000 AXNT20 KNHC 201048 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SUN MAY 20 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 1030 UTC. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 10N14W 6N20W 4N35W 4N45W 3N52W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150 NM EITHER SIDE OF THE AXIS BETWEEN 19W-25W. A LOW LATITUDE TROPICAL WAVE MAY BE ENHANCING THIS ACTIVITY...ALTHOUGH DID NOT ADD THIS TO THE SFC MAP YET BECAUSE TRACKING BACK OVER AFRICA WAS DIFFICULT TO DISCERN. A CLUSTER OF SCATTERED MODERATE IS MOVING OFF THE AFRICAN COAST E OF 15W FROM 8N-10N. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 180 NM N OF THE AXIS W OF 28W. ...DISCUSSION... GULF OF MEXICO... SURFACE HIGH PRES OVER THE SOUTHEAST U.S. IS PROVIDING MOSTLY FAIR WEATHER ACROSS THE MAJORITY OF THE GULF AND MODERATE NE WINDS IN THE ERN AND MID GULF N OF 26N. A WEAK SFC TROUGH HAS BEEN ADDED TO THE ANALYSIS FROM THE FL STRAITS TO SRN LOUISIANA ALONG 25N80W 25N89W 30N91W. THIS WEAK BOUNDARY LIKELY BROKE OFF FROM THE MAIN FRONTAL TROUGH IN THE W ATLC AND IS GETTING PULLED W BY THE LOW-LEVEL FLOW. A BAND OF LOW CLOUDS AND A POSSIBLE SHOWERS MARK THE TROUGH AXIS ALONG WITH AN INCREASE IN WINDS BEHIND IT. THE UPPER FLOW IS FAIRLY UNIFORM WNWLY BETWEEN RIDGING OVER THE S CENTRAL U.S. AND LARGE SCALE TROUGHING OFF THE U.S. EASTERN SEABOARD. THIS PATTERN IS PRODUCING MODEST STABLE AIR ALOFT AIDING IN THE TRANQUIL CONDITIONS. DEBRIS HIGH CLOUDS...WHICH ARE ADVECTED E FROM FIZZLING BURSTS OF CONVECTIVE ACTIVITY OVER MEXICO...IS MOISTENING THE ATMOSPHERE SLIGHTLY W OF 92W. LITTLE CHANGE IN THE OVERALL WEATHER IS EXPECTED OVER THE NEXT DAY OR TWO THOUGH MID-HIGH CLOUDINESS MAY SPREAD FURTHER E AS THE UPPER FLOW VEERS TO THE WSW. CARIBBEAN SEA... A SFC TROUGH EXTENDS FROM PANAMA NWD TO CUBA ROUGHLY ALONG 79W/80W. THIS FEATURE WAS WELL DEPICTED BY LAST EVENING'S QSCAT PASS WHICH SHOWS MODERATE ELY TRADES E OF THE TROUGH AXIS AND LIGHT NELY WINDS TO THE W. ALOFT...A SPRAWLING RIDGE IS CENTERED OVER NRN VENEZUELA. S-SWLY FLOW ON THE WRN PERIPHERY OF THE RIDGE IS TAPPING MOISTURE FROM THE ITCZ AND SPREADING IT ANTICYCLONICALLY AROUND ITS CIRCULATION...ALMOST ENTIRELY CONTAINED W OF 68W. MOST OF THE MOISTURE IS ONLY IN THE FORM OF A MID-HIGH LEVEL CLOUD DECK...ALTHOUGH THERE COULD BE ISOLATED SHOWERS EMBEDDED ESPECIALLY S OF 15N W OF 78W CLOSER TO THE DEEP MOISTURE SOURCE AND N OF 18N BETWEEN 74W-79W IN A WEAK UPPER DIFFLUENT ZONE. THE ERN CARIB IS EXPERIENCING TRANQUIL CONDITIONS UNDER A SUBSIDENT ENVIRONMENT. MOST OF THE GLOBAL MODELS SHOW THE WEAK SFC TROUGH BEING PUSHED VERY SLOWLY W BY THE LOW-LEVEL ELY FLOW AND THE MOISTURE SWATH GENERALLY BECOMING LESS DENSE OVER THE NEXT COUPLE DAYS. ATLANTIC OCEAN... THE SYNOPTIC PICTURE SHOWS A HIGHLY AMPLIFIED TROUGH/RIDGE/TROUGH PATTERN COVERING THE ATLC DISCUSSION AREA THIS MORNING. BEGINNING IN THE W ATLC...THE UPPER TROUGH EXTENDS FROM A VIGOROUS UPPER LOW OVER RHODE ISLAND TO THE WRN BAHAMAS WITH A FAINT INFLUENCE IN THE WINDS ALOFT EXTENDING INTO THE NW CARIB. THIS UPPER SYSTEM IS SUPPORTING A SFC TROUGH WHICH RUNS FROM NEAR 29N65W TO THE CENTRAL BAHAMAS. ANOTHER WEAK BOUNDARY IS EVIDENT ON NIGHT CHANNEL VIS IMAGES EXTENDING FROM JUST W OF BERMUDA TO THE FL STRAITS. THIS WESTERN BOUNDARY...REMNANTS OF AN OLD FRONT...APPEARS TO HAVE STALLED AND ISENTROPIC LIFT IS PRODUCING A FEED OF SHOWERS AND TSTMS ACROSS SE FLORIDA. SCATTERED SHOWERS ARE ALSO OCCURRING BETWEEN 62W-75W NEAR THE SFC TROUGH MENTIONED ABOVE AND IN AN UPPER DIFFLUENT ZONE. IN THE CENTRAL ATLC...WATER VAPOR IMAGERY SHOWS AN AMPLIFIED RIDGE CENTERED WELL N OF THE AREA NEAR 42N44W. AN UPPER LOW IS EMBEDDED IN THE RIDGE NEAR 28N47W BUT IS DOING VERY LITTLE IN GENERATING MUCH WEATHER. MODERATE DRY STABLE AIR EXISTS BETWEEN 40W-60W. THE RIDGE MENTIONED N OF THE AREA IS VERTICALLY STACKED WITH AN ASSOCIATED 1037 MB HIGH CENTERED NEAR 41N42W. THIS HIGH PRES IS AIDING IN THE WIDESPREAD FAIR WEATHER AND PRODUCING MODERATE ELY TRADES ACROSS THE REGION. THE E ATLC IS AN AREA OF UPPER CONVERGENCE BETWEEN A TROUGH WHICH DIGS SWD TO 23N AND UPPER RIDING POKING NWD TOWARD THE TROUGH. AN STRONG SW-WLY JET LIES BETWEEN THESE UPPER FEATURES EXTENDING FROM 17N42W TO W AFRICA NEAR 22N17W. CORE WINDS ALONG THIS JET AXIS ARE BETWEEN 110-130 KT BASED ON SATELLITE DERIVED WINDS. PATCHES OF MID-HIGH LEVEL CLOUDS AND ISOLATED SHOWERS ARE DRAWN NEWD FROM THE ITCZ TO THE JET AXIS...WHILE ABUNDANT SINKING AIR ALOFT IS STABILIZING THE ATMOSPHERE N OF THE JET. IN THE LOWER LEVELS...MODERATE TO STRONG NELY TRADES COVER MUCH OF THE AREA BETWEEN STRONG HIGH PRES IN THE CENTRAL ATLC AND LOWER PRES OVER AFRICA. $$ CANGIALOSI