000 AXNT20 KNHC 071742 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST FRI DEC 07 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1745 UTC ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N10W 3.5N25W 5N38W EQ50W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM THE COAST OF SW AFRICA TO S OF THE EQUATOR E OF 12W TO ACROSS THE PRIME MERIDIAN. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 2N-7N BETWEEN 17W-28W. DISCUSSION... GULF OF MEXICO... HIGH PRES IS IN CONTROL OF THE WEATHER PATTERN ACROSS THE GULF GIVING THE AREA PRETTY QUIET CONDITIONS AND SLY RETURN FLOW. THE REMNANTS OF A FRONTAL BOUNDARY EXTENDING ACROSS THE N GULF WATERS LIFTED N AND DISSIPATED. CURRENTLY...A SFC TROUGH IS ANALYZED OVER SOUTHERN LOUISIANA. PATCHES OF LOW LEVEL MOISTURE DOT THE REGION WITH A NARROW LINE OF SHOWERS AND ISOLATED TSTMS ALONG 27N91W 26N94W. DOPPLER RADAR SHOWS SOME SHOWER ACTIVITY OVER THE LOWER FLORIDA KEYS. ALOFT...A SHORTWAVE TROUGH EXTENDS FROM SE LOUISIANA SW TO NEAR TAMPICO MEXICO. UPPER-LEVEL SWLY FLOW TO THE EAST OF THE TROUGH ARE ADVECTING ABUNDANT MID/UPPER LEVEL MOISTURE ACROSS THE GULF. AN UPPER-LEVEL RIDGE FROM THE CARIBBEAN SEA EXTENDS NW INTO THE YUCATAN PENINSULA AND THE SE GULF. PRES GRADIENT IS EXPECTED TO INCREASE OVER SE GULF AND STRAITS OF FLORIDA LATE SATURDAY THROUGH MONDAY AS STRONG HIGH PRES BUILDS ACROSS THE U.S. EASTERN SEABOARD/W ATLC. CARIBBEAN SEA... A WEAK SFC TROUGH EXTENDS FROM THE SE BAHAMAS ACROSS HAITI INTO THE CARIBBEAN SEA. POCKETS OF LOW LEVEL MOISTURE ARE SEEN JUST BEHIND THE TROUGH AXIS AFFECTING HISPANIOLA WITH MAINLY LIGHT SHOWERS. PATCHES OF LOW LEVEL MOISTURE WITH EMBEDDED LIGHT SHOWERS ARE ALSO SEEN OVER THE ABC ISLANDS AND NORTHERN VENEZUELA. AFTER SEVERAL DAYS WITH A WEAK SURFACE PRESSURE GRADIENT ACROSS THE AREA...WINDS ARE BEGINNING TO INCREASE OVER THE EASTERN CARIBBEAN AS A TROUGH ALONG 50W APPROACHES THE REGION AND SURFACE HIGH PRES BUILDS OVER W ATLC. THE NOAA WAVE WATCH MODEL...NWW3...SHOWS NE TO E WINDS OF 20 TO 25 KT ACROSS A GOOD PORTION OF THE BASIN...INCLUDING ALSO THE ANEGADA...MONA AND WINDWARD PASSAGES. THESE WINDS WILL PERSIST DURING THE UPCOMING WEEKEND. IN THE UPPER LEVELS...BROAD UPPER RIDGE DOMINATES THE CARIBBEAN ANCHORED OVER SOUTH AMERICA AND EXTENDS TO OVER THE GULF OF MEXICO AND THE W ATLC. ATLANTIC OCEAN... LOOKING AT THE BIG PICTURE FROM WEST TO EAST...A WEAK SURFACE TROUGH EXTENDS OFF THE COAST OF THE CAROLINAS THROUGH 31N80W ALONG THE FLORIDA COAST TO NEAR DAYTONA BEACH WITH LITTLE SHOWER ACTIVITY. A COLD FRONT ENTERS THE AREA NEAR 31N57W THEN CONTINUES SW TO NEAR 27N64W. A PRE-FRONTAL TROUGH IS WITHIN 200 NM AHEAD OF THE FRONT AND RUNS FROM 31N52W TO 24N58W. LOW-LEVEL CONVERGENCE ALONG THIS TROUGH IS PRODUCING A 60 NM WIDE BAND OF SCATTERED SHOWERS AND ISOLATED TSTMS. VIS SATELLITE IMAGERY SHOWS A SWIRL OF LOW CLOUDS APPROACHING THE UK/US VIRGIN ISLANDS AND PUERTO RICO. THIS FEATURE WILL AFFECT THOSE ISLANDS THIS AFTERNOON AND THIS EVENING WITH ISOLATED TO SCATTERED SHOWERS. A BROAD SFC TROUGH REMAINS OVER THE CENTRAL ATLC EXTENDING ALONG 49W/5OW FROM 14N-28N. THE WIND SHIFT ASSOCIATED WITH THIS TROUGH IS WELL DEFINED ON AN EARLIER QUIKSCAT PASS AND SURFACE OBSERVATIONS. SOME CYCLONIC TURNING IS SEEN ALONG THE TROUGH AXIS NEAR 17N. THIS TROUGH HAS CLUSTERS OF MODERATE CONVECTION JUST BEHIND THE AXIS BUT PARTICULARLY BETWEEN 17N-22N. THE GFS COMPUTER MODEL HAS MOISTURE FROM THIS TROUGH SPREADING ACROSS THE EASTERN CARIBBEAN DURING THIS WEEKEND. A STRONG SFC RIDGE DOMINATES THE EASTERN ATLC CENTERED ON A 1038 MB HIGH NEAR THE AZORES. A DIFFERENCE IN PRES BETWEEN THIS HIGH AND THE TROUGH OVER THE TROPICAL ATLC IS PRODUCING A LARGE AREA OF STRONG ELY TRADES BETWEEN THE TROUGH AXIS AND THE WEST COAST OF AFRICA. THE MID AND UPPER PATTERN IS QUITE AMPLIFIED CONSISTING OF A LARGE ANTICYCLONE OVER THE AZORES AND A BROAD ELONGATED TROUGH TRAPPED S OF THE HIGH. THE BROAD TROUGH HAS AN EMBEDDED UPPER LOW JUST SW OF THE CAPE VERDE ISLANDS NEAR 24N28W. A JET STREAM BRANCH WITH CORE WINDS OF 70-90 KT LIES ON THE S SIDE OF THE TROUGH. WV IMAGERY SHOWS A BAND OF TRANSVERSE HIGH CLOUDS ASSOCIATED WITH THIS FEATURE. THE REMAINDER OF THE FORECAST AREA...WEST OF 50W IS UNDER A FAIRLY UNIFORM ZONAL UPPER FLOW. $$ GR