Hurricane IGNACIO

ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM
HURRICANE IGNACIO DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT SUN AUG 24 2003
 
DESPITE A CONVECTIVE BURST OVER THE PAST HOUR OR SO...IGNACIO HAS
WEAKEND SLIGHTLY BASED ON LONGER TERM...6 HOUR...TRENDS OBSERVED IN
SATELLITE IMAGERY.  THE SATELLITE INTENSITY ESTIMATE FROM TAFB IS
STILL 90 KT...ALTHOUGH THE T NUMBER IS DOWN TO 4.0...65 KT.  THE
ESTIMATES FROM FROM SAB AND AFWA ARE 77 KT. THE INITIAL INTENSITY
IS PARED DOWN TO 80 KNOTS FOR THIS ADVISORY...MAKING IGNACIO A
CATEGORY ONE HURRICANE ON THE SAFFIR-SIMPSON SCALE. 

IGNACIO HAS MOVED NORTH-NORTHWESTWARD OVER THE PAST 12 HOURS...WHILE
THE SHORTER-TERM MOTION HAS BEEN MORE TOWARD THE NORTHWEST.  WATER
VAPOR IMAGERY DEPICTS A SMALL ANTICYCLONE AND RIDGING TO THE NORTH
OF IGNACIO OVER THE SOUTHWESTERN UNITED STATES...PRODUCING WEAK
STEERING CURRENTS. THERE HAS BEEN LITTLE CHANGE TO THE PREVIOUS
ADVISORY OR FORECAST PHILOSOPHY...AND IN SPITE OF THE WEAK
STEERING...MODEL GUIDANCE IS TIGHTLY CLUSTERED THROUGH 72 HOURS.
AFTER THAT...THE GFS TURNS IGNACIO TOWARD MAINLAND MEXICO. ON THE
OTHER HAND THE GUNS/GUNA ENSEMBLES BEND THE STORM SHARPLY WESTWARD
AFTER 72 HOURS. THE SPLIT IN THE GUIDANCE SUGGESTS A PARTICULARLY
WEAK STEERING CURRENT IN THE LONGER RANGE. THE OFFICIAL FORECAST
INDICATES A VERY SLOW MOTION ON DAYS 4 AND 5. 

THE INTENSITY FORECAST...AS IN THE PREVIOUS ADVISORY...CALLS FOR A
VERY SLOW WEAKENING THROUGH THE PERIOD...KEEPING IGNACIO A
HURRICANE THROUGH 72 HOURS. BEYOND THAT...INCREASING INTERACTION
WITH LAND WEAKENS THE CYCLONE FURTHER TO A TROPICAL STORM.  THE
SHIPS MODEL FORECASTS SOME INTENSIFICATION IN 24-36 HOURS AND
FORECASTS A 90 KNOT HURRICANE AT 72 HOURS. THE VERY WARM SSTS AND
LIGHT SHEAR ARE THE LARGEST CONTRIBUTORS TO THE SHIPS INTENSITY
FORECASTS...AND SUCH A REINTENSIFICATION COULD OCCUR IF IGNACIO CAN
GET FARTHER AWAY FROM LAND.

FORECASTER COBB/FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/0300Z 23.9N 109.3W    80 KT
 12HR VT     25/1200Z 24.3N 109.7W    75 KT
 24HR VT     26/0000Z 24.7N 110.2W    75 KT
 36HR VT     26/1200Z 25.2N 110.6W    70 KT
 48HR VT     27/0000Z 25.9N 111.1W    70 KT
 72HR VT     28/0000Z 27.5N 112.0W    65 KT
 96HR VT     29/0000Z 28.5N 112.5W    60 KT
120HR VT     30/0000Z 29.0N 113.0W    55 KT
 
 
NNNN