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Tropical Storm ISAAC


ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM AST THU AUG 23 2012

OBSERVATIONS FROM A NOAA HURRICANE HUNTER AIRCRAFT SUGGEST THAT
ISAAC HAS STRENGTHENED ONLY SLIGHTLY THIS EVENING.  FLIGHT-LEVEL
AND SFMR-OBSERVED SURFACE WINDS FROM THE AIRCRAFT SUGGEST THAT THE
CURRENT INTENSITY IS NEAR 40 KT.  THE STORM CONTINUES TO HAVE
FAIRLY STRONG UPPER-LEVEL OUTFLOW AND...IF THE INNER CORE BECOMES
BETTER DEFINED...HAS AN OPPORTUNITY TO STRENGTHEN AS LONG AS IT
REMAINS OVER WATER.  HOWEVER...THE CENTER OF THE STORM IS FORECAST
TO MOVE OVER SOUTHWESTERN HISPANIOLA IN 12 HOURS OR SO...AND THIS
WOULD HALT ANY INTENSIFICATION.  A LITTLE LATER ON...LAND
INTERACTIONS WITH EASTERN CUBA WOULD ALSO INHIBIT INTENSIFICATION
OR CAUSE WEAKENING.  ISAAC WILL LIKELY RESTRENGTHEN WHEN IT MOVES
OVER THE STRAITS OF FLORIDA AND THE EASTERN GULF OF MEXICO IN THE
LATTER PART OF THE FORECAST PERIOD.  HOWEVER IT SHOULD BE NOTED
THAT THERE IS SIGNIFICANT UNCERTAINTY IN TROPICAL CYCLONE INTENSITY
PREDICTIONS AT 3-5 DAYS.

THE INITIAL MOTION ESTIMATE IS 290/16.  A MID-TROPOSPHERIC TROUGH
OVER THE SOUTHEASTERN U.S. IS CAUSING A BREAK IN THE SUBTROPICAL
RIDGE.  IN RESPONSE TO THIS...ISAAC SHOULD TURN TOWARD A MORE
NORTHWESTWARD HEADING OVER THE NEXT FEW DAYS.  THE MODEL CONSENSUS
HAS SHIFTED A BIT TO THE RIGHT DURING THE FIRST HALF OF THE FORECAST
PERIOD...PRIMARILY DUE TO AN EASTWARD SHIFT OF THE LATEST GFS
TRACK.  THE OFFICIAL FORECAST IS NUDGED A BIT TO THE RIGHT OF
THE PREVIOUS ONE AND IS SOMEWHAT FASTER BASED ON THE LATEST MODEL
GUIDANCE.

THE INITIAL AND FORECAST WIND RADII HAVE BEEN EXPANDED BASED ON BUOY
AND SHIP DATA.  IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK
BECAUSE OF FORECAST UNCERTAINTIES AND THE FACT THAT ISAAC HAS A
LARGE AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.

A SYNOPTIC SURVEILLANCE MISSION BY THE NOAA G-IV JET AIRCRAFT HAS
BEEN CONDUCTED TO COLLECT ATMOSPHERIC OBSERVATIONS IN THE
LARGE-SCALE ENVIRONMENT OF ISAAC.  THESE DATA WILL BE ASSIMILATED
INTO THE 0000 UTC RUNS OF THE GLOBAL MODELS...AND SHOULD IMPROVE
THE ACCURACY OF THEIR FORECASTS FOR THE NEXT ADVISORY CYCLE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0300Z 16.7N  68.7W   40 KT  45 MPH
 12H  24/1200Z 17.5N  70.7W   55 KT  65 MPH
 24H  25/0000Z 18.8N  73.1W   45 KT  50 MPH
 36H  25/1200Z 20.2N  75.4W   45 KT  50 MPH...INLAND
 48H  26/0000Z 21.8N  77.7W   45 KT  50 MPH...INLAND
 72H  27/0000Z 24.8N  82.0W   55 KT  65 MPH...OVER WATER
 96H  28/0000Z 27.5N  85.5W   70 KT  80 MPH
120H  29/0000Z 30.0N  88.0W   80 KT  90 MPH
 
$$
FORECASTER PASCH
 
NNNN


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Page last modified: Monday, 31-Dec-2012 12:09:26 UTC