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HURRICANE ISAAC DISCUSSION NUMBER  22
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT TUE SEP 26 2000

RECENT IMAGES SHOW BURSTS OF DEEP CONVECTION COVERING THE LOW-LEVEL
CENTER...BUT THE CONVECTION IS NOT VERY SYMMETRIC AND THE MID-LEVEL
CENTER MAY STILL NOT BE VERTICALLY ALIGNED WITH THE LOW-LEVEL
CENTER.  DVORAK CURRENT INTENSITY ESTIMATES ARE NEAR 80 KNOTS SO THE
INITIAL WIND SPEED ESTIMATE IS FIXED AT 80 KNOTS.  OUTFLOW CONTINUES
TO BE POOR TO THE SOUTHWEST OF THE SYSTEM BUT MAY BE EXPANDING EVER
SO SLIGHTLY TO THE NORTHWEST.  THE INCREASE IN CONVECTION NEAR THE
CENTER MAY BE A SIGN OF STRENGTHENING BUT UNTIL THE ORGANIZATION IS
CLEARLY IMPROVED...I WILL NOT FORECAST INTENSIFICATION IN THE SHORT
TERM.  LATER ON...WARMER WATERS AND PERHAPS REDUCED SHEAR MAY ALLOW
SOME STRENGTHENING.

INITIAL MOTION ESTIMATE IS 290/11.  ISAAC HAS NOT YET REACHED THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE BUT IT SHOULD DO SO
WITHIN A COUPLE OF DAYS...AND TURN TOWARD THE NORTHWEST.  THIS IS
SUPPORTED BY ALL OF THE OBJECTIVE GUIDANCE.  THE OFFICIAL FORECAST
IS ROUGHLY OF A CONSENSUS OF THE DYNAMICAL MODELS...AND A BIT FASTER
THAN THAT FROM THE PREVIOUS ADVISORY.

OUTER WIND RADII HAVE BEEN SLIGHTLY REDUCED BASED ON A QUIKSCAT PASS
OVER ISAAC FROM EARLIER TODAY.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     26/2100Z 19.1N  45.5W    80 KTS
12HR VT     27/0600Z 19.7N  47.2W    80 KTS
24HR VT     27/1800Z 21.2N  49.5W    80 KTS
36HR VT     28/0600Z 23.0N  51.5W    85 KTS
48HR VT     28/1800Z 25.0N  53.5W    90 KTS
72HR VT     29/1800Z 29.5N  57.0W    90 KTS
 
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