000 AXNT20 KNHC 131037 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 25W S OF 17N MOVING W NEAR 15 KT. THE DAKAR SOUNDING SHOWED A CLEAR SIGNAL OF THIS WAVE CROSSING THE STATION ON JUL 11 WITH 50 KT WINDS AT 650 MB. THE SATELLITE APPEARANCE OF THE WAVE TONIGHT IS NOT AS IMPRESSIVE AS THE PAST FEW WAVES IN THIS REGION. A BROAD AREA OF LOW-LEVEL CYCLONIC TURNING IS APPARENT ESPECIALLY IN THE 600-800 MB LAYER ACCORDING TO SATELLITE DERIVED WINDS. HOWEVER...ITS ENVELOPE OF MOISTURE BASED ON TOTAL PRECIPITABLE WATER IS RATHER FLAT. DEEP CONVECTION NEAR THE WAVE IS LIKELY BEING MAINLY SUPPORTED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ. A TROPICAL WAVE EXTENDS ALONG 20N51W TO 4N47W MOVING W 20-25 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 AND A SMALL AREA OF CONVECTION ACCOMPANIES THE WAVE FROM 9N-13N BETWEEN 47W-51W ENHANCED BY DIFFLUENCE ALOFT. GFS APPEARS TO HAVE A GOOD HANDLE ON THIS FEATURE AND SHOWS IT MOVING INTO THE LESSER ANTILLES TUE WITH THE N PART LIKELY FRACTURING. A TROPICAL WAVE IS ALONG 86W MOVING W NEAR 20 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 FROM 16N-18N BETWEEN 84W-88W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N16W 10N24W 8N37W 8N47W 6N58W. SCATTERED MODERATE CONVECTION IS FROM 9N-13N E OF 26W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-11N BETWEEN 27W-36W. SCATTERED MODERATE CONVECTION IS FROM 4N-7N BETWEEN 38W-43W. ...DISCUSSION... GULF OF MEXICO... EAST-NORTHEASTERLY UPPER FLOW COVERS MUCH OF THE GULF ON THE SE SIDE OF AN UPPER RIDGE OVER THE SOUTHERN PLAINS...SUPPORTING A SURFACE RIDGE ALONG 26N WITH A 1020 MB SURFACE HIGH NEAR 27N85W. GENERALLY FAIR WEATHER CONDITIONS ARE PRESENT ACROSS THE GULF. THE ONLY EXCEPTION IS OVER THE BAY OF CAMPECHE WHERE INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER SRN MEXICO IS PRODUCING SCATTERED SHOWERS AND TSTMS S OF 21N W OF 93W. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE SURFACE RIDGE ACROSS THE N GULF...WITH ANTICYCLONIC FLOW AROUND THE RIDGE SUPPORTING A BROAD SWATH OF E WINDS OF 10-15 KT ACROSS THE S HALF OF THE GULF. LITTLE CHANGE IS EXPECTED OVER THE NEXT DAY OR TWO AS BOTH THE UPPER AND SFC RIDGE REMAIN NEARLY STATIONARY. CARIBBEAN SEA... FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF COLOMBIA. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL DAYS AS THE SUBTROPICAL RIDGE REMAINS IN PLACE AND A TROPICAL WAVE MOVES INTO THE AREA. ALOFT...INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE N CENTRAL CARIBBEAN IS RESULTING IN SCATTERED SHOWERS N OF 19N BETWEEN 75W-80W INCLUDING PORTIONS OF E CUBA. ACROSS THE SW CARIBBEAN... AN UPPER LEVEL LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER HIGH CENTERED NEAR 14N85W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 12N W OF 78W. DEEP LAYER DRY AIR AND ATMOSPHERIC STABILITY ASSOCIATED WITH AN UPPER LEVEL HIGH OVER THE WINDWARD ISLANDS ARE SUPPORTING GENERALLY FAIR WEATHER ACROSS THE E CARIBBEAN. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS ACROSS THE SW NORTH ATLC WITH AN AXIS EXTENDING FROM AN UPPER LOW OVER THE SE BAHAMAS NEAR 22N72W TO 27N67W TO 32N60W TO NE OF THE DISCUSSION AREA. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER TROUGH AND LOW-LEVEL CONVERGENCE NEAR A SFC TROUGH EXTENDING FROM 27N63W TO 19N65W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITHIN 60 NM OF THE SFC TROUGH. SCATTERED SHOWERS AND ISOLATED TSTMS ARE FARTHER E FROM 20N-27N BETWEEN 49W-55W SUPPORTED BY DIFFLUENCE ALOFT BETWEEN A TROUGH AND RIDGE WITH SOME INFLUENCE OF A TROPICAL WAVE FARTHER TO THE S. SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH A 1029 MB HIGH NEAR 34N43W. A 1023 MB SFC LOW NEAR 33N33W IS PERTURBING THE RIDGE BUT ITS CLOUDINESS/SHOWERS ARE SHALLOW IN NATURE. WINDS ARE LIKELY 20-25 KT N AND W OF THE LOW...DUE TO THE TIGHTENED PRESSURE GRADIENT. $$ CANGIALOSI/COHEN