Tropical Storm LOWELL

ZCZC MIATCDEP3 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM LOWELL DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132008
200 PM PDT SUN SEP 07 2008
 
ALL OF THE LOWELL'S DEEP CONVECTION REMAINS ON THE SOUTHWEST SIDE OF
ITS CENTER DUE TO PERSISTENT NORTHEASTERLY WIND SHEAR. THE CENTER
IS ALSO PARTIALLY EXPOSED...REVEALING A COMPLEX PATTERN OF
MESOVORTICES WITHIN THE LARGER CIRCULATION.  A QUIKSCAT PASS FROM
EARLIER SUGGESTS THE MAXIMUM WINDS WERE ABOUT 45 KT...SO THIS VALUE
WILL BE USED AS THE INITIAL INTENSITY.  ALTHOUGH GLOBAL MODELS
FORECAST A MORE FAVORABLE UPPER ENVIRONMENT FOR STRENGTHENING IN A
DAY OR SO...NONE OF THE DYNAMICAL OR STATISTICAL MODELS FORECAST
MUCH STRENGTHENING.  GIVEN THAT LOWELL SHOULD BE OVER RELATIVELY
WARM WATER AND LIGHT SHEAR FOR AT LEAST 48 HR...I'M GOING TO REDUCE
THE NHC FORECAST ONLY SLIGHTLY FROM THE PREVIOUS ONE...BUT NOT AS
MUCH AS MOST OF THE MODEL GUIDANCE.  A COMBINATION OF COOLER SSTS
AND ENTRAINMENT OF DRIER AIR FROM THE NORTHWEST SHOULD WEAKEN THE
STORM IN THE LONG-TERM.
 
VISIBLE SATELLITE IMAGERY IS GIVING A BETTER IDEA OF THE INITIAL
MOTION...NOW 305/10.  THERE IS NO CHANGE TO THE SYNOPTIC REASONING.
A GENERAL NORTHWESTWARD TRACK IS EXPECTED AS LONG AS THE LOWELL
REMAINS ON THE SOUTHWEST SIDE OF A SUBTROPICAL RIDGE OVER MEXICO.
A WEAKNESS IN THE RIDGE SHOULD DEVELOP IN TWO OR THREE DAYS AS A
TROUGH MOVES DOWN THE WEST COAST OF THE USA...STEERING THE STORM
TOWARD THE NORTH AND EVENTUALLY NORTHEAST.  THERE IS STILL SOME
SPREAD OF WHEN THE TURN BACK TOWARD BAJA OCCURS.  HOWEVER ALL
RELIABLE MODELS EXCEPT THE NOGAPS NOW TURN THE SYSTEM TO THE
NORTHEAST OR EAST BY THE END OF THE FORECAST.  THE OFFICIAL
FORECAST IS SHIFTED TO THE EAST...BUT IS STILL WEST OF THE MODEL
CONSENSUS.  IT WOULD NOT BE SURPRISING IF THE NEXT FORECAST WAS
ADJUSTED EVEN FARTHER NORTHEAST.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/2100Z 17.9N 108.8W    45 KT
 12HR VT     08/0600Z 18.7N 110.0W    45 KT
 24HR VT     08/1800Z 19.6N 111.3W    50 KT
 36HR VT     09/0600Z 20.4N 112.4W    50 KT
 48HR VT     09/1800Z 21.0N 113.2W    50 KT
 72HR VT     10/1800Z 22.0N 113.5W    50 KT
 96HR VT     11/1800Z 23.0N 112.5W    45 KT
120HR VT     12/1800Z 23.5N 111.5W    35 KT
 
$$
FORECASTER BLAKE
 
NNNN