000 AXNT20 KNHC 212306 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU MAY 21 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 74W SOUTH OF 13N MOVING WEST NEAR 15 KT. THIS WAVE IS ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. COMPUTER MODEL GUIDANCE INDICATES THAT THE WAVE COINCIDES WITH AN AREA OF LOW LEVEL CYCLONIC CIRCULATION...WHICH IS ALSO ASSOCIATED WITH A 1006 MB SURFACE LOW ALONG THE TROPICAL WAVE IN N COLOMBIA NEAR 8N74W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE WAVE AXIS FROM 9N-11N. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 7N12W 3N20W 2N29W CROSSING THE EQUATOR NEAR 35W EXTENDING TO 1S37W AND INTO NE BRAZIL NEAR 3S42W. SCATTERED MODERATE CONVECTION IS S OF 2N BETWEEN 1W-2W. SCATTERED MODERATE CONVECTION IS ALSO S OF 5N BETWEEN 10W-22W. SIMILAR CONVECTION IS S OF 4N BETWEEN 25W-36W. ...DISCUSSION... GULF OF MEXICO... A DEEP LAYER TROUGH IS PRESENT ACROSS THE GULF WITH AN UPPER LEVEL LOW NEAR 27N86W AND AN ASSOCIATED 1006 MB SURFACE LOW NEAR 26N86W. LOW LEVEL CONVERGENCE NEAR THE SURFACE LOW...AS WELL AS UPPER LEVEL DIFFLUENCE E OF THE UPPER LOW...ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE GULF N OF 23N E OF 87W....INCLUDING THE W FLORIDA PENINSULA. THE TIGHT SURFACE PRESSURE GRADIENT BETWEEN THE SURFACE LOW AND A SURFACE RIDGE OVER THE SE CONUS IS SUPPORTING WIND SPEEDS OF 20 TO 30 KT AROUND THE LOW ACROSS N PORTIONS OF THE MIDDLE AND E GULF. THE SURFACE LOW IS FORECAST TO MOVE NORTHWESTWARD DURING THE NEXT DAY AND BE LOCATED NEAR 27N89W AS A 1008 MB SURFACE LOW AT 22/1800 UTC. THE WINDS AROUND THE LOW ARE FORECAST TO BECOME LIGHTER THIS WEEKEND AS THE PRESSURE GRADIENT AROUND THE LOW RELAXES. ACROSS THE W GULF...SUBSIDENCE ASSOCIATED WITH NORTHWESTERLY FLOW ALOFT IS SUPPORTING GENERALLY FAIR WEATHER CONDITIONS...WITH UPPER LEVEL MOISTURE AND HIGH LEVEL CLOUDS STREAMING SOUTHEASTWARD. NORTHERLY WINDS UP TO 20 KT ARE OCCURRING ACROSS THE W GULF. CARIBBEAN SEA... NUMEROUS SHOWERS AND THUNDERSTORMS ARE AFFECTING THE NORTH CENTRAL CARIBBEAN N OF 16N BETWEEN 68W-77W...INCLUDING PORTIONS OF JAMAICA...HISPANIOLA...AND PUERTO RICO. THIS ACTIVITY IS BEING SUPPORTED BY STRONG UPPER LEVEL DIFFLUENCE IN MOIST SOUTHWESTERLY FLOW ALOFT BETWEEN AN UPPER LEVEL TROUGH OVER THE W CARIBBEAN AND GULF OF MEXICO...AND AN UPPER LEVEL RIDGE ACROSS THE E CARIBBEAN AND SW NORTH ATLC. THE SHOWERS AND THUNDERSTORMS ARE ASSOCIATED WITH HEAVY RAINFALL...AS WELL AS MAJOR FLOODING OVER PORTIONS OF HISPANIOLA. ADDITIONAL SHOWER AND THUNDERSTORM ACTIVITY IS FORECAST TO AFFECT THE NORTH CENTRAL CARIBBEAN DURING THE NEXT COUPLE DAYS. ADDITIONALLY...ATMOSPHERIC INSTABILITY IS RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS OVER E CUBA. UPPER LEVEL MOISTURE AND HIGH LEVEL CLOUDS ARE STREAMING NORTHEASTWARD ACROSS THE W CARIBBEAN AND EAST-SOUTHEASTWARD ACROSS THE E CARIBBEAN. MEANWHILE...SLIGHT STRENGTHENING OF A SURFACE RIDGE OVER THE CENTRAL ATLC IS MAINTAINING LIGHT TO MODERATE TRADES OVER PORTIONS OF THE E CARIBBEAN...WHERE E TO SE WINDS OF 15 TO 20 KT ARE OCCURRING. ADDITIONALLY...A TROPICAL WAVE IS MOSTLY INLAND OVER COLOMBIA AND IS ASSOCIATED WITH SCATTERED MODERATE CONVECTION ACROSS N COLOMBIA. PLEASE SEE ABOVE FOR FURTHER INFORMATION ON THIS TROPICAL WAVE. ATLANTIC OCEAN... SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING FROM 22N-29N BETWEEN 74W-79W INCLUDING THE NW BAHAMAS...AS WELL AS S OF 22N BETWEEN 65W-75W INCLUDING HISPANIOLA AND PUERTO RICO. THIS ACTIVITY IS BEING SUPPORTED BY STRONG UPPER LEVEL DIFFLUENCE IN MOIST SOUTHWESTERLY FLOW ALOFT BETWEEN AN UPPER LEVEL TROUGH OVER THE W CARIBBEAN AND GULF OF MEXICO...AND AN UPPER LEVEL RIDGE ACROSS THE E CARIBBEAN AND SW NORTH ATLC. THE SHOWERS AND THUNDERSTORMS ARE ASSOCIATED WITH HEAVY RAINFALL...AS WELL AS MAJOR FLOODING OVER PORTIONS OF HISPANIOLA. FARTHER TO THE E...AN UPPER LEVEL TROUGH IS PRESENT WITH AN AXIS EXTENDING FROM AN UPPER LEVEL LOW NEAR 32N46W TO 30N42W. ATMOSPHERIC INSTABILITY NEAR THE UPPER LEVEL LOW AND TROUGH...AS WELL AS UPPER LEVEL DIFFLUENCE IN MOIST SOUTHWESTERLY FLOW ALOFT...ARE SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 27N BETWEEN 38W-49W. ALSO...A SURFACE TROUGH EXTENDS FROM 31N50W TO A 1016 MB SURFACE LOW NEAR 28N55W TO 23N58W. LOW LEVEL CONVERGENCE NEAR THESE FEATURES IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH. DURING THE NEXT DAY...THE 1016 MB SURFACE LOW IS FORECAST TO DISSIPATE. ACROSS THE E ATLC...A SURFACE RIDGE IS PRESENT WHERE MAINLY ZONAL FLOW ALOFT IS OCCURRING AND FAIR WEATHER CONDITIONS PERSIST. HOWEVER...AN UPPER LEVEL TROUGH IS PRESENT N OF 27N E OF 26W WITH AN ASSOCIATED SURFACE COLD FRONT EXTENDING FROM 25N23W TO THE CANARY ISLANDS NEAR 28N17W TO 32N15W TO N OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS COLD FRONT. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS S OF 11N E OF 49W WITH AN UPPER LEVEL HIGH NEAR 7N19W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL HIGH AND UPPER LEVEL RIDGE IS ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ. $$ COHEN