000 AXNT20 KNHC 290006 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU DEC 27 2007 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC ...THE ITCZ... THE ITCZ RUNS ALONG 6N10W AT LIBERIA TO 6N25W 3N37W 1S48W INTO NE BRAZIL. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF AXIS 29W-35W. CLUSTERS OF SHOWERS ARE WITHIN 120 NM OF EITHER SIDE OF AXIS 10W-29W AND 45-48W. ...DISCUSSION... THE GULF OF MEXICO... A MODEST COLD FRONT HAS BEEN PUSHING EASTWARD ACROSS THE GULF DURING THE DAY. LIGHTNING...COASTAL RADAR...AND IR IMAGERY INDICATE THAT MODERATE CONVECTION EXTENDS ALONG A PRE-FRONTAL SQUALL LINE...BUT THIS ONLY IS PRESENT OUT TO ABOUT 120 NM FROM THE US GULF COAST. NORTHERLY WINDS BEHIND THE FRONT ARE GENERALLY ABOUT 10 KT...THOUGH SOME FUNNELING ALONG THE MEXICAN COAST IS PRODUCING UP TO 20 KT OF WIND. AHEAD OF THE FRONT...WINDS ARE GENERALLY OUT OF THE SOUTH AT 10-15 KT. IN THE UPPER LEVELS...SOUTHWESTERLY FLOW DOMINATES REACHING 100 KT ALONG THE NORTH GULF COAST ON THE SOUTH SIDE OF THE JET. THE CURRENT COOL AIR PUSH SHOULD BE SHORT-LIVED AND NOT EXTEND TO THE EASTERN TWO-THIRDS OF THE GULF. CYCLOGENESIS ALONG THE NORTHERN GULF COAST SUNDAY MORNING SHOULD USHER IN ANOTHER BRIEF PERIOD OF NORTHERLY WINDS AND COOLER TEMPS...THOUGH THIS APPEARS TO BE SOMEWHAT STRONGER THAN THAT CURRENTLY IMPACTING THE GULF. THE BIG EVENT LOOKS TO BE SET FOR TUESDAY AND WEDNESDAY WITH A STRONG FRONT RACING ACROSS THE GULF WITH SOME GALE FORCE WINDS PRESENT LIKELY IN THE WESTERN PART OF THE GULF. THE CARIBBEAN SEA... MOST OF THE CARIBBEAN IS CONVECTION FREE UNDER THE SUBSIDENT ENVIRONMENT OF A UPPER-RIDGE CENTERED OVER JAMAICA. THE EXCEPTION IS AN AREA OF SCATTERED SHOWERS AND THUNDERSTORMS ALONG AND JUST EAST OF CENTRAL AMERICA. THIS MAY BE DUE TO THE COMBINATION OF A WEAK SURFACE TROUGH AND UPPER-LEVEL DIFFLUENCE. SURFACE WINDS REMAIN EASTERLY AT 15-20 KT THROUGHOUT MOST OF THE CARIBBEAN. THE WINDS MAY BE ENHANCED SOMEWHAT DURING THE NEXT DAY OR TWO AS THE PRESSURE GRADIENT TIGHTENS OVER THE REGION AS THE HIGH OVER THE NORTH ATLANTIC MOVES NORTH OF THE CARIBBEAN. THE AFOREMENTIONED COLD FRONT SHOULD LIKELY REACH THE NORTHWESTERN CARIBBEAN ON WEDNESDAY...BRINGING MODERATE NORTHEASTERLY WINDS. THE ATLANTIC OCEAN... OF INTEREST IS THE DEEP CYCLONE CENTERED NEAR 26N38W. THIS SYSTEM HAS REMAINED STATIONARY FOR A COUPLE OF DAYS AND ORGANIZED CONVECTION IS STARTING TO DEVELOP. QUIKSCAT WINDS SUGGEST THAT THERE ARE SOME GALE FORCE WINDS ALONG THE NORTHERN SEMI-CIRCLE OF THE SYSTEM...BUT THERE MAY BE SOME RAIN CONTAMINATION IN THE OBSERVED WINDS. THE MAIN BAROCLINIC ZONE REMAINS WELL TO THE NORTH OF THE SYSTEM AND ITS FRONTAL STRUCTURE HAS TRANSITIONED TO A WEAK TRAILING TROUGH. THE FSU CYCLONE PHASE SPACE ANALYSES INDICATED THAT THE CYCLONE MAY BE BECOMING A HYBRID SYSTEM...BUT UNTIL MORE SYMMETRIC DEEP CONVECTION DEVELOPS IT WILL CONTINUE TO BE CONSIDERED AN OCCLUDED LOW. VERTICAL SHEAR ON THE SYSTEM IS RELATIVELY WEAK AS THE UPPER PORTION OF THE CYCLONE IS DISPLACED SOMEWHAT NORTHWEST OF THE SURFACE CIRCULATION. THIS LOW-MODERATE SHEAR ENVIRONMENT MAY ONLY LAST FOR ANOTHER DAY OR SO BEFORE STRONG UPPER WESTERLIES IMPACT THE SYSTEM WITH THE APPROACH OF A VIGOROUS SHORT-WAVE TROUGH. THE CYCLONE SHOULD MEANDER IN PLACE FOR THE NEXT TWO DAYS BEFORE MOVING OFF SLOWLY TO THE WEST OR SOUTHWEST. ELSEWHERE A WEAK SURFACE TROUGH IS PRODUCING MODERATE SCATTERED WIDESPREAD CONVECTION BETWEEN 3-10N AND 42-50W. AS WAS MENTIONED FOR THE GULF AND CARIBBEAN...A VIGOROUS COLD FRONT WILL REACH THE WESTERN ATLANTIC SOUTH OF 31N BY TUESDAY NIGHT-WEDNESDAY MORNING. $$ CWL