Tropical Depression NORA

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TROPICAL DEPRESSION NORA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP172009
800 PM PDT THU SEP 24 2009
 
THE LOW-LEVEL CENTER OF NORA IS NOW COMPLETELY EXPOSED DUE TO STRONG
WESTERLY SHEAR...AND THE LAST LITTLE BIT OF DEEP CONVECTION
DISSIPATED BETWEEN 2300 AND 0000 UTC.  DVORAK FINAL-T NUMBERS HAVE
DECREASED TO T1.5 AND T2.0 FROM TAFB AND SAB...RESPECTIVELY...AND
THE LATEST 3-HOUR AVERAGE FINAL T-NUMBER FROM UW-CIMSS IS T2.0. 
NORA IS THEREFORE DOWNGRADED TO A 30-KT DEPRESSION ON THIS ADVISORY. 
ADDITIONAL WEAKENING IS EXPECTED OVER THE NEXT COUPLE OF DAYS DUE
TO CONTINUED STRONG WESTERLY SHEAR.  OCCASIONAL BURSTS OF DEEP
CONVECTION COULD STILL OCCUR SINCE NORA IS EXPECTED TO REMAIN OVER
WATERS WARMER THAN 26.5C FOR SEVERAL DAYS...BUT IT SHOULD NOT BE
ENOUGH TO MAINTAIN IT AS A TROPICAL CYCLONE.  THE NEW FORECAST
CALLS FOR NORA TO BECOME A REMNANT LOW SOON AND DISSIPATE BY DAY
4...BUT SOME OF THE GLOBAL MODELS SUGGEST THIS COULD OCCUR SOONER.

THE INITIAL MOTION IS 265 DEGREES AT 7 KT.  EXCEPT FOR THE
GFS...WHICH IS A SIGNIFICANT SOUTHERN OUTLIER...THE DYNAMICAL
MODELS ARE IN GOOD AGREEMENT THROUGH 72 HOURS.  THE NHC TRACK
FORECAST IS JUST A LITTLE SOUTH OF THE PREVIOUS FORECAST AND VERY
CLOSE TO THE MODEL CONSENSUS.  NORA IS EXPECTED TO MOVE JUST SOUTH
OF DUE WEST DURING THE NEXT 24-36 HOURS AND THEN TURN TOWARD THE
WEST-NORTHWEST ON DAY 3 DUE TO A WEAKNESS IN THE LOW-LEVEL RIDGE
CAUSED BY A COLD FRONT WEST OF CALIFORNIA.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/0300Z 17.4N 121.6W    30 KT
 12HR VT     25/1200Z 17.3N 122.6W    25 KT
 24HR VT     26/0000Z 17.2N 124.0W    25 KT...REMNANT LOW
 36HR VT     26/1200Z 17.2N 125.6W    20 KT...REMNANT LOW
 48HR VT     27/0000Z 17.5N 127.3W    20 KT...REMNANT LOW
 72HR VT     28/0000Z 18.5N 130.0W    20 KT...REMNANT LOW
 96HR VT     29/0000Z...DISSIPATED
 
$$
FORECASTER BERG
 
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