000 AXNT20 KNHC 231744 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST SAT FEB 23 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1730 UTC ...ITCZ... ITCZ AXIS IS CENTERED ALONG 6N11W 1N22W 2N30W EQUATOR AT 43W 1S48W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 240 NM S OF THE ITCZ AXIS BETWEEN 21W AND 33W. SCATTERED MODERATE NOTED S OF 7N BETWEEN 46W AND 50W. ...DISCUSSION... GULF OF MEXICO... A SHEARING UPPER TROUGH IS SWEEPING EWD ACROSS THE SE CONUS AND EXTENDS INTO THE NE GULF TO NEAR 26N89W. MODERATE MID TO UPPER LEVEL DRY UPPER AIR WAS NOTED WITHIN THE TROUGH AXIS GENERALLY WITHIN 120 NM EITHER SIDE OF LINE FROM 30N85W TO THE COAST OF MEXICO NEAR 23N97W. WEAK SHORTWAVE RIDGE WITH AXIS ALONG 90W WAS MOVING ACROSS THE WRN GULF STATES. THE PERIPHERY OF A LARGE ANTICYCLONE OVER HISPANIOLA AND THE EXTREME SE BAHAMAS CONTINUES TO EXERT AN INFLUENCE ON THE SE GULF OF MEXICO AND IS A MAJOR FACTOR IN THE SHEARING OUT OF THE UPPER TROUGH MOVING ACROSS THE SE. MOSTLY UPPER LEVEL MOISTURE...ORIGINATING FROM FORMER CONVECTION OVER THE E PACIFIC AND CENTRAL AMERICA BETWEEN 85W AND 95W...IS STREAMING NE ALONG THE PERIPHERY OF THE RIDGE. AT 15 UTC A SURFACE COLD FRONT EXTENDS FROM APALACHEE BAY FLORIDA SW TO THE CENTRAL GULF NEAR 26N89W THEN BECOMES STATIONARY TO THE MEXICAN COAST JUST E OF COATZACOALCOS. THE FRONT CONTINUED AS A DISSIPATING STATIONARY FRONT BACKED UP AGAINST THE SIERRA MADRE MOUNTAINS FROM THE CHIVELAS PASS NWD TO THE RIO GRANDE RIVER. WEAKENING UPPER DIFFLUENCE E OF THE THE UPPER TROUGH HAS ALLOWED CONVECTION AHEAD OF THE SURFACE FRONT TO WEAKEN WITH SCATTERED SHOWERS AND THUNDERSTORMS NOTED FROM THE TAMPA BAY CLEARWATER AREA OF FLORIDA TO 27N85W WITH LIGHTNING DATA DECREASING MARKEDLY OVER THE PAST FEW HOURS. E OF THE FRONT...THE ATLC SUBTROPICAL RIDGE EXTENDS W OVER THE AREA WITH ITS AXIS ALONG 25N TO NEAR 85W/86W. CARIBBEAN... A LARGE PERSISTENT UPPER LEVEL ANTICYCLONE CENTERED NEAR HISPANIOLA DOMINATED THE CARIBBEAN W OF 67W. THE WESTWARD EXTENSION OF A CENTRAL ATLC UPPER TROUGH STILL EXTENDS INTO THE FAR EASTERN CARIBBEAN BUT APPEARS TO BE FILLING WITH TIME. THIN BROKEN CIRRIFORM CLOUDS ARE NOTED OVER THE FAR NW CARIBBEAN ALONG THE PERIPHERY OF THE UPPER RIDGE/ANTICYCLONE. STRONG MID TO UPPER LEVEL SUBSIDENCE IS NOTED IN ASSOCIATION WITH THE ANTICYCLONE AND HAS SUPPRESSED ANY CONVECTIVE ACTIVITY. AT THE LOW LEVELS THE ATLC SUBTROPICAL RIDGE EXTENDS W ACROSS THE NW CARIBBEAN WITH ITS AXIS JUST N OF THE AREA ALONG 25N. LOCALLY BROKEN LOW TRADE WIND CLOUDS WITH EMBEDDED SHOWERS ARE NOTED E OF 70W WITH CLOUDINESS BECOMING BROKEN TO OVERCAST IN PATCHES FROM JAMAICA TO W CUBA AND THE YUCATAN CHANNEL. ATLANTIC... AN UPPER ANTICYCLONE CENTERED OVER THE EXTREME SE BAHAMAS WITH A RIDGE EXTENDING NE TO BEYOND 32N65W. A MOISTURE PLUME IS SPILLING OVER THE RIDGE AXIS GENERALLY N OF POINTS 25N80W 25N70W 25N54W. THE CENTRAL SUB-TROPICAL ATLC IS DOMINATED BY A POSITIVELY TILTED MID TO UPPER LEVEL TROUGH EXTENDING THROUGH UPPER LEVEL CYCLONES ALONG 38N15W 24N33W AND 17N51W. DRY UPPER AIR IS NOTED OVER THE SW SEMICIRCLES OF EACH OF THESE CYCLONES WHILE MAINLY UPPER LEVEL CLOUDS AND SHOWERS ARE ENHANCED OVER THE NE SEMICIRCLE. THE TROPICAL E ATLC IS DOMINATED BY AN UPPER LEVEL ANTICYCLONE NEAR 5N23W WITH A RIDGE EXTENDING WWD ALONG 5N TO 40W. UPPER DIFFLUENCE S OF THE RIDGE AXIS IS ENHANCING CONVECTION WITHIN 240 NM N OF THE ITCZ BETWEEN 20W AND 33W WITH THE DEBRIS MOISTURE SPREADING N TO ALONG 15N BETWEEN 15W AND 35W. AT THE SURFACE SPRAWLING 1031 MB HIGH PRES CENTERED NEAR 33N35W WITH A RIDGE EXTENDING SWWD THROUGH THE STRAITS OF FLORIDA. THE SURFACE FRONT STALLED JUST OFFSHORE THE NE FLORIDA COAST EARLIER HAS DISSIPATED AS OF 15 UTC. LOCALLY BROKEN PATCHES OF STRATOCUMULUS ARE MOVING WWD ACROSS THE WATERS S OF THE SURFACE RIDGE. $$ COBB