905 
 WTPZ42 KNHC 260232
 TCDEP2
 TROPICAL STORM IGNACIO DISCUSSION NUMBER   6
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122009
 800 PM PDT TUE AUG 25 2009
  
 IGNACIO NOW CONSISTS OF A SMALL CENTRAL DENSE OVERCAST WITH A
 CONVECTIVE BAND CURLING AROUND THE EASTERN PART OF THE CIRCULATION. 
 THE WESTERN SEMICIRCLE IS MOSTLY VOID OF ANY DEEP CONVECTION...AND
 VISIBLE SATELLITE IMAGERY SHOWS A DECK OF LOW-LEVEL STRATUS BEING
 ADVECTED INTO THE CIRCULATION FROM THE NORTH.  AN ASCAT PASS AT
 1809 UTC INDICATES THAT THE TROPICAL-STORM-FORCE WINDS ARE
 PRIMARILY LIMITED TO THE EASTERN SEMICIRCLE AND THAT THE MAXIMUM
 WINDS AT THE TIME WERE 45 KT.  THEREFORE...THE INITIAL INTENSITY IS
 HELD AT 45 KT FOR THIS ADVISORY AND IS IN AGREEMENT WITH DVORAK
 ESTIMATES OF T3.0 FROM TAFB AND SAB.  THIS COULD BE GENEROUS NOW
 THAT THERE HAS BEEN A RECENT WARMING OF THE CONVECTIVE CLOUD TOPS.
 
 THE CENTER OF IGNACIO IS NOW MOVING OVER SEA SURFACE TEMPERATURES
 NEAR 26C...AND THE SSTS ARE EXPECTED TO DECREASE BY SEVERAL DEGREES
 CELSIUS AS THE STORM MOVES NORTHWESTWARD OVER THE NEXT 48 HOURS. 
 COMBINED WITH THE INGESTION OF DRIER AND MORE STABLE AIR...THIS
 SHOULD CAUSE IGNACIO TO STEADILY WEAKEN OVER THE NEXT 2 DAYS.  SOME
 OF THE GUIDANCE...INCLUDING THE INTENSITY CONSENSUS...HOLDS IGNACIO
 AT ITS CURRENT INTENSITY FOR ANOTHER 36 HOURS OR SO...BUT THIS
 APPEARS UNLIKELY GIVEN THE UNFAVORABLE ENVIRONMENT AHEAD OF THE
 CYCLONE.  THE OFFICIAL FORECAST HAS BEEN ADJUSTED DOWNWARD AND
 SHOWS IGNACIO BECOMING A REMNANT LOW BY 72 HOURS.  ALL OF THE
 GLOBAL MODELS THEN DISSIPATE THE SYSTEM BY 96 HOURS.
 
 THE FORWARD SPEED HAS INCREASED FOR AN INITIAL MOTION OF 305/13. 
 IGNACIO IS MOVING AROUND THE WESTERN PERIPHERY OF A MID-LEVEL RIDGE
 CENTERED OVER THE SOUTHWESTERN UNITED STATES...BUT ONCE IT WEAKENS
 IT IS EXPECTED TO SLOW DOWN AND TURN TO THE WEST WITHIN THE
 LOW-LEVEL TRADE WIND FLOW. 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      26/0300Z 20.4N 121.5W    45 KT
  12HR VT     26/1200Z 21.5N 123.2W    40 KT
  24HR VT     27/0000Z 23.1N 125.2W    40 KT
  36HR VT     27/1200Z 24.8N 127.1W    35 KT
  48HR VT     28/0000Z 26.3N 128.7W    30 KT
  72HR VT     29/0000Z 27.5N 131.5W    20 KT...REMNANT LOW
  96HR VT     30/0000Z...DISSIPATED
  
 $$
 FORECASTER BERG
  
 

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