Tropical Storm CHOI-WAN Advisory Mon Oct 05

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (CHOI-WAN) WARNING
NR 11//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (CHOI-WAN), LOCATED APPROXIMATELY 725 NM
NORTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WESTWARD AT 13 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS TIGHTLY-CURVED BANDS OVER THE NORTHERN AND SOUTHERN
SEMI-CIRCLE WRAPPING INTO THE CONSOLIDATED LOW-LEVEL CIRCULATION
CENTER. THE CURRENT POSITION IS BASED ON THE MSI AND SATELLITE FIXES
FROM PGTW AND RJTD WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 55
KNOTS IS BASED ON THE CURRENT STRUCTURE AND A RECENT 042305Z ASCAT
IMAGE. UPPER-LEVEL ANALYSIS CONTINUES TO INDICATE TS 23W IS LOCATED
IN A FAVORABLE ENVIRONMENT WITH RADIAL OUTFLOW AND LOW VERTICAL WIND
SHEAR (VWS). ADDITIONALLY, WARM SEA SURFACE TEMPERATURES (SSTS) ARE
CONDUCIVE FOR FURTHER DEVELOPMENT. TS 23W IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF A DEEP-LAYERED SUB-TROPICAL RIDGE (STR) TO THE
NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS 23W WILL CONTINUE TRACKING WESTWARD UNDER THE INFLUENCE OF
THE STR OVER THE NEXT 12 TO 18 HOURS. AFTERWARDS, TS CHOI-WAN IS
FORECAST TO ROUND THE STR AND TRACK MORE POLEWARD. FAVORABLE
ENVIRONMENTAL CONDITIONS WILL PERSIST OVER THE NEXT 48 HOURS;
HOWEVER, DUE TO THE BROAD NATURE OF THE SYSTEM, TS 23W IS EXPECTED
TO GRADUALLY INTENSIFY AS IT CONTINUES TO CONSOLIDATE. AS THE SYSTEM
GAINS LATITUDE, IT WILL ENCOUNTER INCREASING VWS AND DECREASING SSTS
WHICH WILL BEGIN TO WEAKEN THE SYSTEM.
   C. CONTINUED UNFAVORABLE CONDITIONS WILL FURTHER DECAY THE
SYSTEM. BY TAU 72, TS CHOI-WAN WILL BEGIN EXTRA-TROPICAL TRANSITION
AS IT INTERACTS WITH THE MIDLATITUDE WESTERLIES. TS 23W WILL BE
FULLY EMBEDDED IN THE BAROCLINIC ZONE, GAINING FRONTAL
CHARACTERISTICS, AND TRANSITIONING TO A STRONG COLD-CORE LOW BY THE
END OF THE FORECAST PERIOD. AVAILABLE MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT; HOWEVER, GIVEN THE UNCERTAINTY IN THE INITIAL POSITION
AND THE CURRENT STORM MOTION, THE JTWC FORECAST TRACK CONFIDENCE
LEVEL REMAINS LOW.//
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