Hurricane LINDA

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HURRICANE LINDA DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152009
800 PM PDT WED SEP 09 2009
 
LINDA HAS BECOME BETTER ORGANIZED DURING THE EVENING.  AN EYE HAS
BECOME APPARENT IN CONVENTIONAL SATELLITE IMAGERY...AND AN AMSU
OVERPASS AT 0030 UTC SHOWED A BETTER DEFINED EYEWALL THAN A FEW
HOURS AGO.  SATELLITE INTENSITY ESTIMATES ARE 77 KT FROM TAFB AND
65 KT FROM SAB...AND THERE HAVE BEEN SEVERAL AMSU ESTIMATES OF
65 KT OR GREATER.  BASED ON THIS...LINDA IS UPGRADED TO A HURRICANE
WITH 70 KT WINDS.
 
THE INITIAL MOTION IS 320/5.  LINDA IS SOUTH OF A LOW-LEVEL RIDGE...
WITH WATER VAPOR IMAGERY SHOWING A MID/UPPER-LEVEL TROUGH WEST OF
THE HURRICANE AND A MID/UPPER-LEVEL RIDGE EAST OF IT.  THE
MID/UPPER-LEVEL FEATURES ARE TRYING TO STEER THE CYCLONE
NORTHWARD...WHILE THE LOW-LEVEL RIDGE IS TRYING TO STEER IT MORE
WESTWARD.  THIS IS RESULTING IN A SLOW NORTHWESTWARD MOTION...
WHICH SHOULD CONTINUE AS LONG AS LINDA KEEPS ITS VERTICALLY DEEP
STRUCTURE.  THE LARGE-SCALE GUIDANCE SUGGESTS THIS WILL BE FOR ABOUT
48-72 HR...AND THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS
TRACK THROUGH THAT TIME.  AFTER THAT TIME...THE ECMWF...GFDN...
NOGAPS...AND UKMET SHOW THE LOW-LEVEL CENTER OF LINDA TURNING MORE
WESTWARD...WHILE THE GFS...HWRF...AND GFDL SHOW A GENERALLY
NORTHWARD MOTION.  THIS SPREAD SUGGESTS THAT THE MOTION SHOULD BE
SLOW...AND THE NEW FORECAST TRACK COMPROMISES BETWEEN THESE
EXTREMES BY SHOWING A SLOW NORTHWARD MOTION.
 
ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SHOW 20 KT OF
SOUTHERLY VERTICAL WIND SHEAR OVER LINDA...AND SIMILAR SHEAR IS
EXPECTED THROUGH THE REST OF THE FORECAST PERIOD.  IN ADDITION...
THE CYCLONE IS MOVING OVER SEA SURFACE TEMPERATURES OF 27C AND
COLDER.  THESE FACTORS SUGGEST THE CURRENT INTENSIFICATION SHOULD
END SOON...AND THAT LINDA SHOULD STEADILY WEAKEN AFTER 12-24 HR.
THE NEW INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS ADVISORY...
AND CALLS FOR LINDA TO WEAKEN TO A TROPICAL STORM IN ABOUT 24
HR...A TROPICAL DEPRESSION IN ABOUT 72 HR...AND A REMNANT LOW IN
ABOUT 96 HR.  THE SHEAR IS FORECAST TO BE STRONG ON THE FORECAST
TRACKS OF THE ECMWF AND THE OTHER WESTWARD-MOTION MODELS...SO EVEN
IF LINDA AVOIDS THE COLD WATERS NORTH OF 20N IT IS STILL LIKELY TO
WEAKEN TO A REMNANT LOW BEFORE 120 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 17.1N 129.4W    70 KT
 12HR VT     10/1200Z 18.1N 130.1W    70 KT
 24HR VT     11/0000Z 19.3N 131.0W    65 KT
 36HR VT     11/1200Z 20.2N 131.7W    55 KT
 48HR VT     12/0000Z 21.2N 132.5W    45 KT
 72HR VT     13/0000Z 22.5N 133.5W    30 KT
 96HR VT     14/0000Z 23.5N 133.5W    20 KT...REMNANT LOW
120HR VT     15/0000Z 24.0N 133.5W    20 KT...REMNANT LOW
 
$$
FORECASTER BEVEN
 
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