Hurricane Isaac Discussion #31

000
WTNT44 KNHC 282053
TCDAT4

HURRICANE ISAAC DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL  AL092012
400 PM CDT TUE AUG 28 2012

SINCE THE LAST RECON FLIGHTS INTO 
ISAAC...WHEN A BIAS-CORRECTED SFMR WIND 
OF 64 KT WAS OBSERVED...THE RADAR AND 
SATELLITE APPEARANCE HAS CONTINUED TO 
BECOME BETTER DEFINED. ON THIS 
BASIS...THE ESTIMATED  INTENSITY HAS BEEN 
INCREASED TO 70 KT.

TRENDING THROUGH ALL OF THE WIGGLES 
AND WOBBLES IN THE AIRCRAFT FIXES YIELDS 
A GENERAL NORTHWESTWARD MOTION OF 
310/07 KT. ISAAC REMAINS ON TRACK...AND 
THERE HAS BEEN NO SIGNIFICANT CHANGE TO 
THE EARLY PART OF THE FORECAST. ISSAC IS 
EXPECTED TO CONTINUE NORTHWESTWARD 
TOWARD A WEAKNESS IN THE SUBTROPICAL 
RIDGE THAT IS ORIENTED EAST-WEST ALONG 
30N LATITUDE. BECAUSE OF THIS WEAKNESS... 
THE STEERING FLOW IS FORECAST TO 
DECREASE OVER THE NEXT 36-48 
HOURS...WHICH WILL RESULT IN ISAAC 
SLOWING DOWN SOME MORE. 
AFTERWARDS...THE RIDGE IS FORECAST TO 
BUILD BACK IN BY ALL OF THE 
MODELS...ALBEIT TO VARYING 
DEGREES...WHICH SHOULD CAUSE THE 
CYCLONE TO TURN SLIGHTLY TOWARD THE 
WEST-NORTHWEST BEFORE IT TURNS 
NORTHWARD BY DAY 4...AND THEN MOVE 
NORTHEASTWARD INTO THE LOWER GREAT 
LAKES AND OHIO VALLEY REGIONS BY DAY 5. 
IN THE LATTER PART OF THE FORECAST 
PERIOD THE FORECAST HAS BEEN NUDGED A 
LITTLE TO THE LEFT OF THE PREVIOUS 
TRACK...BUT REMAINS TO THE RIGHT OF THE 
CONSENSUS MODELS THAT HAVE RECENTLY 
HAD A LEFTWARD BIAS.

ALTHOUGH NOT EXPLICITLY FORECAST DUE 
TO LAND INTERACTION AT 12 
HOURS...FAVORABLE WATER TEMPERATURES 
ALONG WITH AN IMPRESSIVE UPPER-LEVEL 
OUTFLOW REGIME SUGGEST THAT ISAAC 
COULD STRENGTHEN A LITTLE MORE BEFORE 
LANDFALL OCCURS.  HOWEVER...BECAUSE OF 
THE UNUSUALLY LARGE WIND FIELD...RAPID 
INTENSIFICATION IS NOT EXPECTED.

ISAAC REMAINS A LARGE TROPICAL CYCLONE. 
A DANGEROUS STORM SURGE...HEAVY 
RAINFALL...AND STRONG WINDS EXTEND WELL 
AWAY FROM THE CENTER AND ARE EXPECTED 
TO AFFECT A LARGE PORTION OF THE 
NORTHERN GULF COAST. FOR THIS REASON...IT 
IS IMPORTANT NOT TO FOCUS ON THE EXACT 
CENTER LOCATION. THE THREAT OF HEAVY 
RAINFALL AND FLOODING IS ALSO EXPECTED 
TO SPREAD INLAND OVER THE LOWER 
MISSISSIPPI VALLEY REGION DURING THE 
NEXT FEW DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 28.7N  89.2W   70 KT  80 MPH
 12H  29/0600Z 29.4N  90.0W   70 KT  80 MPH
...INLAND
 24H  29/1800Z 30.3N  91.0W   55 KT  65 MPH
...INLAND
 36H  30/0600Z 31.3N  91.9W   35 KT  40 MPH
...INLAND
 48H  30/1800Z 33.0N  92.5W   30 KT  35 MPH
...INLAND
 72H  31/1800Z 36.0N  92.5W   20 KT  25 MPH
...INLAND
 96H  01/1800Z 39.0N  90.5W   15 KT  15 MPH
...POST-TROP/REMNT LOW
120H  02/1800Z 41.5N  86.5W   15 KT  15 MPH
...POST-TROP/REMNT LOW

$$
FORECASTER STEWART