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
