WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KIROGI) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.2N 149.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 244 NM WEST-SOUTHWEST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 11W CONTINUES TO BE SHEARED, WITH A RAGGED MASS OF
DEEP CONVECTION DISPLACED LARGELY NORTHEAST OF THE LOW-LEVEL
CIRCULATION CENTER (LLCC), EVIDENT IN ANIMATED ENHANCED INFRARED
(EIR). TOTAL PRECIPITABLE WATER (TPW) IMAGERY DEPICTS A WEDGE OF
DRY AIR ENTRENCHED ACROSS THE NORTHERN SIDE OF THE SYSTEM, AND
BEGINNING TO WRAP IN CLOSER TO THE CORE FROM THE NORTHWEST. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
ANIMATED EIR IN COMBINATION WITH AGENCY DVORAK POSITION FIXES. THE
INITIAL INTENSITY OF 40 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE,
ROUGHLY AVERAGED BETWEEN PGTW T3.0 (45 KNOTS) AND RJTD T2.5 (35
KNOTS) DVORAK INTENSITY ESTIMATES AND ASSESSED HIGHER THAN ADT. THE
ENVIRONMENT IS ASSESSED AS MARGINALLY UNFAVORABLE, WITH WARM SEA
SURFACE TEMPERATURES (SSTS) AND MODERATE POLEWARD OUTFLOW OFFSET BY
MODERATE TO HIGH VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 43 KTS AT 010540Z
   CIMSS ADT: 30 KTS AT 011010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STROM 11W (KIROGI) WILL CONTINUE
TRACKING NORTHWESTWARD FOR THE NEXT 36 HOURS, ALONG THE WESTERN
PERIPHERY OF THE STEERING RIDGE TO THE EAST. AFTER TAU 36, THE STR
IS EXPECTED TO EXTEND TO THE WEST, WHICH WILL TURN THE SYSTEM
WEST-NORTHWESTWARD INITIALLY, THEN GENERALLY WESTWARD THROUGH TAU
120. IN TERMS OF INTENSITY, NO SIGNIFICANT ENVIRONMENTAL CHANGES
ARE EXPECTED IN THE FIRST 24 HOURS OF THE FORECAST, WITH SUPPORTIVE
SSTS AND ROBUST OUTFLOW COMPETING WITH PERSISTENT HIGH VWS. THE
SYSTEM IS FORECAST TO MAINTAIN A STEADY WEAKENING TREND AS OUTFLOW
BECOMES LESS FAVORABLE AND DRY AIR ENTRAINMENT INCREASES. THUS, THE
ENVIRONMENT WILL BECOME INCREASINGLY UNFAVORABLE, AND 11W IS
EXPECTED TO BEGIN DISSIPATION SOUTH OF HONSHU BEFORE ULTIMATELY
WEAKENING BELOW 25 KNOTS BY TAU 96 AS THE SYSTEM ENTERS THE EAST
CHINA SEA.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT, WITH MINIMAL SPREAD THROUGH TAU 48. BY TAU 72 AND
TAU 96, CROSS TRACK SPREAD INCREASES TO ROUGHLY 300NM, WITH THE GFS
DETERMINISTIC TRACKER FURTHER SOUTH, CLOSER TO AMAMI OSHIMA, WHILE
THE NVGM TRACKER AND THE UKMET ENSEMBLE MEAN TRACKER (UEMN) MAKE UP
THE NORTHERN EDGE OF THE AIDS ENVELOPE CLOSER TO SOUTHERN HONSHU
AND KYUSHU. THUS, THE JTWC FORECAST, LIES NEAR THE MULTI-MODEL
CONSENSUS, IS PLACED WITH HIGH CONFIDENCE THROUGH TAU 72, WITH
MEDIUM CONFIDENCE BY TAU 96. THE INTENSITY GUIDANCE IS IN FAIR
AGREEMENT IN SHOWING A CONTINUED WEAKENING TREND. THE JTWC
INTENSITY FORECAST LIES ON THE LOWER END OF THE GUIDANCE ENVELOPE
AND SLIGHTLY BELOW THE MEAN BY TAU 96. OVERALL, THE JTWC FORECAST
IS PLACED WITH MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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