000 AXNT20 KNHC 131722 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON JUL 13 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 1645 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 27W S OF 16N MOVING W NEAR 15 KT. A BROAD AREA OF LOW-LEVEL CYCLONIC TURNING IS APPARENT IN VISIBLE SATELLITE IMAGERY AS WELL IN THE 600-800 MB LAYER ACCORDING TO SATELLITE DERIVED WINDS. THE WAVE ALSO COINCIDES WITH A LOW AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-13N BETWEEN 24W-30W. DEEP CONVECTION NEAR THE WAVE IS LIKELY BEING MAINLY SUPPORTED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ. A TROPICAL WAVE IS E OF THE LESSER ANTILLES EXTENDING FROM 18N53W TO 5N49W MOVING W 15-20 KT. THIS WAVE HAS BECOME INCREASINGLY TILTED NW-SE BY THE NE WIND SURGE E OF THE AXIS OVER THE N PORTIONS OF THE WAVE AXIS. A WELL DEFINED INVERTED V PATTERN IS EVIDENT IN THE LOW-LEVEL CLOUDS SEEN ON VISIBLE SATELLITE IMAGERY. THE WAVE ALSO COINCIDES WITH A WELL AMPLIFIED MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. A SMALL AREA OF SCATTERED MODERATE CONVECTION IS FROM 9N-12N BETWEEN 50W-53W. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE ALSO N OF THE WAVE AXIS FROM 19N-26N BETWEEN 52W-55W. THIS SHOWER ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE NEAR A SHORTWAVE UPPER LEVEL TROUGH. GFS APPEARS TO HAVE A GOOD HANDLE ON THIS FEATURE AND SHOWS IT MOVING INTO THE LESSER ANTILLES TOMORROW WITH THE N PART LIKELY FRACTURING. A TROPICAL WAVE IS ALONG 88W MOVING W NEAR 18 KT. THE WAVE POSITION IS MAINLY BASED ON A MOISTURE MAXIMUM IN TOTAL PRECIPITABLE WATER AS LITTLE SIGNATURE IS APPARENT IN SATELLITE IMAGERY OR OBSERVATIONS. SCATTERED MODERATE CONVECTION IS IN THE GULF OF HONDURAS AND INLAND OVER GUATEMALA FROM 16N-19N BETWEEN 87W-89W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 13N16W 11N25W 7N37W 9N48W TO THE S AMERICA COAST NEAR 7N58W. SCATTERED MODERATE CONVECTION IS FROM 10N-13N BETWEEN 15W-18W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-12N BETWEEN 30W-39W. ...DISCUSSION... GULF OF MEXICO... A 1018 MB STATIONARY SURFACE HIGH NEAR 27N87N DOMINATES THE MAJORITY OF THE GULF OF MEXICO BRINGING GENERALLY FAIR WEATHER ACROSS THE AREA. E-NE FLOW ALOFT AROUND AN UPPER LEVEL HIGH OVER NW MEXICO NEAR 29N108W IS SUPPORTING THE SURFACE RIDGE. ATMOSPHERIC INSTABILITY NEAR AN UPPER LEVEL LOW S OF MEXICO NEAR 17N107W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER THE S BAY CAMPECHE S OF 20N W OF 93W. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE SURFACE HIGH AND ACROSS THE N GULF...WITH ANTICYCLONIC FLOW AROUND THE RIDGE SUPPORTING E-SE WINDS OF 10-15 KT ACROSS THE S HALF OF THE GULF. EXPECT LITTLE CHANGE OVER THE NEXT COUPLE DAYS. CARIBBEAN SEA... FRESH TO STRONG TRADE WINDS REMAIN ACROSS THE CARIBBEAN BETWEEN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER NRN S AMERICA. FLOW IS STRONGEST NEAR THE COAST OF COLUMBIA. THESE WINDS WILL REMAIN IN THE AREA AS THE SUBTROPICAL RIDGE PERSISTS AND AS A TROPICAL WAVE E OF THE LESSER ANTILLES REACHES THE E CARIBBEAN LATE TONIGHT AND TOMORROW. A TROPICAL WAVE ALONG 88W IS GENERATING SCATTERED SHOWERS/THUNDERSTORMS IN THE GULF OF HONDURAS AND INLAND OVER GUATEMALA FROM 16N-19N BETWEEN 87W-89W. ATMOSPHERIC INSTABILITY NEAR AN UPPER LEVEL LOW OVER THE SE BAHAMAS NEAR 23N73W IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS N OF 18N BETWEEN 74W-80W INCLUDING PORTIONS OF CUBA. IN THE SW CARIBBEAN...SURFACE CONVERGENCE NEAR A 1009 MB SURFACE LOW OVER COLUMBIA NEAR 8N77W AND THE PROXIMITY OF THE E PACIFIC ITCZ...AS WELL AS UPPER LEVEL DIFFLUENCE DUE TO AN UPPER LEVEL HIGH NEAR 14N88W ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS S OF 12N W OF 80W. DEEP LAYER DRY AIR AND ATMOSPHERIC STABILITY ASSOCIATED WITH AN UPPER LEVEL HIGH OVER THE WINDWARD ISLANDS NEAR 13N61W ARE SUPPORTING GENERALLY FAIR WEATHER ACROSS THE E CARIBBEAN. ATLANTIC OCEAN... UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE ERN CONUS AND THE AFOREMENTIONED UPPER LEVEL HIGH OVER NW MEXICO IS SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS N OF 28N BETWEEN 76W-79W. AN UPPER LEVEL TROUGH IS ACROSS THE SW NORTH ATLC EXTENDING FROM AN UPPER LEVEL LOW OVER THE SE BAHAMAS NEAR 23N73W TO 29N67W. THE UPPER LEVEL TROUGH IS SUPPORTING A SURFACE TROUGH EXTENDING FROM 21N66W TO 28N62W. SCATTERED SHOWERS ARE WITHIN 100 NM OF THE TROUGH AXIS BETWEEN 61W-67W. A SHORTWAVE UPPER LEVEL TROUGH IS ALONG 51W SUPPORTING THE TROPICAL WAVE E OF THE LESSER ANTILLES...SEE ABOVE. A BROAD SURFACE RIDGE DOMINATES THE REMAINDER OF THE ATLC ANCHORED BY A 1029 MB SURFACE HIGH N OF THE DISCUSSION AREA NEAR 34N43W...EXCEPT FOR A 1023 MB SURFACE LOW NEAR 34N31W WITH AN ASSOCIATED DYING COLD FRONT THAT ENTERS THE AREA NEAR 32N32W EXTENDING TO 28N41W...AND CONTINUING AS A STATIONARY FRONT TO 30N44W. NO SHOWER ACTIVITY IS CURRENTLY ASSOCIATED WITH THE FRONTAL SYSTEM. A BROAD UPPER LEVEL RIDGE DOMINATES THE E ATLC E OF 50W SUPPORTING CONVECTION ALONG THE ITCZ. $$ WALTON