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Tropical Storm IGNACIO


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TROPICAL STORM IGNACIO DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122009
800 AM PDT TUE AUG 25 2009
 
THE CLOUD PATTERN OF IGNACIO APPEARS DISORGANIZED...WITH THE CENTER
LOCATED NEAR THE NORTHERN EDGE OF AN AMORPHOUS MASS OF VERY DEEP
CONVECTION.  WHILE THE UPPER-LEVEL OUTFLOW IS FAIRLY
WELL-ESTABLISHED IN THE SOUTHERN SEMICIRCLE...IT REMAINS SOMEWHAT
RESTRICTED TO THE NORTH.  DVORAK T-NUMBERS HAVE INCREASED TO
T3.0 FROM TAFB AND SAB AND THE OFFICIAL INTENSITY IS SET AT 45 KT. 
IGNACIO STILL HAS AN OPPORTUNITY TO STRENGTHEN DURING THE NEXT
12-24 HOURS WHILE IT TRACKS OVER WARM WATERS AND ENCOUNTERS
RELATIVELY WEAK SHEAR. THEREAFTER...THE CYCLONE SHOULD REACH
SIGNIFICANTLY COOLER WATERS AND QUICKLY WEAKEN TO A REMNANT LOW BY
72 HOURS.
 
A 1158 UTC TRMM PASS WAS HELPFUL IN LOCATING THE CENTER.  WHILE
STILL UNCERTAIN...THE INITIAL MOTION ESTIMATE IS 295/10.  THE
FORECAST TRACK PHILOSOPHY HAS NOT CHANGED.  IGNACIO IS ON THE
SOUTHWEST SIDE OF A DEEP-LAYER ANTICYCLONE EXTENDING FROM THE
SOUTHERN UNITED STATES INTO THE EAST PACIFIC TO NEAR 130W.  A WEAK
SHORTWAVE TROUGH SHOULD LIFT NORTHEAST AHEAD OF A DEEPENING EAST
PACIFIC/GULF OF ALASKA LONGWAVE TROUGH...KEEPING A WEAKNESS IN THE
SUBTROPICAL RIDGE IN PLACE ALONG 130W.  THIS SHOULD HELP STEER
IGNACIO ON A NORTHWESTERLY COURSE DURING THE NEXT FEW DAYS. TOWARD
THE END OF THE PERIOD...THE CYCLONE SHOULD ASSUME A MORE WESTERLY
TRACK ONCE IGNACIO WEAKENS AND BECOMES MORE SHALLOW.  THE OFFICIAL
TRACK DIFFERS LITTLE FROM THE PREVIOUS ADVISORY AND IS IN GOOD
AGREEMENT WITH THE MODEL CONSENSUS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/1500Z 18.6N 119.3W    45 KT
 12HR VT     26/0000Z 19.4N 120.8W    50 KT
 24HR VT     26/1200Z 20.8N 122.8W    50 KT
 36HR VT     27/0000Z 22.3N 124.6W    45 KT
 48HR VT     27/1200Z 24.0N 126.5W    35 KT
 72HR VT     28/1200Z 26.5N 129.5W    25 KT...REMNANT LOW
 96HR VT     29/1200Z 27.0N 133.0W    20 KT...REMNANT LOW
120HR VT     30/1200Z...DISSIPATED
 
$$
FORECASTER KIMBERLAIN/WALTON
 
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