20 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 INHIBITING THE AREAL COVERAGE OF DEEP CONVECTION NEAR THE WAVE. HOWEVER...SCATTERED MODERATE CONVECTION IS FROM 8N-10N BETWEEN 47W-49W. A TROPICAL WAVE EXTENDS FROM 21N57W TO 12N61W TO 5N62W MOVING W NEAR 20 KT. THIS WAVE IS APPROACHING THE WINDWARD AND LEEWARD ISLANDS...WHERE SURFACE OBSERVATIONS INDICATE MEAN SEA LEVEL PRESSURE FALLS PRIOR TO THE PASSAGE OF THE WAVE. RECENT SURFACE OBSERVATIONS AND THE ASCAT PASS AROUND 20/1350 UTC INDICATE CYCLONIC CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 11N-15N BETWEEN 59W-62W...INCLUDING PORTIONS OF THE WINDWARD ISLANDS. ALSO...SCATTERED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 60W-63W...INCLUDING PORTIONS OF NE VENEZUELA AND NW GUYANA. A TROPICAL WAVE IS ALONG 79W/80W S OF 22N MOVING W NEAR 20 KT. THIS WAVE IS ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. RECENT SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITH A BROAD AREA OF LOW/MID-LEVEL CIRCULATION OVER PORTIONS OF THE SW CARIBBEAN AND E PACIFIC REGION. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS S OF 15N W OF 79W. THIS CONVECTION IS BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE ASSOCIATED WITH A BROAD UPPER LEVEL RIDGE OVER THE CARIBBEAN...WHICH IS BEING ANCHORED BY AN UPPER LEVEL HIGH NEAR 10N76W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 15N17W 12N26W 6N39W 5N47W 7N59W. SCATTERED MODERATE CONVECTION IS FROM 13N-17N E OF 19W. NUMEROUS MODERATE CONVECTION IS FROM 5N-8N BETWEEN 35W-39W. SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN 40W-42W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH AXIS EXTENDS FROM THE E UNITED STATES INTO THE E GULF...WITH AN ASSOCIATED STATIONARY FRONT EXTENDING ACROSS THE N GULF FROM THE FLORIDA BIG BEND NEAR 30N84W TO SE MISSISSIPPI NEAR 30N89W. DRY AIR IN THE BASE OF THE UPPER LEVEL TROUGH IS INHIBITING DEEP CONVECTION NEAR THE FRONT...AS WELL AS ACROSS A LARGE PART OF THE N CENTRAL AND NE GULF. HOWEVER...TO THE SE OF THE STATIONARY FRONT...A SURFACE TROUGH EXTENDS FROM THE W FLORIDA PENINSULA NEAR 27N83W TO 25N85W TO 23N89W. LOW LEVEL CONVERGENCE IS INTERACTING WITH DEEP LAYER MOISTURE OVER THE SE GULF TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH. ACROSS THE W GULF... SUBSIDENCE IN NORTHERLY FLOW ALOFT IS SUPPORTING GENERALLY FAIR WEATHER. HOWEVER...HIGH LEVEL CLOUDS FROM SHOWER AND THUNDERSTORM ACTIVITY OVER TEXAS ARE BEING ADVECTED SOUTHWARD ACROSS THE NW GULF. CARIBBEAN SEA... A BROAD UPPER LEVEL RIDGE IS AFFECTING MUCH OF THE CARIBBEAN... WHICH IS BEING ANCHORED BY AN UPPER LEVEL HIGH NEAR 10N76W. UPPER LEVEL DIVERGENCE ACROSS THE N PERIPHERY OF THE RIDGE IS INTERACTING WITH ATMOSPHERIC INSTABILITY TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS OVER CUBA...HISPANIOLA...JAMAICA...N COLOMBIA...AND THE NE PORTIONS OF THE YUCATAN PENINSULA. THIS ACTIVITY IS AFFECTING THE NEARBY COASTAL WATERS. ADDITIONALLY... SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER THE SW CARIBBEAN IS ASSOCIATED WITH A TROPICAL WAVE ALONG 79W/80W S OF 22N. ALSO...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS AFFECTING PORTIONS OF THE E CARIBBEAN AND IS ASSOCIATED WITH A TROPICAL WAVE EXTENDING FROM 21N57W TO 12N61W TO 5N62W. THESE TROPICAL WAVES ARE INTERACTING WITH A SURFACE RIDGE N OF THE CARIBBEAN TO RESULT IN FRESH TO STRONG WINDS ACROSS THE E AND CENTRAL CARIBBEAN. THESE FRESH TO STRONG WINDS WILL CONTINUE ACROSS THE E AND CENTRAL CARIBBEAN THROUGH THE REMAINDER OF THIS WEEK. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH AXIS IS OVER THE E UNITED STATES AND THE E GULF OF MEXICO. THIS TROUGH IS ASSOCIATED WITH A COLD FRONT EXTENDING FROM N FLORIDA NEAR 30N81W TO 31N80W TO 32N79W TO NE OF THE DISCUSSION AREA...AND A SURFACE TROUGH EXTENDING FROM 29N78W TO THE E FLORIDA PENINSULA NEAR 27N80W. LOW LEVEL CONVERGENCE NEAR THE COLD FRONT AND SURFACE TROUGH...AS WELL AS ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT E OF THE UPPER LEVEL TROUGH AXIS...ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE SW NORTH ATLC N OF 23N W OF 73W. TO THE E...DEEP LAYER MOISTURE IS INTERACTING WITH UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS N OF 23N BETWEEN 64W-71W. 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 1027 MB SURFACE HIGH NEAR 34N79W AND A 1029 MB SURFACE HIGH NEAR 36N57W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM 20N16W TO 18N23W TO 13N35W...AND AN UPPER LEVEL TROUGH AXIS EXTENDS FROM 6N39W TO AN UPPER LOW NEAR 1N48W TO 1N50W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL RIDGE AND UPPER LEVEL TROUGH IS SUPPORTING THE CONVECTION ASSOCIATED WITH THE ITCZ FROM 5N-8N BETWEEN 35W-39W. $$ COHEN