Tropical Storm ATSANI Advisory dom, 16-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (ATSANI) WARNING NR
08//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 17W (ATSANI), LOCATED APPROXIMATELY 206 NM
NORTH-NORTHWEST OF ENEWETAK, HAS TRACKED WEST-SOUTHWESTWARD AT 03
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH TIGHTLY-CURVED BANDING (TCB) WRAPPING INTO A WELL-DEFINED
CENTER. A 152053Z SSMIS 91GHZ IMAGE ALSO REVEALS RAPIDLY IMPROVING
DEEP CONVECTIVE BANDING OVER ALL QUADRANTS WITH A SLIGHTLY BROAD
CENTER. DUE TO THE BROAD CENTER, THERE IS FAIR CONFIDENCE IN THE
CURRENT POSITION. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH NEAR-RADIAL OUTFLOW, ENHANCED BY THE STRONG TUTT TO
THE NORTHEAST. THE CURRENT INTENSITY IS ASSESSED AT 55 KNOTS BASED
ON DVORAK INTENSITY ESTIMATES OF T3.5 (55 KNOTS) FROM PGTW AND KNES,
WHICH ARE CONSISTENT WITH THE OVERALL CONVECTIVE STRUCTURE. TS 17W
REMAINS EMBEDDED WITHIN A COMPETING STEERING ENVIRONMENT BETWEEN THE
STR TO THE NORTH AND THE NER TO THE SOUTH, CONSEQUENTLY, TRACK
MOTION REMAINS SLOW.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 17W IS EXPECTED TO CONTINUE TRACKING SLOWLY WESTWARD TO
WEST-SOUTHWESTWARD THROUGH TAU 12 DUE TO THE COMPETING STEERING
ENVIRONMENT. HOWEVER, AFTER TAU 12, THE NER WILL SHIFT TO THE EAST
ALLOWING THE STR TO BECOME THE DOMINANT STEERING INFLUENCE.
THEREFORE, TS ATSANI SHOULD ACCELERATE NORTHWESTWARD. DYNAMIC MODEL
GUIDANCE IS IN FAIR AGREEMENT AND SUPPORTS THE JTWC FORECAST TRACK,
WHICH IS POSITIONED JUST SOUTH OF THE MULTI-MODEL CONSENSUS FAVORING
THE MORE CONSISTENT ECMWF AND GFS SOLUTIONS. TS 17W IS FORECAST TO
RAPIDLY INTENSIFY AFTER TAU 24 TO AN INTENSITY OF 125 KNOTS BY TAU
72.
   C. IN THE EXTENDED PERIOD, TS ATSANI WILL MAINTAIN A
NORTHWESTWARD TRAJECTORY AS THE SYSTEM TRACKS ALONG THE WESTERN
PERIPHERY OF THE STR. AVAILABLE MODEL GUIDANCE REMAINS IN FAIR
AGREEMENT, BUT DUE TO ITS SLOW, ERRATIC MOVEMENT IN THE SHORT-TERM,
THERE IS LOW OVERALL CONFIDENCE IN THE FORECAST TRACK.//
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