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TROPICAL STORM ILEANA DISCUSSION NUMBER   9
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT TUE AUG 15 2000
 
ILEANA REMAINS IN A NORTHEASTERLY SHEAR PATTERN WITH THE DEEP
CONVECTION DISPLACED TO THE WEST AND SOUTHWEST OF THE LOW-LEVEL
CIRCULATION CENTER BASED ON VISIBLE IMAGERY AND A 1555Z SSMI
OVERPASS. THE INITIAL INTENSITY IS HELD AT 60 KT AND THE INITIAL
WIND RADII WERE ADJUSTED TO FIT THE ASYMMETRICAL CONVECTIVE PATTERN.
 
INITIAL MOTION IS 280/09.  SOME LARGE WOBBLES IN THE TRACK MAY
CONTINUE FOR THE NEXT 24 HOURS DUE TO THE SHEAR PATTERN AND ALSO DUE
TO THE LOW-LEVEL LEESIDE FLOW OFF THE MOUNTAINS OF BAJA CALIFORNIA
CREATING WEAK EDDIES. HOWEVER...THE GENERAL DIRECTION SHOULD BE TO
THE WEST-NORTHWEST THROUGH THE FORECAST PERIOD. BY 48 HOURS...MOST
OF THE GLOBAL MODELS WEAKEN THE SUBTROPICAL RIDGE TO THE NORTHWEST
OF ILEANA...WHICH MAY CAUSE THE CYCLONE TO SLOW ITS FORWARD SPEED
AND GAIN A LITTLE MORE LATITUDE. THE OFFICIAL TRACK IS A LITTLE
SOUTH OF THE PREVIOUS TRACK THROUGH 36 HOURS...AND THEN A LITTLE
NORTH OF THE PREVIOUS TRACK AFTERWARDS. THIS IS CONSISTENT WITH THE
GFDL AND UKMET MODELS...AND THE OFFICIAL TRACK IS ON THE SOUTHERN
EDGE OF THE NHC FORECAST MODELS SUITE.
 
THERE IS NO CHANGE TO THE PREVIOUS INTENSITY FORECAST OR PHILOSOPHY.
ALTHOUGH ILEANA IS CURRENTLY EXPERIENCING NORTHEASTERLY SHEAR...ALL
OF THE GLOBAL MODELS SUGGEST THAT THE 200 MB FLOW WILL SHIFT AROUND
TO EASTERLY AND WEAKEN BY 24 HOURS. THE DECREASING SHEAR MAY ALLOW
ILEANA TO DEVELOP DEEP CONVECTION ON THE NORTH SIDE LATER
TONIGHT...ESPECIALLY DURING THE DIURNAL CONVECTIVE MAXIMUM PERIOD
TUESDAY MORNING. THE SHIPS INTENSITY MODEL ONLY SLOWLY INCREASES THE
INTENSITY TO 75 KT IN 72 HOURS...BUT SMALL SYSTEMS LIKE ILEANA CAN
SPINUP THE INNER CORE WIND FIELD MUCH FASTER THAN THE STATISTICAL
MEANS INDICATE. THE FORECAST TRACK KEEPS ILEANA OVER A NARROW
CHANNEL OF WARM SSTS THROUGH 24 HOURS...WHICH FAVORS CONTINUED
INTENSIFIATION.

 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     15/2100Z 22.2N 111.1W    60 KTS
12HR VT     16/0600Z 22.4N 112.6W    65 KTS
24HR VT     16/1800Z 23.0N 114.4W    70 KTS
36HR VT     17/0600Z 23.4N 115.9W    75 KTS
48HR VT     17/1800Z 23.7N 117.3W    75 KTS
72HR VT     18/1800Z 24.3N 119.7W    65 KTS
 
 
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