000 AXNT20 KNHC 190041 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SUN 18 JAN 2004 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N INCLUDING NORTHERN SECTIONS OF SOUTH AMERICA. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. THE TROPICAL ANALYSIS AND FORECAST BRANCH OF THE NATIONAL HURRICANE CENTER/TROPICAL PREDICTION CENTER IS CONSIDERING CHANGING THE FORMAT OF THIS PRODUCT. A SUMMARY OF THE PROPOSED CHANGES AND AN EXAMPLE ARE POSTED AT THE FOLLOWING WEB ADDRESS: WWW.NHC.NOAA.GOV/NEWTWDFORMAT.SHTML. THE EVALUATION PERIOD WILL END APRIL 30 2004. DURING THIS PERIOD WE ENCOURAGE YOUR COMMENTS OR SUGGESTIONS FOR IMPROVEMENTS. A LINK TO A FEEDBACK FORM IS AVAILABLE ON THE WEB SITE GIVEN ABOVE. YOUR FEEDBACK WILL HELP US TO DETERMINE PRODUCT QUALITY...IF MODIFICATIONS ARE NEEDED...AND WHETHER THE PROPOSED CHANGES WILL BE ADOPTED. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. SPECIAL FEATURES... NONE. TROPICAL WAVES/ITCZ... AXIS OF ITCZ-RELATED CLOUDS/CONVECTION IS CENTERED ALONG 5N1W 4N16W 1N40W 1S46W. MIDDLE/UPPER LEVEL SYNOPTIC FEATURES... GULF OF MEXICO... A S STREAM DISTURBANCE OVER THE S UNITED STATES AND A STRONG SUBTROPICAL JET TO 130 KT FROM N MEXICO TO N FLORIDA ARE RESPONSIBLE FOR THE ACTIVE WEATHER OVER THE GLFMEX TODAY. WATER VAPOR IMAGERY INDICATES THAT THE MID/UPPER LEVEL TROUGH HAS BECOME ELONGATED AND SPLIT WITH THE MAIN CIRCULATION OVER SE TEXAS WHILE A SECOND BRANCH RACES EWD OVER THE SE UNITED STATES. THIS EASTERNMOST BRANCH IS SUPPORTING A LINE OF STRONG SHOWERS/THUNDERSTORMS EXTENDING FROM THE W ATLC SWD OVER THE S TIP OF FLORIDA TO THE SE GLFMEX. THE SURFACE COLD FRONT LAGS FURTHER W WITH THE W GLFMEX FROM SE LOUISIANA TO THE BAY OF CAMPECHE. THE TRAILING BRANCH OF THE UPPER TROUGH WILL MOVE EWD OVER THE S UNITED STATES SWINGING THE COLD FRONT ACROSS THE GLFMEX TONIGHT AND TOMORROW SUPPORTING A SECOND ROUND OF SHOWERS/THUNDERSTORMS OVER THE E GLFMEX AND FLORIDA. CARIBBEAN... WEAK MID/UPPER LEVEL RIDGING EXISTS OVER THE CARIBBEAN WITH PRIMARILY ZONAL WLY FLOW. STRONG SUBSIDENCE CONTINUES TO DOMINATE THE ENTIRE AREA PREVENTING ANY SIGNIFICANT CLOUDS/CONVECTION SAVE THE EXTREME NE CARIBBEAN WHERE THE S EXTENT OF AN ATLC FRONTAL BOUNDARY IS CAUSING A FEW SHOWERS OVER THE VIRGIN ISLANDS/PUERTO RICO. ATLANTIC... MID/UPPER LEVEL RIDGE OVER THE E UNITED STATES HAS MOVED INTO THE W ATLC TODAY NOW ROUGHLY HALFWAY BETWEEN BERMUDA AND THE E UNITED STATES COAST. A SHORTWAVE DISTURBANCE MOVING RAPIDLY EWD OVER THE SE UNITED IS SUPPORTING A LINE OF SHOWERS/THUNDERSTORMS OVER THE W ATLC FROM 30N73W TO THE FLORIDA STRAITS. ELSEWHERE...MODERATE SUBSIDENCE AND DRY AIR S OF 25N TO 35W PREVAILS. TROUGH OVER THE CENTRAL ATLC BETWEEN 30W-40W HAS BECOME NEGATIVELY TILTED ALLOWING MOST OF THE MID/UPPER LEVEL DYNAMICS TO LIFT JUST N OF THE AREA. ASSOCIATED SHOWERS/THUNDERSTORMS SKIRT THE N EXTENT OF THE AREA N OF 28N BETWEEN 30W-35W. OVER THE E ATLC...PERSISTENT TROUGH OVER W AFRICA FROM 25N5W TO 10N15W IS PRODUCING STRONG SUBSIDENCE OVER THE TRPCL E ATLC AND SW AFRICA. SLY FLOW AROUND W PERIPHERY OF RIDGE TO THE SOUTH OF THE TROUGH IS ADVECTING TRPCL MOISTURE NWD WITH A LARGE AREA OF MID/UPPER LEVEL CLOUDINESS S OF 10N. SURFACE SYNOPTIC FEATURES... COLD FRONT ENTERS THE GULF OF MEXICO OVER SE LOUISIANA AND EXTENDS SW ALONG 23N96W TO THE BAY OF CAMPECHE NEAR 19N96W THEN NW AND INLAND OVER MEXICO ON THE LEE SIDE OF THE SIERRA MADRE ORIENTAL MOUNTAINS. PRE-FRONTAL TROF LIES AHEAD OF THE COLD FRONT FROM THE W ATLC NEAR 30N77W SWD ACROSS S FLORIDA TO THE S GLFMEX NEAR 21N93W. A LINE OF SCATTERED TO LOCALLY NUMEROUS SHOWERS/THUNDERSTORMS IS WITHIN 100 NM AHEAD OF TROUGH E OF 85W. 1018 MB HIGH IS CENTERED OVER THE W ATLC NEAR 25N63W WITH RIDGE AXIS EXTENDING SW OVER E CUBA. CENTRAL ATLC COLD FRONT ENTERS AREA NEAR 31N36W SWD ALONG 24N43W TO 21N55W WHERE IT BECOMES DISSIPATING TO PUERTO RICO. WIDELY SCATTERED MODERATE CONVECTION N OF 28N BETWEEN 30W-35W. HIGH PRES RIDGE OVER THE E ATLC ALONG 30N21W TO 21N38W. SIGNIFICANT CLOUDS/CONVECTION... GULF OF MEXICO... SEE SURFACE SYNOPTIC FOR LINE OF SHOWERS/THUNDERSTORMS ALONG PRE-FRONTAL TROUGH. CARIBBEAN SEA... STRATOCUMULUS CLUSTERS AND RAIN SHOWERS FROM A DISSIPATING FRONT OVER THE ATLC ARE SKIRTING THE NE LEEWARD ISLANDS TROPICAL ATLANTIC... SEE ITCZ. SUBTROPICAL ATLANTIC... WIDELY SCATTERED MODERATE CONVECTION N OF 28N BETWEEN 30W-35W. $$ RHOME