000 AXNT20 KNHC 172353 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU JAN 17 2008 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 6N11W 3N20W 1N30W 1S40W 2N48W 1N50W. WIDELY SCATTERED MODERATE CONVECTION IS FROM EQ-7N BETWEEN 44W-52W. SCATTERED MODERATE CONVECTION IS FROM 1S-1N BETWEEN 40W-42W. SCATTERED SHOWERS ARE WITHIN 120NM OF THE AXIS BETWEEN 20W-40W. ...DISCUSSION... GULF OF MEXICO... AS OF 2100 UTC...A WEAKENING SHORTWAVE OVER THE CENTRAL APPALACHIANS IS PRODUCING A 1011MB LOW CENTERED OVER THE FL PANHANDLE NEAR 30N84W AND SHOULD MOVE NE IN DEEP SWLY FLOW ALOFT. A COLD FRONT EXTENDS SOUTHWARD TO THE YUCATAN PENINSULA ALONG 25N84W 22N88W. THE FRONT BECOMES STATIONARY INTO THE BAY OF CAMPECHE ALONG 19N96W 23N100W. AN ASSOCIATED SQUALL LINE CONTINUES AHEAD OF THE COLD FRONT ALONG 26N83W 23N86W. RADAR TRENDS INDICATE A GRADUAL WEAKENING OF THIS ACTIVITY DURING THE PAST SEVERAL HOURS...AS UPPER-LEVEL SUPPORT SHIFTS WELL NORTHEAST. A DISSIPATING COLD FRONT LOCATED OVER THE NW GULF OF MEXICO IS ALONG 29N93W 26N97W. A WEAK 1019MB SFC HIGH IS LOCATED IN BETWEEN THE TWO FRONTS...JUST SOUTH OF THE MOUTH OF THE MISSISSIPPI RIVER AT 28N89W. OF NOTE...A 20-25KT SLY FLOW CONTINUES AHEAD OF THE SQUALL OVER THE STRAITS OF FLORIDA FROM 23N-26N 80W-85W. AS THE FIRST SHORTWAVE DEPARTS THE ERN CONUS TONIGHT...EXPECT THE UPPER-LEVEL FLOW TO REMAIN SWLY OVER THE GULF WHILE ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY REINFORCES THE LONGWAVE TROUGH OVER THE CENTRAL CONUS WITHIN 24 HRS. AS THIS OCCURS...THE FRONTAL BOUNDARY OVER THE GULF SHOULD STALL OUT AND BEGIN RETURNING AS A WARM FRONT IN RESPONSE TO A NEW ROUND OF CYCLOGENESIS BEGINNING OVER THE W CNTRL/NWRN GULF OF MEXICO FRI NIGHT. UNTIL THEN...OVERRUNNING PACIFIC MOISTURE SHOULD CONTINUE TO BRING A THIN VEIL OF HIGH CLOUDS FROM MEXICO INTO THE SERN STATES TONIGHT...WITH CLOUDS AND CONVECTION ON THE INCREASE OVER THE WRN AND CNTRL GULF OF MEXICO FRI NIGHT. CARIBBEAN SEA... A STRONG MID-TO UPPER-LEVEL RIDGE OVER NWRN SOUTH AMERICA WITH A RIDGE AXIS EXTENDING NWD ALONG 75W THROUGH THE CARIBBEAN SEA SHOULD CONTINUE TO DOMINATE THE WEATHER THROUGH AT LEAST FRI. UNDERNEATH THE RIDGE...STRONG SUBSIDENCE IS NOTED IN WATER VAPOR IMAGERY OVER MOST OF THE CARIBBEAN...ESPECIALLY FROM NRN VENEZUELA INTO THE SOUTHWESTERN CARIBBEAN SEA. DESPITE THIS...A MODERATELY STRONG TRADE WIND FLOW CONTINUES TO PRODUCE SCATTERED BANDS OF SHOWERS FROM PORTIONS OF THE LESSER ANTILLES TO JAMAICA. THE SHOWERS ARE MORE CONCENTRATED IN THE VICINITY OF THE BRITISH/U.S. VIRGIN ISLANDS...WHERE STREAMERS ARE CARRYING SHOWERS DOWNSTREAM TO PUERTO RICO. ADDITIONAL CONCENTRATED BANDS OF SHOWERS ARE ALSO OBSERVED IN THE W CNTRL CARIBBEAN... LIKELY RELATED TO THE SHEAR OF THE LOW-LEVEL WIND/SPEED CONVERGENCE. THE SPEED CONVERGENCE OVER THIS REGION IS A RESULT OF STRONG TRADES OVER THE CENTRAL CARIBBEAN...WITH WEAKER TRADES LYING TO THE WEST. A STRONG COLD FRONT IS EXPECTED TO MOVE INTO THE NW CARIBBEAN SAT NIGHT ACCOMPANIED BY STRONG N WINDS AND BUILDING SEAS. ATLANTIC OCEAN... A COLD FRONT ENTERS THE AREA NEAR 32N42W AND EXTENDS SW TO E OF THE BAHAMAS ALONG 27N50W 24N70W. BROKEN LOW CLOUDS AND A FEW SHOWERS ARE WITHIN 90NM EITHER SIDE OF THE FRONT. SCATTERED MODERATE CONVECTION LIES E OF THE FRONT FROM 30N TO BEYOND 32N BETWEEN 39W-43W. BEHIND THE BOUNDARY...A 1025 MB SFC HIGH IS CENTERED NEAR 33N67W. IN THE ERN ATL...A 1030 MB IS LOCATED OFF THE COAST OF PORTUGAL NEAR 36N10W...WITH A RIDGE AXIS EXTENDING SW TO 27N35W. IN THE TROPICS...A SFC TROUGH IS NORTH OF THE NRN COAST OF BRAZIL ALONG 48W FROM 1N-8N. ASSOCIATED CONVECTION IS WIDELY SCATTERED FROM EQ-7N BETWEEN 44W-52W. AT UPPER LEVELS...A BROAD LONGWAVE TROUGH LIES EAST OF THE CARIBBEAN HIGH CENTER... COVERING MUCH OF THE CNTRL AND ERN ATL. AROUND THE BASE OF THE TROUGH...A STRONG 70KT-90KT JET IS PUMPING CONSIDERABLE ATLANTIC MOISTURE EWD INTO THE CNTRL AND ERN TROPICAL ATLANTIC. $$ TK