WDPN32 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NAMTHEUN) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2N 158.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 443 NM NORTH-NORTHWEST OF ENEWETAK
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS ENHANCED
AND DEEPENED CENTRAL CONVECTION WITH A PARTIALLY-EXPOSED LOW LEVEL
CIRCULATION (LLC). A WIDE SWATH OF FRAGMENTED FORMATIVE BANDING IS
WRAPPING IN FROM THE EAST SIDE. THE INITIAL POSITION AND INTENSITY
OF 45KTS ARE PLACED WITH MEDIUM CONFIDENCE BASED ON MULTIPLE AGENCY
DVORAK FIXES AND STRUCTURE OF THE SYSTEM, AND IS HEDGED HIGHER THAN
THE ADVANCED DVORAK TECHNIQUE (ADT). ENVIRONMENTAL ANALYSIS
INDICATES MARGINALLY FAVORABLE CONDITIONS FOR DEVELOPMENT WITH
MODERATE POLEWARD OUTFLOW, MODERATE TO HIGH VWS, AND WARM SSTS. TS 
23W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EASTERN
EXTENSION OF THE MID-LAYER OF THE STR TO THE NORTHWEST.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: EXTENSION OF THE SUBTROPICAL RIDGE
(STR) TO THE NORTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 37 KTS AT 101940Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 23W WILL CONTINUE ON ITS CURRENT TRACK TO
THE NORTHWEST UP TO TAU 48. AFTERWARD, A SECONDARY STR TO THE
EAST-SOUTHEAST WILL ASSUME STEERING AND DRIVE THE SYSTEM POLEWARD,
CREST THE STR AXIS NEAR TAU 72, THEN RECURVE IT NORTHEASTWARD. THE
FAVORABLE CONDITIONS WILL PROMOTE A STEADY INTENSIFICATION TO A
PEAK OF 65KTS BY TAU 72. AFTERWARD, INCREASING VWS AND COOLING SSTS
WILL GRADUALLY DECAY THE SYSTEM DOWN TO 40KTS BY TAU 120. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH
TAU 36 WITH A MODEST SPREAD OF 150 NM, HOWEVER, AFTER TAU 36 THE
MODEL GUIDANCE WANES QUICKLY WITH THE SHIFT IN STEERING AND WIDENS
TO 450+ NM BY TAU 72. GFS IS THE FAR RIGHT OUTLIER, WITH THE UKMET
MODEL BEING THE MOST LEFT OUTLIER OF THE MODEL ENVELOPE. IN VIEW OF
THIS, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK UP TO TAU 48 AND
LOW CONFIDENCE AFTERWARD. THERE IS MEDIUM CONFIDENCE IN THE
INTENSITY FORECAST UP TO TAU 120.

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