Tropical Storm ATSANI Advisory пн, 17.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 239 NM NORTHWEST
OF ENEWETAK, HAS TRACKED WESTWARD AT 06 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A SLOWLY
CONSOLIDATING SYSTEM WITH DEEP CONVECTIVE BANDING STRUGGLING TO FORM
OVER THE NORTHWESTERN QUADRANT. THIS IS EVIDENT IN A 161528Z NOAA-19
89GHZ IMAGE, WHICH SHOWS FRAGMENTED BANDING WRAPPING TIGHTLY INTO A
WEAK MICROWAVE EYE FEATURE. RECENT IMAGERY HAS INDICATED STRONGER
CONVECTIVE BANDING AND A MORE DEFINED CENTER; HOWEVER, THE SYSTEM
APPEARS TO HAVE WEAKENED SLIGHTLY. DESPITE THE SLIGHT WEAKENING
TREND, THE CURRENT INTENSITY IS HELD AT 65 KNOTS BASED ON T4.0
DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES. ANIMATED WATER VAPOR
IMAGERY CONTINUES TO SHOW EXCELLENT OVERALL OUTFLOW, ENHANCED BY A
TUTT CELL NEAR THE DATELINE; HOWEVER, THE IMAGERY SUGGESTS UPPER-
LEVEL CONVERGENCE ASSOCIATED WITH THE TUTT PRESSING DOWN OVER THE
NORTHERN PERIPHERY OF THE SYSTEM. TY 17W REMAINS IN A COMPETING
STEERING ENVIRONMENT BETWEEN A WEAK NEAR-EQUATORIAL RIDGE TO THE
SOUTH AND THE STRONG STR TO THE NORTH. THIS STEERING INFLUENCE HAS
GENRALLY PRODUCED A SLOW WESTWARD TRACK.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 17W WILL CONTINUE TRACKING SLOWLY WESTWARD THROUGH TAU 12
DUE TO THE COMPETING STEERING ENVIRONMENT. BEYOND TAU 12, THE NER
WILL SHIFT TO THE EAST ALLOWING THE STR TO BECOME THE DOMINANT
STEERING INFLUENCE. THEREFORE, TY 17W WILL ACCELERATE NORTHWESTWARD
ALONG THE SOUTHWEST PRIPHERY OF THE STR. DUE TO THE BROAD NATURE OF
THE LLCC AND THE MARGINALLY-FAVORABLE ENVIRONMENT, THE SYSTEM IS
EXPECTED TO INTENSIFY AT A CLIMATOLOGICAL RATE THROUGH TAU 72.
   C. IN THE EXTENDED FORECAST PERIOD, AN APPROACHING MID-LATITUDE
SHORTWAVE TROUGH OVER THE KOREAN PENINSULA AND WESTERN JAPAN WILL
ERODE THE WESTERN PERIPHERY OF THE STR, WHICH WILL ALLOW TY 17W TO
MAINTAIN A NORTHWESTWARD TRACK TOWARD IWO TO. AVAILABLE MODEL
GUIDANCE REMAINS IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK. AFTER TAU 120, CURRENT
GUIDANCE SUPPORTS A RE-CURVE SCENARIO TOWARD WESTERN OR CENTRAL
JAPAN ALTHOUGH THERE IS CURRENTLY A HIGH DEGREE OF UNCERTAINTY IN
THE EXACT TIMING OF THE RE-CURVE.//
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