WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.6N 145.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 173 NM EAST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 04W HAS MAINTAINED A COMPLEX UPPER-LEVEL OUTFLOW 
PATTERN, WITH AN UPPER-LEVEL CYCLONE POSITIONED OVER THE CENTER AND 
STRONG EASTWARD, DIFFLUENT OUTFLOW ENHANCED BY A JET TO THE NORTHEAST. 
THE PRESENCE OF THE UPPER-LEVEL LOW AND DRY AIR ENTRAINMENT WITHIN THE 
CORE OF THE SYSTEM IS HINDERING CONVECTIVE DEVELOPMENT. DESPITE THIS 
LIMITATION, ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS TIGHTLY 
WRAPPED LOW-LEVEL BANDING AND A WELL-DEFINED LOW-LEVEL CIRCULATION 
CENTER SUPPORTING THE INITIAL POSITION WITH HIGH CONFIDENCE. THE 
INITIAL INTENSITY IS ASSESSED AT 50 KNOTS BASED ON THE PGTW AND KNES 
DVORAK ESTIMATES, WHICH ARE CONSISTENT WITH RECENT ASCAT UHR DATA 
SHOWING A PATCH OF 50-55 KNOT WINDS. CIMSS OBJECTIVE ESTIMATES REMAIN 
TOO LOW, RANGING FROM 33-39 KNOTS. AS INDICATED IN THE DYNAMIC MODELS, 
THE CORE IS EXPECTED TO MOISTEN AND CONSOLIDATE WITHIN THE NEXT 12 
HOURS, WHICH IS EXPECTED TO LEAD TO A SHARPER INTENSIFICATION RATE. 
OVER THE PAST FEW HOURS, THERE APPEARS TO BE SOME EVIDENCE THAT THIS 
IS COMMENCING, WITH ANIMATED INFRARED SATELLITE IMAGERY REVEALING 
BETTER ORGANIZED CORE CONVECTION, WITH CLOUD TOP TEMPERATURES NEAR 
-59C.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: EXTENSIVE DEEP-LAYERED SUBTROPICAL RIDGE 
(STR) PATTERN TO THE SOUTH, EXTENDING NORTHEASTWARD OVER THE EASTERN 
PERIPHERY OF THE SYSTEM, WITH A WEAK STR EXTENSION TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 33 KTS AT 030530Z
   CIMSS AIDT: 37 KTS AT 030530Z
   CIMSS D-MINT: 38 KTS AT 030348Z
   CIMSS D-PRINT: 39 KTS AT 030530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG EASTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT OVER THE WESTERN SEMICIRCLE

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TS 04W IS FORECAST TO TRACK NORTHWARD THROUGH
TAU 24 ALONG THE WESTERN PERIPHERY OF THE STR. AFTER TAU 24, THE
SYSTEM IS EXPECTED TO TURN SHARPLY NORTHEASTWARD AS THE STR REORIENTS 
IN RESPONSE TO AN APPROACHING SHORTWAVE TROUGH OVER NORTHERN JAPAN. 
THE SHORTWAVE TROUGH WILL RAPIDLY PROPAGATE EASTWARD ALLOWING THE STR 
TO REBUILD, WHICH WILL DRIVE THE SYSTEM ON A MORE POLEWARD TRAJECTORY 
THROUGH TAU 120. AS ALLUDED TO EARLIER, ENVIRONMENTAL CONDITIONS ARE 
EXPECTED TO IMPROVE, WHICH SHOULD SUPPORT A SHORT PERIOD OF 
INTENSIFICATION, DRIVEN LARGELY BY THE ROBUST EASTWARD OUTFLOW, WITH A 
PEAK INTENSITY OF 70 KNOTS FORECAST BY TAU 48. SST VALUES WILL COOL 
STEADILY FROM TAU 36 TO TAU 120, WITH VALUES DECREASING TO ABOUT 25C 
BY TAU 48 THEN STEADILY DOWN TO 20-21C BY TAU 120. THEREFORE, THE 
TIMING OF THE PEAK INTENSITY MAY OCCUR EARLIER. AFTER TAU 72, 
ENVIRONMENTAL CONDITIONS WILL DEGRADE QUICKLY, WITH INCREASING 
VERTICAL WIND SHEAR (VWS) OF 25-30 KNOTS AFTER TAU 96, WHICH WILL LEAD 
TO RAPID WEAKENING. THE SYSTEM IS EXPECTED TO TRANSITION TO A 
SUBTROPICAL SYSTEM NEAR TAU 120.        

MODEL DISCUSSION: DUE TO THE COMPLEX STEERING ENVIRONMENT AND RUN-TO-
RUN INCONSISTENCIES, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK 
FORECAST THROUGH TAU 72. THERE IS A 150NM CROSS-TRACK SPREAD IN THE 
GUIDANCE AT TAU 72, HOWEVER, THERE ARE SIGNIFICANT DIFFERENCES IN THE
ALONG-TRACK SPEEDS. THE 030000Z GEFS RUN, IN PARTICULAR, INDICATES
A WIDE SWATH OF SOLUTIONS FROM CENTRAL JAPAN TO 160E. THE GFS
DETERMINISTIC MODEL HAS JUMPED AROUND ERRATICALLY THE PAST TWO RUNS, 
AND NOW SHOWS A DISSIPATING, WEAK SYSTEM TRACKING TOWARD MAINLAND 
JAPAN. ALTHOUGH THERE ARE ROUGHLY SIX ECENS SOLUTIONS TRACKING TOWARD 
MAINLAND JAPAN, THE BULK OF THE ECENS GUIDANCE SUPPORTS A MORE 
POLEWARD ORIENTED TRACK. RELIABLE INTENSITY GUIDANCE IS MORE COHESIVE, 
WITH THE BULK OF THE GUIDANCE SHOWING A BRIEF INTENSIFICATION PERIOD 
FROM TAU 24 TO TAU 60. HAFS-A INDICATES A PEAK INTENSITY OF 88 KNOTS 
BY TAU 60 WHILE COAMPS-TC (GFS) SHOWS A PEAK OF 80 KNOTS BY TAU 84. 
DUE TO HIGH UNCERTAINTY AFTER TAU 72, THERE IS LOW CONFIDENCE IN THE 
EXTENDED JTWC FORECAST TRACK.      

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