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Tropical Storm LINDA


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TROPICAL STORM LINDA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152009
800 PM PDT MON SEP 07 2009
 
THE SATELLITE PRESENTATION OF LINDA HAS BECOME SOMEWHAT RAGGED...AND
DVORAK ESTIMATES FROM TAFB AND SAB ARE 35 AND 45 KT...RESPECTIVELY.
HOWEVER...AN 1841 UTC ASCAT PASS OVER THE WESTERN HALF OF THE
CYCLONE INDICATED THAT MAXIMUM WINDS WERE 45 KT...AND IT IS
POSSIBLE THAT THERE COULD BE 50 KT WITHIN THE EASTERN SEMICIRCLE.
THE INITIAL INTENSITY IS THEREFORE HELD AT 50 KT.

A 2119 UTC TRMM AND A 2217 UTC AMSU PASS WERE HELPFUL IN LOCATING
THE LOW-LEVEL CENTER AT THOSE TIMES. HOWEVER...THE RECENT CLOUD
MOTIONS HAVE NOT MATCHED THE EXTRAPOLATED MOTION...AND THIS COULD
BE A SIGNAL THAT THE LOW- AND MID-LEVEL CIRCULATIONS ARE BECOMING A
LITTLE DISPLACED FROM EACH OTHER. THE INITIAL POSITION...AND THE
INITIAL MOTION OF 275/6...ARE THEREFORE A LITTLE UNCERTAIN. THE
MID-LEVEL RIDGE NORTH OF LINDA IS EXPECTED TO BREAK DOWN OVER THE
NEXT DAY OR SO AND WILL CAUSE THE STORM TO TURN TOWARD THE
NORTHWEST IN ABOUT 48 HOURS. HOWEVER...THERE IS SOME SIGNIFICANT
SPREAD IN THE MODEL GUIDANCE. THE UKMET AND NOGAPS ARE ON THE
SOUTHERN SIDE OF THE ENVELOPE WHILE THE GFS...GFDL...AND HWRF
MAINTAIN A DEEP SYSTEM AND TURN LINDA TOWARD THE NORTH. THE
OFFICIAL FORECAST IS VERY CLOSE TO THE PREVIOUS FORECAST AND
TVCN...AND ENDS UP NEAR THE BAM SHALLOW MODEL BY DAY 5 WHEN LINDA
SHOULD BE A REMNANT LOW. 

VISIBLE IMAGERY SHOWS THAT LINDA IS INGESTING DRIER AND MORE STABLE
AIR FROM THE NORTH INTO THE WESTERN SIDE OF ITS CIRCULATION...AND
THE CYCLONE HAS BEEN PRODUCING SOME ARC CLOUDS TO ITS SOUTH.  IN
ADDITION...WATER VAPOR IMAGERY SHOWS NO EXPANSION OF THE MOISTURE
CANOPY THAT SHOULD BE MOVING WESTWARD IN TANDEM WITH THE STORM. 
ALL THIS LEADS ME TO BELIEVE THAT ANY SHORT-TERM STRENGTHENING WILL
BE LIMITED. THE SHIPS...LGEM...AND GFDL MODELS FOLLOW THIS TREND
AND SHOW LINDA REACHING HURRICANE STRENGTH...OR JUST BELOW
HURRICANE STRENGTH...IN ABOUT 36-48 HOURS. THEREFORE...THE NEW
OFFICIAL FORECAST SHOWS SLOWER STRENGTHENING THAN PREVIOUSLY
INDICATED...BUT STILL SHOWS LINDA BECOMING A HURRICANE IN 36 HOURS.
INCREASING SOUTHERLY TO SOUTHWESTERLY SHEAR AND DECREASING SEA
SURFACE TEMPERATURES ARE THEN EXPECTED TO WEAKEN THE SYSTEM BEYOND
48 HOURS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 15.3N 127.8W    50 KT
 12HR VT     08/1200Z 15.4N 128.6W    55 KT
 24HR VT     09/0000Z 15.7N 129.3W    60 KT
 36HR VT     09/1200Z 16.3N 129.9W    65 KT
 48HR VT     10/0000Z 17.3N 130.6W    60 KT
 72HR VT     11/0000Z 19.5N 132.0W    45 KT
 96HR VT     12/0000Z 21.5N 133.5W    30 KT
120HR VT     13/0000Z 23.5N 134.0W    20 KT...REMNANT LOW
 
$$
FORECASTER BERG
 
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