000 AXNT20 KNHC 211137 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST FRI DEC 21 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N9W 5N20W 5N30W 3N40W AND INTO SOUTH AMERICA NEAR THE EQUATOR AND 50W. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE WITHIN 60 NM EITHER SIDE OF THE AXIS BETWEEN 20W-34W. SCATTERED MODERATE CONVECTION IS FROM 4N-7N AND 33W-40W. UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG THE ITCZ. DISCUSSION... GULF OF MEXICO... CONVECTION HAS DECREASED IN THE E GULF AND DIMINISHED IN THE CENTRAL GULF THIS MORNING AS THE SFC LOW AND ASSOCIATED TROUGH MOVED E TOWARD FLORIDA. AS OF 09Z...THE LOW WAS CENTERED OVER N FLORIDA NEAR 30N83W AND THE TROUGH EXTENDED FROM THE LOW ALONG 29N82W 26N85W TO 25N89W. THIS LOW HAS BECOME THE MAIN LOW OF THE SYSTEM AND THE WEAK COLD FRONT NOW ATTACHES TO IT AND STRETCHES TO 28N88W THEN BEGINS TO DISSIPATE ALONG 25N93W TO THE COAST OF MEXICO NEAR 23N98W. THE COLD FRONT IS MARKED BY A DEW POINT GRADIENT AND ALL OF THE CONVECTIVE ACTIVITY WITH THIS SYSTEM LIES TO THE EAST OF THE SFC TROUGH. COMPOSITE RADAR IMAGERY INDICATES THAT MOST OF THE CONVECTION IS NOW OVER CENTRAL FLORIDA...HOWEVER...A FEW SHOWERS AND ISOLATED TSTMS REMAIN OVER THE E GULF E OF 85W N OF 25N. MODERATE TO STRONG S WINDS ARE ALONG THE AXIS OF THE TROUGH. THE REMAINDER OF THE GULF REMAINS UNDER A WEAK PRESSURE PATTERN RESULTING IN LIGHT WINDS ACROSS THE REGION. ALOFT...NEAR ZONAL FLOW CONTINUES TO MAINTAIN DRY AND STABLE CONDITIONS. THE NORTHERN PERIPHERY OF AN UPPER RIDGE IS DRAWING UPPER-LEVEL MOISTURE FROM THE E PAC OVER THE SW GULF. A STRONGER COLD FRONT IS EXPECTED TO MOVE INTO THE NW GULF SAT EVENING. MODERATE TO STRONG NLY WINDS AND BUILDING SEAS CAN BE EXPECTED BEHIND THE FRONT. CARIBBEAN SEA... TRANQUIL WEATHER CONDITIONS PERSIST ACROSS THE CARIBBEAN THIS MORNING UNDER THE INFLUENCE OF A MID/UPPER-LEVEL RIDGE WHICH IS PRODUCING STRONG SUBSIDENCE AND A DRY/STABLE AIRMASS. A FEW PATCHES OF LOW LEVEL CLOUDS WITH ISOLATED SHOWERS REMAIN OVER THE AREA. SAN JUAN RADAR SHOWS ISOLATED SHOWERS MOVING SOUTH OF PUERTO RICO. A SMALL CLUSTER OF SHOWERS AND ISOLATED TSTMS IS MOVING OFF PANAMA INTO THE SW CARIBBEAN. LIGHT TO MODERATE TRADES WILL PREVAIL OVER MUCH OF THE AREA THROUGH MONDAY. ATLANTIC OCEAN... THE BAND OF CONVECTIVE ACTIVITY ASSOCIATED WITH THE LOW AND SFC TROUGH OVER THE E GULF OF MEXICO IS BEGINNING TO ENTER THE W ATLC. THIS CONVECTION WILL CONTINUE TO PUSH EASTWARD AS THE SFC LOW MOVES ACROSS FLORIDA AND ENTERS THE W ATLC THIS AFTERNOON. THE PRESSURE GRADIENT BETWEEN THIS LOW AND HIGH PRESSURE BUILDING TO THE NORTH WILL TIGHTEN RESULTING IN INCREASED WINDS AND SEAS. A PRE-FRONTAL TROUGH ASSOCIATED WITH A COLD FRONT NORTH OF THE DISCUSSION AREA ENTERS THE REGION NEAR 31N62W AND EXTENDS SW TO 27N68W. A NARROW BAND OF SHOWERS/ ISOLATED TSTMS LIES ALONG THE TROUGH AXIS. A WEAK 1016 MB LOW IS CENTERED NEAR 29N52W. A SFC TROUGH EXTENDS FROM THE LOW CENTER ALONG 25N58W TO 23N66W. A BAND OF SHOWERS AND TSTMS EXTENDS UP TO 200 NM AHEAD OF THE TROUGH. A WARM FRONT ALSO EXTENDS FROM THE LOW CENTER ALONG 31N51W 32N45W TO 31N36W WHERE IT CONNECTS TO A COLD FRONT AND CONTINUES ALONG 30N30W EXITING THE REGION NEAR 32N23W. A LARGE SFC RIDGE REMAINS FIXED OVER THE E ATLC TRANSPORTING FAIR WEATHER STRATOCUMULUS CLOUDS AROUND ITS PERIPHERY. IN THE TROPICAL ATLC...UPPER DIFFLUENCE IS SUPPORTING CONVECTION ALONG THE ITCZ. A SFC TROUGH IS ANALYZED JUST EAST OF THE WINDWARD ISLANDS ALONG 60W FROM 9N-14N. SCATTERED MODERATE CONVECTION IN THIS AREA IS ENHANCED BY UPPER DIFFLUENCE. $$ WADDINGTON