Tropical Storm ATSANI Advisory ven, 21.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 28//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 287 NM EAST OF
IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY INDICATES THAT
THE SYSTEM HAS MAINTAINED INTENSITY WITH DECREASING DEEP CONVECTION
OVER THE NORTHERN SEMI-CIRCLE; HOWEVER, THE SYSTEM HAS MAINTAINED A
43-NM ROUND EYE. A 202052Z CORIOLIS 37GHZ IMAGE SUGGESTS AN EYEWALL
REPLACEMENT CYCLE IS OCCURRING WITH CONCENTRIC EYEWALLS AND TIGHTLY-
CURVED CONVECTIVE BANDING. OVERALL, THERE IS GOOD CONFIDENCE IN THE
CURRENT POSITION BASED ON THE EYE. UPPER-LEVEL ANALYSIS CONTINUES TO
REVEAL RADIAL OUTFLOW AND LOW VWS. THE CURRENT INTENSITY IS ASSESSED
AT 115 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T6.0
(115 KNOTS). TY 17W IS TRACKING ALONG THE WESTERN PERIPHERY OF THE
DEEP-LAYERED STR.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 17W WILL CONTINUE TO TRACK NORTHWESTWARD TO NORTHWARD
THROUGH TAU 36 UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED
STR. AFTER TAU 36, TY 17W WILL TURN NORTH-NORTHEASTWARD TO
NORTHEASTWARD AS IT ROUNDS THE NORTHWEST PERIPHERY OF THE STR AND
BEGINS TO ACCELERATE INTO THE WESTERLIES. UPPER-LEVEL CONDITIONS ARE
EXPECTED TO SLOWLY BECOME LESS FAVORABLE WITH INCREASING VWS.
ADDITIONALLY, TY 17W WILL ENCOUNTER MARGINAL SST, THEREFORE, GRADUAL
WEAKENING IS FORECAST THROUGH TAU 72.
   C. IN THE EXTENDED PERIOD, TY 17W WILL TRACK NORTHEASTWARD AND
WILL BEGIN TO INTERACT WITH A WEAK BAROCLINIC ZONE, WHICH WILL SERVE
TO FURTHER WEAKEN THE CONVECTIVE STRUCTURE. THE SYSTEM SHOULD REMAIN
AT STORM-FORCE STRENGTH AFTER TAU 96 DESPITE THE RAPIDLY DWINDLING
DEEP CONVECTION. AVAILABLE MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT
LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN
NNNN