000 AXNT20 KNHC 181752 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED APR 18 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ... ITCZ AXIS EXTENDS FROM 6N9W 3N20W CROSSING THE EQUATOR AT 33W INTO NE BRAZIL NEAR 4S41W. CLUSTERS OF MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 200-300 NM S OF THE AXIS E OF 12W. ISOLATED MODERATE CONVECTION IS WITHIN 90 NM S OF THE AXIS BETWEEN 26W-29W. A BAND OF MODERATE TO STRONG CONVECTION EXISTS ALONG THE COAST OF NE BRAZIL STRETCHING FROM 2S42W TO 7S32W. ...DISCUSSION... GULF OF MEXICO... A SHORTWAVE TROUGH OVER THE EAST COAST OF THE US IS SUPPORTING THE COLD FRONT THAT EXTENDS FROM THE 1006 MB SFC LOW CENTERED OVER SE LOUISIANA ACROSS THE NW GULF AND INTO TEXAS NEAR CORPUS CRISTI. A BAND OF LOW/MID CLOUDS WITH EMBEDDED SHOWERS/POSSIBLE THUNDERSTORMS EXTENDS 60-90 NM AHEAD OF THE FRONT N OF 27N. THE FRONT IS EXPECTED TO CONTINUE MOVING SE ACROSS THE GULF AND REACH THE STRAITS OF FLORIDA AND THE YUCATAN CHANNEL BY EARLY THURS NIGHT. MODERATE SLY WINDS AHEAD OF THE FRONT WILL WEAKEN TO 10-15 KT AND BECOME NLY FOLLOWING THE FRONTAL PASSAGE. A WEAK 1011 MB HIGH OVER CUBA IS KEEPING THE REMAINDER OF THE GULF UNDER A DRY AND STABLE AIRMASS WITH FAIR WEATHER STRATOCUMULUS CLOUDS COVERING THE S GULF AND THE YUCATAN CHANNEL. ALOFT...FLOW AROUND AN UPPER HIGH CENTERED OVER HONDURAS IS TRANSPORTING A PLUME OF UPPER LEVEL MOISTURE/HIGH CLOUDS ACROSS N-CENTRAL MEXICO INTO THE SOUTHERN GULF WATERS. CARIBBEAN SEA... THE STRONG COLD FRONT OVER THE ATLANTIC EXTENDS TO JUST S OF PUERTO RICO AND CONTINUES TO GENERATE SHOWERS OVER THE ISLAND. AS OF 12Z...THE 24 HR RAINFALL TOTAL IN SAN JUAN WAS 1.71 IN. THIS MOISTURE IS EXPECTED TO MEANDER ACROSS THE REGION OVER THE NEXT 24-48 HRS. COLD AIR STRATOCUMULUS CLOUDS REMAIN OVER THE YUCATAN CHANNEL AND THE NW CARIBBEAN. ALOFT...AN UPPER HIGH CONTINUES TO DOMINATE THE CARIBBEAN...HOWEVER IT HAS SHIFTED WEST AND IS NOW CENTERED OVER HONDURAS. THIS IS PROVIDING DRY AIR AND MODERATE TO STRONG SUBSIDENCE OVER THE ENTIRE CARIBBEAN. A BAND OF CIRRUS CLOUDS IS BEING TRANSPORTED AROUND THE HIGH AND IS ENTERING THE NW CARIBBEAN FROM THE GULF. THE TRADES ARE LIGHT TO MODERATE ACROSS MUCH OF THE AREA DUE TO A WEAK PRES GRADIENT. ATLANTIC OCEAN... THE STRONG COLD FRONT CONTINUES TO MARCH EWD ACROSS THE ATLC AND ENTERS THE REGION NEAR 31N50W EXTENDING SW THROUGH PUERTO RICO. THE FRONT IS NO LONGER PRODUCING GALE FORCE WINDS...HOWEVER STRONG WINDS AND HAZARDOUS MARINE CONDITIONS CONTINUE TO EXIST...PARTICULARLY N OF 24N WITHIN 330 NM AHEAD OF THE FRONT...AND N OF 26N BEHIND THE FRONT TO 69W. A BROAD BAND OF MOISTURE WITH EMBEDDED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS EXTENDS 100-200 NM AHEAD OF THE FRONT. A 15Z QSCAT PASS SHOWS 20-35 KT ON EITHER SIDE OF THE FRONT...WHEREAS 12Z SHIP OBS WITHIN 100NM OF THE FRONT REPORTED 20-25 KT WINDS. WINDS OVER THE W-CENTRAL ATLC WILL DIMINISH TO 15 KT AS THE FRONT CONTINUES TO MOVE EWD. A TROUGH ENTERS THE REGION NEAR 31N25W EXTENDING FROM A COLD FRONT AND SFC LOW WELL NORTH OF THE AREA. THE TROUGH CONTINUES SW TO NEAR 25N39W WITH A BAND OF MOISTURE EXTENDING 60-90 NM AHEAD OF THE TROUGH. A SFC HIGH REMAINS E OF THE TROUGH CENTERED NEAR 26N25W EXTENDING A RIDGE OVER THE E-CENTRAL ATLC TO NEAR THE LESSER ANTILLES. ALOFT...A SHORTWAVE TROUGH IS ADVECTING UPPER LEVEL MOISTURE OVER THE NW ATLC. A DEEP LAYERED TROUGH IS SUPPORTING THE FRONTAL BOUNDARY OVER THE CENTRAL ATLC. THE RIDGE OVER THE CARIBBEAN EXTENDS ENE INTO THE S-CENTRAL ATLC THROUGH THE LEEWARD ISLANDS. A SECOND UPPER TROUGH DOMINATES THE E ATLC WITH THE AXIS EXTENDING SW TO THE DEEP TROPICS NEAR 2N45W. STRONG SWLY WINDS AHEAD OF THE TROUGH ARE TRANSPORTING UPPER LEVEL MOISTURE FROM N SOUTH AMERICA TO THE AFRICAN COAST. $$ RJW