Tropical Storm IGNACIO

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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
 
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FORECASTER BERG
 
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