000 AXNT20 KNHC 130555 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 24W S OF 14N 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. CONVECTION IS MINIMAL NEAR THE WAVE. A TROPICAL WAVE EXTENDS ALONG 20N51W TO 03N44W MOVING W 20-25 KT. THIS WAVE HAS BECOME INCREASINGLY TILTED NW-SE BY THE NE WIND SURGE E OF THE AXIS. A WELL DEFINED INVERTED V PATTERN IS EVIDENT IN THE LOW-LEVEL CLOUDS AND A SMALL AREA OF CONVECTION HAS RECENTLY DEVELOPED FROM 10N-12N BETWEEN 47W-50W 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 85W 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. EARLIER CONVECTION NEAR THE AXIS HAS DIMINISHED. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 14N17W 7N28W 7N40W 6N57W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 10N-16N E OF 21W AND FROM 4N-9N BETWEEN 28W-35W. ...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 28N. GENERALLY FAIR WEATHER CONDITIONS ARE PRESENT ACROSS THE GULF. 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 91W. 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 ISOLATED SHOWERS AND THUNDERSTORMS N OF 19N BETWEEN 72W-78W INCLUDING PORTIONS OF E CUBA AND HISPANIOLA. ACROSS THE SW CARIBBEAN...AN UPPER LEVEL HIGH IS CENTERED NEAR 13N82W...WITH DIVERGENCE ALOFT PRODUCING CLOUDINESS AND ISOLATED SHOWERS. 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 TO 26N75W TO 32N61W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER TROUGH AND LOW-LEVEL CONVERGENCE NEAR A SFC TROUGH FROM 27N66W TO 23N68W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITHIN 90 NM OF THE SFC TROUGH. ANOTHER SURFACE TROUGH EXTENDS FROM 26N59W TO 19N61W...BUT IS PRODUCING LITTLE SENSIBLE WEATHER AT THE MOMENT. SCATTERED SHOWERS AND ISOLATED TSTMS ARE FARTHER E FROM 20N-26N BETWEEN 48W-52W SUPPORTED BY DIFFLUENCE ALOFT BETWEEN A TROUGH AND RIDGE WITH SOME INFLUENCE FROM THE N PERIPHERY OF A TROPICAL WAVE. SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH A 1030 MB HIGH NEAR 36N41W. A 1023 MB SFC LOW NEAR 32N35W 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