000 AXNT20 KNHC 212338 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST WED JAN 21 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...THE ITCZ... THE ITCZ IS PRETTY ACTIVE THIS EVENING. ITS AXIS IS CENTERED ALONG 5N3W 2N15W CROSSING THE EQUATOR AT 19W THEN EXTENDING TO 2S30W INTO NORTHEASTERN BRAZIL NEAR 4S40W. A CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 150 NM N OF AXIS BETWEEN 15W-18W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 125 NM N OF AXIS BETWEEN 22W-33W...AND FROM THE EQUATOR TO 3N BETWEEN 34W-40W. SIMILAR CONVECTION IS NEAR 3N47W. ...DISCUSSION... GULF OF MEXICO... A STRONG COLD AIR OUTBREAK IS CURRENTLY OCCURRING ACROSS THE GULF AND THE FLORIDA PENINSULA. AT 2100 UTC...A 1025 MB HIGH LOCATED OVER SE LOUISIANA COVERS THE ENTIRE AREA. COLD AIR STRATOCUMULUS CLOUDS DUE TO THE COLD ADVECTION OVER RELATIVELY WARM WATERS ARE NOTED MAINLY OVER THE EASTERN HALF OF THE GULF REGION. SURFACE WINDS ARE GENERALLY NORTHERLY AT 20 KT. WINDS SHOULD RELAX BY TOMORROW AS SURFACE HIGH MOVES EWD TO NORTHERN FLORIDA. TEMPERATURES WILL CONTINUE ON THE COLD SIDE TONIGHT OVER FLORIDA UNDER CLEAR SKIES AND RELAXING WINDS. A WARMING TREND WILL BEGIN ACROSS THE AREA TOMORROW. NO DEEP CONVECTION IS OBSERVED IN THE REGION BECAUSE OF THE STABLE AND DRY AIR MASS THAT IS PREVAILING. IN THE UPPER LEVELS...A SHARP SHORT-WAVE TROUGH IS OBSERVED JUST OFF THE SOUTHEASTERN U.S...WHICH IS SUPPORTING A COLD FRONT OVER THE W ATLC/CARIBBEAN SEA AND THE COLD AIR ADVECTION. W TO NW UPPER LEVEL WINDS DOMINATE THE ENTIRE GULF OF MEXICO. CARIBBEAN SEA... THE AFOREMENTIONED COLD FRONT ENTERS THE CARIBBEAN SEA THROUGH THE WINDWARD PASSAGE THEN CONTINUES SW TO NEAR LIMON COSTA RICA. LOW LEVEL CONVERGENCE NEAR THE TAIL END OF THE FRONT IS SUPPORTING A PATCH OF MOISTURE WITH EMBEDDED LIGHT SHOWERS OVER WESTERN PANAMA AND COSTA RICA. FRAGMENTS OF LOW/MID CLOUDS ARE NOTED OVER CUBA AND THE NW CARIBBEAN. NORTHERLY SURFACE WINDS OF UP TO 25 KT ARE OCCURRING WEST OF THE FRONTAL BOUNDARY WITH SIGNIFICANT COOL AND DRY AIR ADVECTION. A COLD NIGHT IS IN STORE FOR WEST-CENTRAL CUBA PARTICULARLY ACROSS THE INTERIOR SECTIONS OF THE PROVINCES OF HAVANA AND MATANZAS AS A TONGUE OF COLD AIR PUSHES SWD ACROSS THE STRAITS OF FLORIDA. TEMPERATURES BELOW 10 DEGREES CELSIUS OR 50 DEGREES FAHRENHEIT ARE POSSIBLE IN SOME LOCALES. THE FRONT WILL SHIFT FURTHER SE OVER HISPANIOLA TONIGHT BEFORE DISSIPATING ON THU. EAST OF THE FRONT...SURFACE WINDS ARE GENERALLY EASTERLY 15 KT OR LESS AND ARE EXPECTED TO REMAIN THIS WAY THROUGH THURSDAY. AN ELONGATED AREA OF MOISTURE MOVING AROUND THE PERIPHERY OF THE ATLANTIC RIDGE IS PRODUCING SCATTERED TO NUMEROUS PASSING SHOWERS ACROSS EASTERN PUERTO RICO AND THE VIRGIN ISLANDS. THESE WEATHER CONDITIONS ARE EXPECTED TO CONTINUE TONIGHT THROUGH TOMORROW MORNING. IN THE UPPER LEVELS...THE BASE OF THE ABOVE MENTIONED VIGOROUS SHORT-WAVE TROUGH REACHES THE NW CARIBBEAN. SOUTHWESTERLIES OF UP TO 80 KT ON THE SOUTHEAST SIDE OF THIS TROUGH DOMINATES MOST OF THE WEST AND CENTRAL CARIBBEAN. A WEAK HIGH IS CENTERED JUST WEST OF ISLA DE MARGARITA VENEZUELA. SUBSIDENCE AND THE ASSOCIATED DRY AIR COVERS MOST OF THE BASIN AND NORTHERN VENEZUELA. ATLANTIC OCEAN... A COLD FRONT EXTENDS FROM BERMUDA TO THE TURKS AND CAICOS ISLANDS ENTERING THE CARIBBEAN SEA THROUGH THE WINDWARD PASSAGE. SCATTERED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THE FRONTAL BOUNDARY. NW WINDS OF 20 TO 25 KT ARE BLOWING BEHIND THE FRONT WHERE BROKEN COLD AIR STRATOCUMULUS CLOUDS ARE ALSO OBSERVED. A LARGE SURFACE 1030 MB HIGH NEAR 30N36W DOMINATES THE REMAINDER OF THE FORECAST AREA. ALOFT...UPPER LEVEL RIDGING PREVAILS ALONG 30N WITH GENERAL SUBSIDENCE ALONG AND SOUTH OF THE RIDGE. AN UPPER LOW IS LOCATED NEAR 14N50W GENERATING SOME SHOWER ACTIVITY ON ITS NORTHEASTERN SEMICIRCLE. NUMEROUS CIRRUS CLOUDS ARE ALSO OBSERVED EQUATORWARD OF 15N BEING ADVECTED FROM THE ITCZ CONVECTION. $$ GR