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TROPICAL STORM LANE DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT TUE SEP 05 2000
 
LANE CONTINUES TO PRESENT AN IMPROVING SATELLITE DEPICTION WITH
TIGHT BANDING AROUND A WELL-DEFINED CENTER IN THE LAST VISIBLE
IMAGES...AND THE AREAL COVERAGE OF COLD CLOUD TOPS HAS BEEN
EXPANDING SINCE THEN.  DVORAK INTENSITY ESTIMATES ARE 45 AND 55 KT
FROM TAFB AND SAB RESPECTIVELY.  THE SHIP THAT EARLIER REPORTED 12
KT EAST OF THE CENTER REPORTED 27 KT ABOUT 70 NM NORTH OF THE CENTER
AT 00Z.  THE INTENSITY IS RAISED TO 45 KT FOR THIS ADVISORY...BUT
THESE WINDS COVER ONLY A VERY SMALL AREA NEAR THE CENTER.

THE TRACK FORECAST TONIGHT PRESENTS SOME CHALLENGES ATYPICAL OF THE
EAST PACIFIC.  THE INITIAL MOTION HAS SLOWED CONSIDERABLY...AND IS
CHARITABLY ESTIMATED AS 260/9.  THE 18Z AVN DOES NOT SEEM TO HAVE A
GOOD INITIALIZATION OF THE STORM...SHOWING LANE AT THE WESTERN END
OF AN ELONGATED VORTICITY MAXIMUM.  THE AVN ROTATES LANE
SOUTHWESTWARD AROUND THE LATTER FEATURE...WHICH ITSELF IS FORECAST
TO STRENGTHEN BY THE MODEL...AND THEN TAKES THE CYCLONE SLOWLY
NORTHWARD.  THE BAM MODELS AND THE GFDL ALL RESPOND TO THIS WITH A
CONTINUED TURNING TO THE SOUTH.  THE UKMET INITIALIZATION AND LOW
LEVEL EVOLUTION APPEARS MORE REALISTIC...BUT IT TOO SHOWS LITTLE NET
WESTWARD PROGRESS OF THE CYCLONE.  THE KEY MAY BE SOME SOUTHWESTERLY
MID-TROPOSPHERIC FLOW AHEAD OF LANE ASSOCIATED WITH THE BROAD LOW
NEAR 16N AND 123W...AS INDICATED BY SATELLITE WINDS FROM THE CIMSS
WEB PAGE.  THIS COULD CREATE A WEAK STEERING ENVIRONMENT FOR LANE. 
THE OFFICIAL FORECAST FOR THIS ADVISORY IS SIGNIFICANTLY SLOWER THAN
THE PREVIOUS TRACK...AND EVEN SO RETAINS A STRONGER WESTWARD
COMPONENT THAN ANY OF THE CURRENT DYNAMICAL GUIDANCE.

IF THIS SCENARIO PLAYS OUT...THERE COULD BE SIGNIFICANT SHEAR OVER
LANE AT THE END OF THE FORECAST PERIOD AND SO LITTLE INTENSIFICATION
IS SHOWN BEYOND 36 HOURS.

FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     06/0300Z 15.7N 107.5W    45 KTS
12HR VT     06/1200Z 15.5N 108.6W    50 KTS
24HR VT     07/0000Z 15.3N 110.0W    60 KTS
36HR VT     07/1200Z 15.1N 111.5W    70 KTS
48HR VT     08/0000Z 15.0N 113.0W    75 KTS
72HR VT     09/0000Z 15.0N 116.0W    75 KTS
 
 
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