Tropical Storm ATSANI Advisory 19 Αυγ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 577 NM EAST-
NORTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED NORTHWESTWARD AT 12
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY CONTINUES TO SHOW THE SYSTEM HAS MAINTAINED OVERALL
CONVECTIVE SIGNATURE WITH CURVED BANDS WRAPPING INTO A 18-NM
DIAMETER EYE. THE CURRENT POSITION IS BASED ON THE EYE FEATURE WITH
HIGH CONFIDENCE. THE INITIAL INTENSITY OF 120 KNOTS IS HELD SLIGHTLY
HIGHER THAN THE CONGRUENT DVORAK FIXES FROM PGTW, KNES, AND RJTD TO
REFLECT THE SLIGHTLY IMPROVED STRUCTURE. UPPER-LEVEL ANALYSIS
INDICATES TY ATSANI IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW
(05 TO 10 KNOT) VWS AND EXCELLENT RADIAL OUTFLOW. THE CYCLONE IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A STR TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 17W WILL REMAIN ON A NORTHWESTWARD TRAJECTORY THROUGH TAU
72 UNDER THE STEERING STR. VERY FAVORABLE ENVIRONMENTAL AND UPPER-
LEVEL CONDITIONS ARE EXPECTED TO PERSIST ALLOWING THE SYSTEM TO
FURTHER INTENSIFY LEADING TO A PEAK INTENSITY OF 140 BY TAU 24.
AFTER TAU 48, INCREASING VWS WILL BEGIN TO WEAKEN THE SYSTEM.
   C. TY 17W WILL CONTINUE TO TRACK NORTHWESTWARD UNDER THE STEERING
STR THROUGH TAU 96. AFTERWARD, AN UPPER-LEVEL TROUGH PASSING TO THE
NORTH WILL CAUSE A WEAKNESS IN THE STR, TURNING TY 17W POLEWARD.
CONCURRENTLY, THE COMBINED EFFECTS OF LOWER OHC VALUES AND INCREASED
VWS WILL CONTINUE TO DECAY TY ATSANI. AVAILABLE MODEL GUIDANCE
REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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