000 AXNT20 KNHC 272343 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE APR 25 2006 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...WEATHER OBSERVATIONS... RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 4N4W 1N23W 1N34W 1N50W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS NOTED WITHIN 300 NM N OF THE AXIS E OF 19W. SCATTERED...BUT DISORGANIZED...MODERATE CONVECTION IS NOTED FROM 5N TO 5S BETWEEN 19W AND 50W. ...DISCUSSION... GULF OF MEXICO... AN UPPER ANTICYCLONE IS CENTERED OVER THE E PAC NEAR 12N106W. A RIDGE EXTENDS N ACROSS OLD MEXICO ALONG 22N102W CRESTING OVER CENTRAL TEXAS ALONG POINTS 28N107W 32N99W. THE UPPER FLOWS DIVES SE ACROSS THE MISSISSIPPI DELTA INTO THE E CENTRAL GULF NEAR 26N85W WHERE THE UPPER FLOW THEN TURNS CYCLONIC INTO A SHORTWAVE TROUGH WITH ITS MEAN AXIS CURRENTLY ALONG 32N80W 20N75W. A MOISTURE PLUME...ORIGINATING FROM ITCZ CONVECTION OVER THE E PACIFIC BETWEEN 112W AND 129W...STREAMS ACROSS CENTRAL OLD MEXICO ALONG THE PERIPHERY OF THE RIDGE...ROUGHLY WITHIN 300 NM EITHER SIDE OF LINE 23N106W 27N97W AND EVAPORATES ALONG A LINE 28N89W 21N96W. AT THE SURFACE THE 21Z ANALYSIS HAS A COLD FRONT EXTENDING W ALONG 27N82W TO 26N91W WHERE THE FRONT BECOMES QUASI STATIONARY...AND ILL DEFINED...AND EXTENDS WNW ALONG 27N97W TO 29N102W. A NARROW LINE OF TOWERING CUMULUS DEFINES THE COLD FRONTAL BOUNDARY LATE THIS AFTERNOON BUT WILL LIKELY DISSIPATE AFTER SUNSET. A RIDGE IS BUILDING SE OFF THE CENTRAL LOUISIANA COAST TO THE N CENTRAL GULF REMAINING N OF THE WEAK FRONT AND WILL LIKELY BRIDGE THE FRONTAL REMNANTS TONIGHT. DRY UPPER AIR IS INDICATED OVER THE REMAINDER OF THE GULF WATERS SUPPRESSING CONVECTION. CARIBBEAN SEA... ALOFT...A BROAD SHORTWAVE RIDGE...ORIGINATING FROM AN UPPER ANTICYCLONE ESTIMATED NEAR 7N50W...EXTENDS NW OFF THE VENEZUELAN COAST ALONG 12N74W TO A CREST ALONG POINTS 15N87W 19N70W 17N60W. TO THE N OF THE UPPER RIDGE...A SHORTWAVE TROUGH WITH ITS MEAN AXIS MOVING THROUGH THE NORTHERN BAHAMAS ATTM EXTENDS S THROUGH THE WINDWARD PASSAGE. EVEN THE DRY UPPER AIR...AND ASSOCIATED SUBSIDENCE...W OF THE UPPER TROUGH AXIS COULD NOT SUPPRESS SEABREEZE CONVECTION FROM FLARING OVER THE CUBAN PENINSULA THIS AFTERNOON. BUT THE UPPER DRY AIR DOES SEEM TO EVAPORATE THE RESULTANT DEBRIS MOISTURE JUST NE OF THE CUBAN. DEBRIS MOISTURE FROM CONVECTION S OF 11N BETWEEN 69W AND 83W SPREADS NE IN THE ANTICYCLONIC FLOW ACROSS THE CENTRAL AND EASTERN CARIBBEAN SEA. OTHERWISE ISOLATED TRADE WIND CUMULUS IS MOVING W THROUGH THE WATERS S OF 20N. ATLANTIC OCEAN... THE WESTERN SW N ATLC IS DOMINATED BY A SHORTWAVE TROUGH WITH ITS MEAN AXIS LYING N TO S ALONG 77W. DIFFLUENCE E OF THE TROUGH IS ENHANCING CONVECTION ALONG SEVERAL PRE-FRONTAL TROUGHS ASSOCIATED WITH A SURFACE COLD FRONT THAT CURRENTLY EXTENDS FROM 32N76W TO CENTRAL FLORIDA. THE CONVECTION IS CONCENTRATED WITHIN 90 NM EITHER SIDE OF LINE 25N77W 33N71W ATTM. THE RESULTANT DEBRIS MOISTURE IS ADVECTED NE ACROSS THE SUBTROPICAL ATLC... THROUGH THE SHORTWAVE RIDGE...AND WILL SOON SPILL BACK SE INTO THE DISCUSSION AREA ALONG 32N BETWEEN 60W AND 45W. A MOISTURE PLUME FROM EARLIER CONVECTION OVER HISPANIOLA IS OBSERVED WITHIN 120 NM EITHER SIDE OF LINE 19N69W 24N62W. IMMEDIATELY E...A SHORTWAVE RIDGE EXTENDS N FROM THE EASTERN CARIBBEAN ALONG 26N65W 32N62W...THEN CONTINUES NE TO WELL BEYOND 45N40W EFFECTIVELY SEPARATING THE TROUGH ALONG THE E COAST OF CONUS FROM A LONGWAVE TROUGH THAT DOMINATES THE CENTRAL N ATLC. EMBEDDED CYCLONES ARE NOTED NEAR 49N30W AND 27N43W. AT THE SURFACE...THE REMNANTS OF A FRONT LIE ALONG 32N35W 18N53W WITH BROKEN TO LOCALLY OVERCAST MULTILAYERED CLOUDS OBSERVED WITHIN 300 NM EITHER SIDE OF THE FRONTAL BOUNDARY. A SURFACE HIGH 1025 MB IS NEAR 36N43W RIDGES SW TO THE N CENTRAL CARIBBEAN. THE EXTREME E ATLC IS DOMINATED ALOFT BY A LONGWAVE TROUGH THAT WILL SOON SHIFT E OF THE AREA. AN UPPER ANTICYCLONE IS ESTIMATED NEAR 11N21W AND RIDGES N ALONG 25N20W TO A SHARP CREST NEAR 40N20W. DEBRIS MOISTURE FROM CONVECTION OF S AMERICA...AND THE ITCZ BETWEEN 25W AND 50W...IS STREAMING NE ACROSS THE TROPICAL ATLC WATERS S OF 19N W OF 22W. OTHERWISE...A BAND OF DRY UPPER AIR IS NOTED WITHIN 540 NM EITHER SIDE OF LINE 29N5W 15N20W AND IS SUPPRESSING CONVECTION OF THE E ATLC. $$ NELSON