000 AXNT20 KNHC 202339 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON MAY 20 2013 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 7N34W TO EQ36W MOVING WEST AT 10-15 KT. THE WAVE SHOWS A GOOD SIGNAL IN 700 MB STREAMLINES AND SATELLITE DERIVED WINDS. IT ALSO COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED MODERATE CONVECTION IS WITHIN 100 NM OF THE AXIS. TROPICAL WAVE EXTENDS FROM 14N62W TO 9N63W MOVING W AT 5-10 KT. THE WAVE IS PARTIALLY OVER SOUTH AMERICA...BUT THE MOISTURE SIGNAL IN TOTAL PRECIPITABLE WATER IMAGERY EXTENDS UP TO 15N. SCATTERED MODERATE CONVECTION IS WITHIN 200 NM TO EITHER SIDE SOUTH OF 12N. THE DEEPEST MOISTURE ASSOCIATED WITH THE WAVE IS STILL MOVING OVER THE WINDWARD ISLANDS...SO A RISK OF HEAVY RAINFALL IS STILL PRESENT OVER THIS AREA. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE COAST OF GUINEA-BISSAU NEAR 11N15W TO ALONG 5N20W 4N30W. THE ITCZ BEGINS NEAR 4N30W AND CONTINUES ALONG EQ38W 3S49W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-8N BETWEEN 17W-20W. ISOLATED MODERATE CONVECTION IS FROM 1N-7N BETWEEN 22W-32W. ...DISCUSSION... GULF OF MEXICO... MOSTLY FAIR WEATHER SPREADS ACROSS THE GULF OF MEXICO...WITH THE EXCEPTION OF FLORIDA...ALONG WITH BROAD SURFACE RIDGING EXTENDING FROM THE W ATLC. DRY AIR ALOFT COVERS THE MAJORITY OF THE BASIN AROUND BROAD UPPER LEVEL RIDGING EXTENDING FROM THE EAST PACIFIC JUST SOUTH OF GUATEMALA. HOWEVER...A SHORTWAVE UPPER TROUGH EXTENDS DOWN THE WEST COAST OF FLORIDA PROVIDING DIFFLUENCE ALOFT ACROSS THE PENINSULA. THIS COMBINED WITH DAYTIME HEATING AND INSTABILITY HAS LED TO HEAVY SHOWERS AND THUNDERSTORMS ACROSS FLORIDA WITH SOME BEING SEVERE. THE ACTIVITY OVER SOUTH FLORIDA HAS DIED DOWN SOME...BUT HEAVY ACTIVITY STILL SPREADS OVER MUCH OF THE WEST CENTRAL AND NORTHERN PORTIONS. PRIMARILY SOUTHEAST WINDS SPREAD THROUGHOUT THE BASIN RANGING FROM 10-15 KT WITH A FEW AREAS OF 20 KT WINDS OVER THE WESTERN GULF ESPECIALLY ALONG THE TEXAS COAST. LITTLE CHANGE IS EXPECTED OVER THE NEXT 24 HOURS. MODEL GUIDANCE CONTINUES TO SHOW HIGH MOISTURE AND PRECIPITATION POTENTIAL THROUGHOUT THE FLORIDA PENINSULA. CARIBBEAN SEA... NORTHWEST TO WEST FLOW ALOFT COVERS THE CARIBBEAN ALONG WITH MOSTLY DRY AIR. THE DRY AIR IS PROVIDING FAIR CONDITIONS ACROSS MUCH OF THE BASIN. HOWEVER...DAYTIME HEATING AND INSTABILITY HAVE LED TO WIDESPREAD SHOWERS AND THUNDERSTORMS OVER THE NORTHERN CARIBBEAN ISLANDS INCLUDING CUBA...HISPANIOLA...JAMAICA...AND PUERTO RICO. HEAVY SHOWERS AND THUNDERSTORMS ARE ALSO IN THE FAR SW CARIBBEAN SOUTH OF 11N FROM COSTA RICA TO COLOMBIA INCLUDING PANAMA. THIS ACTIVITY IS CONNECTED TO THE MONSOON TROUGH EXTENDING THROUGH BOTH COSTA RICA AND PANAMA. THE ACTIVITY IS ENHANCED BY DIFFLUENT FLOW ALOFT ACROSS THAT AREA. A TROPICAL WAVE HAS MOVING INTO THE SE CARIBBEAN JUST WEST OF THE WINDWARD ISLANDS. SCATTERED SHOWERS ARE EAST OF 63W SOUTH OF 16N. THERE IS STILL SOME MOISTURE WITH THE WAVE EAST OF THE WINDWARD ISLANDS...AND AS THE WAVE MOVES WEST MORE SHOWERS AND POSSIBLE THUNDERSTORMS COULD OCCUR OVER THE ISLANDS. ELSEWHERE...TRADEWIND FLOW OF 15-20 KT DOMINATES WITH A FEW 25 KT WINDS OFF THE COAST OF COLOMBIA. MOIST CONDITIONS AND LIKELY PRECIPITATION WILL REMAIN OVER THE SW CARIBBEAN AS WELL AS THE NORTHERN CARIBBEAN ISLANDS ESPECIALLY IN THE AFTERNOON HOURS. AS THE TROPICAL WAVE IN THE SE CORNER MOVES WEST...MOISTURE WILL INCREASE AND WILL SUPPORT HEAVIER THAN NORMAL AFTERNOON CONVECTION. THIS WILL LIKELY BE THE CASE TOMORROW OVER PUERTO RICO AND SPREAD WESTWARD ON WEDNESDAY. HISPANIOLA... CURRENTLY AFTERNOON SHOWERS AND THUNDERSTORMS CONTINUE TO IMPACT THE ISLAND OF HISPANIOLA MAINLY CONCENTRATED BETWEEN 70W-73W. AS THE SUN GOES DOWN THIS ACTIVITY SHOULD DIE DOWN. MODEL GUIDANCE INDICATES A SIMILAR PATTERN WILL PERSIST TOMORROW WITH THE MOST LIKELY PRECIPITATION TO BE DURING THE AFTERNOON AND EARLY EVENING HOURS ACROSS THE ISLAND WHEN PEAK DAYTIME HEATING AND INSTABILITY OCCUR. ANY AREAS THAT RECEIVE MEASURABLE AMOUNTS OF RAINFALL WILL LIKELY BE PRONE TO LOCALIZED FLOODING. MOISTURE FROM A TROPICAL WAVE MAY INCREASE ACTIVITY OVER THE ISLAND ON WEDNESDAY. ATLANTIC OCEAN... A SHORTWAVE UPPER TROUGH ALONG THE WEST COAST OF FLORIDA IS SUPPORTING HEAVY SHOWERS AND THUNDERSTORMS ACROSS THE FLORIDA PENINSULA...WHICH CONTINUE INTO THE ATLC TO NEAR 78W. AN UPPER LEVEL RIDGE IS ALONG 76W SUPPORTING A SURFACE RIDGE ACROSS THE WEST ATLC AROUND A 1026 MB HIGH NEAR 35N62W. FARTHER EAST...AN UPPER LEVEL TROUGH ALONG 49W SUPPORTS A COLD FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N49W AND CONTINUES ALONG 29N55W 27N59W. ISOLATED SHOWERS ARE WITHIN 30 NM OF THE AXIS. A WEAK 1019 MB SURFACE LOW IS TO THE EAST NEAR 27N48W. A SURFACE TROUGH EXTENDS THROUGH THE LOW CENTER FROM 30N49W 24N44W. NO SHOWERS ARE ASSOCIATED WITH THE SYSTEM. THE REMAINDER OF THE EASTERN ATLC IS DOMINATED BY BROAD SURFACE RIDGING ANCHORED BY A 1034 MB HIGH NEAR 44N29W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED NEAR 43N26W. BROAD UPPER RIDGING ALSO COVERS THE TROPICAL ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON