000 AXNT20 KNHC 200546 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT THU SEP 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURE... A 1007 MB SURFACE LOW PRESSURE AREA ALONG THE COAST OF FLORIDA NEAR 28N81W AND AN UPPER-LEVEL LOW IN THE EASTERN GULF OF MEXICO ARE PRODUCING A LARGE AREA OF DISTURBED WEATHER OVER THE WESTERN ATLANTIC...THE CENTRAL AND NORTHWESTERN BAHAMAS... PORTIONS OF THE FLORIDA PENINSULA...AND THE EASTERN GULF MEXICO. THE SFC LOW IS MOVING SLOWLY WESTWARD ACROSS NORTH CENTRAL FLORIDA. HOWEVER...SATELLITE IMAGES INDICATE THAT THE SHOWER ACTIVITY REMAINS DISORGANIZED. SURFACE PRESSURES ARE STILL FALLING SHARPLY AND THE ENVIRONMENT IS GRADUALLY BECOMING FAVORABLE FOR A SUBTROPICAL OR TROPICAL CYCLONE TO FORM...AS THE SYSTEM MOVES WESTWARD INTO THE EASTERN GULF OF MEXICO TODAY. SHOWERS AND SQUALLS ASSOCIATED WITH THIS SYSTEM ARE EXPECTED TO SPREAD OVER PORTIONS OF FLORIDA DURING THE NEXT DAY OR TWO. THE SURFACE WINDS IN THE IMMEDIATE VICINITY OF THE LOW ARE NOT VERY STRONG...MOSTLY 15 KT OR LESS. STRONGER WINDS ARE DISPLACED FURTHER N OF THE LOW WHERE THE INTERACTION BETWEEN THE LOW ITSELF...STRONG CONTINENTAL HIGH PRESSURE CENTERED OVER NEW ENGLAND...AND A SLOW MOVING COASTAL WARM FRONT ARE PRODUCING 20-25 KT NE TO E WINDS OFF THE COAST OF SOUTH CAROLINA AND GEORGIA. MODERATE N TO NE WINDS OF 20 KT ARE ALSO BLOWING OVER THE NE CORNER OF THE GULF. ALL INTEREST ALONG THE NORTHERN GULF OF MEXICO COAST SHOULD MONITOR THE PROGRESS OF THIS WEATHER DISTURBANCE. ...TROPICAL WAVES... A NEW TROPICAL WAVE WILL BE ADDED TO THE 0600 UTC ANALYSIS/SFC MAP ALONG 2OW/21W BASED ON SATELLITE IMAGERY AND THE VERTICAL SOUNDING FROM DAKAR SENEGAL THAT SHOWED THE PASSAGE OF THE WAVE YESTERDAY. THE 20/00Z SOUNDING FROM SAL CAPE VERDE ISLANDS IS SHOWING NE WINDS OF 15 TO 20 KT AT LOW LEVEL INDICATING THE APPROACH OF THE WAVE. IN ADDITION...850 MB AND 700 MB MODEL GUIDANCE INDICATE THE WIND SHIFT ASSOCIATED WITH THE WAVE. ALSO...THE CIMSS VORTICITY PRODUCT PROVIDES SOME SUPPORT FOR THE WAVE POSITION INDICATED. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF THE AXIS FROM 11N-15N. A LOW AMPLITUDE TROPICAL WAVE IS OVER THE ATLC ALONG 32W S OF 15N MOVING W 10-15 KT. THIS WAVE STILL SHOWS UP WELL IN LOW LEVEL SATELLITE DERIVED WINDS AND VORTICITY...AND THE UW CIMSS TPW PRODUCTS. SCATTERED MODERATE CONVECTION IS SEEN NEAR THE INTERSECTION OF THE WAVE AND THE ITCZ. TROPICAL WAVE IS ALONG 56W/57W S OF 21N MOVING W NEAR 15 KT. THIS WAVE IS NOT VERY WELL ORGANIZED. ONLY ISOLATED SHOWERS ARE NEAR THE WAVE AXIS BETWEEN 15N-16N. A CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION REMAINS WITHIN 230 NM E OF THE NRN PORTION OF THE WAVE. THIS ACTIVITY IS BEING ENHANCED BY UPPER DIFFLUENCE. TROPICAL WAVE IS OVER THE YUCATAN PENINSULA AND BELIZE ALONG 88W S OF 21W MOVING W 10-15 KT. SHOWER ACTIVITY REMAINS LIMITED IN ASSOCIATION WITH THIS WAVE. THE WAVE...COUPLED WITH STRONG UPPER WLY FLOW IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE AREA. THESE WINDS ARE PUSHING THE STORM TOPS TO THE E. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N17W 10N25W 7N35W 6N45W 5N56W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVE... CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE FROM 5N-10N BETWEEN 34W-43W. DISCUSSION... GULF OF MEXICO... ATTENTION REMAINS FOCUSED ON A LARGE AREA OF DISTURBED WEATHER MOVING SLOWLY WESTWARD ACROSS NORTH-CENTRAL FLORIDA. THIS ACTIVITY IS ASSOCIATED WITH A WEAK SURFACE LOW PRES AREA AND A WELL DEFINED UPPER-LEVEL LOW LOCATED OVER THE ERN GULF NEAR 26N84W. A SWATH OF VERY DRY MID TO UPPER AIR CONTINUES TO WRAP AROUND THE PERIPHERY OF THIS FEATURE THROUGH THE MIDDLE GULF THEN SE TO FAR WRN CUBA AND NE ACROSS THE FLORIDA PENINSULA. HOWEVER...SCATTERED SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE SYSTEM ARE NOW AFFECTING THE ERN GULF FROM 25N-27N E OF 86W. A 1007 MB SURFACE LOW NEAR THE COAST OF E FLORIDA IS INTERACTING WITH THE UPPER LOW. SEE SPECIAL FEATURE SECTION ABOVE FOR MORE DETAILS. UPPER RIDGING DOMINATES THE FAR NW AND SW PORTIONS OF THE GULF WHILE ANOTHER UPPER LOW CONTINUES TO MOVE SLOWLY WWD ACROSS MEXICO. WIDELY SCATTERED SHOWERS ARE OBSERVED OVER THE WESTERN HALF OF THE GULF. ELSEWHERE AT THE SURFACE RIDGING DOMINATES N OF 25N FROM THE LARGE FALL-LIKE SURFACE HIGH EXTENDING FROM NEW ENGLAND JUST TO THE W OF THE APPALACHIAN MOUNTAINS. THIS IS PRODUCING MODERATE NE TO E WINDS OVER THE N GULF...WHILE LIGHTER MORE VARIABLE WINDS PERSIST FURTHER S AROUND TROUGHING. CARIBBEAN SEA... TONIGHT...CONVECTION CONTINUES TO FIRE UP OVER PARTS OF VENEZUELA AND NORTHERN COLOMBIA IN ASSOCIATION WITH THE ITCZ AND A DIFFLUENT PATTERN ALOFT. SCATTERED MODERATE CONVECTION IS ALSO SEEN OVER PARTS OF CENTRAL AMERICA AND THE YUCATAN PENINSULA DUE TO A TROPICAL WAVE LOCATED OVER THE YUCATAN PENINSULA/BELIZE. THE SURFACE PRES GRADIENT REMAINS FAIRLY RELAXED ACROSS THE AREA. THIS IS KEEPING THE TRADE WINDS MOSTLY LIGHT...EXCEPT SLIGHTLY STRONGER NEAR THE COAST OF COLOMBIA. EXTENSIVE WLY FLOW ALOFT IS OVER THE MAJORITY OF THE BASIN...WITH RIDGING OVER NORTHERN SOUTH AMERICA AND CENTRAL AMERICA. ATLANTIC OCEAN... SHOWERS AND THUNDERSTORM ACTIVITY CONTINUES OVER THE WRN ATLC AND THE BAHAMAS ASSOCIATED WITH A LARGE AREA OF DISTURBED WEATHER. SEE SPECIAL FEATURE ABOVE. CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE FOUND OVER THE CENTRAL ATLC FROM 16N-30N BETWEEN 42W-53W...WHICH IS IN A REGION OF PRONOUNCED UPPER DIFFLUENCE BETWEEN AN UPPER LOW NEAR 31N51W AND AN UPPER HIGH LOCATED EAST OF THE LESSER ANTILLES NEAR 15N55W. AN UPPER RIDGE EXTENDS FROM THIS HIGH N THROUGH THE CENTRAL ATLC ALONG 45W. THE NEXT WEATHER PRODUCER IS THE REMNANTS OF INGRID... ANALYZED AS A 1012 MB LOW NEAR 22N65W WITH A WEAK SURFACE TROUGH EXTENDING ALONG 65W FROM 20N-26N. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ASSOCIATED WITH THIS FEATURE. A WEAK 1016 MB SURFACE LOW IS NEAR 30N50W THAT HAS A TRAILING TROUGH EXTENDING SW TO NEAR 27N52W. ANOTHER UPPER LOW IS OVER THE E ATLC NEAR 30N25W. AN UPPER TROUGH EXTENDS FROM THIS LOW TO NEAR 17N37W. RIDGING DOMINATES THE TROPICAL ATLC. THE E ATLC SURFACE PATTERN CONTINUES TO BE DOMINATED BY RIDGING S OF A 1029 MB HIGH LOCATED N OF THE AZORES. THIS IS PRODUCING MODERATE NE TRADES E OF 35W...EXCEPT SLIGHTLY STRONG NEAR THE COAST OF NW AFRICA WHERE THE USUAL STRONGER GRADIENT EXISTS. $$ GR