367 
 WTPZ43 KNHC 100236
 TCDEP3
 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