000 AXNT20 KNHC 201755 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT SEP 20 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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 FEATURES... TROPICAL WAVE IS ALONG 66W S OF 19N MOVING W NEAR 10 KT. THIS WAVE IS EMBEDDED WITHIN A BROAD AREA OF LOWER PRESSURE ACROSS THE E CARIBBEAN AND IS GENERATING A LARGE AREA OF CLOUDINESS WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM THE WAVE AXIS ACROSS THE LESSER ANTILLES. THIS SYSTEM IS SHOWING SIGNS OF IMPROVED ORGANIZATION TODAY AND UPPER-LEVEL WINDS ARE EXPECTED TO BECOME SOMEWHAT MORE FAVORABLE OVER THE NEXT COUPLE DAYS FOR SOME ADDITIONAL DEVELOPMENT TO OCCUR. ...TROPICAL WAVES... TROPICAL WAVE WAS INTRODUCED ALONG 20W/21W S OF 10N MOVING W NEAR 10-15 KT BASED ON THE SATELLITE IMAGERY AND A RECENT PASS OF QUIKSCAT. A LOWER TO MID LEVEL LOW IS ALONG THE WAVE NEAR 5N. BROAD AREA OF CLOUDINESS WITH EMBEDDED SHOWERS COVERS THE AREA FROM THE EQUATOR TO 13N BETWEEN 16W-24W. TROPICAL WAVE WAS RELOCATED FROM 30W TO ALONG 36W FROM 12N-18N BASED ON LONG-TERM SATELLITE IMAGES MOVING W 10-15 KT. WEAK AND SMALL AREA OF INVERTED-V CURVATURE IS OBSERVED BETWEEN 14N-18N. WAVE IS EMBEDDED WITHIN A RATHER DRY AIR...THUS NO ASSOCIATED SHOWER ACTIVITY. TROPICAL WAVE IS ALONG 53W/54W S OF 18N MOVING W 10-15 KT. WAVE IS BENEATH AN UPPER RIDGE PROVIDING UPPER LEVEL DIFFLUENCE MASKING THE SATELLITE SIGNATURE AND ENHANCING AN AREA OF CLOUDINESS WITH SCATTERED SHOWERS WITHIN 120 NM OF LINE FROM 20N46W ACROSS THE WAVE TO NEAR 14N55W. TROPICAL WAVE IS ALONG 79W S OF 19N MOVING W 10-15 KT. WELL DEFINED INVERTED-V CURVATURE S OF JAMAICA WITH CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION S OF 16N TO INLAND OVER SOUTH AND CENTRAL AMERICA BETWEEN 74W-84W. ...THE ITCZ... ITCZ AXIS IS ANALYZED ALONG 8N12W 8N19W 5N25W 7N37W 7N50W 9N59W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 2N-10N BETWEEN 26W-31W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH EXTENDS OFF THE COAST OF TEXAS AND MEXICO FROM 28N96W 24N97W TO THE BAY OF CAMPECHE NEAR 20N95W. A BROAD UPPER LEVEL RIDGE DOMINATES THE GULF ANCHORED OVER S/CENTRAL MEXICO EXTENDING NE JUST N OF VERACRUZ TO OVER THE FLORIDA PENINSULA NEAR NAPLES AND COUPLED WITH THE SURFACE TROUGH IS PRODUCING WIDESPREAD CLOUDINESS WITH CLUSTERS OF SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS N OF 22N BETWEEN 87W-93W AND W OF 93W INTO THE BAY OF CAMPECHE. A SURFACE RIDGE COVERS THE US TO THE N GULF COAST STATES. THE SURFACE TROUGH IS EXPECTED TO SLOWLY WEAKEN AND DRIFT W THROUGH SUN AS THE SURFACE RIDGE WILL STRENGTHEN DURING THE FIRST OF THE WORKWEEK. CARIBBEAN SEA... THE TROPICAL WAVE IN THE E CARIBBEAN IS BECOMING AN AREA TO WATCH AS SLOW DEVELOPMENT COULD OCCUR OVER THE NEXT FEW DAYS. SEE SPECIAL FEATURES ABOVE. THE W CARIBBEAN TROPICAL WAVE CONTINUES TO GENERATE PLENTY OF ACTIVITY BUT DEVELOPMENT IS NOT EXPECTED. THE UPPER LEVEL ARE DOMINATED BY THE UPPER RIDGE OVER THE GULF TO THE W AND A SECOND UPPER RIDGE ANCHORED OVER SOUTH AMERICA EXTENDING NE ACROSS THE ABC ISLANDS INTO THE W TROPICAL ATLC OVER THE LEEWARD ISLANDS. BETWEEN THESE UPPER RIDGES IS AN UPPER TROUGH EXTENDING FROM THE W ATLC ACROSS CENTRAL CUBA S TO PANAMA. THE UPPER LEVEL FEATURES ARE ENHANCING THE ACTIVITY ASSOCIATED WITH BOTH TROPICAL WAVES WHILE THE REMAINDER OF THE CARIBBEAN IS ENJOYING FAIR WEATHER THIS AFTERNOON. ATLANTIC OCEAN... A NARROW UPPER TROUGH IS OVER THE FAR W ATLC EXTENDING THROUGH 32N78W ACROSS CENTRAL CUBA AND OVER THE CARIBBEAN. A SURFACE TROUGH ENTERS THE W ATLC FROM A 1016 MB LOW N OF THE REGION THROUGH 32N73W OVER THE N BAHAMA ISLANDS TO NEAR 24N79W. ISOLATED SHOWERS ARE WITHIN 200 NM E OF THE SURFACE TROUGH WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OFF THE COAST OF NE FLORIDA AND GEORGIA FROM 29N-33N BETWEEN 76W-81W. A PAIR OF BENIGN UPPER LOWS ARE TO THE E CENTERED NEAR 27N46W AND 23N66W. THE UPPER RIDGE OVER THE E CARIBBEAN EXTENDS OVER THE W TROPICAL ATLC ACROSS THE LEEWARD ISLANDS TO 18N50W. AN UPPER TROUGH IS OVER THE NE ATLC EXTENDING FROM A DEEP LAYERED LOW N OF THE REGION TO 24N E OF 30W TO OVER THE CANARY ISLANDS. A SURFACE TROUGH ENTERS THE E ATLC NEAR 32N20W EXTENDING TO 27N26W BUT AS THIS SYSTEM IS IN AN AREA OF DRY STABLE AIR...THUS NO SHOWER ACTIVITY. THE TYPICAL E/W UPPER RIDGE DOMINATES THE REMAINDER OF THE TROPICAL ATLC TO 43W S OF THE UPPER TROUGH MENTIONED ABOVE. OTHERWISE THE ATLC IS DOMINATED BY A WEAK BUT BROAD SURFACE RIDGE BETWEEN 28W-65W ANCHORED BY A 1023 MB HIGH NEAR 32N41W. $$ WALLACE