000 AXNT20 KNHC 302324 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT SEP 30 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...SPECIAL FEATURES... HURRICANE ISAAC IS CENTERED NEAR 31.6N 59.5W AT 30/2100 UTC MOVING NORTHWEST AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED WIND SPEED IS 70 KT WITH GUSTS TO 85 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. THE EYE HAS BECOME BETTER DEFINED OVER PAST FEW HOURS HAS THE WINDS HAVE INCREASED. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 30N-34N BETWEEN 58W-62W. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 36W S OF 22N MOVING W 15 KT. WEAK INVERTED-V SIGNATURE WITH A SMALL LOW LEVEL SWIRL ALONG THE N PORTION OF THE WAVE AXIS. WAVE IS EMBEDDED WITHIN DRY AIR...THUS NO SHOWERS/CONVECTION NOTED. TROPICAL WAVE IS ALONG 62W/63W S OF 18N MOVING W 15 KT. WAVE HAS PASSED THE LESSER ANTILLES MASKING THE TYPICAL INVERTED-V SIGNATURE. CONVECTION IN THE AREA IS ASSOCIATED WITH UPPER LEVEL FEATURES. TROPICAL WAVE IS ALONG 72W MOVING W AT 15 KT. WEAK WAVE INVERTED-V SIGNATURE WITH AFTERNOON THUNDERSTORMS FIRING UP OVER HISPANIOLA IN RESPONSE TO THE PASSING OF THE WAVE AXIS AND DEEP CONVECTION IS INLAND OVER COLOMBIA. TROPICAL WAVE IS ALONG 95W/96W OVER S MEXICO AND THE E PACIFIC REGION WITH SCATTERED SHOWERS EXTENDING OVER THE BAY OF CAMPECHE S OF 20N FROM 93W-95W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N14W 7N23W 8N43W 10N62W. SCATTERED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 2N-10N BETWEEN 14W-35W. ...DISCUSSION... GULF OF MEXICO... DEEP LAYERED TROUGH COVERS THE E HALF OF THE US INTO THE GULF N OF 26N WITH THE LEADING EDGE OF THE UPPER TROUGH AND ASSOCIATED FRONTAL BOUNDARY IN THE W ATLC. A SHORTWAVE TROUGH AND SECOND FRONTAL BOUNDARY ARE MOVING THROUGH THE UPPER MISSISSIPPI VALLEY. BROAD UPPER RIDGE ANCHORED OVER CENTRAL AMERICA AND IN THE E PACIFIC REGION COVERS THE REMAINDER OF THE S GULF. A SURFACE RIDGE EXTENDS FROM THE NW ATLC ALONG THE US E COAST COVERS THE GULF WITH A 1020 MB HIGH SITUATED OVER THE MISSISSIPPI DELTA. THIS IS GIVING THE ENTIRE GULF FAIR CONDITIONS THIS EVENING. CARIBBEAN SEA... BROAD UPPER RIDGE ANCHORED OVER CENTRAL AMERICA AND IN THE E PACIFIC REGION COVERS THE W CARIBBEAN W OF 73W WITH AN EXTENSION OF THE RIDGE EXTENDING ACROSS E CUBA INTO THE W ATLC. HEAVY SHOWERS/SCATTERED THUNDERSTORMS COVER MUCH OF CUBA AND THE SURROUNDING AREA INCLUDING JAMAICA AND THE CAYMAN ISLANDS WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE REMAINDER OF THE NW CARIBBEAN. A 1008 MB LOW IS IN THE SW CARIBBEAN NEAR 11N79W AND WITH THE ITCZ AXIS THAT CROSSES INTO THE E PACIFIC REGION IN THE VICINITY ARE GENERATING SCATTERED MODERATE/ ISOLATED STRONG CONVECTION S OF 12N FROM COLOMBIA TO CENTRAL AMERICA. AN UPPER LOW IN THE NE CARIBBEAN IS S OF THE MONA PASSAGE NEAR 16N68W COVERING THE REMAINDER OF THE CARIBBEAN WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 15N BETWEEN 60W-68W INCLUDING THE WINDWARD ISLANDS. ATLANTIC OCEAN... DEEP LAYERED TROUGH OVER THE E US EXTENDS INTO THE W ATLC W OF 73W WITH THE ASSOCIATED COLD FRONT ENTERING THE AREA NEAR 32N68W SW TO THE SE FLORIDA COAST NEAR MIAMI. A SURFACE PRE-FRONTAL TROUGH EXTENDS FROM 26N74W ACROSS THE BAHAMAS TO OVER CENTRAL CUBA. SCATTERED SHOWERS/THUNDERSTORMS COVER THE W ATLC W OF A LINE FROM THE WINDWARD PASSAGE TO BEYOND 32N67W AND E OF 79W WITH THE EXCEPTION OF SOME ISOLATED SHOWERS IN THE STRAITS OF FLORIDA. JUST TO THE E IS A SURFACE TROUGH...PREVIOUSLY THE N PORTION OF A TROPICAL WAVE IN THE CARIBBEAN...EXTENDS FROM 25N65W TO THE N COAST OF THE DOMINICAN REPUBLIC NEAR 19N69W WITH ISOLATED SHOWERS FROM 22N-26N BETWEEN 62W 68W. A CUT-OFF UPPER LOW IS IN THE CENTRAL ATLC NEAR 20N46W DRIFTING WESTWARD FROM THE UPPER TROUGH IN THE E ATLC THAT IS N OF 20N FROM 27W-41W. A WEAK SURFACE REFLECTION IN THE FORM OF A SURFACE TROUGH EXTENDS FROM 26N45W-19N48W. HOWEVER...THE ENTIRE AREA FROM 30-60W IS RATHER DRY THUS NO SHOWERS OR CONVECTION. BROAD UPPER RIDGE COVERS THE E ATLC E OF 27W WITH A 1019 MB HIGH CENTERED W OF THE CANARY ISLANDS NEAR 29N25W. DIFFLUENCE BETWEEN THE UPPER TROUGH OF THE NE ATLC AND THE UPPER RIDGE IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 26N FROM 25W-31W. $$ WALLACE