Tropical Storm LOWELL

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TROPICAL STORM LOWELL DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132008
200 AM PDT SUN SEP 07 2008
 
MICROWAVE PASSES SUGGEST THAT THE CENTER OF LOWELL IS A LITTLE
NORTHEAST OF EARLIER ESTIMATES...NEAR THE NORTHEASTERN EDGE OF A
MASS OF CONVECTION THAT IS VERY COLD BUT RELATIVELY SHAPELESS.  THE
SYSTEM IS EXPERIENCING NORTHEASTERLY SHEAR OF ABOUT 20 KT...BUT
THIS SHEAR IS FORECAST TO LESSEN SOMEWHAT OVER THE NEXT 24-36
HOURS.  THE GFDL SHOWS LITTLE DEVELOPMENT...BUT THE HWRF AND SHIPS
MODELS BRING LOWELL UP TO ABOUT 60 KT AND THE OFFICIAL FORECAST
FOLLOWS THE LATTER TWO MODELS.  NEAR THE END OF THE FORECAST PERIOD
COOLER WATERS AND SOUTHWESTERLY SHEAR ARE EXPECTED TO INDUCE
WEAKENING.

LOWELL IS CURRENTLY MOVING AROUND THE PERIPHERY OF A SUBTROPICAL
RIDGE EXTENDING WESTWARD FROM MEXICO.  THE MODEL GUIDANCE HAS
CHANGED SUBSTANTIALLY WITH THE 00Z RUNS...WITH ALL THE DYNAMICAL
MODELS NOW SHOWING A MID- TO UPPER LEVEL TROUGH EXTENDING SOUTHWARD
FROM CALIFORNIA THAT TURNS LOWELL NORTHWARD AND NORTHEASTWARD BY DAY
THREE.  IN FACT...THE GFDL AND ECMWF TURN LOWELL SO SHARPLY THAT IT
RECURVES SOUTH OF THE BAJA CALIFORNIA PENINSULA.  THE OFFICIAL
FORECAST IS ADJUSTED TO THE RIGHT OF THE PREVIOUS ADVISORY BUT
STILL LIES ON THE EXTREME LEFT OF THE GUIDANCE ENVELOPE.  THERE ARE
SOME HINTS IN THE MODELS THAT THE LOW AND MID-LEVEL CIRCULATIONS
COULD SEPARATE BY DAY THREE...AND THIS LOWERS CONFIDENCE IN THE
LONGER TERM TRACK FORECAST. 

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 16.6N 107.2W    35 KT
 12HR VT     07/1800Z 17.3N 108.6W    40 KT
 24HR VT     08/0600Z 18.2N 110.5W    50 KT
 36HR VT     08/1800Z 18.7N 112.0W    60 KT
 48HR VT     09/0600Z 19.4N 113.4W    60 KT
 72HR VT     10/0600Z 20.5N 114.5W    55 KT
 96HR VT     11/0600Z 21.5N 115.0W    45 KT
120HR VT     12/0600Z 22.5N 114.5W    35 KT
 
$$
FORECASTER FRANKLIN
 
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