WDPN32 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NAMTHEUN) WARNING 
NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.0N 162.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 484 NM EAST-NORTHEAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
MEDIUM SIZED SYSTEM WITH A PERSISTENT DEEP CENTRAL CONVECTION THAT IS
TRAILING A FEEDER BAND TO THE SOUTH. THE NORTHERN PERIPHERIES ARE
NOW GETTING FRAYED AND ELONGATED WITH EXPOSURE TO THE STRONG
PREVAILING WESTERLIES, AS EVIDENCED BY TRANSVERSE BANDING IN THE
CIRRI CLOUDS. THE INITIAL POSITION AND INTENSITY ARE PLACED WITH
HIGH CONFIDENCE BASED ON A 151059Z 25-KM RESOLUTION ASCAT AND LINED
UP WITH A LOW LEVEL CIRCULATION FEATURE IN THE 1500855Z GPM
MICROWAVE IMAGE. ANALYSIS INDICATES THE SYSTEM IS IN A MARGINALLY
FAVORABLE ENVIRONMENT WITH WARM SSTS AND STRONG EQUATORWARD OUTFLOW
OFFSET BY STRONG VWS. THE CYCLONE IS TRACKING ALONG THE
SOUTHWESTERN EXTENSION OF THE STR TO THE EAST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 53 KTS AT 151140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: UNDER THE STEERING INFLUENCE OF THE STR TO THE
EAST, TS NAMTHEUN WILL CONTINUE ON ITS CURRENT TRACK UP TO TAU 24
THEN NORTHWARD UP TO TAU 48 BEFORE ACCELERATING NORTHEASTWARD. 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 THEN TRANSFORM INTO A MODERATE GALE-FORCE COLD CORE 
LOW BY TAU 72. 

MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN VERY TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST THAT IS LAID
CLOSE TO 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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