000 AXNT20 KNHC 180834 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST THU DEC 18 2008 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 10N14W 5N21W 5N37W 5N53W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM EITHER SIDE OF THE AXIS BETWEEN 16W-30W. SCATTERED MODERATE IS WITHIN 120 NM N AND 240 NM S OF THE AXIS BETWEEN 40W-47W. ...DISCUSSION... GULF OF MEXICO... A LARGE AND FAIRLY AMPLIFIED MID TO UPPER HIGH IS CENTERED OVER THE BAY OF CAMPECHE PROVIDING MAINLY LIGHT FLOW AND STABLE AIR ALOFT....EXCEPT FOR OVER FLORIDA WHERE HIGH CLOUDINESS IS BEING DRIVEN S ON THE E PERIPHERY OF THE RIDGE. IN THE LOWER LEVELS...A DISSIPATING FRONT IS STILL STALLED ALONG THE TEXAS AND MEXICO COASTS. SLIGHT LOW-LEVEL CONVERGENCE ALONG THE FRONT IS PRODUCING LOW-LEVEL CLOUDS AND LIGHT SHOWERS. OTHERWISE... MAINLY FAIR CONDITIONS EXIST ELSEWHERE WITH ONLY PATCHY LOW-LEVEL CLOUDS DRIVEN BY LIGHT TO MODERATE E FLOW ON THE S/SW SIDE OF A 1026 MB HIGH OVER THE SUBTROPICAL W ATLC. LITTLE SIGNIFICANT CHANGE IS EXPECTED OVER THE NEXT COUPLE OF DAYS UNTIL THE NEXT COLD FRONT APPROACHES THE NW GULF THIS WEEKEND. CARIBBEAN SEA... CONFLUENCE NEAR THE BASE OF AN UPPER TROUGH OVER THE CENTRAL ATLC IS ENHANCING SUBSIDENCE ACROSS THE ENTIRE AREA...LIMITING THE DEVELOPMENT OF ANY DEEP CONVECTION. HOWEVER...SCATTERED SHOWERS AND LOW TOPPED TSTMS ARE AFFECTING MUCH OF THE AREA...BENEATH THE MID-LEVEL CAP...GENERATED BY AN ELONGATED SFC TROUGH OVER THE CENTRAL ATLC AND DRIVEN SOUTH BY STIFF N/NE WINDS ON THE W SIDE OF THE CIRCULATION. N TO NE WINDS IN THE CARIBBEAN ARE MAINLY IN THE 20-25 KT RANGE W OF 67W. SIMILAR WINDS/SHOWERS ARE EXPECTED OVER THE NEXT COUPLE OF DAYS BEFORE HIGH PRES SHIFTS S OVER THE W ATLC ALLOWING THE FLOW TO WEAKEN AND VEER E. ATLANTIC OCEAN... DEEP LAYER LOW PRESSURE OVER THE CENTRAL ATLC IS CAUSING SOME ACTIVE WEATHER TONIGHT...BUT MUCH LESS SO THAN A DAY OR TWO AGO. THE SFC CENTER IS ANALYZED 1010 MB NEAR 26N58W WITH ITS ASSOCIATED TROUGH EXTENDING BOTH N TO 30N56W AND S TO 21N62W. SCATTEROMETER AND TO SOME DEGREE SFC OBS SHOW A FAIRLY WELL DEFINED SFC CIRCULATION WITHIN AN INCREASINGLY ELONGATED TROUGH. LOW-LEVEL CONVERGENCE AND INSTABILITY NEAR THE LOW IS PRODUCING SCATTERED SHOWERS AND TSTMS WITHIN 240 NM OF THE CENTER. A LARGER AREA OF SHOWERS AND TSTMS EXIST FARTHER E FROM 12N-29N BETWEEN 46W-51W IN AN UPPER DIFFLUENT ZONE. THIS LOW IS EXPECTED BECOME GREATLY SHEARED AND SPLIT APART BY A SHORTWAVE TROUGH LATER THIS WEEK AND WEEKEND. THE W ATLC IS RELATIVELY TRANQUIL BENEATH ABUNDANT DRY AIR ALOFT ON THE W SIDE OF THE UPPER LOW. HOWEVER...AS MENTIONED ABOVE... STRONG N/NE LOW-LEVEL WINDS AND INSTABILITY ARE STIRRING UP SHOWERS AND LOW-TOPPED TSTMS MAINLY E OF 75W. OVER THE TROPICAL E ATLC...STRONG WLY FLOW ALOFT IS TRANSPORTING WIDESPREAD MID-HIGH LEVEL CLOUDINESS AND ENHANCING ITCZ CONVECTION. $$ CANGIALOSI