000
WTPZ42 KNHC 232033
TCDEP2
TROPICAL STORM NORA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP172009
200 PM PDT WED SEP 23 2009
 
THE ORGANIZATION OF THE CLOUD PATTERN IS DEFINITELY IN AN UPWARD
TREND. THE PATTERN RESEMBLES A NUMBER SIX WITH A WELL DEFINED
CYCLONICALLY-CURVED CONVECTIVE BAND WHICH WRAPS AROUND A SMALL
CENTRAL DENSE OVERCAST. THERE ARE NO SIGNS OF SHEAR GIVEN
THAT THE OUTFLOW IS FAIR IN ALL DIRECTIONS. T-NUMBERS FROM BOTH TAFB
AND SAB ARE 3.0 ON THE DVORAK SCALE...AND BASED ON THESE NUMBERS...
THE INITIAL INTENSITY IS SET AT 45 KNOTS. NORA HAS A DAY OR TWO TO
STRENGTHEN BEFORE THE SHEAR INCREASES AS INDICATED BY MOST OF THE
GLOBAL MODELS. THE OFFICIAL FORECAST IS VERY SIMILAR TO THE PREVIOUS
ONE AND FOLLOWS THE SHIPS MODEL. THE GFDL/HWRF MODEL PAIR MAKES
NORA A HURRICANE IN A DAY OR SO AND ALTHOUGH THIS SOLUTION DOES NOT
SEEM LIKELY AT THIS TIME...IT IS NOT OUT OF THE QUESTION.
 
BEST ESTIMATE OF THE INITIAL MOTION IS 290 DEGREES AT 6 KNOTS.
GLOBAL MODELS INDICATE THAT THE SUBTROPICAL RIDE NORTH OF NORA WILL
EXPAND WESTWARD. THIS PATTERN SHOULD FORCE NORA TO TURN MORE TO THE
WEST DURING THE NEXT TWO TO THREE DAYS BEFORE NORA BECOMES A
REMNANT LOW. IN FACT...THE MODEL CONSENSUS SHOWS A DEFINITELY
WESTWARD TRACK DURING THE NEXT THREE DAYS AND SO DOES THE OFFICIAL
FORECAST. THE GFDL/HWRF PAIR MOVE NORA ON A MORE NORTHERLY TRACK
BUT THIS SOLUTION DOES NOT APPEAR TO BE REALISTIC AT THIS TIME WITH
THE EXPECTED STEERING PATTERN.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/2100Z 16.8N 118.6W    45 KT
 12HR VT     24/0600Z 17.2N 119.6W    55 KT
 24HR VT     24/1800Z 17.3N 120.5W    55 KT
 36HR VT     25/0600Z 17.3N 121.5W    50 KT
 48HR VT     25/1800Z 17.3N 122.5W    40 KT
 72HR VT     26/1800Z 17.5N 125.5W    30 KT
 96HR VT     27/1800Z 19.0N 128.0W    20 KT...REMNANT LOW
120HR VT     28/1800Z 20.5N 130.0W    20 KT...REMNANT LOW
 
$$
FORECASTER AVILA