WDPN31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 122.0E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 188 NM SOUTH OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 39 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) DEPICTS TYPHOON
(TY) APPROACHING TAIWAN AND BEGINNING TO INTERACT WITH THE
MOUNTAINOUS TERRAIN OF THE CENTRAL MOUNTAIN RANGE. A
DISTINGUISHABLE LINE OF VERY COOL EIR BRIGHTNESS TEMPERATURES
OUTLINES THE CREST OF THE SIGNIFICANT TOPOGRAPHICAL FEATURE AND
EVIDENCES WINDS IN THE FRONT RIGHT QUADRANT OF TY 14W FLOWING INTO
THE RANGE ALLOWING OROGRAPHIC LIFTING TO OCCUR, BUT MORE
IMPORTANTLY CAUSING A SIGNIFICANT DISRUPTION IN LOW TO MID-LEVEL
FLOW AROUND THE SYSTEM. OUTFLOW ALOFT RESUMES EQUATORWARD, BUT HAS
IN THE PAST SIX HOURS BECOME MORE RADIAL IN APPEARANCE. THE RAGGED
EYE OF THE SYSTEM HAS DECREASED TO 12NM IN DIAMETER AND HAD CYCLIC
OBSCURATION AND CLEARING SINCE 040600Z. VERTICAL WIND SHEAR HAS
INCREASED (20-25KTS), WITH THE 24 HOUR VWS TENDENCY INCREASING AS 
WELL (10KTS). SEA SURFACE TEMPERATURES WEST OF THE SYSTEM AND ALONG 
THE FORECASTED TRACK FALL SLIGHTLY, YET REMAIN CONDUCIVE FOR
INTENSIFICATION TO OCCUR (28-29 DEGEES CELSIUS). THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 041200Z CIRA
PROXYVIS IMAGE. THE INITIAL INTENSITY OF 115 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON MULTI-AGENCY SUBJECTIVE DVORAK INTENSITY
ESTIMATES OF 115KTS, AS WELL AS CIMSS AIDT (041230Z) AND DPRINT
(041300Z) ESTIMATING 116 KTS AND 118KTS, RESPECTIVELY.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
BUILDING TO THE NORTH.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 124 KTS AT 041130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

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 TRACK WESTWARD THROUGH
TAU 72, WHEN IT WILL THEN TURN TO A MORE WEST-SOUTHWESTWARD TRACK. 
WITH THE ONSET OF FRICTIONAL FORCING AT TIME OF ANALYSIS, THE
INTENSITY OF THE SYSTEM IS ANTICIPATED TO DECREASE THROUGH TAU 24
AS 14W TRACKS WESTWARD PAST TAIWAN. ADDITIONALLY, VERTICAL WIND
SHEAR IS ANTICIPATED TO BE MODERATE THROUGH TAU 24 AND LOWER
THEREAFTER. FORWARD OF TAU 24, THE SYSTEM IS ANTICIPATED TO TRACK
INTO A SIZABLE DRY AIR MASS (AROUND 20 PERCENT RELATIVE HUMIDITY)
AND THE EFFECTS OF DRY AIR ENTRAINMENT WILL GRADUALLY WEAKEN THE
INTENSITY THROUGH TAU 120.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE CONTINUES TO
BETTER ALIGN AND IS IN GOOD AGREEMENT TY 14W WILL CONTINUE ON A
WESTWARD TRACK THROUGH TAU 72. A CROSS-TRACK SPREAD AT TAU 72 OF
112 NM, HOWEVER, LEAVES UNCERTAINTY IN BOTH THE TRACK AND INTENSITY
FORECAST.  THEREFORE, THE FORECAST CONFIDENCE DURING THIS TIME
INTERVAL IS MEDIUM FOR BOTH TRACK AND INTENSITY. MOGREPS AND JGSM
CONTINUE TO SHOW ALTERNATE SOLUTIONS THAT ARE DISSIMILAR TO THE
OTHER CONSENSUS MEMBERS, WITH MOGREPS TURNING THE TRACK NORTHEASTWARD 
AT TAU 60 THROUGH THE TAIWAN STRAIT AND JGSM CHECKMARKING BACK ONTO A 
RECIPROCAL COURSE NEAR TAU 72. WITH THE EXCEPTION OF JGSM AND 
MOGREPS, THE JTWC CONSENSUS HAS BECOME BETTER ALIGNED BETWEEN TAU 72 
AND TAU 120. HOWEVER, A SIMILAR COMPARISON OF ALONG-TRACK SPREAD AT 
TAU 120 (WITH THE EXCEPTION OF JGSM AND MOGREPS) YIELDS 398NM, 
DEMONSTRATING MUCH UNCERTAINTY REGARDING TRACK SPEED AND THE RELATED 
INTENSITY OF THE SYSTEM. AS SUCH, THE FORECAST CONFIDENCE OF THE TAU 
72 TO TAU 120 IS LOW.

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