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Tropical Storm ISAAC (Text)

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TROPICAL STORM ISAAC DISCUSSION NUMBER  35
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 PM CDT WED AUG 29 2012
 
ISAAC CONTINUES TO TRUDGE SLOWLY TO THE NORTHWEST ACROSS
SOUTHEASTERN LOUISIANA...AND THE INITIAL MOTION REMAINS  310/5
KT...BASED ON DOPPLER RADAR DATA FROM SLIDELL AND FT. POLK
LOUISIANA. THE MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH
THE PREVIOUS OFFICIAL TRACK...SO NO SIGNIFICANT CHANGES WERE MADE
FOR THIS ADVISORY. ISAAC SHOULD CONTINUE TO MOVE NORTHWESTWARD AND
EVENTALLY NORTHWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE
OVER THE NEXT 36-48 HOURS. BY DAY 3 WHEN THE REMNANT CYCLONE IS
OVER THE UPPER-MIDWEST...ISAAC SHOULD TURN EAST-NORTHEASTWARD WHEN
IT INTERACTS WITH WEAK MID-LATITUDE WESTERLY FLOW. THE OFFICIAL
FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS ADVISORY
TRACK...AND LIES BETWEEN THE MODEL CONSENSUS AND THE ECMWF MODEL.

STRONG BANDS OF THUNDERSTORMS CONTINUE TO DEVELOP OVER WATER IN THE
THE EASTERN SEMICIRCLE AND ALSO SOUTHWEST OF THE CENTER. THEY HAVE
OCCASIONALLY PRODUCED SUSTAINED TROPICAL-STORM-FORCE WINDS ALONG
WITH GUSTS EXCEEDING 60 KT. THOSE STRONG RAINBANDS WILL GRADUALLY
SPREAD WESTWARD TONIGHT ACROSS THE COASTAL AREAS OF SOUTHEASTERN
LOUISIANA AND SOUTHERN MISSISSIPPI...INCLUDING THE NEW ORLEANS
METROPOLITAN AREA. BY THURSDAY NIGHT...ISAAC COULD WEAKEN TO A
TROPICAL DEPRESSION...AND IT SHOULD BECOME A POST-TROPICAL REMNANT
LOW PRESSURE SYSTEM BY FRIDAY. THERE REMAINS NO INDICATION IN ANY
OF THE NHC MODEL GUIDANCE THAT ISAAC WILL BE ABLE TO ACQUIRE ANY
BAROCLINIC ENERGY THAT COULD CAUSE IT TO STRENGTHEN INTO A
SIGNIFICANT EXTRATROPICAL LOW WHILE IT IS OVER THE UNITED STATES.
 
SINCE ISAAC WILL CONTINUE TO MOVE SLOWLY OVER THE NEXT 24-36
HOURS...THERE WILL BE A PROLONGED THREAT OF FLOODING FROM HEAVY
RAINS OVER THE NORTHERN GULF COAST AREA AND THE SOUTH-CENTRAL
UNITED STATES.
 
NATIONAL OCEAN SERVICE TIDE GAGES INDICATE THAT STORM SURGE HEIGHTS
OF NEAR 7 FEET ARE STILL 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 THROUGH TONIGHT.

PUBLIC ADVISORY TIMES HAVE REVERTED BACK TO A 3-HOURLY CYCLE. THE
NEXT INTERMEDIATE PUBLIC ADVISORY WILL BE ISSUED AT 700 PM
CDT/0000Z.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 30.0N  91.1W   60 KT  70 MPH...INLAND
 12H  30/0600Z 30.7N  91.7W   50 KT  60 MPH...INLAND
 24H  30/1800Z 32.0N  92.6W   40 KT  45 MPH...INLAND
 36H  31/0600Z 33.8N  93.3W   30 KT  35 MPH...INLAND
 48H  31/1800Z 35.7N  93.4W   25 KT  30 MPH...INLAND
 72H  01/1800Z 38.6N  91.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/1800Z 40.0N  88.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  03/1800Z 40.5N  83.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 
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