WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 127.3E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 439 NM SOUTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT
TYPHOON (TY) 14W (KOINU) HAS RAPIDLY INTENSIFIED OVER THE PAST SIX
HOURS, WITH A RAGGED, 16NM WIDE, CLOUD FILLED EYE HAVING FORMED
ABOUT FOUR HOURS AGO. HOWEVER, WHILE VORTICAL HOT TOWERS (VHTS)
CONTINUE TO FIRE UP IN THE SOUTHWESTERN SECTOR AND THEN ROTATE
UPSHEAR, THEY ARE STRUGGLING TO PERSIST IN THE NORTH-NORTHEASTERN
SECTOR OF THE ROTATION. A PERSISTENT NORTHEASTERLY SHEAR VECTOR IS
USHERING IN A WEDGE OF MID-LEVEL DRY AIR, WHICH IS PENETRATING INTO
THE CORE OF THE SYSTEM, AND INDUCING SOME DOWNWARD VERTICAL MOTION
WHICH IS PUTTING A BIT OF BRAKE ON THE INTENSIFICATION TREND.
HAVING SAID ALL THAT, THE SYSTEM HAS STILL BEEN ABLE TO QUICKLY
INTENSIFY UP TO 100 KNOTS. THE INITIAL POSITION IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE POSITIONING OF THE 16NM EYE IN THE MSI
AND EXTRAPOLATION OF THE EYE FEATURE SEEN IN A 012122Z RCM-3 SAR
IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, ON
THE HIGHER END OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES,
SUPPORTED BY THE AIDT ESTIMATE OF 96 KNOTS AND AN EXTRAPOLATION OF
THE 89 KNOT FIX INTENSITY FROM THE SAR DATA. ENVIRONMENTAL ANALYSIS
REVEALS A FAVORABLE ENVIRONMENT, WITH LOW (5-10 KNOTS) OF
NORTHEASTERLY SHEAR, VERY WARM SSTS AND ROBUST RADIAL OUTFLOW,
OFFSET SLIGHTLY BY MID-LEVEL DRY AIR, PARTICULARLY IN THE
EAST-NORTHEASTERN PORTION OF THE SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 92 KTS AT 020030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 14W IS FORECAST TO CONTINUE TRACKING
NORTHWEST ALONG THE WEST SIDE OF THE STEERING RIDGE CENTERED TO THE
EAST THROUGH THE FIRST 48 HOURS OF THE FORECAST. AROUND TAU 48, THE
STEERING PATTERN SHIFTS, WITH A NEW STR CENTER DEVELOPING TO THE
EAST AT ROUGHLY THE SAME LATITUDE AT TY 14W WITH A RIDGE AXIS
DEVELOPING ALONG ABOUT THE 27N LATITUDE LINE TO ANOTHER RIDGE
CENTER OVER SOUTHEASTERN CHINA. AS THIS RIDGE COMPLEX DEVELOPS AND
STRENGTHENS, TY 14W WILL SHIFT TO A MORE WESTWARD TRACK TOWARDS THE
SOUTHERN TIP OF TAIWAN AFTER TAU 48. HOWEVER, A WEAKNESS IN THE
RIDGE TO THE NORTH MEANS THAT THE STEERING GRADIENT WILL BE
RELATIVELY WEAK, THUS THE SYSTEM WILL START TO SLOW DOWN AS IT
TURNS TOWARDS THE WEST. LANDFALL ALONG THE SOUTHEASTERN COAST OF
TAIWAN IS EXPECTED JUST PRIOR TO TAU 72. AFTER LANDFALL, TRACK
MOTION WILL LIKELY BECOMING HIGHLY ERRATIC DUE TO THE COMPLEX
INTERPLAY BETWEEN THE VORTEX AND THE TERRAIN OF SOUTHERN TAIWAN,
BUT OVERALL, A SLOW TRACK TOWARDS THE WEST IS FORECAST, WITH THE
SYSTEM FORECASTED TO BE IN THE SOUTHERN PORTION OF THE TAIWAN
STRAIT BY TAU 120. HAVING RAPIDLY INTENSIFIED OVER THE PAST SIX
HOURS, THE SYSTEM IS ALREADY SHOWING SIGNS OF STRUGGLING A BIT
AGAINST THE MID-LEVEL DRY AIR AND SHEAR AND THE CONVECTION IS STILL
HAVING A HARD TIME PERSISTING ON THE NORTHERN SIDE. THE MODEL
FIELDS ARE SHOWING THE SHEAR BACKING OFF A BIT AND A SLIGHT
MOISTENING OF THE ENVIRONMENT OVER THE NEXT 24 HOURS, WHICH SHOULD
ALLOW FOR THE SYSTEM TO CONTINUE TO INTENSIFY UP TO A PEAK OF 115
KNOTS. THEREAFTER, AN INCREASE IN EASTERLY SHEAR, CONVERGENT FLOW
ALOFT AND ANOTHER INFLUX OF DRY AIR USHERED IN THE EASTERLY SHEAR,
WILL LEAD TO A SLOW WEAKENING TREND UP THROUGH LANDFALL. AFTER
LANDFALL, TERRAIN INTERACTION WILL SHRED THE LOW-LEVEL VORTEX
LEADING TO SIGNIFICANT WEAKENING AS THE SYSTEM MOVES BACK INTO THE
TAIWAN STRAIT. AFTER MOVING BACK OVER WATER, A REDUCTION OF OUTFLOW
ALOFT AND AN INFLUX OF COOL, DRY AIR DOWN THE TAIWAN STRAIT WILL
CONTINUE TO WEAKEN THE SYSTEM THROUGH THE END OF THE FORECAST
PERIOD. 

MODEL DISCUSSION: THROUGH TAU 48, DETERMINISTIC MODEL TRACKERS ARE
IN GOOD AGREEMENT, THOUGH THE EGRR AND UKMET ENSEMBLE TURN THE
SYSTEM POLEWARD AFTER ABOUT TAU 36. THE REMAINDER OF THE CONSENSUS
MEMBERS ARE CONTAINED WITHIN A 60NM WIDE ENVELOPE THROUGH TAU 72.
THE JTWC FORECAST TRACK REMAINS CONSISTENT WITH THE PREVIOUS
FORECAST AND LIES JUST SOUTH OF THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE. AFTER TAU 72, CONFIDENCE IS MUCH LOWER DUE TO THE
LIKELIHOOD OF A HIGHLY ERRATIC TRACK AFTER PASSING TAIWAN AND A
DIVERGENCE IN THE MODEL GUIDANCE. THE GFS AND ECMWF ARE NOW SHOWING
THE SYSTEM MOVING SOUTHWESTWARD AFTER TAU 96, WHILE THE GALWEM,
JGSM AND NAVGEM TURN THE SYSTEM SHARPLY POLEWARD AFTER TAU 96,
LEADING TO A 350NM SPREAD BY TAU 120. THE JTWC FORECAST LIES NAER
THE GFS SOLUTION WITH LOW CONFIDENCE. INTENSITY GUIDANCE REMAINS
SOMEWHAT MIXED, WITH THE HAFS-A SHOWING THE SYSTEM CONTINUING TO
RAPIDLY INTENSIFY TO 135 KNOTS BY TAU 60, WHILE THE REMAINDER OF
THE GUIDANCE INDICATES A PEAK NEAR TAU 24, FOLLOWED BY WEAKENING
THEREAFTER. THE JTWC FORECAST LIES SLIGHTLY ABOVE THE CONSENSUS
MEAN, WITH MEDIUM CONFIDENCE TO TAU 72, AND LOW CONFIDENCE
THEREAFTER. 

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