000
WTNT44 KNHC 290252
TCDAT4
 
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
 
$$
FORECASTER BROWN