000 AXNT20 KNHC 181757 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU SEP 18 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 1645 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS OVER THE CAPE VERDE ISLANDS ALONG 24W/25W S OF 17N MOVING W NEAR 10 KT. A LOW/MID LEVEL LOW IS OVER THE CAPE VERDE ISLANDS WITH THE WAVE EMBEDDED WITHIN AN AREA OF DEEP LAYERED MOISTURE AS INDICATED BY THE MIMIC TPW ANIMATION. HOWEVER...THE AREA LACKS ANY ASSOCIATED DEEP CONVECTION OR SHOWERS. TROPICAL WAVE IS ALONG 44W/45W S OF 19N MOVING WNW NEAR 10 KT. MID LEVEL LOW IS ALONG THE WAVE AXIS NEAR 17N. THIS WAVE IS EMBEDDED WITHIN AN AREA OF DRY SOMEWHAT STABLE AIR...THUS NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE AS ADDED TO THE 1200 UTC ANALYSIS BASED ON A LONG-TERM SATELLITE LOOP ALONG 62W S OF 20N MOVING W NEAR 10 KT. AN UPPER TROUGH IS TO THE W OF THE WAVE AND AN UPPER RIDGE TO THE E IS GREATLY ENHANCING THE ACTIVITY ASSOCIATED WITH THIS WAVE. BROAD AREA OF SCATTERED MODERATE TO SCATTERED STRONG CONVECTION COVERS THE AREA FROM 12N-19N BETWEEN 57W-64W INCLUDING THE LESSER ANTILLES. TROPICAL WAVE IS ALONG 71W/72W S OF 19N MOVING W NEAR 15 KT. AN UPPER RIDGE IS JUST TO THE W OF THE WAVE AXIS ENHANCING CONVECTION ASSOCIATED WITH THIS WAVE. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE OVER THE CENTRAL CARIBBEAN FROM 11N-18N BETWEEN 70W-77W. TROPICAL WAVE IS ALONG 88W S OF 22N MOVING W 10-15 KT. WAVE IS ALONG THE COAST OF YUCATAN PENINSULA WITH ANY ASSOCIATED CONVECTION INLAND OVER CENTRAL AMERICA AND THE E PACIFIC REGION. ...THE ITCZ... ITCZ AXIS IS ANALYZED ALONG 16N16W 8N29W 11N48W 13N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150 NM N OF THE ITCZ FROM 53W-57W AND WITHIN 90/120 NM S OF THE ITCZ FROM 52W-58W. AN UPPER RIDGE COVERS THE LESSER ANTILLES AND FAR E CARIBBEAN INTO THE W TROPICAL ATLC PROVIDING UPPER LEVEL DIFFLUENCE ENHANCING THIS CONVECTION. ...DISCUSSION... GULF OF MEXICO... A WEAK STATIONARY FRONT EXTENDS FROM NEAR TAMPA FLORIDA TO 27N92.5W. SOUTH OF THIS POINT...A WARM FRONT EXTENDS S TO 1012 MB LOW AT 21.5N96W...WITH A STATIONARY FRONT STRETCHING SE FROM THE LOW TO 18.5N94.5W. THESE FEATURES ARE RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS OVER THE W GULF S OF THE FRONT TO 90W. AN UPPER LEVEL TROUGH ASSOCIATED WITH THE FRONT IS SLIPPING S ACROSS THE NE GULF...WITH DRY AIR DROPPING S TO NEAR TAMPA FLORIDA E OF 88W. INSTABILITY NEAR THE TROUGH AXIS IS PRODUCING ISOLATED SHOWERS AND THUNDERSTORMS OVER THE FAR NE GULF. AN UPPER LEVEL RIDGE EXTENDING FROM AN UPPER HIGH NEAR 20.5N97W COVERS THE S GULF. UPPER LEVEL DIFFLUENCE E OF THE HIGH IS FURTHER AIDING SCATTERED MODERATE CONVECTION IN THE BAY OF CAMPECHE. ACROSS THE SE GULF...MAINLY FAIR WEATHER UNDER THE INFLUENCE OF CONFLUENT NORTHWESTERLY FLOW ALOFT. THE SURFACE LOW IS EXPECTED TO DRIFT NORTHWARD AS THE FRONT BEGINS TO DISSIPATE INTO THE WEEKEND. CARIBBEAN SEA... TWO TROPICAL WAVES ARE OVER THE CARIBBEAN SEA AND CENTRAL AMERICA. SEE ABOVE. DIFFLUENCE IN NORTHERLY FLOW ALOFT IN THE S CARIBBEAN IS GENERATING SEVERAL CLUSTERS OF MODERATE WITH ISOLATED STRONG CONVECTION S OF 17N W OF 77W TO INLAND OVER CENTRAL AMERICA. A WEAK 1010 MB LOW HAS FORMED OVER PANAMA NEAR 9.5N79.5W...WHICH IS FURTHER AIDING THE CONVECTION NEAR PANAMA. FURTHERMORE...AN UPPER LEVEL TROUGH EXTENDS FROM AN UPPER LOW OVER PUERTO RICO TO VENEZUELA NEAR THE ABC ISLANDS AND IS ENHANCING CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 62W...AFFECTING MUCH OF THE LESSER ANTILLES. AN UPPER RIDGE COVERS THE FAR E CARIBBEAN INTO THE W ATLC ANCHORED NEAR TRINIDAD. MOSTLY FAIR WEATHER IS OCCURRING ACROSS THE NORTHWEST CARIBBEAN WHERE DRY AIR IN NORTHERLY FLOW ALOFT PREDOMINATES. ATLANTIC OCEAN... TWO TROPICAL WAVES ARE OVER THE ATLANTIC OCEAN WITH NO ASSOCIATED CONVECTION. SEE ABOVE. A COLD FRONT EXTENDS SW FROM A 1014 MB LOW NEAR 32.5N74W ACROSS FLORIDA NEAR MELBOURNE INTO THE GULF AS STATIONARY BOUNDARY. A WEAK SURFACE TROUGH EXTENDS FROM 30.5N69W TO 25.5N73.5W. THESE FEATURES ARE RESULTING IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE W ATLC... W OF LINE FROM 30N68W TO THE N CUBA COAST NEAR 21N77W INCLUDING THE N BAHAMA ISLANDS AND THE FLORIDA PENINSULA. MOIST SOUTHWESTERLY FLOW ALOFT AHEAD OF AN UPPER LEVEL TROUGH ASSOCIATED WITH THE FRONT IS OVER THE E CONUS COAST AND IS FURTHER AIDING THIS ACTIVITY. A SURFACE RIDGE EXTENDING SOUTHWESTWARD FROM A 1023 MB HIGH IN THE N/CENTRAL ATLC IS BRINGING FAIR WEATHER TO MUCH OF THE AREA. AN UPPER LEVEL LOW NEAR 22.5N41.5W AND ASSOCIATED SURFACE TROUGH FROM 32N40W TO 29N42.5W TO 27N47W ARE GENERATING CLOUDINESS OVER PORTIONS OF THE CENTRAL ATLANTIC WITH POSSIBLE ISOLATED SHOWERS. AN UPPER LEVEL TROUGH OVER THE NE ATLC IS GENERATING CLOUDS AND SCATTERED SHOWERS N OF 27N AND E OF 20W TO OVER THE CANARY ISLANDS. THE TYPICAL LARGE E/W UPPER LEVEL RIDGE IS ACROSS THE REMAINDER OF THE TROPICAL ATLC BRINGING FAIR WEATHER TO THE CENTRAL AND E TROPICAL ATLC. $$ COHEN/WALLACE