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Tropical Storm LOWELL (Text)

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TROPICAL STORM LOWELL DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132008
800 PM PDT TUE SEP 09 2008
 
INTERMITTENT BURSTS OF MODERATE CONVECTION HAVE CONTINUE TO FORM IN
THE WESTERN SEMICIRCLE...WHILE THE ASSOCIATED CIRRUS CANOPY HAS
SPREAD EASTWARD AND HAS OBSCURED THE LOW-LEVEL CENTER. SATELLITE
CURRENT INTENSITY ESTIMATES ARE T2.5/35 KT FROM BOTH TAFB AND
SAB...BUT DATA T-NUMBERS ARE T2.0/30 KT. HOWEVER...LOW-CLOUD
ELEMENTS IN THE EASTERN SEMICIRCLE HAVE BEEN MOVING AT 35-40 KT...
SO THE INTENSITY IS BEING HELD AT 40 KT FOR THIS ADVISORY BASED ON
THE ASSUMPTION THAT SLIGHTLY STRONGER WINDS EXIST WITHIN THE
CONVECTION ON THE WEST SIDE OF THE LOW-LEVEL CENTER.
 
THE MOTION ESTIMATE IS NOW 015/05. IT APPEARS THAT LOWELL IS NOW
PASSING ALONG OR JUST NORTH OF THE SUBTROPICAL RIDGE AXIS AND WATER
VAPOR IMAGERY INDICATES A BROAD MID-LATITUDE TROUGH TO THE NORTH
CONTINUES TO DROP SLOWLY SOUTHWARD. SOUTHWESTERLY UPPER-LEVEL WINDS
ARE BEGINNING TO IMPINGE ON THE WEST SIDE OF THE WEAK OUTFLOW
PATTERN...WHICH MEANS THAT GRADUAL RECURVATURE TO THE NORTHEAST
SHOULD BEGIN WITHIN THE NEXT 12 HOURS. THE NHC MODEL GUIDANCE IS
TIGHTLY CLUSTERED ABOUT THE PREVIOUS FORECAST TRACK ACROSS SOUTHERN
BAJA CALIFORNIA IN 24-36 HOURS...SO NO SIGNIFICANT CHANGES HAVE
BEEN MADE TO THE PREVIOUS ADVISORY.

LOWELL HAS BEEN INGESTING COOLER AND MORE STABLE AIR INTO THE
CIRCULATION...WHICH HAS BEEN INHIBITING CONVECTIVE DEVELOPMENT. THE
CYCLONE IS ALSO PASSING OVER THE COOLEST WATER ALONG THE FORECAST
TRACK. VERTICAL SHEAR IS LOW AND IS EXPECTED TO REMAIN THAT WAY
UNTIL LANDFALL OCCURS OVER SOUTHERN BAJA CALIFORNIA. SINCE LOWELL
WILL BE MOVING RELATIVELY SLOWLY OVER SSTS THAT INCREASE TO NEAR
28C...SOME ADDITIONAL CONVECTION MAY DEVELOP BEFORE LANDFALL
OCCURS...AND FOR THIS REASON THE INTENSITY IS BEING MAINTAINED AT
35 KT FOR THE NEXT 24-30 HOURS. THE OFFICIAL INTENSITY FORECAST IS
IDENTICAL TO THE PREVIOUS ADVISORY AND IS SLIGHTLY LOWER THAN THE
SHIPS INTENSITY MODEL FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 21.3N 113.1W    40 KT
 12HR VT     10/1200Z 22.2N 112.6W    35 KT
 24HR VT     11/0000Z 23.3N 111.8W    35 KT
 36HR VT     11/1200Z 24.4N 110.9W    30 KT...INLAND OVER BAJA
 48HR VT     12/0000Z 25.9N 110.2W    25 KT...OVER GULF OF CALIF
 72HR VT     13/0000Z 27.3N 109.9W    20 KT...INLAND OVER MEXICO
 96HR VT     14/0000Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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