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HURRICANE NARDA DISCUSSION NUMBER   7
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT SUN OCT 21 2001

VISIBLE AND INFRARED SATELLITE IMAGERY INDICATE THAT NARDA HAS 
CONTINUED TO RAPIDLY INTENSIFY.  A SMALL CDO AND AN INTERMITTENT EYE 
HAVE DEVELOPED DURING THE PAST 6 HOURS...AND A BURST OF VERY DEEP 
EYEWALL CONVECTION HAS DEVELOPED DURING THE PAST 3 HOURS. 
THEREFORE...THE INITIAL INTENSITY IS INCREASED TO 75 KT BASED ON A 
DVORAK SATELLITE INTENSITY ESTIMATE OF 77 KT...T4.5...FROM TAFB PLUS 
A 3-HOUR OBJECTIVE DVORAK INTENSITY OF 80 KT...ODT4.6.  UPPER-LEVEL 
OUTFLOW IS GOOD IN ALL QUADRANTS AND CONTINUES TO IMPROVE.
 
THE INITIAL MOTION ESTIMATE IS 300/09.  THERE HAS BEEN SOME 
SIGNIFICANT WOBBLES IN THE TRACK OVER THE PAST 6 TO 12 HOURS...
WHICH IS NOT UNUSUAL FOR RAPIDLY INTENSIFYING TROPICAL CYCLONES. 
OTHERWISE...NARDA IS EXPECTED TO TRACK WEST-NORTHWEST OR SLIGHTLY 
NORTHWESTWARD FOR THE NEXT 24 TO 36 HOURS AS IT BEGINS TO COME UNDER 
THE INFLUENCE OF INCREASING MID- TO UPPER-LEVEL SOUTHWESTERLY FLOW 
ON THE EAST SIDE OF THE DEEP MID-OCEANIC TROUGH CURRENTLY EXTENDING 
SOUTHWARD ACROSS THE HAWAIIAN ISLANDS.  NARDA IS FORECAST TO BECOME 
SEVERELY SHEARED BY 48 HOURS AND DEGRADE INTO MORE OF A SHALLOW 
SYSTEM BY...THUS BEING STEERED MORE WESTWARD BY THE STRONG LOW-LEVEL 
EASTERLY FLOW ON THE SOUTHERN SIDE OF THE SUBTROPICAL HIGH TO ITS 
NORTH.  THE OFFICIAL FORECAST IS CLOSE TO THE PREVIOUS FORECAST 
TRACK AND THE 21/12Z NOGAPS MODEL...BUT MUCH SLOWER AND A LITTLE 
FARTHER NORTH THAN THE AVN AND UKMET SOLUTIONS.
 
NARDA APPEARS TO BE ABOUT 18 HOURS INTO ITS RAPID INTENSIFICATION 
PERIOD.  GIVEN THE DUAL OUTFLOW CHANNELS THAT EXISTS...THE RAPID 
INTENSIFICATION PROCESS WOULD GENERALLY CONTINUE FOR ANOTHER 12 
HOURS OR SO. HOWEVER...INCREASING VERTICAL SHEAR IN THE NEXT 12 TO 
18 HOURS IS EXPECTED TO SUPPRESS THE INTENSIFICATION PROCESS. AS 
SUCH...NARDA IS ONLY FORECAST TO REACH 85 KT...WHICH IS SIMILAR TO 
THE LATEST GFDL AND SHIPS INTENSITY MODEL FORECASTS.  BUT IF THE 
VERTICAL SHEAR DOES NOT BECOME AS STRONG AS THE 25 TO 36 KT THAT THE 
AVN MODEL IS FORECASTING...THEN NARDA COULD PEAK BETWEEN 90 AND 100 
KT IN 12 TO 18 HOURS.  BY 24 HOURS...THE CYCLONE IS EXPECTED TO 
TRACK FAR ENOUGH WEST TO BE SEVERELY AFFECTED BY STRONG UPPER-LEVEL 
WESTERLIES...WHICH SHOULD BRING ABOUT RAPID WEAKENING.
 
NARDA IS A FAIRLY COMPACT SYSTEM AND SINCE IT IS FORECAST TO PEAK IN 
INTENSITY WITHIN 24 HOURS...THE WIND FIELD SHOULD HAVE LITTLE TIME 
TO INCREASE. AS SUCH...THE WIND RADII WERE KEPT SMALLER THAN WHAT 
WOULD TYPICALLY BE EXPECTED FOR AN 85 TO 90 KT HURRICANE.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     22/0300Z 14.6N 131.8W    75 KTS
12HR VT     22/1200Z 15.5N 133.4W    85 KTS
24HR VT     23/0000Z 16.6N 135.7W    75 KTS
36HR VT     23/1200Z 17.5N 138.4W    65 KTS
48HR VT     24/0000Z 18.0N 141.1W    55 KTS
72HR VT     25/0000Z 18.5N 145.5W    40 KTS
 
 
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