000 AXNT20 KNHC 192331 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED MAR 19 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 2315 UTC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N10W 3N22W 1N30W CROSSING THE EQUATOR NEAR 35W TO 3S40W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN 16W-20W. ISOLATED MODERATE CONVECTION IS FROM THE EQUATOR TO 5N BETWEEN 28W-42W. ...DISCUSSION... GULF OF MEXICO... A COLD FRONT IS TRACKING EWD ACROSS THE GULF FROM THE FLORIDA PANHANDLE TO S MEXICO ALONG 30N86W 23N89W 17N92W. AHEAD OF THE FRONT...BRISK SLY WINDS ARE CREATING A MILD/HUMID EVENING WITH MAINLY FAIR SKIES. BEHIND THE FRONT...WINDS SHIFT TO THE W N OF 24N ALLOWING SOME COOLING TO TAKE PLACE...BUT MOST OF THE AIRMASS CHANGE IS BEHIND A POST-FRONTAL TROUGH...ASSOCIATED WITH A MID-LEVEL SHORTWAVE...FROM SRN MISSISSIPPI TO 25N93W. THE SFC FRONT ACTS AS THE MAIN BOUNDARY S OF 24N WHERE NLY GALE FORCE WINDS ARE STILL OCCURRING. THE COMBINATION OF LOW-LEVEL CONVERGENCE NEAR THE FRONT AND STRONG SWLY FLOW ALOFT...BETWEEN AN UPPER TROUGH OVER MEXICO AND RIDGING OVER THE BAHAMAS...IS PRODUCING WIDESPREAD MULTILAYER CLOUDINESS WITHIN 300 NM SE OF A LINE FROM MOBILE ALABAMA TO 22N98W. THE ONLY SIGNIFICANT EMBEDDED TSTM ACTIVITY IS OVER THE FLA PANHANDLE AND COASTAL WATERS WITHIN 60 NM E OF THE FRONT. THE FRONT IS EXPECTED TO PUSH THROUGH THE REMAINDER OF THE AREA OVER THE NEXT 24 HOURS AS IT WEAKENS. CARIBBEAN SEA... THE TAIL END OF A WEAKENING COLD FRONT CUTS ACROSS THE LESSER ANTILLES NEAR 15N62W. COOLER AND DRIER AIR HAS SPREAD WELL S INTO THE E CARIBBEAN BEHIND THE FRONT. TEMPS ARE MAINLY IN THE 70'S F WITH DEWPOINTS IN THE LOW 60'S F OVER PUERTO RICO...THE VIRGIN ISLANDS AND THE NRN LEEWARDS. HOWEVER...THE BIG STORY IS THE TREMENDOUS N SWELLS AFFECTING THESE ISLANDS FROM THE CONTINUOUS FETCH DRIVEN BY A LARGE LINGERING AND ONCE VERY POWERFUL LOW PRES SYSTEM OVER THE N ATLC. SCATTERED SHOWERS ARE AFFECTING MUCH OF THE NE ISLANDS. ELSEWHERE...TRANQUIL WEATHER PREVAILS BENEATH A STRONGLY SUBSIDENT MID TO UPPER ENVIRONMENT. THE TIGHT PRES GRADIENT BETWEEN SEMI-PERMANENT LOW PRES OVER NRN SOUTH AMERICA AND A 1025 MB HIGH NEAR 30N70W IS PRODUCING GALE FORCE TRADES NEAR THE COLOMBIAN COAST. THESE CONDITIONS ARE EXPECTED TO SUBSIDE IN ABOUT 24 HOURS. ATLANTIC OCEAN... DEEP LAYER RIDGING DOMINATES THE WRN ATLC...W OF 65W...WITH THE SFC CENTER ANALYZED 1025 MB NEAR 30N70W. WEATHER CONDITIONS ARE FAIR BENEATH THIS RIDGE...BUT LARGE SWELLS ARE OBSERVED OVER MOST OF THIS AREA CREATING HAZARDOUS MARINE CONDITIONS AND LARGE BREAKING WAVES. SEE THE HIGH SEAS FORECAST (MIAHSFAT2) FOR DETAILS. THE PATTERN FOLDS INTO DEEP LAYER TROUGHING BETWEEN 35W-65W WITH THE ASSOCIATED SLOW MOVING COLD FRONT ENTERING THE REGION NEAR 32N41W AND CONTINUING SW TO THE LESSER ANTILLES ALONG 23N45W 15N62W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 120 NM E OF THE FRONT N OF 25N AND BEHIND THE FRONT N OF 25N BETWEEN 45W-55W ASSOCIATED WITH A POST-FRONTAL TROUGH. GALE CONDITIONS ARE OCCURRING N OF 28N WITHIN 240 NM E OF THE FRONT AND N OF 27N BETWEEN 54W-60W...DUE TO THE TIGHT PRES GRADIENT BETWEEN THE FRONT AND THE HIGH TO THE W. THE E ATLC REMAINS IN A TRANQUIL REGIME ON THE S SIDE OF MODEST SFC RIDGING AND BENEATH FAIRLY ZONAL FLOW AND DRY AIR ALOFT. THIS PATTERN IS LIMITING LARGE CLUSTERS OF CONVECTION...EVEN WITHIN THE ITCZ. $$ CANGIALOSI