Tropical Storm IGNACIO

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TROPICAL STORM IGNACIO DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT SAT AUG 23 2003
 
SATELLITE IMAGERY INDICATES THAT THE DEPRESSION HAS STRENGTHENED AND
IS NOW A TROPICAL STORM.  DVORAK INTENSITY ESTIMATES AT 12Z WERE 45
KT FROM TAFB AND SAB AND 35 KT FROM AFWA.  THE EARLIER PARTLY-
EXPOSED CENTER IS NO LONGER APPARENT...AND GOOD BANDING HAS
DEVELOPED SOUTH AND EAST OF THE CENTER.  FIRST VISIBLE IMAGES SHOW
ROTATING OVERSHOOTING TOPS.  THE LOCATION OF THIS APPARENT CENTER
IS NOT IN REAL GOOD AGREEMENT WITH EARLIER POSITIONS...BUT IF THE
CENTER IS THERE THEN THE INITIAL INTENSITY OF 40 KT IS TOO LOW.   
 
THE INITIAL MOTION IS ESTIMATED AT 310/05...BUT THERE IS STILL
CONSIDERABLE UNCERTAINTY AS TO THE LOCATION OF THE CENTER AND HENCE
THE MOTION. IGNACIO IS LOCATED ON THE SOUTHWEST SIDE OF A WEAK
MID-LEVEL RIDGE THAT IS ANCHORED IN CENTRAL MEXICO...AND THE
CYCLONE NOW SEEMS TO BE RESPONDING TO THIS AS INDICATED BY THE
RECENT INCREASE IN FORWARD SPEED.  THERE IS A FAIR AMOUNT OF SPREAD
IN THE MODEL GUIDANCE.  THE NOGAPS AND GFNI TAKE IGNACIO ALMOST DUE
NORTHWARD...WHILE MOST OF THE REMAINING GUIDANCE IS NEAR OR JUST
OFF THE WEST COAST OF THE BAJA PENINSULA. THE UKMET HAS A TRACK
ALONG THE EAST COAST OF THE PENINSULA. THE OFFICIAL FORECAST HAS
BEEN SHIFTED A LITTLE TO THE LEFT OF THE PREVIOUS TRACK AND IS VERY
CLOSE TO THE CONSENSUS OF THE GFS...GFDL...AND UKMET MODELS. THE
OFFICIAL FORECAST IS ALSO A LITTLE FASTER THAN THE PREVIOUS
ADVISORY FOR THE FIRST 36 HOURS. 
 
THE RECENT MARKED IMPROVEMENT IN STRUCTURE SUGGESTS THAT IGNACIO
WILL BE STRONGER THAN PREVIOUSLY FORECAST AND THE OFFICIAL
INTENSITY FORECAST HAS HAD TO BE ADJUSTED UPWARD.  THERE IS
CURRENTLY NO EVIDENCE OF THE NORTHERLY SHEAR OBSERVED EARLIER.  AS
LONG AS IGNACIO CONTINUES ON A NORTHWESTERLY TRACK IT SHOULD AVOID
THE NORTHERLY SHEAR ASSOCIATED WITH AN UPPER LOW CENTERED OVER
NORTH-CENTRAL MEXICO.  IGNACIO IS A SMALL SYSTEM OVER VERY WARM
WATER...AND IT IS NOT INCONCIEVABLE THAT IT COULD REACH HURRICANE
STATUS PRIOR TO LANDFALL.  SHOULD THE RECENT DEVELOPMENT TREND
CONTINUE THEN A SHORT-FUSED HURRICANE WARNING MIGHT BE REQUIRED IN
A FEW HOURS.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/1500Z 21.8N 108.5W    40 KT
 12HR VT     24/0000Z 22.3N 109.1W    45 KT
 24HR VT     24/1200Z 23.2N 110.0W    55 KT...INLAND
 36HR VT     25/0000Z 24.0N 111.0W    45 KT...ALONG THE COAST
 48HR VT     25/1200Z 24.5N 111.8W    35 KT...ALONG THE COAST
 72HR VT     26/1200Z 25.5N 113.0W    25 KT...DISSIPATING
 96HR VT     27/1200Z 26.5N 114.0W    20 KT...REMNANT LOW
120HR VT     28/1200Z...DISSIPATED
 
 
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