Tropical Storm ATSANI Advisory mar, 18-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 16//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 670 NM EAST-
NORTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS DEEPENED CONVECTION WITH TIGHTLY-CURVED
BANDS WRAPPING INTO A PERSISTENT 8 NM DIAMETER EYE THAT SUPPORTS THE
HIGH CONFIDENCE IN THE CURRENT POSITION. THE INITIAL INTENSITY OF
115 KNOTS IS BASED ON CORRESPONDING DVORAK INTENSITY ESTIMATES OF
T6.0 (115 KNOTS) FROM PGTW AND RJTD. UPPER-LEVEL ANALYSIS INDICATES
TY ATSANI IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW (05 TO 10
KNOT) VWS AND RADIAL OUTFLOW AS EVIDENT ON THE WATER VAPOR IMAGERY.
TY 17W 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 36.
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 SLIGHTLY
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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