000 AXNT20 KNHC 201805 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURE... AS OF 1500 UTC...A 1008 MB SURFACE LOW PRESSURE AREA IS OVER THE EASTERN GULF NEAR 27N84W IN ASSOCIATION WITH AN UPPER-LEVEL LOW. SHOWER ACTIVITY WITH THIS NON-TROPICAL SYSTEM REMAINS LIMITED AND DISORGANIZED...WITH SCATTERED SHOWERS AND ISOLATED TSTMS GENERALLY N OF 24N BETWEEN 81W-87W. HOWEVER...THIS SYSTEM HAS THE POTENTIAL TO ACQUIRE SUBTROPICAL CHARACTERISTICS LATER TODAY OR TOMORROW AS IT MOVES WEST-NORTHWESTWARD OVER THE WARM WATERS OF THE GULF OF MEXICO. AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO MONITOR THE SYSTEM THIS AFTERNOON. ALL INTERESTS ALONG THE NORTHERN GULF COAST SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. AN EARLIER QUIKSCAT PASS AND THE SURROUNDING SURFACE OBSERVATIONS SHOW WINDS OF MOSTLY IN THE 15-25 KT OVER THE EASTERN GULF N OF 23N E OF 89W. THE LOW IS FORECAST TO MOVE NW TO A POSITION ABOUT 150 NM S OF PENSACOLA BY TOMORROW MORNING. ...TROPICAL WAVES... AN EAST ATLC TROPICAL WAVE IS ALONG 22W S OF 18N ESTIMATED TO BE MOVING W 10-15 KT. THIS WAVE SHOWS UP WELL IN BOTH CONVENTIONAL AND DERIVED SATELLITE PRODUCTS...AND WAS EVIDENT IN RECENT SOUNDING DATA FROM DAKAR. THE ASSOCIATED SHOWER ACTIVITY REMAINS DISORGANIZED...WITH SCATTERED CLUSTERS OF MODERATE CONVECTION NOTED WITHIN 120NM E AND 60NM W OF THE AXIS. A LOW AMPLITUDE TROPICAL WAVE IS OVER THE ATLC ALONG 34W 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 S PORTION OF THE WAVE AND THE ITCZ FROM 7N-11N BETWEEN 31W-38W. TROPICAL WAVE IS ALONG 61W/62W S OF 14N ESTIMATED TO BE MOVING W CLOSER TO 15-20 KT NOW. THIS WAVE HAS BECOME INCREASINGLY DIFFICULT TO TRACK OVER THE LAST 24 HOURS. IT APPEARS AS IF A GOOD PORTION OF THE ASSOCIATED VORTICITY AND MOISTURE HAS BECOME DETACHED FURTHER NE...WHERE THE ENERGY ROUNDED THE E ATLC RIDGING AND IS BECOMING ABSORBED INTO A BROADER FRONTAL TROUGH OVER THE CENTRAL ATLC. HOWEVER...IT IS STILL POSSIBLE TO LOCATE A LOW AMPLITUDE SURGE OF MOISTURE MOVING QUICKLY WWD THROUGH THE SE CARIBBEAN VIA THE UW-CIMSS TPW PRODUCT. BASED ON THIS...THE AXIS MAY NEED TO BE ADJUSTED FURTHER W AGAIN ON FUTURE MAPS. OVERALL THOUGH...I HAVE LOW CONFIDENCE ON THIS WAVE THAT APPEARS TO HAVE DAMPENED A BIT. TROPICAL WAVE IS OVER THE YUCATAN PENINSULA AND GUATEMALA ALONG 91W S OF 21W MOVING W 10-15 KT. SHOWER ACTIVITY REMAINS LIMITED IN ASSOCIATION WITH THIS WAVE...AND THE POSN IS BASED MOSTLY ON CONTINUITY. MORE INFO ON THIS FEATURE CAN BE FOUND UNDER THE PACIFIC DISCUSSION UNDER AWIPS/WMO HEADER MIATWDEP/AXPZ20 KNHC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 13N16W 9N32W 7N40W 5N53W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS WITHIN 120NM EITHER SIDE OF THE AXIS BETWEEN 38W-42W. ISOLATED MODERATE IS WITHIN 120NM N E OF 42W. DISCUSSION... GULF OF MEXICO... ATTENTION REMAINS FOCUSED ON THE DEEP LAYER LOW IN THE ERN GULF...SEE SPECIAL FEATURE FOR MORE DETAILS. THE ASSOCIATED DISORGANIZED SHOWER ACTIVITY IS GENERALLY N OF 24N E OF 86W. A SWATH OF VERY DRY MID TO UPPER AIR CONTINUES TO WRAP AROUND THE PERIPHERY OF THE UPPER-LEVEL LOW THROUGH THE MIDDLE AND WESTERN GULF THEN E TO NE ACROSS WRN CUBA AND THE STRAITS OF FLORIDA. UPPER RIDGING DOMINATES THE FAR NW AND SW PORTIONS OF THE GULF WHILE A WEAKENING UPPER LOW CONTINUES TO MOVE SLOWLY OVER MEXICO NEAR 22N101W. DIFFLUENCE BETWEEN THESE FEATURES IS SUPPORTING A FEW ISOLATED SHOWERS IN THE FAR WRN GULF MAINLY W OF 94W. ELSEWHERE AT THE SURFACE RIDGING DOMINATES THE SE US AND THE NW GULF WITH WEAK TROUGHING ELSEWHERE. CARIBBEAN SEA... SCATTERED SHOWERS AND ISOLATED TSTMS ARE AFFECTING THE WRN CARIBBEAN BETWEEN 76W-85W...MOST CONCENTRATED WITHIN 60NM OF 13N79W. THIS ACTIVITY IS ASSOCIATED WITH DIFFLUENT FLOW ALOFT AROUND UPPER RIDGING EXTENDING E FROM CENTRAL AMERICA...IN ADDITION TO LOW LEVEL CONFLUENCE IN THE VICINITY. WLY FLOW ALOFT N OF THE UPPER RIDGING IS STRETCHING THE ASSOCIATED CLOUD TOPS EWD N OF 15N. DRIER MID TO UPPER AIR AND BROAD TROUGHING ARE OVER THE E CARIBBEAN...S OF THE UPPER LOW NNW OF PUERTO RICO. THE SURFACE PRES GRADIENT REMAINS FAIRLY RELAXED ACROSS THE AREA...DUE TO THE LOW IN THE ERN GULF AND WEAK TROUGHING IN THE WRN ATLC. THIS IS KEEPING THE TRADE WINDS MOSTLY LIGHT...EXCEPT SLIGHTLY STRONGER NEAR THE COAST OF COLOMBIA. LIGHT TO MODERATE TRADES TO PERSIST THROUGH FRI WHILE SHOWER ACTIVITY REMAINS FOCUSED MOSTLY IN THE WRN CARIB. ATLANTIC OCEAN... SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE OVER THE WRN ATLC AND BAHAMAS E OF 72W ASSOCIATED WITH THE MOIST AND UNSTABLE ENVIRONMENT E OF THE SPECIAL FEATURE IN THE GULF...AND S OF THE STATIONARY COASTAL FRONT JUST OFFSHORE THE CAROLINAS THROUGH N FLORIDA. THE UPPER PATTERN OVER THIS AREA REMAINS VERY DIFFLUENT BETWEEN THE UPPER LOW OVER THE ERN GULF AND AN UPPER HIGH NEAR 29N72W. THE REMAINS OF INGRID HAVE CONTINUED TO FIZZLE TODAY...WITH A LINGERING WEAK SFC TROUGH NOW ALONG 26N63W 21N67W. THIS FEATURE IS INTERACTING WITH THE UPPER LOW JUST TO ITS NW NEAR 22N68W TO PRODUCE ISOLATED SHOWERS AND TSTMS S OF 25N BETWEEN 60W-69W...MOST CONCENTRATED JUST N OF THE MONA PASSAGE. THE CENTRAL ATLC SFC PATTERN IS DOMINATED BY A 1012 MB LOW NEAR 32N49W THAT HAS A TRAILING TROUGH EXTENDING SSW THROUGH 24N52W 16N55W. THIS...ALONG WITH ITS SUPPORTING UPPER LOW NEAR 32N48W...ARE GENERATING CLOUDINESS AND SCATTERED SHOWERS FROM 15N-23N BETWEEN 49W-55W AND ALSO N OF 21N BETWEEN 41W-49W. THE REMAINDER OF THE E ATLC IS DOMINATED BY TYPICAL SFC RIDGING S OF A 1027 MB HIGH E OF THE AZORES NEAR 40N23W. THIS IS PRODUCING MODERATE NE TRADES E OF 35W...EXCEPT STRONGER PER USUAL ALONG THE COAST OF NW AFRICA WHERE A TIGHTER GRADIENT EXISTS. A BENIGN UPPER LOW IS NEAR 29N27W WHILE UPPER RIDGING GENERALLY DOMINATES THE REMAINDER OF THE E AND TROPICAL ATLC. WEAK SFC RIDGING WILL GRADUALLY TAKE OVER THE WRN ATLC OVER THE NEXT COUPLE OF DAYS AS THE LOW IN THE GULF MOVES NW TOWARDS THE NRN GULF COAST. STRONGER RIDGING WILL CONTINUE TO SIT OVER THE E ATLC. CONFLUENCE BETWEEN THE SFC RIDGES WILL ALLOW BROAD TROUGHING AND SCATTERED SHOWER ACTIVITY TO PERSIST OVER PARTS OF THE CENTRAL ATLC MAINLY N OF 18N. $$ WILLIS