WDPN31 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.4N 134.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 486 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM
CONTINUED TO STRUGGLE TO CONSOLIDATE UNDER STRONG VERTICAL WIND
SHEAR (VWS) AS EVIDENCED BY ITS COLD DENSE OVERCAST OFFSET EASTWARD
AND PARTLY EXPOSING THE LOW LEVEL CIRCULATION (LLC). THE INITIAL
INTENSITY IS PLACED WITH HIGH CONFIDENCE BASED ON THE LLC FEATURE
IN THE MSI LOOP. THE INITIAL INTENSITY OF 30KTS IS ALSO PLACED WITH 
HIGH CONFIDENCE BASED ON THE AVERAGE OF CLOSELY-VALUED AGENCY AND
AUTOMATED DVORAK ESTIMATES AND REFLECTS THE MOSTLY SUSTAINED 6-HR
CONVECTIVE SIGNATURE. ANALYSIS INDICATES A MARGINAL ENVIRONMENT
WITH WARM SSTS AND MODERATE DUAL OUTFLOW OFFSET BY STRONG VWS.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE EXTENSION TO THE
EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 37 KTS AT 242330Z
   CIMSS DPRNT: 30 KTS AT 242330Z
   CIMSS DMNT: 31 KTS AT 242330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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: TD 18W WILL CONTINUE TO TRACK NORTHWESTWARD
UNDER THE STR EXTENSION TO THE EAST. SHORTLY AFTER TAU 24, IT WILL
CREST THE STR AXIS THEN RECURVE AND ACCELERATE NORTHEASTWARD ON THE
POLEWARD SIDE OF THE STR. THE MARGINAL ENVIRONMENT WILL SUSTAIN THE
CURRENT INTENSITY UP TO TAU 12; AFTERWARD, THE ENVIRONMENT WILL
BECOME UNFAVORABLE AS THE CYCLONE DRIFTS INTO EVEN STRONGER VWS,
ERODING THE CYCLONE DOWN TO 25KTS. AFTER TAU 48, TD 18W IS EXPECTED
TO SLIGHTLY RE-INTENSIFY TO 30KTS AS THE VWS RELAXES. CONCURRENTLY,
IT WILL BEGIN EXTRA-TROPICAL TRANSITION AS IT ENTERS THE BAROCLINIC
ZONE, AND BY TAU 96, WILL TRANSFORM INTO A COLD CORE LOW. THERE IS
A DISTINCT POSSIBILITY THAT TD 18W WILL DISSIPATE AFTER TAU 24
MOSTLY DUE TO THE INCREASED VWS. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH THE TRACK FORECAST WITH NVGM AS THE NOTABLE OUTLIER REVERSING
THE TRAJECTORY SOUTHWESTWARD AFTER TAU 48. THERE ARE ALSO NOTABLE
DIFFERENCES IN ALONG-TRACK SPEED AMONG THE CONSENSUS MEMBERS. THE
MAIN PACK, HOWEVER, SPREADS OUT TO A MERE 110NM ACROSS-TRACK AT TAU
96. IN VIEW OF THESE AND THE POSSIBILITY OF AN EARLY DISSIPATION,
THERE IS MEDIUM CONFIDENCE TO THE JTWC TRACK FORECAST AND LOW
CONFIDENCE IN THE INTENSITY FORECAST.


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