000 AXNT20 KNHC 172312 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN MAY 17 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 EXTENDS FROM 11N40W TO 1N43W MOVING W NEAR 10 KT. THIS WAVE IS EMBEDDED WITHIN A BROAD INVERTED-V STRUCTURE IN THE LOW-LEVEL CLOUD COVERAGE...AND 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. SCATTERED MODERATE CONVECTION IS OCCURRING WITHIN 180 NM E OF THE WAVE S OF 4N. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 7N11W 3N17W CROSSING THE EQUATOR NEAR 22W EXTENDING TO 2S30W 3S35W AND INTO NE BRAZIL NEAR 3S46W. SCATTERED MODERATE CONVECTION IS S OF 3N BETWEEN 13W-20W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS S OF 3N BETWEEN 21W-29W. ...DISCUSSION... GULF OF MEXICO... A DEEP LAYER TROUGH OVER THE SOUTH CENTRAL CONUS IS ASSOCIATED WITH A SURFACE STATIONARY FRONT OVER THE W GULF THAT EXTENDS FROM SOUTH CENTRAL LOUISIANA NEAR 29N91W TO 26N95W TO THE COAST OF MEXICO NEAR 22N98W. ALSO...A SURFACE TROUGH IS LOCATED TO THE E OF THE FRONT AND EXTENDS FROM S MISSISSIPPI NEAR 30N89W TO N OF THE YUCATAN PENINSULA NEAR 22N89W. LOW LEVEL CONVERGENCE NEAR THE SURFACE FRONT AND SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE GULF N OF 26N BETWEEN 86W-95W...WITH SCATTERED SHOWERS S OF 23N W OF 91W. ADDITIONALLY...RELATIVELY UNSTABLE ATMOSPHERIC CONDITIONS ASSOCIATED WITH MOIST SOUTHEASTERLY FLOW OVER THE E GULF ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS FROM 23N TO 29N E OF 84W INCLUDING THE W FLORIDA PENINSULA...THE FLORIDA KEYS...THE STRAITS OF FLORIDA...AND W CUBA. ALL OF THE SHOWER AND THUNDERSTORM ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE AFOREMENTIONED DEEP TROUGH AND AN UPPER LEVEL RIDGE OVER THE SW GULF. THE FRONT IS EXPECTED TO MOVE SOUTHEASTWARD AS A COLD FRONT THROUGH TUESDAY. ALSO... DURING THE NEXT DAY...MANY OF THE GLOBAL MODELS ARE SHOWING LOW PRESSURE DEVELOPING OVER THE N CENTRAL CARIBBEAN...EITHER EXTRATROPICAL OR SUBTROPICAL...AND MOVING GENERALLY N. THE DEVELOPMENT AND TRACK OF THE LOW REMAIN UNCERTAIN...THOUGH COMPUTER MODELS SUGGEST THAT WINDS WILL INCREASE AROUND THE LOW. CARIBBEAN SEA... NUMEROUS SHOWERS AND THUNDERSTORMS ARE AFFECTING PORTIONS OF THE NORTH CENTRAL CARIBBEAN N OF 16N BETWEEN 71W-79W...INCLUDING JAMAICA...E CUBA...AND W HISPANIOLA. THIS ACTIVITY IS BEING SUPPORTED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH THAT EXTENDS FROM E CUBA NEAR 20N76W TO 16N76W. THE ACTIVITY IS ALSO BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER RIDGE OVER THE SW NORTH ATLC AND AN UPPER TROUGH OVER THE S CARIBBEAN. DURING THE NEXT DAY...A SURFACE LOW IS FORECAST TO DEVELOP ALONG THE SURFACE TROUGH AND MOVE N OF THE CARIBBEAN MONDAY NIGHT. UPPER LEVEL DIVERGENCE AND ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER TROUGH OVER THE S CARIBBEAN IS ALSO SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE SW CARIBBEAN S OF 10N AND SCATTERED SHOWERS OVER THE E CARIBBEAN FROM 14N TO 17N BETWEEN 63W-69W. ADDITIONALLY...ATMOSPHERIC INSTABILITY IS RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS OVER W CUBA...IMPACTING THE ADJACENT COASTAL WATERS. ALSO... SCATTERED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF A SURFACE TROUGH OVER THE NW CARIBBEAN THAT EXTENDS FROM 19N85W TO 16N85W. MEANWHILE...SURFACE HIGH PRESSURE CENTERED W OF BERMUDA IS MAINTAINING 15-20 KT EASTERLY TRADE WINDS ACROSS MUCH OF THE E CARIBBEAN. ATLANTIC OCEAN... AN OCCLUDED 1006 MB SURFACE LOW IS NEARLY STATIONARY NEAR 32N53W. AN ASSOCIATED SURFACE COLD FRONT EXTENDS FROM 32N46W TO 27N47W TO 24N49W AND CONTINUING SOUTHWESTWARD AS A STATIONARY FRONT TO 19N56W. FROM 19N56W...THE BOUNDARY WEAKENS TO A SURFACE TROUGH AND EXTENDS SW TO 16N59W. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND WITHIN 300 NM E OF THE SURFACE FRONTS AND SURFACE TROUGH. A SURFACE TROUGH IS ALSO PRESENT TO THE W OF THE COLD AND STATIONARY FRONTS AND EXTENDS FROM 30N48W TO 27N52W TO 27N58W. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS SURFACE TROUGH. ALL OF THIS SHOWER AND THUNDERSTORM ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE NEAR AN UPPER TROUGH THAT EXTENDS FROM AN UPPER LOW NEAR 32N52W TO 28N49W TO 26N49W. FARTHER TO THE W...A SURFACE RIDGE EXTENDS SOUTHWESTWARD FROM SURFACE HIGH PRESSURE CENTERED W OF BERMUDA. SUBSIDENCE ASSOCIATED WITH THIS SURFACE RIDGE...COMBINED WITH ATMOSPHERIC STABILITY ASSOCIATED WITH AN UPPER RIDGE OVER THE SW NORTH ATLC...IS SUPPORTING GENERALLY FAIR WEATHER CONDITIONS ACROSS MUCH OF THE SW NORTH ATLC. HOWEVER...MOIST SOUTHEASTERLY LOW LEVEL FLOW OVER PORTIONS OF THE SW NORTH ATLC IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 25N W OF 78W. ADDITIONALLY...NUMEROUS SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE SURFACE TROUGH OVER THE NORTH CENTRAL CARIBBEAN ARE MOVING NORTHWARD INTO THE SW N ATLC...AFFECTING LOCATIONS S OF 22N BETWEEN 71W-79W...INCLUDING PORTIONS OF E CUBA AND W HISPANIOLA. DURING THE NEXT DAY...MANY OF THE GLOBAL MODELS ARE SHOWING LOW PRESSURE DEVELOPING OVER THE N CENTRAL CARIBBEAN...EITHER EXTRATROPICAL OR SUBTROPICAL... AND MOVING GENERALLY N INTO THE SW NORTH ATLC. THE PRESSURE GRADIENT AROUND THE LOW IS FORECAST TO RESULT IN GALE CONDITIONS N OF 28N W OF 75W MONDAY NIGHT THROUGH WEDNESDAY. ACROSS THE E ATLC...A SURFACE RIDGE IS PRESENT WHERE MAINLY ZONAL FLOW ALOFT IS OCCURRING AND FAIR WEATHER CONDITIONS PERSIST. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS PRESENT S OF 11N E OF 58W WITH UPPER LEVEL HIGHS CENTERED NEAR 6N46W AND 5N25W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL HIGHS AND UPPER LEVEL RIDGE IS ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ AND WITH THE TROPICAL WAVE THAT EXTENDS FROM 11N40W TO 1N43W. $$ COHEN