000 AXNT20 KNHC 191754 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN APR 19 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 1730 UTC. ...ITCZ... THE ITCZ IS CENTERED CROSSES TO SOUTH OF THE EQUATOR NEAR 00N00W TO 04S10W TO 04S25W TO NE BRAZIL NEAR 00.5N50W. SCATTERED MODERATE CONVECTION IS CENTERED ON THE EQUATOR WEST OF 40W IN A 90 NM WIDE BAND. OTHERWISE CONVECTION ASSOCIATED WITH THE ITCZ IS SOUTH OF THE EQUATOR. ...DISCUSSION... GULF OF MEXICO... MOIST SOUTHWEST TO WEST FLOW ALOFT IS OBSERVED OVER THE GULF REGION AS A DEEP LAYER TROUGH PROGRESSES ACROSS THE CENTRAL CONUS. THE RETURN FLOW AROUND A 1022 MB SURFACE HIGH CENTERED OVER THE W ATLC NEAR 31N72W IS RESULTING IN SE WINDS OF 15 TO 20 KT ACROSS THE GULF REGION MOSTLY EAST OF 90W AS THE PRESSURE GRADIENT IS WEAKER OVER THE WESTERN GULF IN ADVANCE OF A COLD FRONT OVER EAST TEXAS. THESE WINDS ARE ADVECTING ABUNDANT LOW-LEVEL MOISTURE ACROSS THE GULF REGION...RESULTING IN INCREASED INSTABILITY ACROSS MUCH OF THE NRN GULF. THIS INSTABILITY AND A BROAD SURFACE TROUGH OVER THE WESTERN GULF IS COMBINING WITH MIDDLE TO UPPER LEVEL ATMOSPHERIC DIFFLUENCE ACROSS THE NW AND N/CENTRAL GULF TO SUPPORT SCATTERED SHOWERS AND TSTMS N OF 26N EAST OF 92W TO ABOUT 85W. ACROSS THE SE GULF ...STABLE ATMOSPHERIC CONDITIONS ARE RESULTING IN GENERALLY FAIR WEATHER CONDITIONS. THE SURFACE COLD FRONT ASSOCIATED WITH THE CENTRAL CONUS DEEP LAYER TROUGH IS FORECAST TO MOVE OFF THE TEXAS COAST THIS AFTERNOON...AND EXTEND FROM THE FLORIDA BIG BEND TO THE BAY OF CAMPECHE BY MONDAY. INCREASED NLY WINDS AND RELATIVELY COOLER AND DRIER CONDITIONS ARE FORECAST WITH THE PASSAGE OF THIS FRONT. CARIBBEAN SEA... A SURFACE RIDGE LOCATED OVER THE W ATLC IS FORECAST TO MAINTAIN FRESH NE TO E TRADE WINDS ACROSS THE CARIBBEAN SEA THROUGH WEDNESDAY. GENERALLY FAIR WEATHER IS PRESENT ACROSS THE CARIBBEAN...WHERE DEEP LAYER DRY AIR AND SUBSIDENCE IS RESULTING FROM CONFLUENT WESTERLY FLOW ALOFT. HOWEVER...LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF A WEAKENING SURFACE COLD FRONT IN THE MONA PASSAGE. A COUPLE OF SMALL AREAS OF SHOWERS IS NEAR 80W NORTH OF 15N MOVING WEST ABOUT 10 KNOTS. SCATTERED SHOWERS HAVE DEVELOPED IN THE LESSER ANTILLES FROM SAINT LUCIA TO ANTIGUA. THESE SHOWERS ARE MOVING NORTHEAST 10 TO 15 KNOTS AND ARE PART OF AN AREA THAT EXTENDS ABOUT 300 NM NORTHEAST OF THESE ISLANDS. ATLANTIC OCEAN... A FRONTAL SYSTEM IS LOCATED IN THE REGION WITH A WARM FRONT THROUGH 32N52W TO A WEAKENING 1017 MB LOW NEAR 27N57W AND A COLD FRONT FROM THE LOW TO NORTHWEST PUERTO RICO. SUBSIDENCE IN UPPER 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 FLORIDA. AT THE SURFACE A 1022 MB HIGH IS CENTERED NEAR 31N72W AND IS MOVING EAST 15 TO 20 KT. GENERALLY FAIR WEATHER CONDITIONS ARE PRESENT WEST OF THE FRONT EXCEPT FOR SOME SHOWERS IN THE NORTHEAST FLOW THAT EXTENDS ABOUT 300 NM NW OF THE COLD FRONT. SCATTERED SHOWERS AND THUNDERSTORMS ARE ALONG THE FRONT MOSTLY EAST OF 80W. THE AREA OF CONVECTION BROADENS FROM A NARROW BAND ALONG THE FRONT SOUTH OF 25N TO A 360 NM WIDE REGION NEAR 30N. ACROSS THE E ATLC...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE IS RESULTING IN GENERALLY FAIR WEATHER CONDITIONS. THIS SURFACE RIDGE IS ANCHORED BY A 1029 MB SURFACE HIGH NEAR 33N27W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS S OF 15N E OF 60W WITH THE UPPER LEVEL HIGH CENTERED NEAR 4N49W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THIS FEATURE IS ENHANCING CONVECTION ALONG THE ITCZ. $$ LL