WDPN32 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (CHANTHU) WARNING 
NR 034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.5N 124.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 299 NM WEST-SOUTHWEST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH THE 
REMAINING ASSOCIATED CONVECTION REMAINING TO THE NORTH AND WEST. THE 
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE LLCC 
SEEN IN EIR AND A 140952Z SSMIS 91GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 45 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
SCATTEROMETER DATA AND DVORAK INTENSITY ESTIMATES. THE OVERALL
MARGINALLY UNFAVORABLE ENVIRONMENTAL CONDITIONS ARE DUE TO THE LOW
OCEAN HEAT CONTENT OFFSET BY THE STRONG UPPER LEVEL DIVERGENCE
NEAR THE LLCC.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COL BETWEEN SUBTROPICAL RIDGE (STR) TO
THE NORTHWEST AND STR TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 47 KTS AT 140710Z
   CIMSS ADT: 35 KTS AT 141140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS CHANTHU IS EXPECTED TO REMAIN
QUASI-STATIONARY (QS) OVER THE NEXT TWO DAYS IN THE COL. AFTERWARD,
THE STR TO THE NORTHWEST WILL WEAKEN, ALLOWING THE SECONDARY STR TO
THE SOUTHEAST TO ASSUME STEERING AND DRIVE THE SYSTEM NORTHEASTWARD
THROUGH THE SEA OF JAPAN (SOJ), CROSSING NORTHERN HONSHU NEAR
MISAWA AND EXITING INTO THE PACIFIC OCEAN SHORTLY BEFORE TAU 96.
THE MARGINALLY UNFAVORABLE CONDITIONS, EXACERBATED BY FURTHER
COOLING OF THE SSTS AS THE QS SYSTEM CONTINUES TO UPWELL COLD
WATER, WILL PROMOTE STEADY WEAKENING DOWN TO 35 KNOTS BY TAU 48.
AFTERWARD, THE NORTHEASTWARD TRACK INTO HIGHER VWS AND COLDER SSTS
OF THE SOJ WILL FURTHER WEAKEN IT TO 30KTS BY TAU 96 AS IT BECOMES
FULLY EXTRATROPICAL.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT ON
TRACK GUIDANCE. HOWEVER, GIVEN THE UNCERTAINTY IN THE CURRENT STORM
MOTION AND DURATION IN THE COL AREA, THERE IS LOW CONFIDENCE IN THE
JTWC TRACK FORECAST THAT IS LAID CLOSE TO THE MODEL CONSENSUS. THE 
PRIMARY UNCERTAINTY IN THE INTENSITY GUIDANCE IS DUE TO COMPETING 
ENVIRONMENTAL FACTORS OVER THE NEXT 48 HOURS.

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