WDPN33 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (KRATHON) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.7N 124.9E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 490 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
STEADILY DEVELOPING TROPICAL STORM 20W (KRATHON) WITH A LOW-LEVEL
CIRCULATION CENTER OBSCURED BY A CENTRAL DENSE OVERCAST (CDO)
FEATURE. THE SYSTEM EXHIBITS STRONG EQUATORWARD OUTFLOW, AS WELL AS
A WEAKER, POLAR CHANNEL. CIRRUS FILAMENTS PRESENT OVER THE LAST FEW
HOURS BEGAN TO INDICATE A BEGINNING OF A MORE RADIAL OUTFLOW
DEVELOPING WHILE THE SYSTEM INTENSIFIES. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON A MICROWAVE EYE IN THE 281708Z 
AMSR2 37GHZ IMAGE. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND AUTOMATED FIXES 
LISTED BELOW AND IS CONSISTENT WITH THE NEWLY-FORMED MICROWAVE EYE.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: TWO COMPETING STEERING FEATURES IN A
FORM OF SUBTROPICAL RIDGES TO THE WEST AND TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 56 KTS AT 281530Z
   CIMSS ADT: 55 KTS AT 281730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM KRATHON IS CURRENTLY FORECAST
TO STEADILY INTENSIFY, WHILE IT SPEEDS UP ON ITS WEST-NORTHWESTWARD
TRACK UNTIL TAU 48, BY WHICH TIME IT WILL BEGIN TO TURN NORTHWARD, AS 
IT ROUNDS THE AXIS OF THE SUBTROPICAL RIDGE TO THE NORTHEAST. UNTIL
THEN, THE CONDITIONS WILL REMAIN FAVORABLE, WITH LOW VERTICAL WIND
SHEAR, HIGH SEA SURFACE TEMPERATURES AND HIGH OCEAN HEAT CONTENT.
AS THE SYSTEM RECURVES, IT WILL INTENSIFY FURTHER, REACHING 105 KTS 
PEAK INTENSITY. PAST TAU 48, LAND INTERACTION WITH TAIWAN ALONG THE
WESTERN PART OF THE WIND FIELD, UPPER-LEVEL TROUGHING TO THE
NORTHEAST, AND DRY COLD AIR INTRUSION FROM THE SAME DIRECTION COMBINED
WITH INCREASING VERTICAL WIND SHEAR WILL LEAD TO STEADY WEAKENING, 
OFFSET ONLY BY INCREASED POLEWARD OUTFLOW AHEAD OF AN APPROACHING MID-
LATITUDE TROUGH.

MODEL DISCUSSION: UNCERTAINTY IN REGARD TO THE TIMING OF THE TRACK
RECURVING REMAINS IN THE FORECAST PAST TAU 36. THE CROSS-TRACK
SPREAD BETWEEN ECMWF AND GFS ENSEMBLES IS APPROXIMATELY 50 NM,
LEADING TO THE SYSTEM PROXIMITY TO TAIWAN REMAINING UNRESOLVED.
JTWC TRACK FORECAST IS LAID IN CLOSE PROXIMITY TO THE MULTI-MODEL
CONSENSUS AND IN BETWEEN THE TWO AFOREMENTIONED ENSEMBLES, WITH
BOTH COMING TO A CLOSER AGREEMENT WITH EACH NEW RUN. JTWC INTENSITY
FORECAST IS CURRENTLY SLIGHTLY ABOVE THE CONSENSUS, ACCOUNTING FOR
PREDOMINANTLY FAVORABLE ENVIRONMENTAL CONDITIONS, AT LEAST UNTIL
TAU 48, AS WELL AS MODERATE POTENTIAL FOR RAPID INTENSIFICATION
INDICATED BY COAMPS-TC

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