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Hurricane ISAAC


ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
 
HURRICANE ISAAC DISCUSSION NUMBER  34
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 AM CDT WED AUG 29 2012
 
HURRICANE ISAAC IS INLAND OVER SOUTHEASTERN LOUISIANA NEAR HOUMA.
THE CYCLONE HAS MAINTAINED AN IMPRESSIVE RADAR SIGNATURE...WHICH
INCLUDES A RAGGED 40-NMI DIAMETER EYE. CURVED CONVECTIVE RAINBANDS
HAVE INCREASED IN THE EASTERN SEMICIRCLE...AND DOPPLER RADAR
VELOCITIES OF NEAR 80 KT OVER WATER SUPPORT KEEPING ISAAC AS A
MINIMAL HURRICANE FOR THIS ADVISORY. SIMILAR DOPPLER VELOCITIES
OVER LAND AND OVER LAKE PONTCHARTRAIN SUGGEST WIND GUSTS TO NEAR 80
KT COULD OCCUR INLAND OVER SOUTHEASTERN LOUISIANA INTO THIS
AFTERNOON. BY LATE THIS AFTERNOON OR EVENING...HOWEVER...ISAAC IS
FORECAST TO WEAKEN TO A TROPICAL STORM...AND BECOME A TROPICAL
DEPRESSION BY THURSDAY NIGHT.

THE INITIAL MOTION ESTIMATE IS 310/5. ISAAC IS EXPECTED TO MOVE
SLOWLY NORTHWESTWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE
FOR THE NEXT 24 HOURS...AND THEN TURN NORTH-NORTHWESTWARD AND
NORTHWARD AROUND THE WESTERN PERIPHERY OF THE RIDGE BY 36 AND 48
HOURS...RESPECTIVELY. BY 72 HOURS...ISAAC IS FORECAST TO BECOME A
POST-TROPICAL REMNANT LOW PRESSURE SYSTEM THAT SHOULD MOVE
NORTHEASTWARD TO EAST-NORTHEASTWARD WHEN IT WILL BE CAUGHT UP IN
WEAK MID-LATITUDE WESTERLIES. THERE ARE CURRENTLY NO INDICATIONS IN
ANY OF THE MODEL GUIDANCE SUGGESTING THAT ISAAC WILL TAP INTO ANY
BAROCLINIC ENERGY SOURCES THAT COULD RESULT IN EXTRATROPICAL
STRENGTHENING OVER THE CENTRAL UNITED STATES. THE OFFICIAL TRACK
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND IS JUST EAST
OF THE MODEL CONSENSUS.
 
SINCE ISAAC IS FORECAST 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 6 TO 8 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 TODAY.
 
A SPECIAL THANKS TO THE CREWS OF THE AIR FORCE RESERVE AND NOAA
HURRICANE HUNTERS WHO FLEW A TOTAL OF 34 HAZARDOUS MISSIONS INTO
ISAAC...WHICH RESULTED IN AN IMPRESSIVE TOTAL OF 95 CENTER FIXES.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 29.6N  90.7W   65 KT  75 MPH...INLAND
 12H  30/0000Z 30.2N  91.4W   55 KT  65 MPH...INLAND
 24H  30/1200Z 31.2N  92.2W   45 KT  50 MPH...INLAND
 36H  31/0000Z 32.8N  93.1W   30 KT  35 MPH...INLAND
 48H  31/1200Z 34.6N  93.5W   25 KT  30 MPH...INLAND
 72H  01/1200Z 38.0N  92.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 40.0N  89.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  03/1200Z 41.0N  85.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 
NNNN


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Page last modified: Monday, 31-Dec-2012 12:09:27 UTC