000 AXNT20 KNHC 290006 AAA TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU SEP 28 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 2345 UTC. ...SPECIAL FEATURE... TROPICAL STORM ISAAC AT 28/2100 UTC WAS NEAR 28.9N 54.9W...OR ABOUT 550 NM EAST-SOUTHEAST OF BERMUDA. ISAAC IS MOVING TOWARD THE NORTH-NORTHWEST AT 7 KT AND A TURN TOWARD THE NORTHWEST IS EXPECTED LATER TONIGHT OR TOMORROW. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 40 KT WITH GUSTS TO 50 KT. SOME SLOW INCREASE IS STRENGTH IS FORECAST DURING THE NEXT 24 HOURS. PLEASE READ THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. A CLUSTER OF MODERATE CONVECTION IS MOSTLY N AND NW OF THE CENTER OF ISAAC FROM 29N-31N BETWEEN 54W-56W. ...TROPICAL WAVES... AN EASTERN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 25W SOUTH OF 22N MOVING WEST NEAR 10 KT. A 1011 MB LOW PRESSURE CENTER IS ALONG THE WAVE AXIS NEAR 15N...NEAR THE SW CAPE VERDE ISLANDS. A QUIKSCAT PASS AT 28/1930 UTC SUGGESTS THERE IS STILL A BROAD LOW PRESSURE AREA IN THIS REGION...THOUGH THE CONVECTION IS WELL NORTH OF THE AREA DUE TO SW SHEAR OVER THE SYSTEM. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 17N-23N BETWEEN 24W-29W. MINIMAL SHOWER/TSTM ACTIVITY IS NOTED WITHIN 200NM OF THE WAVE AXIS S OF 17N. A LOW AMPLITUDE ATLANTIC OCEAN TROPICAL WAVE IS ALONG 48W SOUTH OF 14N MOVING WEST 10-15 KT. THE SCATTERED MODERATE CONVECTION THAT WAS SURROUNDING 50W FROM 8N-13N THIS AFTERNOON HAS BEEN DIMINISHING TO ISOLATED SHOWERS/TSTMS OVER THE LAST FEW HOURS. A TROPICAL WAVE IS MOVING THROUGH THE LESSER ANTILLES ALONG 62W S OF 21N MOVING WEST 10-15 KT. A 1012 MB LOW IS ON THE WAVE AXIS NEAR 18N. THE ASSOCIATED SHOWER AND THUNDERSTORM ACTIVITY HAS DIMINISHED THIS AFTERNOON AND SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED AS IT MOVES WEST-NORTHWESTWARD. REGARDLESS OF DEVELOPMENT...SOME SHOWERS WILL LIKELY SPREAD ACROSS PORTIONS OF THE NORTHERN LEEWARD ISLANDS...THE VIRGIN ISLANDS...AND PUERTO RICO DURING THE NEXT COUPLE OF DAYS. ISOLATED MODERATE CONVECTION IS SEEN WITHIN 75NM OF THE WAVE AXIS. A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 84W SOUTH OF 22N MOVING WEST NEAR 10 KT. SCATTERED MODERATE CONVECTION IS AFFECTING NICARAGUA...HONDURAS...AND THE NW CARIBBEAN FROM 11N-21N BETWEEN 81W-86W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N14W 14N23W 12N30W 10N40 10N60W. BESIDES CONVECTION ASSOCIATED WITH TROPICAL WAVES...A CLUSTER OF NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS OVER AFRICA AND THE ADJACENT ATLANTIC WATERS FROM 10N-14N BETWEEN 12W-16W. ISOLATED MODERATE CONVECTION IS WITHIN 100NM OF THE AXIS BETWEEN 30W-45W. ...DISCUSSION... THE GULF OF MEXICO... A SLOW MOVING COLD FRONT EXTENDS FROM JUST BEYOND THE SE TIP OF FLORIDA TO THE SOUTH CENTRAL GULF OF MEXICO ALONG 25N80W 23N87W. SATELLITE AND AVAILABLE RADAR DATA SHOW VERY LITTLE CONVECTION ASSOCIATED WITH THE FRONT ASIDE FROM A FEW ISOLATED CELLS BETWEEN CENTRAL CUBA AND THE FLORIDA KEYS...MOSTLY AFFECTING THE FLORIDA STRAITS. HIGH CLOUDS ARE STREAMING TO THE NE ACROSS THE EASTERN GULF AND SOUTH CENTRAL FLORIDA ASSOCIATED WITH AN UPPER SW JET. IN FACT...CYCLONIC UPPER W/SW FLOW IS SEEN OVER MOST OF THE GULF THIS EVENING SOUTH OF A DEEP MID TO UPPER LEVEL TROUGH MOVING OVER THE EASTERN THIRD OF THE UNITED STATES. UPPER DIFFLUENCE BETWEEN THIS TROUGH AND RIDGING EXTENDING E THROUGH CENTRAL MEXICO HAS BEEN GENERATING A FEW ISOLATED SHOWERS IN THE WRN BAY OF CAMPECHE AND NE MEXICO THE LAST FEW HOURS. A 1017MB SURFACE HIGH IS LINGERING IN THE NW GULF NEAR 25N93W...WHILE A WEAK COLD FRONT IS BEGINNING TO MOVE INTO THE EXTREME NW GULF/COASTAL TEXAS. THIS FRONT WILL CONTINUE TO PUSH SLOWLY E/SE OVER THE NEXT 24HRS WITH A FEW ISOLATED SHOWERS/TSTMS POSSIBLE NEAR THE BOUNDARY...THOUGH CURRENTLY NOT MUCH SEEN IN THE MIDST OF DRY AIR AND MOST OF THE UPPER SUPPORT WELL NE OF THE AREA. THE CARIBBEAN SEA... MOST OF THE WEATHER IN THE CARIBBEAN TONIGHT IS ASSOCIATED WITH THE TROPICAL WAVES AS DESCRIBED ABOVE. THERE IS A BROAD UPPER HIGH CENTERED JUST NORTH OF PANAMA NEAR 11N79W THAT IS AFFECTING MUCH OF THE WESTERN CARIBBEAN SEA. THERE IS A MID TO UPPER LOW SEEN ON WV IMAGERY JUST SOUTH OF THE DOMINICAN REPUBLIC NEAR 17N71W...THAT HAS ISOLATED SHOWERS SPINNING CYCLONICALLY WITHIN 200NM OF ANY SIDE OF THE CENTER. 10 TO 20 KT TRADES PERSIST THIS EVENING WITH SW PORTION OF THE ATLC HIGH INTERACTING WITH LOWER PRESSURE NEAR THE COLOMBIAN COAST. THE ATLANTIC OCEAN... A SLOW MOVING COLD FRONT IS OVER THE W ATLC ALONG 30N76W 25N80W. ASSOCIATED CLOUDINESS WITH ISOLATED SHOWERS/TSTMS MOSTLY AHEAD OF THE FRONT ARE FROM 25N-30N BETWEEN 68W-80W...ALSO BEING SUPPORTED BY UPPER DIFFLUENCE BETWEEN AN UPPER RIDGE EXTENDING NE THROUGH THE SE BAHAMAS AND THE DEEP TROUGHING OVER THE EASTERN THIRD OF THE COUNTRY. THERE IS AN UPPER LOW VERY CLOSE TO TROPICAL STORM ISAAC NEAR 29N55W PRODUCING SOUTHERLY SHEAR OVER THE STORM. THERE IS A MID TO UPPER LEVEL ANTICYCLONE NE OF THE LEEWARD ISLANDS NEAR 24N51W. A WELL DEFINED UPPER LOW IS NEAR 24N31W IN THE ERN ATLC. SCATTERED MODERATE CONVECTION IS JUST E OF THIS UPPER LOW IN THE ERN ATLC FROM 17N-28N BETWEEN 21W-30W. THIS IS ASSOCIATED WITH UPPER DIFFLUENCE BETWEEN THE UPPER LOW TO THE W AND AN UPPER HIGH OVER WRN AFRICA...AND SOME ENHANCEMENT BY THE TROPICAL WAVE/LOW MOVING W/SW OF THE CAPE VERDE ISLANDS. ELSEWHERE AT THE SURFACE...A 1024MB HIGH IS AFFECTING PORTIONS OF THE REGION OUTSIDE OF THE TROPICAL WAVES...ISAAC...AND THE COLD FRONT...FROM ITS CENTER IN THE CENTRAL ATLANTIC NEAR 36N45W. A VERY SMALL LOW LEVEL VORTICITY MAXIMUM IS SEEN AS A SWIRL OF LOW CLOUDS WITH NO CONVECTION NEAR 23N67W...NORTH OF THE MONA PASSAGE. A SHIP REPORTED A 10 KT E WIND ABOUT 100 NM WSW OF THIS SWIRL...SO NO LOW HAS CURRENTLY BEEN ADDED FOR THIS FEATURE. $$ WILLIS