000 AXNT20 KNHC 121730 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE MAY 12 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 8N13W 4N21W 1N32W CROSSING THE EQUATOR NEAR 41W EXTENDING TO NE BRAZIL NEAR 1S48W. SCATTERED MODERATE CONVECTION IS FROM 5N-7N BETWEEN 14W-17W...FROM 3N-5N BETWEEN 19W-23W...AND FROM 1N-3N BETWEEN 34W-36W. RECENT SATELLITE IMAGERY DEPICTS ENHANCED CYCLONIC VORTICITY IN THE VICINITY OF THE EASTERNMOST AREA OF THIS CONVECTIVE ACTIVITY... WHICH LIKELY IS ASSOCIATED WITH A TROPICAL WAVE. ...DISCUSSION... GULF OF MEXICO... WEAK COLD AIR ADVECTION W OF A WEAK SURFACE LOW OVER CENTRAL FLORIDA HAS FORCED A WEAKENING COLD FRONT TO SURGE S FROM SARASOTA FLORIDA TO NEAR MOBILE ALABAMA. VISIBLE SATELLITE IMAGERY AND RADAR TRENDS DEPICT THIS FEATURE WELL...BUT IT IS BECOMING INCREASINGLY DIFFUSE. A QUIKSCAT PASS AROUND 11/1130 UTC SHOWS N TO NE 10-15 KT WINDS NE OF THE FRONT. THIS LOW IS LIKELY BEING DRIVEN BY A WEAK MID/UPPER-LEVEL TROUGH TRAILING SW FROM THE W ATLC. THIS UPPER FORCING IS ALSO PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE FAR NE WATERS. E TO SE FLOW AND MAINLY FAIR WEATHER EXISTS ACROSS THE REMAINDER OF THE REGION ON THE S/SW PERIPHERY OF SFC HIGH PRES OVER THE OHIO VALLEY AND NWLY FLOW ALOFT. CARIBBEAN SEA... BROAD RIDGING ALOFT COVERS THE SOUTHWESTERN TWO-THIRDS OF THE CARIBBEAN...WITH UPPER LEVEL DIFFLUENCE BETWEEN THE CARIBBEAN RIDGE...AND A TROUGH OVER THE NW CARIBBEAN AND EPAC...SUPPORTING SCATTERED SHOWERS AND TSTMS ACROSS THE SW CARIBBEAN S OF 12N INCLUDING ADJACENT PORTIONS OF PANAMA AND COSTA RICA. HOWEVER...SUBSTANTIALLY MORE CONVECTIVE ACTIVITY IS FOUND OVER THE NEARBY E PAC WATERS S OF PANAMA AND COSTA RICA...WHERE LOW-LEVEL CONVERGENCE ALONG THE ITCZ IS AN ENHANCING FACTOR. MEANWHILE...SURFACE HIGH PRESSURE N OF THE CARIBBEAN SEA IS RESULTING IN FRESH E TRADE WINDS. THESE FRESH E TRADE WINDS ARE FORECAST TO PERSIST THROUGH THE WEEK. THE STRONGEST WINDS ARE FOUND NEAR THE COAST OF COLOMBIA...WHERE NE TO E 20-25 KT WINDS ARE OCCURRING. POCKETS OF LOW LEVEL MOISTURE AND ISOLATED SHOWERS ARE BEING ADVECTED WESTWARD ACROSS THE CARIBBEAN...WITH THE GREATEST CONCENTRATION OF THESE SHOWERS WITHIN 90 NM EITHER SIDE OF A SURFACE TROUGH OVER THE NE CARIBBEAN THAT EXTENDS FROM 15N63W TO E OF PUERTO RICO NEAR 18N64W. SURFACE OBSERVATIONS CONTINUE TO INDICATE A WEAK CYCLONIC WIND SHIFT IN THE VICINITY OF THIS TROUGH. ACROSS THE NORTHWESTERN ONE-THIRD OF THE CARIBBEAN...DEEP LAYER DRY AIR IS RESULTING IN GENERALLY FAIR WEATHER CONDITIONS. ATLANTIC OCEAN... A SURFACE RIDGE ASSOCIATED WITH A PAIR OF 1026 MB SURFACE HIGHS OVER THE CENTRAL ATLC IS AFFECTING MUCH OF THE ATLC PORTION OF THE DISCUSSION AREA. SUBSIDENCE ASSOCIATED WITH THE SURFACE RIDGE ARE RESULTING IN GENERALLY FAIR WEATHER CONDITIONS ACROSS MUCH OF THE ATLC PORTION OF THE DISCUSSION AREA. HOWEVER... POCKETS OF LOW LEVEL MOISTURE WITH ISOLATED SHOWERS ARE MOVING W ACROSS PORTIONS OF THE SW NORTH ATLC. THE GREATEST OF THESE SHOWERS IS LOCATED WITHIN 90 NM EITHER SIDE OF A RATHER DISORGANIZED SURFACE TROUGH THAT EXTENDS FROM 20N64W TO 18N64W. THIS TROUGH IS MOVING W NEAR 15 KT AND WILL LIKELY CONTINUE TO LOSE ITS ORGANIZATION WHILE THE ASSOCIATED SHOWER ACTIVITY DECREASES IN AREAL COVERAGE. ALSO...ATMOSPHERIC LIFT ASSOCIATED WITH A MID/UPPER-LEVEL VORTICITY MAXIMUM OVER THE W ATLC IS SUPPORTING A COLD FRONT FROM 31N75W TO A 1016 MB SURFACE LOW NEAR 30N79W TO THE E FLORIDA PENINSULA NEAR 28N81W. NE WINDS TO 20 KT ARE PRESENT N OF THE FRONT...AND WILL LIKELY INCREASE ACROSS THE N SEMICIRCLE OF THE LOW DURING THE NEXT DAY AS IT TRACKS NW TOWARD THE SURFACE RIDGE AXIS. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND WITHIN 90 NM SE OF THE COLD FRONT. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS PRESENT WITH AN AXIS EXTENDING FROM 12N14W TO 2N48W WITH AN UPPER HIGH CENTERED NEAR 4N35W. ASSOCIATED UPPER LEVEL DIVERGENCE IS ENHANCING ITCZ CONVECTION. $$ COHEN/CANGIALOSI