000 AXNT20 KNHC 141129 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST SUN DEC 14 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1115 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 8N14W 4N20W 5N40W 3N51W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 150 NM S OF THE AXIS BETWEEN 19W-27W...WITHIN 120 NM N AND 90 NM S OF THE AXIS BETWEEN 27W-33W...AND FROM 6N-9N BETWEEN 45W-51W. SCATTERED MODERATE IS WITHIN 150 NM S OF THE AXIS E OF 15W AND FROM 6N-8N BETWEEN 35W-38W. ...DISCUSSION... GULF OF MEXICO... STRONG W TO NW MID-UPPER FLOW...ON THE N PERIPHERY OF A RIDGE CENTERED OVER THE YUCATAN PENINSULA...IS SPREADING WIDESPREAD PACIFIC MOISTURE N OF 25N. ONLY ISOLATED SHOWERS ARE LIKELY EMBEDDED AS MUCH OF THE MOISTURE APPEARS TO BE IN THE FORM OF MID-HIGH LEVEL CLOUDINESS. DRIER AIR IS PRESENT S OF 25N CLOSER TO THE UPPER RIDGE AXIS. IN THE LOWER LEVELS...STRONG HIGH PRES OFF THE MID-ATLC COAST IS MAINTAINING STRONG E TO SE WINDS OVER THE E GULF AND SE TO S WINDS ELSEWHERE. THESE WINDS WILL BECOME MORE UNIFORM S TO SE LATER TODAY AND MON AS THE NEXT COLD FRONT APPROACHES THE TEXAS COAST...INCREASING THE CHANCE OF SHOWERS OVER THE NW GULF. CARIBBEAN SEA... AN UPPER HIGH CENTERED OVER THE YUCATAN PENINSULA HAS HELPED SET UP ZONAL TO NW FLOW AND ABUNDANT DRY SINKING AIR OVER MUCH OF THE AREA. ONLY AREA OF SIGNIFICANT MOISTURE IS NEAR THE COAST OF COSTA RICA AND NICARAGUA...LIKELY PRODUCED BY LOW-LEVEL SPEED CONVERGENCE (EVIDENT IN QSCAT DATA) AND DIFFLUENCE ALOFT NEAR THE UPPER HIGH CENTER. HOWEVER...EVEN THIS CONVECTION HAS BEEN DECREASING IN INTENSITY AND COVERAGE OVER THE PAST FEW HOURS. OTHERWISE...PATCHES OF LOW-LEVEL MOISTURE WITH EMBEDDED SHOWERS ARE SCATTERED ACROSS THE REMAINDER OF THE W CARIBBEAN ASSOCIATED WITH THE REMNANTS OF AN OLD FRONTAL BOUNDARY. LITTLE LARGE SCALE CHANGES ARE EXPECTED OVER THE NEXT COUPLE OF DAYS. ATLANTIC OCEAN... AN UPPER TROUGH ALONG 61W IS FLATTENING BUT STILL PROVIDING SOME SUPPORT FOR A COLD FRONT EXTENDING FROM 32N58W TO 25N68W THEN STATIONARY TO THE WINDWARD PASSAGE. THE TIGHT PRES GRADIENT BETWEEN THE FRONT AND A 1033 MB HIGH OFF THE NEW JERSEY COAST IS PRODUCING A LARGE AREA OF 20-30 KT NE WINDS W OF THE FRONT. UPPER DIFFLUENCE E OF THE UPPER TROUGH AXIS IS PRODUCING A SWATH OF SCATTERED SHOWERS AND TSTMS N OF 28N BETWEEN 57W-60W. FARTHER E...A WEAKENING UPPER LOW NEAR 27N54W AND A HIGHLY DIFFLUENT UPPER PATTERN IS PRODUCING A LARGE AREA OF SCATTERED SHOWERS AND TSTMS N OF 16N BETWEEN 39W-50W. SHORTWAVE IR IMAGES AND QSCAT DATA REVEALS AN ASSOCIATED SFC TROUGH ALONG 55W N OF 26N...BUT NEARLY ALL OF THE ASSOCIATED WEATHER (OUTLINED ABOVE) IS LOCATED IN THE DIFFLUENT ZONE TO ITS E. THE SFC PRES PATTERN IS VERY TIGHT BETWEEN THE TROUGH AND A 1037 MB HIGH JUST W OF THE AZORES PRODUCING 20-30 KT E WINDS ACROSS THE SUBTROPICAL ATLC E OF THE TROUGH AXIS. NWP MODELS CONTINUE TO SUGGEST POSSIBLE LOW PRESSURE DEVELOPMENT DURING THE NEXT FEW DAYS OVER THE CENTRAL ATLC...ASSOCIATED WITH THE COMBINED EFFECTS OF THE DEEP LAYER TROUGHING AND THE TAIL END OF THE WEAKENING FRONT MOVING INTO THE AREA. IN ANTICIPATION OF THE LOW DEVELOPMENT...A GALE WARNING IS POSTED FOR AN AREA NW OF THE LOW...DUE TO THE STRONG GRADIENT BETWEEN IT AND HIGH PRES OVER THE N CENTRAL ATLC. OVER THE FAR TROPICAL E ATLC...AN UPPER JET ALONG 19N/20N IS ADVECTING ABUNDANT MID-HIGH LEVEL MOISTURE TO ITS S E OF 40W AND ENHANCING CONVECTION WITHIN THE ITCZ. $$ CANGIALOSI