WDPN31 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (JANGMI) WARNING NR 
023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.9N 127.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 336 NM SOUTH-SOUTHWEST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 06W (JANGMI) AS A BROAD LOW-LEVEL CIRCULATION (LLC) THAT
CONTINUES TO DECOUPLE FROM UPPER LEVEL CIRCULATION. SURFACE
OBSERVATIONS FROM OKINAWA SHOW WEST-NORTHWESTERLY WINDS OF 30 KTS,
WHILE AMAMI TO THE NORTHEAST IS REPORTING 45 KTS OUT OF THE
SOUTHEAST, SUPPORTING BOTH THE INITIAL POSITION AND INITIAL
INTENSITY. DUE TO A LACK OF SATELLITE IMAGERY BEYOND THE SLIGHTLY
OBSCURED LLC VISIBLE ON EIR, THE INITIAL POSITION IS PLACED WITH
LOW CONFIDENCE. ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY
UNFAVORABLE CONDITIONS AS TS 06W TRANSITS NORTHWARD INTO COOL
(25-26 C) SEA SURFACE TEMPERATURES (SSTS), MODERATE TO HIGH (20-25
KTS) VERTICAL WIND SHEAR (VWS), AND DRY AIR ENTRAINMENT ON THE
SOUTHWESTERN QUADRANT, ONLY SLIGHTLY OFFSET BY MODERATE POLEWARD
OUTFLOW ALOFT. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AFOREMENTIONED SURFACE OBSERVATIONS, CIMMS
OBJECTIVE ESTIMATES, AND AGENCY DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: ADJUSTED THE 50 KT WIND RADII USING THE
011227Z ASCAT DATA.

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED NEAR IWO TO. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 54 KTS AT 1800Z
   CIMSS ADT: 32 KTS AT 1830Z
   CIMSS AIDT: 54 KTS AT 1830Z
   CIMSS D-MINT: 50 KTS AT 1739Z
   CIMSS D-PRINT: 55 KTS AT 1830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY MID-LEVEL SUBSIDENT AIR ENTRAINING INTO THE
SOUTHWESTERN FLANK OF THE CIRCULATION. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: AS TS JANGMI CONTINUES ITS RECURVATURE PATH
AROUND THE SUBTROPICAL RIDGE (STR) CENTERED NEAR IWO TO, IT IS
EXPECTED TO ACCELERATE PAST THE NORTHERN RYUKU ISLANDS AND PASS
JUST SOUTH OF KYUSHU, WITH THE POTENTIAL TO MAKE MULTIPLE LANDFALLS
ACROSS HONSHU WITH THE FINAL LANDFALL OCCURRING NEAR YOKOSUKA AND
TOKYO BEFORE EMERGING OVER WATER AND BEGINNING EXTRATROPICAL
TRANSITION (ETT) NO LATER THAN TAU 36. TS 06W IS FORECAST TO
COMPLETE ETT BY TAU 60 AS IT ENCOUNTERS HIGHER VWS, COOLER SSTS,
AND THE SOUTHERN PERIPHERY OF THE UPPER LEVEL JET. JANGMI HAS
BECOME DECOUPLED FROM THE UPPER-LEVEL CIRCULATION, LEAVING ONLY A
BROAD AND WEAK LLC. AS A RESULT, 06W IS FORECAST TO MAINTAIN
INTENSITY THROUGH TAU 24 FOLLOWED BY THE TERMINAL WEAKENING AS THE
SURFACE WINDS SPIN DOWN SIMULTANEOUS TO ETT, THOUGH TROPICAL
STORM-STRENGTH WINDS ARE ANTICIPATED THROUGH ETT.

MODEL DISCUSSION: FORECAST TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT FOR THE REMAINDER OF THE FORECAST PERIOD, WITH THE LARGEST
CROSS TRACK SPREAD OF 70 NM AT TAU 60. THE JTWC TRACK FORECAST IS
LAID NEAR THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. THE MODEL
INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT AND LAID WITH HIGH
CONFIDENCE SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS IN AGREEMENT
WITH THE MESOSCALE MODELS AND GFS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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