Tropical Storm KROVANH Advisory Tue Sep 15

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (TWENTY) WARNING NR
04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 20W (TWENTY), LOCATED APPROXIMATELY 391 NM
NORTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS DEEPENED CENTRAL CONVECTION OBSCURING THE LLCC. A
151115Z METOP-A MICROWAVE IMAGE CONTINUES TO SHOW THE BULK OF THE
DEEP CONVECTION OVER THE NORTHWESTERN QUADRANT WITH CURVED BANDS
WRAPPING INTO THE CENTER. THE CURRENT POSITION IS BASED ON THE EIR
LOOP, AFOREMENTIONED MICROWAVE IMAGE ALONG WITH SATELLITE FIXES FROM
PGTW WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 35 KNOTS IS
BASED ON THE SLIGHTLY IMPROVED STRUCTURE AND DVORAK INTENSITY
ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS
INDICATES TS 20W IS LOCATED IN A MARGINALLY-FAVORABLE ENVIRONMENT
WITH LOW TO MODERATE (10 TO 20 KNOT) VWS AND GOOD DUAL OUTFLOW. THE
SYSTEM IS CURRENTLY TRACKING UNDER THE STEERING INFLUENCE OF A
BUILDING STR TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 20W WILL CONTINUE TRACKING GENERALLY NORTHWESTWARD AS THE
STR BECOMES FIRMLY ESTABLISHED TO THE NORTH. UPPER-LEVEL CONDITIONS
ARE FORECAST TO IMPROVE ALLOWING STEADY INTENSIFICATION. BY TAU 72,
ENHANCED POLEWARD OUTFLOW IS EXPECTED AS TS 20W ROUNDS THE STEERING
RIDGE AXIS, LEADING TO A PEAK INTENSITY OF 105 KNOTS.
   C. THE CYCLONE WILL TRACK NORTHEASTWARD ALONG THE NORTHWESTERN
PERIPHERY OF THE STR THROUGH THE REMAINDER OF THE FORECAST PERIOD.
CONCURRENTLY, INCREASING VWS AND COOLER SSTS WILL BEGIN TO WEAKEN
THE SYSTEM. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
REGARDING TIMING OF THE TURN AROUND TAU 72; HOWEVER, DUE TO THE
UNCERTAINTY IN THE INITIAL POSITIONING AND THE SPREAD AMONG
AVAILABLE TRACKERS IN THE EXTENDED TAUS, THERE IS OVERALL LOW
CONFIDENCE IN THE JTWC FORECAST.//
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