WDPN32 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (PULASAN) 
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.5N 122.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 317 NM WEST-SOUTHWEST OF CHINHAE, SOUTH
KOREA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND SURFACE
REPORTS FROM CHEJU DO AND SHIPPING IN THE EAST CHINA SEA INDICATE
THAT PULASAN IS IN THE EARLIEST PHASE OF EXTRA-TROPICAL TRANSITION
(ETT). THERE REMAINS SOME SEPARATION FROM THE CONVECTIVE MASS WHICH
IS JUST EQUATORWARD OF THE LOW LEVEL CIRCULATION CENTER (LLCC). 
THE SYSTEM TRACKED OFF-SHORE DURING THE EVENING AND HAS BEEN SLOW
TO INTENSIFY AS IT IS TRACKING OVER A POOL OF SLIGHTLY COOLER WATER
(26C) AT THE MOMENT, BUT WILL RE-ENTER 28C WATER WITHIN THE NEXT 12
HOURS. THE SYSTEM IS HOLDING ITS WARM CORE BUT BEGINNING TO MERGE
WITH A WEAK BAROCLINIC ZONE ENCROACHING FROM THE WEST SEA AND
VERTICAL WIND SHEAR HAS RISEN TO OVER 20KTS. WATER VAPOR ANIMATION
SHOWS IMPINGEMENT OVER THE POLEWARD SECTOR AND THE VERY BEGINNINGS
OF STRETCHING IN THE CONVECTIVE SHIELD. PLACEMENT OF THE LLCC AND
THE INTENSITY HAS BEEN AIDED BY A 201543Z SCATTEROMETERY
PASS AND SUPPORTED BY DVORAK ASSESSMENTS FROM BOTH JAPAN AND TAIWAN
BUT THE LLCC IS PLACED POLEWARD OF THE SCATTEROMETERY BASED ON
MOMENTUM AND THE TWO AGENCY FIXES AND THE OSCAT PRACTICE OF
FORCING MODEL VORTICES INTO THE WIND FIELDS.

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

CURRENT STEERING MECHANISM: THE FURTHERMOST EXTENSION OF THE
OCEANIC SUBTROPICAL RIDGE AND THE ENCROACHING POLAR FRONT. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 37 KTS AT 201730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25 KTS
   SST: 26-28 CELSIUS
   OUTFLOW: MODERATE EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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: TROPICAL DEPRESSION PULASAN WILL MOVE OUT OF
THE COOLER WATERS AND BUILD TO LOW TROPICAL STORM STRENGTH AS IT
ACCELERATES AND MERGES WITH THE POLAR FRONT. THE SYSTEM WILL FLARE
UP MODERATELY AS IT GOES EXTRA-TROPICAL, BUT SHARPLY INCREASING
VERTICAL WIND SHEAR WILL CAP EXTREME DEVELOPMENT DESPITE SEA WATERS
ALONG TRACK BEING PLENTY WARM ENOUGH TO SUSTAIN A VIGOROUS SYSTEM
THROUGH THE TRANSITION. THE BAROCLINIC ZONE WILL PROVIDE GOOD
CERTAINTY FOR A LAND STRIKE AT THE SOUTHWESTERN TIP OF THE KOREAN
PENINSULA AT LOW GALE FORCE. THE SPEED OF ADVANCE AND VIGOROUS TROUGH
ALOFT WILL KEEP THE SYSTEM STRONG AS IT TRACKS OVER CHIN HAE AND
INTO THE WEST SEA.  EXTRA-TROPICAL TRANSITION WILL BE NEARLY
COMPLETED BY THE TIME PULASAN TRACKS OVER OR NEAR SADOSHIMA AND THE
RUGGED TERRAIN OF THE JAPANESE ALPS COMBINED WITH THE ETT WILL MAKE
THE SYSTEM UNFINDABLE AS IT FULLY MERGES WITH THE BAROCLINIC ZONE
BETWEEN TAU 24 AND 36.  

MODEL DISCUSSION: TRACK GUIDANCE IS TIGHT LENDING HIGH CERTAINTY TO
THE TRACK. INTENSITY IS ALSO BOTH COHERENT AND UNANIMOUS AS FAR AS
A PEAK INTENSITY AT LOW GALE FORCE NEAR TAU 24 AND THEN A VERY
GRADUAL TAPERING OFF THROUGH LANDFALL. THE JTWC INTENSITY FORECAST
FOLLOWS HAFS-A THROUGH TAU 24 AND THEN TAKES THE SYSTEM DOWN MUCH
FASTER IN THE OVERLAND STAGES.  

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