WDPN32 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NAMTHEUN) WARNING 
NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.2N 161.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 430 NM EAST-NORTHEAST OF MINAMI TORI
SHIMA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A MEDIUM
SIZED SYSTEM WITH PERSISTENT AND DEEPENED CENTRAL CONVECTION
TRAILING A FEEDER BAND TO THE SOUTH. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON A LOW LEVEL CIRCULATION FEATURE IN
THE 150443Z SSMIS MICROWAVE IMAGE. THE INITIAL INTENSITY OF 45KTS
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE HIGHER END OF AGENCY 
DVORAK ESTIMATES (SEE BELOW) AND REFLECTS THE 6-HR IMPROVEMENT IN 
THE CENTRAL CONVECTION. ANALYSIS INDICATES THE SYSTEM IS IN A 
MARGINALLY FAVORABLE ENVIRONMENT WITH WARM SSTS AND STRONG 
EQUATORWARD OUTFLOW OFFSET BY MODERATE TO STRONG VWS. THE CYCLONE IS 
TRACKING ALONG THE
NORTHWESTERN PERIPHERY OF THE STR TO THE SOUTHEAST.

INITIAL WIND RADII BASIS: RECENT SCATTEROMETER DATA. 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 54 KTS AT 150250Z
   CIMSS ADT: 57 KTS AT 150540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS NAMTHEUN WILL CONTINUE ON ITS CURRENT TRACK
UP TO TAU 24. AFTERWARD, A SECONDARY STR TO THE EAST WILL ASSUME
STEERING AND DRIVE THE SYSTEM NORTH-NORTHEASTWARD, ACCELERATING IT
AFTER TAU 48. THE MARGINALLY FAVORABLE ENVIRONMENT WILL SUSTAIN THE
CURRENT INTENSITY UP TO TAU 24. AFTERWARD, INCREASING VWS AND
COOLING SSTS WILL ERODE THE SYSTEM DOWN TO 30KTS BY TAU 72. 
CONCURRENTLY BY TAU 48, TS 23W WILL BEGIN EXTRA-TROPICAL TRANSITION
(ETT) AS IT ENTERS THE COLD BAROCLINIC ZONE AND TRANSFORM INTO A
MODERATE GALE-FORCE COLD CORE LOW BY TAU 72. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY TIGHT AGREEMENT
LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST THAT IS LAID
OVER THE MODEL CONSENSUS. CONFIDENCE IN THE INTENSITY FORECAST IS
SET AT MEDIUM DUE TO UNCERTAINTIES ASSOCIATED WITH ETT.  

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