WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 34.1N 149.3E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 479 NM EAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 04W (MUN) WITH A SMALL PATCH OF CONVECTION OBSCURING THE
EASTERN PORTION OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE
LOW-LEVEL STRUCTURE REMAINS WELL-DEFINED EVEN THOUGH NORTHEASTERLY
SHEAR HAS GREATLY INCREASED OVER THE PAST 6-12 HOURS. ENVIRONMENTAL
ANALYSIS INDICATES THAT 04W IS NOW IN AN UNFAVORABLE ENVIRONMENT
CHARACTERIZED BY WEAK EQUATORWARD OUTFLOW, HIGH (25-30 KTS)
NORTHEASTERLY VERTICAL WIND SHEAR, AND BORDERLINE (25-26 C) SEA
SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED EIR
IMAGERY. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW. THE INTENSITY IS HELD SLIGHTLY HIGHER DUE TO 
THE INTENSITY ESTIMATES UNDERESTIMATING THE WIND SPEED IN RESPONSE TO 
THE DISSIPATING CONVECTION.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF BUILDING RIDGING
TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 41 KTS AT 061800Z
   CIMSS AIDT: 42 KTS AT 061800Z
   CIMSS DPRINT: 44 KTS 061800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 04W IS FORECAST TO TRACK GENERALLY
NORTH-NORTHWESTWARD ALONG THE WESTERN BOUNDARY OF AN EXTENSION OF
RIDGING TO THE EAST THROUGH TAU 24. AFTER TAU 24, THE SYSTEM WILL
ROUND THE RIDGE AXIS AND TURN TO THE NORTHEAST. SUBTROPICAL
TRANSITION IS FORECAST TO BEGIN AT TAU 24 AND COMPLETE BY TAU 36 AS
THE VORTEX QUICKLY BECOMES ENGULFED BY DRY AIR AND SEA SURFACE
TEMPERATURES CONTINUE TO COOL. ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO ONLY WORSEN OVER THE NEXT 36 HOURS, WHICH WILL CAUSE
04W TO WEAKEN THROUGHOUT THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN OVERALL GOOD
AGREEMENT ON THE TRACK OF 04W WITH A 77 NM CROSS-TRACK SPREAD AT
TAU 24. THERE IS SOME INCREASED ALONG-TRACK SPREAD AFTER TAU 24 DUE
TO THE VORTEX BEGINNING TO INTERACT WITH THE STRONG UPPER-LEVEL
WESTERLIES. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE
AGREES ON WEAKENING FROM TAU 0 THROUGH TAU 36 WITH MINIMAL SPREAD
BETWEEN MODELS. THEREFORE, THE JTWC INTENSITY FORECAST IS ALSO
PLACED WITH HIGH CONFIDENCE, CLOSE TO CONSENSUS.

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