000 AXNT20 KNHC 212359 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU DEC 21 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA... CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA... NORTHEASTERN 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 2330 UTC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N10W 4N30W 6N47W 4N54W. SCATTERED MODERATE CONVECTION FROM 3N TO 7N BETWEEN 37W AND 47W. ...DISCUSSION... GULF OF MEXICO... DYNAMIC WEATHER PATTERN CONTINUES OVER THE NW GULF THIS AFTERNOON. BROAD UPPER TROUGH EXTENDS FROM A CUTOFF UPPER LOW OVER KANSAS TO SOUTHERN BAJA. AHEAD OF THIS TROUGH...UPPER AIR ANALYSIS SHOWS RIGHT FRONT QUADRANT OF A 120 KT SW JET NOSING INTO THE NW GULF WATERS FROM CENTRAL MEXICO...ACCOMPANIED BY ABUNDANT DEEP LAYER MOISTURE. AT THE SURFACE...A 1013 MB LOW IS EMERGING OFF THE S TEXAS COAST BETWEEN BRO AND CRP...WITH A STATIONARY BOUNDARY EXTENDING TO THE NE TOWARD LCH. THESE FACTORS ARE SUPPORTING WIDESPREAD THUNDERSTORM ACTIVITY ACROSS THE NW GULF AS EVIDENCED BY AREAS RADAR IMAGERY...FROM S TEXAS TO COASTAL ALABAMA. ELSEWHERE OVER THE GULF W OF 85W ONLY SCATTERED CIRRUS DECKS ARE EVIDENT ON VISIBLE IMAGERY UNDER FLATTENING UPPER RIDGE AXIS OVER THE CENTRAL GULF. OVER THE EASTERN GULF...UPPER TROUGH EXTENDS ALONG 82W...AIDING WEAK SHOWER DEVELOPMENT NEAR 26N85W. AT THE SURFACE...BUOY AND SHIP OBSERVATIONS SHOW MODERATE TO FRESH SE FLOW ACROSS THE GULF ON THE PERIPHERY OF 1030 MB HIGH PRES CENTERED OVER THE CAROLINAS. SLIGHTLY STRONGER E TO SE WINDS ARE EVIDENT IN THE STRAITS OF FLORIDA...AT THE BASE OF THE HIGH PRES. LOOKING AHEAD...THE FRONT WILL SHIFT E AND STALL FROM THE FLORIDA BIG BEND TO MATAMOROS MEXICO BY SAT. MEANWHILE A REINFORCING SHORT WAVE WILL PUSH DOWN THE ROCKIES THROUGH SAT...AND INTO THE NW GULF BY LATE SAT. WINDS WILL INCREASE OVER THE WESTERN GULF TO GALE FORCE BEHIND THE SECOND FRONT. CARIBBEAN SEA... SURFACE OBSERVATIONS ARE SHOWING FRESH ELY TRADES ACROSS THE CARIBBEAN E OF 80W...WITH MODERATE SE WINDS OVER THE NW CARIBBEAN...AND LIGHT ELY NEAR THE CENTRAL AMERICAN COAST. ALOFT...UPPER TROUGH EXTENDS FROM CENTRAL CUBA TO WESTERN PANAMA. WEAK CONVECTION IS EVIDENT ON VISIBLE IMAGERY UNDER THE TROUGH AXIS N OF 12N...LIKELY AIDED BY MODEST LOW LEVEL SPEED CONVERGENCE ACROSS THE CARIBBEAN. OTHERWISE DRY MID AND UPPER LEVEL AIR IS ADVECTING SWD ON THE W SIDE OF THE TROUGH...KEEPING FAIRLY STABLE CONDITIONS IN PLACE ACROSS THE BASIN. UPPER LEVEL ISOTACH ANALYSIS SHOWS 50 TO 60 KT SWLY FLOW ALOFT FROM EASTERN PANAMA TO THE LEEWARD ISLANDS...BETWEEN THE TROUGH TO THE NW AND A PERSISTENT UPPER RIDGE CENTERED OVER SOUTHERN GUYANA...BRINGING SCATTERED CIRRUS DECKS ACROSS THE EASTERN CARIBBEAN. FORECAST CALLS FOR FRESH TO STRONG ELY WINDS OVER THE EASTERN CARIBBEAN THIS WEEKEND AS HIGH PRES BUILDS TO THE N. A COLD FRONT WILL PENETRATE TROUGH THE YUCATAN CHANNEL AND INTO THE NW CARIBBEAN EARLY NEXT WEEK...FOLLOWED BY FRESH TO STRONG NLY WINDS. ATLANTIC OCEAN... WATER VAPOR IMAGERY SHOWS SOMEWHAT AMPLIFIED UPPER AIR PATTERN ACROSS THE SUBTROPICAL ATLC. UPPER TROUGH IS EVIDENT FROM 32N48W TO 23N60W...AHEAD OF A FLAT UPPER RIDGE EMERGING OFF THE U.S. SOUTHEAST COAST N OF THE BAHAMAS. LIGHT CONVECTION IS EVIDENT ON THE DIVERGENT E SIDE OF THE UPPER TROUGH FROM 25N TO 32N BETWEEN 43W AND 49W...ALONG A SURFACE FRONT THAT EXTENDS FROM 32N41W TO A 1019 MB LOW PRES AREA NEAR 25N53W. A SURFACE TROUGH EXTENDS FROM THE LOW SW TO 21N63W. S OF THE RIDGE...A WEAK UPPER TROUGH AND LOW LEVEL SPEED CONVERGENCE DUE TO FRESH TO STRONG ELY TRADES ARE PROMOTING SCATTERED LIGHT TO MODERATE CONVECTION OVER THE SOUTHERN BAHAMAS AND TURKS AND CAICOS ISLANDS. THE TRADE WINDS ARE ON THE SOUTHERN PERIPHERY OF 1030 MB SURFACE HIGH PRES N OF THE AREA. FURTHER E...FAIRLY STABLE CONDITIONS PERSIST UNDER AN UPPER RIDGE AXIS CENTERED ALONG 28W...WITH AN ASSOCIATED 1024 MB SURFACE HIGH AHEAD OF THE FRONT. AN STATIONARY UPPER TROUGH REMAINS E OF THE RIDGE FROM CENTRAL SPAIN TO 21N20W. AN ASSOCIATED WEAKENING 1018 MB SURFACE LOW REMAINS CENTERED W OF THE CAPE VERDE ISLANDS NEAR 27N27N. MEANWHILE THE TROPICAL ATLC S OF 20N...AFTERNOON QUIKSCAT DATA SHOW GENERALLY MODERATE NELY TRADE FLOW ACROSS THE ATLC. ALOFT...UPPER RIDGE REMAIN IN PLACE FROM GUYANA EWD ALONG 3N TO 15W. WLY UPPER LEVEL WINDS OF 50 TO 60 KT PERSIST N OF THE RIDGE AXIS. THE RIDGING IS ENHANCING CONVECTION ALONG THE ITCZ W OF 37W. $$ CHRISTENSEN