000 AXNT20 KNHC 060538 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST SUN DEC 06 2009 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 0500 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 7N12W 6N20W 3N30W 1N40W INTO EXTREME NORTHERN BRAZIL NEAR 1N50W. SCATTERED MODERATE CONVECTION WITHIN 60 NM N AND 90 NM S OF THE ITCZ AXIS BETWEEN 16W AND 28W. ...DISCUSSION... GULF OF MEXICO... THE 1025 MB HIGH PRES SYSTEM OVER THE LOWER MISSISSIPPI VALLEY WILL RETREAT NORTHEASTWARD THROUGH THE DAY...DECREASING THE PRES GRADIENT OVER THE EASTERN GULF. THE STRONG NORTHERLY WINDS BEHIND THE COLD FRONT THAT PASSED THROUGH THE EASTERN GULF AND FLORIDA TODAY ARE ALREADY BEGINNING TO DIMINISH AS A RESULT. HOWEVER...THE EASTERN GULF IF STILL MARKED BY STRONG SUBSIDENCE BEHIND THE FRONT. OVER THE WESTERN GULF...WINDS HAVE ALREADY BEGUN TO TURN EASTERLY TO SOUTHEASTERLY ON THE SW SIDE OF THIS HIGH PRES CENTER. THESE SOUTHERLY WINDS ARE FOUND WELL INTO THE SOUTHERN PLAINS AND ARE FEEDING INTO A LOW PRES SYSTEM CURRENTLY TRAVERSING THE ROCKIES. SATELLITE-BASED TOTAL PRECIPITABLE WATER IMAGERY REVEALS THAT THIS SOUTHERLY RETURN FLOW IS ALREADY INCREASING THE AVAILABLE MOISTURE IN THE WESTERN GULF. INFRARED IMAGERY AND RADAR CONFIRMS SOME SHOWER ACTIVITY OVER THE SE RIO GRANDE VALLEY AT THE MOMENT. SHOWER ACTIVITY IS EXPECTED TO INCREASE OVER THE NW GULF TODAY AND SHIFT EASTWARD INTO THE CENTRAL GULF MON AS THE LOW PRES SYSTEM IN THE ROCKIES MOVES EAST AND DRAGS A WEAK SURFACE BOUNDARY WITH IT INTO THE MISSISSIPPI VALLEY. CARIBBEAN SEA... THE TRADE WINDS OVER THE CARIBBEAN HAVE WEAKENED DUE TO THE SLACKENING PRES GRADIENT BETWEEN CLIMATOLOGICAL LOW PRES OVER NORTHERN COLOMBIA AND THE RIDGE EXTENDING FROM A 1024 MB HIGH NEAR 32N52N TO THE NW CARIBBEAN NEAR 20N80W. THE 0144 UTC ASCAT CONFIRMS THIS...WITH 20 TO 25 KT EASTERLY TRADEWINDS NOW CONFINED TO NEAR THE COAST OF NORTHERN COLOMBIA. THE RIDGE N OF THE AREA HAS SHIFTED EASTWARD DUE TO THE PROGRESSION OF THE COLD FRONT THAT MOVED THROUGH FLORIDA SAT AND INTO THE SW N ATLANTIC. THE SOUTHERN EDGE OF THIS FRONT HAS MOVED INTO THE NW CARIBBEAN...BRINGING SHOWERS NEAR THE FRONT AND 20 TO 25 KT N WINDS N OF THE FRONT. THE FRONT IS EXPECTED TO STALL OVER THE NW CARIBBEAN AND DISSIPATE LATER TODAY. ELSEWHERE...THE CARIBBEAN CONTINUES TO BE MARKED BY STRONG SUBSIDENCE AND LIMITED MOISTURE...BRINGING TRANQUIL WEATHER TO MUCH OF THE AREA. SCATTERED SHOWERS ARE PRIMARILY LIMITED TO THE EASTERN CARIBBEAN E OF 70W AND THE CENTRAL CARIBBEAN N OF 15N BETWEEN 70W AND 80W AT THIS TIME. ATLANTIC OCEAN... A COLD FRONT LIES OVER THE SW N ATLANTIC FROM 31N74W TO 27N78W TO 23N81W. THE 0148 ASCAT PASS SHOWS NW WINDS IN THE 20 TO 25 KT RANGE N OF THE BAHAMAS AND W OF THE COLD FRONT. SCATTERED SHOWERS AND THUNDERSTORMS LIE WITHIN 180 NM E OF THE COLD FRONT AT THE MOMENT. THE DEEP LAYER LOW SUPPORTING THIS FRONTAL BOUNDARY IS LIFTING NORTHEAST OFF THE NEW ENGLAND COAST THIS MORNING AND THE UPPER LEVEL TROUGHING OVER THE SW N ATLANTIC WILL QUICKLY BE REPLACED BY WESTWARD BUILDING RIDGING FROM THE CENTRAL ATLANTIC ACROSS THE BAHAMAS. AS A RESULT...THE COLD FRONT WILL ADVANCE EASTWARD THROUGH THE NORTHERN PORTION OF THE FORECAST AREA BUT STALL NEAR THE STRAITS OF FLORIDA TODAY AND BEGIN LIFTING NORTH AS A WEAK WARM FRONT BY MON. THE ADVANCING COLD FRONT HAS ALREADY SHIFTED THE SURFACE RIDGE FARTHER EAST OVER THE PAST 24 HOURS...WITH THE RIDGE NOW EXTENDING FROM 1024 MB HIGH NEAR 32N52N TO THE NW CARIBBEAN NEAR 20N80W. THIS RIDGING IS EXPECTED TO WEAKEN FURTHER AS THE ADVANCING PORTION OF THE COLD FRONT ENCROACHES UPON IT. TO THE WEST OF THIS RIDGE LIES AN UPPER TROUGH THAT WILL AMPLIFY AND BECOMING MORE POSITIVELY OVER THE NEXT FEW DAYS. A 100 KT WEST-SOUTHWESTERLY UPPER JET LIES ON THE LEADING EDGE OF THIS TROUGH AND IS TRANSPORTING TROPICAL MOISTURE NORTHEASTWARD TOWARD WEST AFRICA...WITH MAINLY CLOUDY SKIES FOUND ALONG THE ROUTE FROM THE FRENCH GUIANA TO CAPE VERDE ISLANDS AS A RESULT. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE REAR RIGHT QUADRANT OF THIS UPPER JET IS CURRENTLY SUPPORTING SCATTERED MODERATE SHOWERS AND THUNDERSTORMS ALONG THE ITCZ AXIS BETWEEN 16W AND 28W. $$ SCHAUER