HOME	PRODUCTS	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
HURRICANE ISAAC DISCUSSION NUMBER  11
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT SAT SEP 23 2000

ISAAC HAS CONTINUED TO RAPIDLY INTENSIFY THIS EVENING AND IS NOW A
MAJOR HURRICANE.  THE INITIAL INTENSITY OF 105 KT IS BASED ON
SATELLITE INTENSITY ESTIMATES RANGING FROM 102 KT FROM BOTH SAB AND
KGWC AND NEAR 115 KT FROM TAFB.  THE SMALL 10 NM DIAMETER EYE HAS
PERIODICALLY BEEN CLOUD-FILLED...SO THE LOWER END OF THE INTENSITY
ESTIMATES WAS USED FOR THIS ADVISORY.  THE OUTFLOW PATTERN REMAINS
VERY IMPRESSIVE AND CONTINUES TO EXPAND ON THE WEST SIDE. ISAAC HAS
MAINLY A SMALL INNER CORE CONVECTIVE PATTERN WITH LITTLE OR NO
BANDING FEATURES EVIDENT.
 
THE INITIAL MOTION IS 285/09.  ALL OF THE MODEL GUIDANCE REMAINS IN
GENERAL AGREEMENT ON KEEPING ISAAC ON A 285 TO 290 DEGREES TRACK
THROUGHOUT THE PERIOD.  THE UKMET IS FASTER THAN THE NOGAPS...AVN...
AND GFDL MODELS.  THIS RESULTS IN ISAAC MOVING INTO THE WESTERN
PERIPHERY OF THE 200 MB SYNOPTIC-SCALE ANTICYCLONE WHERE SOUTHERLY
FLOW FORCES ISAAC MORE POLEWARD.  THE AVN AND NOGAPS SOLUTIONS ARE
PREFERRED WHICH ACTUALLY BRING WEAK NORTHERLY FLOW ONTO ISAAC BY 36
TO 48 HOURS...WHICH WOULD ACT TO TAKE THE HURRICANE MORE WESTWARD.
HOWEVER...ALL OF THE GLOBAL MODELS AGREE ON MOVING THE MID-LEVEL
SUBTROPICAL RIDGE AXIS CURRENTLY ALONG 30N LATITUDE NORTHWARD TO 35N
LATITUDE BY THE END OF THE FORECAST PERIOD.  THAT SCENARIO ALONE
SHOULD ALLOW ISAAC TO GRADUALLY SHIFT POLEWARD EVEN THOUGH THE
STEERING FLOW WILL BE FROM AN EASTERLY DIRECTION.  THE OFFICIAL
FORECAST IS ALONG THE SOUTHERN PORTION OF THE MODEL GUIDANCE
ENVELOPE...BUT WELL NORTH...OR RIGHT..OF THE FSU SUPERENSEMBLE
EXPERIMENTAL MODELS.

NOW THAT ISAAC HAS DEFIED ALL ODDS AND HAS BECOME A MAJOR HURRICANE
OVER SST WATER LESS THAN 27C...THERE IS NOT MUCH ROOM FOR ADDITIONAL
INTENSIFICATION TO OCCUR.  BOTH THE SHIPS AND SHIFOR INTENSITY
MODELS TAKE ISAAC UP TO 115 KT IN 12 TO 24 HOURS...WITH GRADUAL
WEAKENING AFTERWARDS.  THIS SCENARIO SEEMS REASONABLE GIVEN THE
IMPRESSIVE INFLOW-OUTFLOW PATTERN THAT IS ALREADY ESTABLISHED..AND
ISAAC COULD POSSIBLY REACH MINIMAL CATEGORY 4 INTENSITY DURING THE
NEXT 24 HOURS.  THE OFFICIAL INTENSITY FORECAST KEEPS THE INTENSITY
A LITTLE HIGHER THAN THE SHIPS MODEL AFTER 48 TO 72 HOURS DUE TO THE
EXCELLENT OUTFLOW PATTERN.

 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     24/0300Z 15.0N  35.4W   105 KTS
12HR VT     24/1200Z 15.2N  36.6W   110 KTS
24HR VT     25/0000Z 15.6N  38.2W   115 KTS
36HR VT     25/1200Z 16.0N  39.8W   115 KTS
48HR VT     26/0000Z 16.5N  41.5W   110 KTS
72HR VT     27/0000Z 17.5N  44.5W   105 KTS

  
NNNN