WDPN31 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN)         
WARNING NR 037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 42.1N 137.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 211 NM WEST-NORTHWEST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD
LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DISORGANIZED DEEP
CONVECTION SHEARED TO THE NORTHWEST AND NORTH DUE TO HIGH SOUTHERLY
VERTICAL WIND SHEAR (VWS). A 161512Z GMI MICROWAVE IMAGE REVEALS
SHALLOW BANDING WRAPPING INTO A RAGGED, BROAD LLCC WITH DEEP
CONVECTION CONFINED TO THE NORTHWESTERN AND NORTHERN PERIPHERIES. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE EIR
IMAGERY AND THE GMI IMAGE WITH MEDIUM CONFIDENCE. THE INITIAL
INTENSITY IS BASED ON A RECENT ASCAT-C IMAGE SHOWING 35-40 KNOT
WINDS OVER THE NORTHWEST QUADRANT AS WELL AS A 161810Z AIDT
ESTIMATE OF 41 KNOTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 29 KTS AT 161740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY ENVIRONMENT

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: TROPICAL STORM (TS) 07W IS FORECAST TO
ACCELERATE NORTHEASTWARD THROUGH THE FORECAST PERIOD WITHIN A
REGION OF STRONG UPPER-LEVEL SOUTHWESTERLY MIDLATITUDE FLOW. TS 07W
WILL WEAKEN STEADILY THROUGH THE FORECAST PERIOD DUE TO STRONG
VERTICAL WIND SHEAR (30 TO 35 KNOTS), RAPIDLY COOLING SST
(CURRENTLY 24 CELSIUS DECREASING TO AS LOW AS 16 CELSIUS BY TAU
24), AND A VERY DRY ENVIRONMENT. THE SYSTEM IS UNDERGOING
EXTRA-TROPICAL TRANSITION (ETT) AND WILL COMPLETE ETT WITHIN THE
NEXT 12 TO 24 HOURS AS IT TRACKS UNDER A JET AND GAINS WEAK FRONTAL
CHARACTERISTICS.   

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
(MEDIUM CONFIDENCE) WITH A 40 NM TO 80 NM CROSS-TRACK SPREAD IN
GUIDANCE FROM TAU 12 TO TAU 24. RELIABLE INTENSITY GUIDANCE
SUPPORTS THE STEADY WEAKENING TREND WITH HIGH CONFIDENCE. THE ETT 
TIMING IS ALSO SUPPORTED BY THE 161200Z GFS FSU CYCLONE PHASE 
PRODUCT. 

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