000 AXNT20 KNHC 200546 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT MON APR 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...ITCZ... THE ITCZ IS CENTERED ALONG 4N AND THE PRIME MERIDIAN CROSSING THE EQUATOR NEAR 10W AND CONTINUES ALONG 2S20W AND INTO NE BRAZIL NEAR 3S40W. SCATTERED MODERATE CONVECTION IS WITHIN 50 NM OF A LINE FROM 6N13W TO 3N19W. OTHERWISE ISOLATED CONVECTION ASSOCIATED WITH THE ITCZ IS SOUTH OF THE EQUATOR. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH IS ACROSS THE ERN CONUS AND AS OF 0300 UTC SUPPORTS A COLD FRONT THAT ENTERS THE GULF NEAR NEW ORLEANS LOUISIANA AND EXTENDS SW ALONG 28N90W 25N94W TO THE NE MEXICO COAST NEAR 24N98W. LOW-LEVEL CONVERGENCE ALONG AND TO THE EAST OF THE FRONT...ANALYZED AS A SURFACE TROUGH EXTENDING FROM 29N88W TO 24N91W...IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS IN THE WRN BAY OF CAMPECHE W OF 94W AND ACROSS THE NE GULF N OF 25N. MOIST MIDDLE TO UPPER LEVEL SOUTHWEST FLOW ALOFT IS PROVIDING ADDITIONAL SUPPORT FOR THIS CONVECTIVE ACTIVITY. THE COLD FRONT IS FORECAST TO CONTINUE PROGRESSING EWD AND POSITION ITSELF SE OF THE REGION BY TUESDAY. A HIGH PRESSURE RIDGE WILL BUILD IN BEHIND THIS FRONT POSSESSING NLY WINDS UP TO 20 KTS WITH A RELATIVELY COOLER AND DRIER AIRMASS IN PLACE. CARIBBEAN SEA... A SURFACE RIDGE LOCATED OVER THE W ATLC IS MAINTAINING FRESH ELY TRADE WINDS ACROSS THE CARIBBEAN SEA. THE STRONGEST OF THESE WINDS...UP TO 25 KTS...ARE ACROSS THE CENTRAL CARIBBEAN AND ALONG THE NRN COLOMBIA COAST. GENERALLY FAIR WEATHER IS PRESENT BASIN WIDE...WHERE DEEP LAYER DRY AIR AND SUBSIDENCE IS RESULTING FROM ZONAL WESTERLY FLOW ALOFT. HOWEVER...AN UPPER LEVEL TROUGH ACROSS THE W AND CENTRAL ATLC DIPS OVER THE NE CARIBBEAN AND SUPPORTS THE TAIL END OF A COLD FRONT N OF PUERTO RICO. LOW-LEVEL CONVERGENCE E OF THE FRONT IS GENERATING ISOLATED SHOWERS N OF 18N W OF THE MONA PASSAGE WHILE MOIST SW UPPER FLOW ACROSS THE ERN CARIBBEAN COUPLED WITH MIDDLE LEVEL INSTABILITY IS GENERATING ELEVATED SCATTERED SHOWERS OVER THE LESSER ANTILLES S OF 16N AND TO THE E OVER THE TROPICAL ATLC EXTENDING TO 55W. ATLANTIC OCEAN... A FRONTAL SYSTEM IS LOCATED IN THE CENTRAL ATLC WITH A WARM FRONT THROUGH 31N52W TO A WEAKENING 1016 MB LOW NEAR 28N54W AND A COLD FRONT EXTENDING SW FROM THE LOW TO NW PUERTO RICO AND THE MONA PASSAGE. SCATTERED SHOWERS E OF THE FRONT ARE N OF 24N BETWEEN 46W-53W. SUBSIDENCE IN UPPER W TO NW FLOW ALOFT ACROSS THE W ATLC WEST OF THE COLD FRONT IS ASSOCIATED WITH A LARGE SCALE TROUGH OVER THIS AREA AND AN UPSTREAM RIDGE LOCATED OVER THE ERN U.S. SEABOARD. AT THE SURFACE...A 1022 MB HIGH IS CENTERED NEAR 31N65W AND IS REMAINING STATIONARY. GENERALLY FAIR WEATHER CONDITIONS ARE PRESENT WEST OF THE FRONT EXCEPT FOR SOME ISOLATED SHOWERS IN E TO SE FLOW ON THE SWRN PERIPHERY OF THE SURFACE HIGH S OF 26N W OF 67W. ACROSS THE E ATLC...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE IS RESULTING IN GENERALLY FAIR WEATHER CONDITIONS. THIS SURFACE RIDGE IS ANCHORED BY A 1032 MB SURFACE HIGH NEAR 34N27W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL HIGH IS CENTERED NEAR 4N44W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THIS FEATURE IS ENHANCING CONVECTION ALONG THE ITCZ. $$ HUFFMAN