000 AXNT20 KNHC 221755 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED JUL 22 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 47W S OF 18N MOVING W NEAR 25 KT. THIS WAVE COINCIDES WITH A WEAK MAXIMUM IN TOTAL PRECIPITABLE WATER AND EXHIBITS WEAK LOW LEVEL CYCLONIC CIRCULATION IN THE SATELLITE CLOUD DRIFT WINDS. CONFLUENT SELY FLOW ALOFT TO THE E OF THE WAVE AXIS AND THE PRESENCE OF DRY LOW/MID-LEVEL SAHARAN AIR ARE LIMITING DEEP CONVECTION TO THE W OF THE WAVE AXIS WITH SCATTERED MODERATE CONVECTION FROM 10N-13N BETWEEN 47W-53W. HOWEVER...MUCH OF THIS ACTIVITY APPEARS TO BE MORE ASSOCIATED WITH THE ITCZ AXIS ALONG 9N W OF 49W. A TROPICAL WAVE IS ALONG 65W S OF 20N MOVING W NEAR 18 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS AND IS FOLLOWED BY ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR...WHICH IS INHIBITING THE AREAL COVERAGE OF DEEP CONVECTION NEAR THE WAVE ACROSS THE ERN CARIBBEAN. HOWEVER...ISOLATED SHOWERS ARE WITHIN 90 NM EITHER SIDE OF THE WAVE AXIS. A TROPICAL WAVE IS ALONG 79W S OF 23N MOVING W NEAR 25 KT. WHILE THE WAVE IS BEING STRETCHED NWD AS AN UPPER LEVEL TROUGH IS PRESENT OVER THE FLORIDA PENINSULA AND ALONG THE ERN U.S. SEABOARD...LOW-LEVEL CONVERGENCE LOCATED NE OF THE WAVE ACROSS THE SW NORTH ATLC IS GENERATING SCATTERED MODERATE/ISOLATED STRONG CONVECTION N OF 17N BETWEEN 68W-78W. UPPER DIFFLUENCE E OF THE UPPER TROUGH AXIS IS ACTING TO ENHANCE THIS ACTIVITY ACROSS HISPANIOLA...THE TURKS AND CAICOS ISLANDS...AND BAHAMAS WITH LOCALLY HEAVY RAINFALL AND GUSTY WINDS POSSIBLE. A TROPICAL WAVE IS ALONG 93W S OF 20N MOVING W NEAR 18 KT. RECENT SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITH A BROAD AREA OF LOW/MID-LEVEL CYCLONIC TURNING OVER PORTIONS OF SRN MEXICO EXTENDING INTO THE E PACIFIC REGION. THIS WAVE IS ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. MOST CONVECTION WITH THIS WAVE IS LOCATED IN THE E PACIFIC REGION S OF 16N. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 13N16W 12N45W 11N49W 7N59W. SCATTERED MODERATE CONVECTION IS FROM 10N-15N BETWEEN 18W-22W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-13N BETWEEN 49W-60W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL TROUGHING IS ACROSS THE ERN CONUS AND DIPS SWD OVER THE SE CONUS TO THE FLORIDA PANHANDLE. THIS TROUGH IS SUPPORTING A STATIONARY FRONT DRAPED ACROSS CENTRAL LOUISIANA AND INTO ERN TEXAS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS ALONG AND S OF THE FRONTAL BOUNDARY TO 29N BETWEEN 90W-95W. THE REMAINDER OF THE GULF IS UNDER ANTICYCLONIC FLOW ALOFT EXTENDING FROM AN UPPER LEVEL HIGH CENTERED OVER NWRN MEXICO. STABLE AND DRY AIR PREVAILS S OF 29N WITH GENERALLY 10-15 KT SE TO SLY SURFACE FLOW PER SHIP AND BUOY OBSERVATIONS A WELL AS A 1230 UTC QSCAT PASS. HIGH CONVECTIVE DEBRIS CLOUDS ARE SEEN ON VISIBLE SATELLITE IMAGERY STREAMING SWD FROM THE INLAND CONVECTION ACROSS MISSISSIPPI...LOUISIANA AND ERN TEXAS. THE SURFACE RIDGE IS FORECAST TO PERSIST THROUGH THE WEEKEND WITH E TO SE RETURN FLOW ACROSS MUCH OF THE GULF. CARIBBEAN SEA... A BROAD UPPER LEVEL ANTICYCLONE IS OVER THE WRN CARIBBEAN... CENTERED NEAR 17N79W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS ANTICYCLONE IS SUPPORTING SCATTERED SHOWERS AND TSTMS ACROSS THE SW CARIBBEAN S OF 12N W OF 76W TO INLAND OVER PORTIONS OF CENTRAL AMERICA AS WELL AS SCATTERED SHOWERS AND TSTMS ALONG AND E OF THE TROPICAL WAVE ALONG 79W N OF 17N BETWEEN 69W-80W. ACROSS THE ERN CARIBBEAN...N-NE FLOW ALOFT IS ADVECTING DRY AIR E OF 70W PROMOTING SUBSIDENCE. HOWEVER...AS THE TROPICAL WAVE ALONG 65W TRACKS WWD...ISOLATED SHOWERS ARE CONTINUING TO BE USHERED IN ON 15-20 KT ELY TRADE WIND FLOW. THESE TRADES ARE FORECAST TO REMAIN FRESH TO STRONG THROUGH THE WEEKEND AS THE CENTRAL ATLC SURFACE RIDGE STRENGTHENS. ATLANTIC OCEAN... A SHARP UPPER LEVEL TROUGH IS LOCATED OFF THE NE FLORIDA COAST AND EXTENDS UPPER LEVEL TROUGHING TO WRN CUBA. THIS TROUGH SUPPORTS A SURFACE TROUGH ANALYZED FROM 25N79W TO 30N78W. STRONG UPPER LEVEL DIFFLUENCE IN MOIST SWLY FLOW ALOFT BETWEEN THE UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE FARTHER TO THE E WITH AXIS ALONG 70W IS SUPPORTING NUMEROUS SHOWERS AND SCATTERED TSTMS WITHIN 150 NM OF A LINE FROM 20N69W 31N77W. THIS ACTIVITY IS ALSO BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE SURFACE TROUGH AND NEAR NRN PORTIONS OF THE TROPICAL WAVE ALONG 79W S OF 23N. THE SURFACE PRESSURE GRADIENT SE OF THE SURFACE TROUGH IS SUPPORTING SE WINDS OF 20 TO 25 KT FROM 18N-27N BETWEEN 60W-75W BASED ON A 1100 UTC QSCAT PASS AND GLOBAL MODEL GUIDANCE. 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 1028 MB SURFACE HIGH NEAR 39N54W. HOWEVER...A STATIONARY FRONT EXTENDS ALONG 32N BETWEEN 22W-40W OVER THE NE ATLC WITH SCATTERED SHOWERS LOCATED WITHIN 150 NM S OF THE FRONT. $$ HUFFMAN