10:00 PM CDT Tue Aug 28

Location: 29.0°N 89.7°W

Moving: NW at 8 mph

Min pressure: 968 mb

Max sustained: 80 mph

 

HURRICANE ISAAC DISCUSSION NUMBER  32

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012

1000 PM CDT TUE AUG 28 2012

 

ISAAC PASSED OVER THE MISSISSIPPI RIVER DELTA IN EXTREME SOUTHEAST

LOUISIANA AROUND 2345 UTC.  SINCE THAT TIME…THE CENTER HAS

WOBBLED WESTWARD AND HAS MOVED BACK OVER WATER. A NORTHWESTWARD MOTION HAS RECENTLY RESUMED AND A SECOND LANDFALL SHOULD OCCUR LATER TONIGHT NEAR GRAND ISLE.  DATA FROM NOAA AND AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE MINIMUM

PRESSURE HAS CONTINUED TO GRADUALLY FALL AND IS NOW 968 MB. THE AIR

FORCE RESERVE AIRCRAFT HAS MEASURED A PEAK 850-MB FLIGHT-LEVEL WIND

OF 96 KT AND BIAS-CORRECTED SFMR WINDS OF AROUND 65 KT.  BASED ON

THESE DATA…THE INITIAL INTENSITY REMAINS 70 KT.  LITTLE CHANGE IN

STRENGTH IS EXPECTED DURING THE NEXT 12 HOURS OR SO AS THE CENTER

MOVES ACROSS THE BAYOUS OF SOUTHEASTERN LOUISIANA.  STEADY

WEAKENING SHOULD COMMENCE LATER WEDNESDAY AS THE CENTER MOVES

FARTHER INLAND.

 

SMOOTHING THROUGH THE WOBBLES DURING THE PAST FEW HOURS…THE LONGER TERM MOTION ESTIMATE IS 310/7 KT.  ISAAC IS EXPECTED TO MOVE SLOWLY NORTHWESTWARD DURING THE NEXT 24 TO 36 HOURS AS A MID-LEVEL RIDGE TO THE NORTHWEST OF THE CYCLONE SLIDES EASTWARD.  AS THE RIDGE MOVES ACROSS THE OHIO VALLEY AND INTO THE MID-ATLANTIC REGION…THIS

SHOULD CAUSE ISAAC TO TURN NORTH-NORTHWESTWARD AND NORTHWARD IN A COUPLE OF DAYS.  AFTER THAT TIME…THE CYCLONE IS EXPECTED TO TURN

NORTHEASTWARD AS IT ENTERS THE MID-LATITUDE WESTERLY FLOW.  THE

GLOBAL MODEL GUIDANCE HAS BEEN SHIFTING WESTWARD DURING THE PAST

COUPLE OF RUNS…AND THE NHC FORECAST HAS BEEN ADJUSTED IN THAT

DIRECTION.

 

BECAUSE OF THE SLOW MOTION OF ISAAC…A PROLONGED PERIOD OF STRONG

WINDS AND HEAVY RAINFALL ARE EXPECTED OVER A LARGE PORTION OF THE

NORTHERN GULF COAST.  THE THREAT OF HEAVY RAINFALL AND FLOODING IS

ALSO EXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY

REGION DURING THE NEXT FEW DAYS.

 

NATIONAL OCEAN SERVICE TIDE GAUGES INDICATE THAT STORM SURGE HEIGHTS OF 6 TO 10 FEET ARE OCCURRING ALONG PORTIONS OF THE COAST OF

SOUTHEASTERN LOUISIANA AND MISSISSIPPI.  GIVEN THE LONG DURATION

OF ONSHORE FLOW IN THESE AREAS…WATER LEVELS ARE EXPECTED TO REMAIN

HIGH FOR THE NEXT 12 TO 24 HOURS.

 

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  29/0300Z 29.0N  89.7W   70 KT  80 MPH

12H  29/1200Z 29.6N  90.6W   65 KT  75 MPH…INLAND

24H  30/0000Z 30.3N  91.4W   55 KT  65 MPH…INLAND

36H  30/1200Z 31.5N  92.3W   35 KT  40 MPH…INLAND

48H  31/0000Z 33.2N  93.2W   25 KT  30 MPH…INLAND

72H  01/0000Z 37.0N  94.0W   20 KT  25 MPH…POST-TROP/REMNT LOW

96H  02/0000Z 40.0N  91.5W   15 KT  15 MPH…POST-TROP/REMNT LOW

120H  03/0000Z 41.5N  86.5W   15 KT  15 MPH…POST-TROP/REMNT LOW