357 
 WTPZ42 KNHC 231451
 TCDEP2
 TROPICAL STORM NORA DISCUSSION NUMBER   3
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP172009
 800 AM PDT WED SEP 23 2009
 
 NORA HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING...AS A
 CENTRAL CONVECTIVE FEATURE HAS FORMED WITH AN OUTER BAND IN THE
 WESTERN SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM
 TAFB AND 35 KT FROM SAB...AND BASED ON THIS THE INITIAL INTENSITY
 IS INCREASED TO 40 KT.  THE CIRRUS OUTFLOW IS CURRENTLY FAIR TO
 GOOD IN ALL DIRECTIONS.
 
 THE INITIAL MOTION IS 300/8...A LITTLE TO THE LEFT AND SLIGHTLY
 FASTER THAN PREVIOUSLY.  NORA IS ON THE SOUTH SIDE OF A LOW-LEVEL
 RIDGE...AND ALSO SOUTH OF A WEAKNESS IN THE MID-LEVEL RIDGE.  THE
 LARGE-SCALE MODELS FORECAST THE LOW-LEVEL RIDGE TO REMAIN IN PLACE
 FOR THE NEXT SEVERAL DAYS WHILE A MID/UPPER-LEVEL LOW FORMS TO THE
 NORTHWEST OF NORA.  THIS EVOLUTION SHOULD STEER NORA GENERALLY
 WEST-NORTHWESTWARD OR WESTWARD FOR THE NEXT 24-36 HR.  THE MOTION
 BEYOND THAT TIME DEPENDS ON HOW STRONG NORA GETS.  A STRONGER AND
 VERTICALLY DEEPER SYSTEM SHOULD TURN MORE TOWARD THE NORTHWEST AS
 FORECAST BY THE GFDL...HWRF...AND CANADIAN MODELS.  A WEAKER AND
 SHALLOWER NORA SHOULD MOVE MORE WESTWARD AS FORECAST BY THE
 BAMS...GFS...AND ECMWF.  THE TRACK FORECAST WILL LEAN TOWARD THE
 LATTER SCENARIO...WITH A SLOW AND GENERALLY WESTWARD MOTION AFTER
 36 HR.
 
 NORA IS CURRENTLY IN AN ENVIRONMENT OF LIGHT SOUTHERLY VERTICAL WIND
 SHEAR.  THE LARGE-SCALE MODELS SUGGEST THAT THE CYCLONE WILL REMAIN
 IN A FAVORABLE ENVIRONMENT FOR ABOUT 24 HR MORE...FOLLOWED BY A
 SIGNIFICANT INCREASE IN THE SHEAR AS NORA REACHES COOLER SEA
 SURFACE TEMPERATURES.  THIS SUGGESTS THAT NORA SHOULD STRENGTHEN
 FOR A DAY OR SO...FOLLOWED BY A STEADY WEAKENING.  THE NEW
 INTENSITY FORECAST FOLLOWS THE SHIPS AND LGEM GUIDANCE...CALLING
 FOR A PEAK INTENSITY OF 55 KT IN 24 HR AND WEAKENING TO A REMNANT
 LOW BY 72 HR.  THE SHIPS RAPID INTENSIFICATION INDEX SHOWS A
 25 PERCENT CHANCE OF A 30 KT INCREASE IN STRENGTH DURING THE NEXT
 24 HR...SO IT CANNOT BE RULED OUT THAT NORA COULD BECOME A HURRICANE
 BEFORE ENCOUNTERING THE STRONGER SHEAR.  THE GFDL AND HWRF SUPPORT
 THIS POSSIBILITY BY FORECASTING NORA TO BECOME A HURRICANE. 
 HOWEVER...THIS OCCURS IN BOTH MODELS ONLY AFTER THE STRONGER SHEAR
 DEVELOPS.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      23/1500Z 16.5N 117.5W    40 KT
  12HR VT     24/0000Z 16.9N 118.4W    50 KT
  24HR VT     24/1200Z 17.1N 119.4W    55 KT
  36HR VT     25/0000Z 17.2N 120.4W    50 KT
  48HR VT     25/1200Z 17.3N 121.4W    40 KT
  72HR VT     26/1200Z 17.5N 123.5W    25 KT...REMNANT LOW
  96HR VT     27/1200Z 18.0N 126.0W    20 KT...REMNANT LOW
 120HR VT     28/1200Z...DISSIPATED
  
 $$
 FORECASTER BEVEN