WDPN32 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NAMTHEUN) WARNING 
NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 157.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 394 NM SOUTH-SOUTHEAST OF MINAMI TORI
SHIMA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 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). THE INITIAL POSITION AND INTENSITY OF 45KTS ARE
PLACED WITH HIGH CONFIDENCE BASED ON MULTIPLE AGENCY DVORAK FIXES
AND A TIMELY 102331Z ASCAT-B BULLSEYE PASS. 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: SCATTEROMETER DATA 

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: T3.5 - 55 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 110110Z

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

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: TS 23W WILL CONTINUE ON A NORTHWEST 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 JUST AT THE RIDGE AXIS. AFTERWARD,
INCREASING VWS AND COOLING SSTS WILL GRADUALLY DECAY THE SYSTEM
DOWN TO 50KTS BY TAU 96. THEREAFTER, NAMTHEUN IS EXPECTED TO BEGIN 
EXTRATROPICAL TRANSITION BY TAU 120 AS IT CONTINUES TRACKING TO THE 
NORTHEAST. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT THROUGH
TAU 36 WITH A MODEST SPREAD OF 165 NM, HOWEVER, AFTER TAU 36 THE
MODEL GUIDANCE SPREADS QUICKLY WITH THE SHIFT IN STEERING AND
WIDENS TO 440+ NM BY TAU 72. NAVGEM REPLACED GFS AS THE FAR RIGHT
OUTLIER, BUT UKMET REMAINS THE MOST LEFT OUTLIER OF THE MODEL
ENVELOPE. GIVEN 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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