000WTNT44 KNHC 281459TCDAT4TROPICAL STORM ISAAC DISCUSSION NUMBER 30NWS NATIONAL HURRICANE CENTER MIAMI FL AL0920121000 AM CDT TUE AUG 28 2012REPORTS FROM AIR FORCE AND NOAA HURRICANE HUNTER AIRCRAFT INDICATETHE CENTRAL PRESSURE HAS DECREASED TO ABOUT 976 MB SINCE THEPREVIOUS ADVISORY...BUT IT HAS LEVELED OFF OVER THE PAST FEW HOURS.THE MAXIMUM 850 MB FLIGHT-LEVEL WIND OBSERVED HAS BEEN 89 KT...WHICH EQUATES TO A SURFACE WIND OF ABOUT 71 KT. HOWEVER...BIAS-ADJUSTED SFMR SURFACE WINDS HAVE ONLY BEEN AROUND 60-62 KT...WHICH CORRELATES WELL WITH DROPSONDE BOUNDARY LAYER-DERIVED SURFACEWINDS. AS SUCH...THE INTENSITY OF ISAAC IS BEING MAINTAINED AT 60KT...WHICH IS JUST BELOW HURRICANE STATUS.CENTER FIXES FROM THE AIRCRAFT INDICATE THAT ISAAC HAS BEEN WOBBLINGIN A GENERAL NORTHWESTWARD MOTION OF 310/09 KT. THERE REMAINS NOSIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. ISAAC IS FORECAST TO MOVE INTO A WEAKNESS IN THE SUBTROPICAL RIDGENEAR THE NORTH-CENTRAL GULF COAST OVER THE NEXT 24-36 HOURS...ACCOMPANIED BY A GRADUAL DECREASE IN THE FORWARD SPEED. AS THE RIDGE BUILDS BACK IN TO THE NORTH OF THE CYCLONE...ISAAC ISEXPECTED TO TURN A LITTLE MORE TOWARD THE WEST-NORTHWEST BEFORE ITTURNS NORTHWARD ON DAY 4...AND MOVES NORTHEASTWARD INTO THE OHIOVALLEY REGION ON DAY 5. THE OFFICIAL FORECAST TRACK HAS BEEN NUDGEDA LITTLE TO THE LEFT OF THE PREVIOUS ADVISORY TRACK AND LIES JUSTTO THE RIGHT OF THE CONSENSUS MODELS TV15 AND TCVA.MID-LEVEL DRY AIR ENTRAINMENT CONTINUES TO PLAGUE ISAAC. AS SOON ASTHE CYCLONE DEVELOPS INNER-CORE CONVECTION AND THE APPEARANCE OF ANEYE IN RADAR AND SATELLITE IMAGERY...THE CONVECTION ERODES DUE TOTHE DRY AIR. DESPITE THE FAVORABLE OCEANIC CONDITIONS ANDUPPER-LEVEL OUTFLOW REGIME...ISAAC ONLY HAS ABOUT 12-18 HOURS FORFURTHER STRENGTHENING TO OCCUR. THE OFFICIAL INTENSITY FORECAST ISSIMILAR TO THE PREVIOUS ADVISORY...WITH ONLY TIMING ADJUSTMENTSMADE TO THE INTENSITY FORECAST...AND CLOSELY FOLLOWS THE INTENSITYMODEL CONSENSUS.ISAAC IS A LARGE TROPICAL CYCLONE. A DANGEROUS STORM SURGE...HEAVYRAINFALL...AND STRONG WINDS EXTEND WELL AWAY FROM THE CENTER ANDARE EXPECTED TO AFFECT A LARGE PORTION OF THE NORTHERN GULF COAST.FOR THIS REASON...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT CENTERLOCATION. THE THREAT OF HEAVY RAINFALL AND FLOODING IS ALSOEXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY REGIONDURING THE NEXT FEW DAYS.FORECAST POSITIONS AND MAX WINDSINIT 28/1500Z 28.1N 88.5W 60 KT 70 MPH 12H 29/0000Z 28.8N 89.4W 70 KT 80 MPH 24H 29/1200Z 29.7N 90.4W 65 KT 75 MPH...INLAND 36H 30/0000Z 30.5N 91.5W 45 KT 50 MPH...INLAND 48H 30/1200Z 32.0N 92.0W 35 KT 40 MPH...INLAND 72H 31/1200Z 35.0N 92.5W 20 KT 25 MPH...INLAND 96H 01/1200Z 38.5N 90.5W 15 KT 15 MPH...POST-TROP/REMNT LOW120H 02/1200Z 41.0N 86.0W 15 KT 15 MPH...POST-TROP/REMNT LOW$$FORECASTER STEWART
000WTNT64 KNHC 281618TCUAT4HURRICANE ISAAC TROPICAL CYCLONE UPDATENWS NATIONAL HURRICANE CENTER MIAMI FL AL0920121120 AM CDT TUE AUG 28 2012...RECONNAISSANCE DATA INDICATE ISAAC FINALLY ACHIEVES HURRICANESTATUS...REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT MAXIMUM WINDS ASSOCIATED WITH ISAAC HAVE INCREASED TO 75 MPH...120 KM/H. ON THIS BASIS...ISAAC IS BEING UPGRADED TO A HURRICANE.SUMMARY OF 1120 AM CDT...1620 UTC...INFORMATION
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