WDPN31 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR)          
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.4N 143.2E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 825 NM EAST OF KADENA AB, OKINAWA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 12W HAS RAPIDLY INTENSIFIED (35 KNOTS) FROM 40 KNOTS AT 280600Z
TO 75 KNOTS AT 290600Z. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS A COMPACT, 90NM DIAMETER CENTRAL DENSE OVERCAST
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). RECENT MSI SHOWS
A DEVELOPING EYE OVER THE WESTERN EDGE OF THE CDO. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED THE MSI AS WELL AS ON A 
290327Z AMSR2 89GHZ MICROWAVE IMAGE, WHICH REVEALS A SMALL, WELL-
DEFINED MICROWAVE EYE FEATURE. THE INITIAL INTENSITY OF 75 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CIMSS ADT ESTIMATE AND 
AN AMSR2 WINDSPEED IMAGE SHOWING MAXIMUM WINDS OF 69 KNOTS OVER THE 
WESTERN QUADRANT. DVORAK ESTIMATES HAVE INCREASED BUT REMAIN TOO LOW 
BASED ON CONSTRAINTS AND THE COMPACT SIZE OF THE SYSTEM, WHICH IS NOT 
TYPICALLY HANDLED WELL BY THE DVORAK METHOD. ENVIRONMENTAL CONDITIONS 
ARE HIGHLY FAVORABLE WITH RADIAL OUTFLOW, LOW VERTICAL WIND SHEAR AND 
VERY WARM SST VALUES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED EXTENSION OF THE
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 61 KTS AT 290058Z
   CIMSS ADT: 74 KTS AT 290540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: INCREASED THE PEAK INTENSITY TO 140
KNOTS. SHIFTED THE 3-DAY TO 5-DAY FORECAST TRACK SOUTH OF OKINAWA. 

FORECAST DISCUSSION: TY 12W IS FORECAST TO TRACK QUICKLY WESTWARD
TO WEST-SOUTHWESTWARD OVER THE NEXT TWO DAYS AS IT TRACKS ALONG THE
SOUTHERN PERIPHERY OF THE STR, TRANSITIONING FROM THE EASTERN STR
TO THE WESTERN STR POSITIONED OVER THE EAST CHINA SEA. A
MIDLATITUDE SHORTWAVE TROUGH IS STILL EXPECTED TO DIG OVER THE
KOREAN PENINSULA NEAR 311200Z, HOWEVER, THE TROUGH IS TOO FAR NORTH
AND PROPAGATES NORTHEASTWARD QUICKLY WITH LITTLE IMPACT ON TY 12W'S
TRACK. TY 12W IS EXPECTED TO RAPIDLY INTENSIFY OVER THE NEXT 24 TO
36 HOURS REACHING A PEAK INTENSITY OF 140 KNOTS BY TAU 48. NEAR TAU
72, TY 12W WILL ENCOUNTER A COMPETING STEERING SYNOPTIC PATTERN
WITH A STR TO THE NORTHEAST AND WEST AND THE NEAR-EQUATORIAL
RIDGE TO THE SOUTH, WHICH WILL ESSENTIALLY BOX THE SYSTEM IN,
LEADING TO AN EXTENDED PERIOD OF SLOW, QUASI-STATIONARY MOTION. AS
THE SYSTEM SLOWS, UPWELLING COOLER WATER WILL SERVE TO GRADUALLY
WEAKEN THE SYSTEM THROUGH TAU 120. DUE TO THE COMPETING STEERING, 
THERE IS HIGH UNCERTAINTY IN THE EXACT TRACK OF THE CENTER. 
REGARDLESS, THE SYSTEM IS EXPECTED TO TRANSITION INTO A LARGE SYSTEM 
WITH A 400-500NM DIAMETER.         

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 48 WITH A 120NM SPREAD IN SOLUTIONS AT TAU 48. AFTER
TAU 48, HOWEVER, DETERMINISTIC GUIDANCE DIVERGES AND IS IN POOR
AGREEMENT. ALL THE MODELS INDICATE THE SYSTEM WILL SLOW AND BECOME
QUASI-STATIONARY BUT DISAGREE ON WHERE THE SYSTEM WILL STALL. THE
BULK OF THE DETERMINISTIC AND PROBABILISTIC GUIDANCE (ECMWF
ENSEMBLE AND GEFS) INDICATES THE SYSTEM WILL STALL SOUTH TO
SOUTH-SOUTHWEST OF OKINAWA FOR AT LEAST TWO DAYS. THERE IS A HIGH
PROBABILITY OF RAPID INTENSIFICATION CONTINUING OVER THE NEXT TWO
DAYS WITH JTWC'S RAPID INTENSIFICATION (RI) GUIDANCE TRIGGERED AT
60 TO 75 PERCENT. ADDITIONALLY, THE 281800Z COAMPS-TC ENSEMBLE
INDICATES THE PROBABILITY OF RI AT 80 TO 100 PERCENT IN THE NEXT
06-42 HOURS.        

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