161 
 WTPZ42 KNHC 250234
 TCDEP2
 TROPICAL STORM IGNACIO DISCUSSION NUMBER   2
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122009
 800 PM PDT MON AUG 24 2009
  
 ALTHOUGH SOME OF THE DEEP CONVECTION WITHIN THE CURVED BAND TO THE
 WEST OF THE CYCLONE CENTER HAS DIMINISHED...SATELLITE INTENSITY
 ESTIMATES ARE NOW T3.0 FROM TAFB AND T2.5 FROM SAB. BASED ON
 THIS...THE DEPRESSION IS BEING UPGRADED TO TROPICAL STORM IGNACIO.
 THE LOW-LEVEL CENTER POSITION REMAINS A LITTLE UNCERTAIN...AND THE
 POSITION GIVEN HERE IS LIKELY A MEAN POSITION OF SEVERAL SWIRLS
 ROTATING AROUND A COMMON CENTER. A 2056 UTC AMSR-E PASS INDICATED
 THAT THIS MEAN CENTER IS PROBABLY A LITTLE FARTHER NORTH THAN
 PREVIOUSLY THOUGHT...AND THE NEW FORECAST TRACK HAS CONSEQUENTLY
 BEEN SHIFTED A LITTLE TO THE NORTH THROUGH THE FIRST 72 HOURS. THE
 INITIAL MOTION IS 290/09...BUT IGNACIO IS EXPECTED TO TURN TOWARD
 THE NORTHWEST BY 36 HOURS AS IT BEGINS TO MOVE AROUND THE WESTERN
 PERIPHERY OF A SUBTROPICAL RIDGE EXTENDING WEST OF NORTHERN MEXICO.
 ONCE THE CYCLONE WEAKENS BY 96 AND 120 HOURS...IT IS EXPECTED TO
 TURN BACK TOWARD THE WEST-NORTHWEST AS IT IS STEERED BY THE
 LOW-LEVEL FLOW. THE TRACK GUIDANCE IS IN REASONABLY GOOD AGREEMENT
 THROUGH 120 HOURS...AND VERY LITTLE CHANGE WAS MADE TO THE PREVIOUS
 FORECAST.
  
 IGNACIO WILL BE MOVING OVER WATER THAT IS AT LEAST 26 DEG CELSIUS
 FOR ANOTHER 36 HOURS OR SO. VERTICAL SHEAR IS EXPECTED TO REMAIN
 LIGHT...SO SOME STRENGTHENING IS ANTICIPATED UNTIL THE SEA SURFACE
 TEMPERATURES BEGIN TO DECREASE. THE OFFICIAL FORECAST REMAINS AT
 THE UPPER END OF THE INTENSITY GUIDANCE AND IS VERY CLOSE TO THE
 SHIPS MODEL THROUGH 36 HOURS. WHILE THE DYNAMICAL GFDL AND HWRF
 MODELS...AS WELL AS THE STATISTICAL LGEM...ONLY STRENGTHEN IGNACIO
 TO ABOUT 40-45 KT...THE PEAK INTENSITY SHOWN IN THE FORECAST IS NOT
 BEING LOWERED...SINCE ONLY A SLIGHT INCREASE IN ORGANIZATION WOULD
 SUPPORT SATELLITE INTENSITY ESTIMATES OF 55 KT.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      25/0300Z 17.0N 117.8W    35 KT
  12HR VT     25/1200Z 17.4N 119.1W    40 KT
  24HR VT     26/0000Z 18.1N 120.9W    50 KT
  36HR VT     26/1200Z 19.2N 122.6W    55 KT
  48HR VT     27/0000Z 20.8N 124.3W    50 KT
  72HR VT     28/0000Z 24.0N 127.5W    40 KT
  96HR VT     29/0000Z 26.5N 131.0W    25 KT...REMNANT LOW
 120HR VT     30/0000Z 27.5N 134.5W    20 KT...REMNANT LOW
  
 $$
 FORECASTER BERG
  
 

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