000 AXNT20 KNHC 181802 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE SEP 18 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 1730 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 24W/25W S OF 16N MOVING W NEAR 15 KT. THIS WAVE WAS ADJUSTED SLIGHTLY TO THE W BASED ON THIS MORNINGS SOUNDING DATA FROM SAL...IN ADDITION TO METSAT-9 LOW TO MID LEVEL CLOUD DRIFT WINDS AND SATELLITE DERIVED 850 MB VORTICITY. SCATTERED MODERATE CONVECTION IS LOCATED NEAR THE INTERSECTION OF THE SRN PORTION OF THE WAVE AND THE ITCZ...WITHIN 180NM OF THE AXIS FROM 5N-9N. ANOTHER AREA OF SHOWERS/TSTMS HAS RACED AHEAD OF THE AXIS...WITH SCATTERED MODERATE ALSO FROM 5N-13N BETWEEN 27W-30W. TROPICAL WAVE IS ALONG 49W S OF 19N MOVING WEST NEAR 10-15 KT. A WEAK 1012 MB LOW IS ALONG THE WAVE AXIS NEAR 14N...BUT IS NOT WELL DEFINED AND MAY SOON BE DROPPED FROM THE ANALYSIS. SCATTERED MODERATE CONVECTION IS ALONG THE N PORTION OF THE AXIS FROM 15N-19N BETWEEN 46W-51W. OVERALL THOUGH...SHOWER ACTIVITY REMAINS LIMITED IN ASSOCIATION WITH THIS WAVE. UPPER-LEVEL WINDS ARE BECOMING LESS FAVORABLE...AND ANY DEVELOPMENT OF THIS SYSTEM IS EXPECTED TO BE SLOW TO OCCUR. TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 79W/80W S OF 20W MOVING W 10-15 KT. SHOWER ACTIVITY REMAINS LIMITED IN ASSOCIATION WITH THIS WAVE. HOWEVER...THE NRN PORTION OF THE WAVE SEEMS TO HAVE FRACTURED AND IS LIKELY ENHANCING THE ACTIVITY NEAR THE WRN BAHAMAS AND FLORIDA. PLEASE REFER TO ATLC SECTION FOR DETAILS ON THAT. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N15W 5N33W 14N46W 10N53W 9N62W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS FROM 5N-9N E OF 22W. DISCUSSION... GULF OF MEXICO... SFC RIDGING HAS BUILT INTO THE NE AND N CENTRAL GULF...PRODUCING MODERATE NE TO E WINDS GENERALLY N OF THE LINE 24N82W TO THE TEXAS/LOUISIANA BORDER NEAR 30N94W. SPEED CONVERGENCE DOWNSTREAM FROM THESE WINDS IS PRODUCING ISOLATED SHOWERS AND TSTMS WITHIN 60NM EITHER SIDE OF THE SAME LINE. BROAD...WEAK TROUGHING AND LIGHTER/MORE VARIABLE WINDS DOMINATE THE REMAINDER OF THE SFC PATTERN. THE WEAK TROUGHING IS HELPING TO SPARK THE SCATTERED SHOWERS/ISOLATED TSTMS NOTED BETWEEN THE NW TIP OF THE YUCATAN PENINSULA AND CORPUS CHRISTI. A WELL DEFINED UPPER LOW IS CUTTING OFF NEAR TAMPA FLORIDA. NLY UPPER FLOW W OF THIS SYSTEM IS ADVECTING VERY DRY AIR INTO THE ERN GULF. ANOTHER UPPER LOW OVER MEXICO NEAR 22N100W IS SPREADING MOISTURE N/NW THROUGH THE SW GULF/BAY OF CAMPECHE. THE MAIN FORECAST CHALLENGE OVER THE NEXT FEW DAYS WILL BE THE EXACT TIMING...TRACK...AND INTENSITY OF THE SFC LOW WHICH CURRENTLY APPEARS TO BE FORMING BETWEEN THE WRN BAHAMAS AND S FLORIDA. THIS SYSTEM HAS THE POTENTIAL FOR SUBTROPICAL OR TROPICAL CYCLONE FORMATION OVER THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD OVER FLORIDA AND INTO THE EASTERN GULF OF MEXICO. PLEASE CONTINUE TO MONITOR PRODUCTS FROM THE NATIONAL HURRICANE CENTER FOR UPDATES. CARIBBEAN SEA... OVERALL THE CARIBBEAN IS FAIRLY QUIET THIS AFTERNOON. A WEAK SFC TROUGH IS OVER THE FAR NW CARIBBEAN EXTENDING THROUGH THE YUCATAN CHANNEL TO THE GULF OF HONDURAS ALONG 86W FROM 17N-24N. THIS...ALONG WITH THE TROPICAL WAVE NEAR 80W IS PRODUCING ISOLATED SHOWERS/TSTMS IN THE NW CARIB N OF 15N W OF 80W. ANOTHER WEAK SFC TROUGH IS OVER THE NE PORTION OF THE BASIN EXTENDING S FROM THE REMNANT CIRCULATION ASSOCIATED WITH TROPICAL DEPRESSION INGRID IN THE ATLC ALONG 19N62W 14N63W. ISOLATED SHOWERS ARE WITHIN 120NM OF THIS TROUGHING. ALL OF THIS WEAK TROUGHING IS LEADING TO LIGHT TRADE WINDS...WHICH ARE EXPECTED TO STAY ON THE LIGHT SIDE OVER THE NEXT COUPLE OF DAYS EXCEPT FOR MORE TYPICAL MODERATE TRADES IN THE CENTRAL CARIBBEAN. THE UPPER PATTERN REMAINS DOMINATED BY TROUGHING OVER THE WRN PORTION WITH RIDGING E OF 70W. ATLANTIC OCEAN... A VERY COMPLEX AND MESSY WEATHER PATTERN IS AFFECTING THE WRN ATLC. THE SFC PATTERN CONSISTS OF AN OLD STATIONARY FRONT THAT ENTERS THE AREA NEAR 32N73W AND CONTINUES WSW TO NEAR 29N80W OR NEAR THE COAST OF CENTRAL FLORIDA. A SFC TROUGH...WHICH APPEARS TO BE ASSOCIATED THE N PORTION OF THE TROPICAL WAVE MOVING INTO THE WRN CARIBBEAN...ALSO EXTENDS THROUGH THE WRN BAHAMAS ALONG 28N77W 23N79W. FINALLY...A WELL DEFINED UPPER LOW IS CUTTING OFF NEAR TAMPA FLORIDA. ALL OF THIS IS LEADING TO NUMEROUS SHOWERS AND TSTMS N OF 23N W OF 72W TO THE COAST OF FLORIDA. IN ADDITION TO THE CONVECTIVE ACTIVITY...STRONG SFC HIGH PRESSURE BUILDING DOWN THE EASTERN SEABOARD IS PRODUCING MODERATE TO STRONG NE WINDS BEHIND THE FRONT. A LOW LEVEL VORTICITY MAXIMUM IS NOTED NEAR 26N79W...JUST OFFSHORE S FLORIDA. THIS SYSTEM HAS THE POTENTIAL FOR SUBTROPICAL OR TROPICAL CYCLONE FORMATION OVER THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD OVER FLORIDA AND INTO THE EASTERN GULF OF MEXICO. LOCALLY HEAVY RAINFALL IS POSSIBLE OVER PORTIONS OF THE FLORIDA PENINSULA AND THE BAHAMAS DURING THE NEXT DAY OR TWO. THE REMNANT CIRCULATION ASSOCIATED WITH TROPICAL DEPRESSION INGRID WAS ANALYZED AS 1012 MB NEAR 19N62W AT 18/1200 UTC BUT APPEARS TO BE MORE OF AN OPEN TROUGH NOW...AND WILL BE ANALYZED ACCORDINGLY ON THE 1800 UTC MAP. AN ELONGATED SFC TROUGH EXTENDS N/NE FROM THIS OLD CIRCULATION THROUGH 24N59W 29N51W. SCATTERED SHOWERS/ISOLATED TSTMS ARE GENERALLY WITHIN 210 NM E OF THIS TROUGHING WITH ACTIVITY MORE ISOLATED IN NATURE TO THE W OF THE TROUGH AXIS...WITH PERSISTENT W/SW SHEAR OVER THE AREA AHEAD OF UPPER TROUGHING. REDEVELOPMENT IS NOT EXPECTED DURING THE NEXT COUPLE OF DAYS AS THIS SYSTEM MOVES SLOWLY NORTHWESTWARD. THE REMAINDER OF THE E ATLC SFC PATTERN IS DOMINATED BY RIDGING...WITH MODERATE NE TRADES NOTED E OF 30W EXCEPT STRONGER PER USUAL NEAR THE COAST OF NW AFRICA WHERE A TIGHTER GRADIENT EXISTS. UPPER RIDGING GENERALLY ALONG 15N EXTENDS W FROM AFRICA OVER MUCH OF THE TROPICAL ATLC. UPPER WLY FLOW IS WIDESPREAD N OF THIS RIDGING OVER MUCH OF THE REMAINDER OF THE DISCUSSION AREA E OF 55W. $$ WILLIS