WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 119.1E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 223 NM SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND ANIMATED
RADAR IMAGERY DEPICT A DEGRADED TYPHOON STRENGTH CIRCULATION THAT
CONTINUES TO TRACK WESTWARD AWAY FROM THE SOUTHERN TIP OF TAIWAN
UNDER THE INFLUENCE OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) ACROSS
THE EAST CHINA SEA. A 052310Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE
IMAGE REVEALS DEEP CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE.
ANIMATED RADAR IMAGERY INDICATES A WELL-DEFINED CIRCULATION CENTER
WITH THE NORTHEASTERN SEMICIRCLE STRUGGLING TO MAINTAIN COHESION.
ANIMATED WATER VAPOR IMAGERY SHOWS THE OUTFLOW CONTINUES TO SHOW A
STEADY REDUCTION AS MOST OF THE OUTFLOW ALOFT IS CONSTRAINED
EQUATORWARD. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON BOTH THE RADAR AND SSMIS MICROWAVE IMAGERY. THE INITIAL
INTENSITY OF 80 KTS IS HEDGED ABOVE SUBJECTIVE DVORAK CURRENT
INTENSITY ESTIMATES BASED ON ADT AND AIDT ESTIMATES OF 84 AND 79
KNOTS, RESPECTIVELY. ENVIRONMENTAL CONDITIONS REMAIN MARGINAL, WITH
WARM SSTS AND MODERATE EQUATORWARD OUTFLOW OFFSET BY LOW-MODERATE
NORTHEASTERLY SHEAR AND DRY AIR ENTRAINMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST



AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   CIMSS ADT: 84 KTS AT 051200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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: OVER THE PAST SIX HOURS, TYPHOON 14W (KOINU)
HAS TRACKED GENERALLY WESTWARD AND IS FORECAST TO CONTINUE THROUGH
TAU 48. AFTER TAU 48, 14W IS EXPECTED TO SLOW DOWN AS IT APPROACHES
THE SOUTHEASTERN COAST OF CHINA. A STR OVER EAST-CENTRAL CHINA
BECOMES THE DOMINANT STEERING FEATURE, WHICH WILL TURN 14W
SOUTHWESTWARD AND FORCE THE SYSTEM EQUATORWARD TOWARD THE VICINITY
OF HAINAN THROUGH THE END OF THE FORECAST. IN TERMS OF INTENSITY,
THE SYSTEM WILL MOVE INTO AN AREA OF VERY WEAK UPPER-LEVEL OUTFLOW,
AS WELL AS A COOLER, MORE STABLE AIRMASS, WITH AN INCREASE IN DRY
AIR ENTRAINMENT ANTICIPATED THROUGH TAU 72. THE LESS FAVORABLE
ENVIRONMENTAL FACTORS, ALONG WITH THE POTENTIAL OF LAND INTERACTION
OF THE OUTERMOST WIND FIELD, WILL ALSO CONTRIBUTE TO THE
DISSIPATION BY TAU 120.


MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH A
BULK OF THE GUIDANCE GENERALLY FOLLOWS THE JTWC FORECAST TRACK
THROUGH TAU 72, AFTER WHICH CROSS-TRACK AND ALONG-TRACK SPREAD
INCREASES THROUGH TAU 120. ALL CONSENSUS MEMBERS AGREE ON A SHARP
TURN TOWARDS THE SOUTHWEST NEAR THE SOUTHEASTERN COAST OF CHINA BY
TAU 48. ADDITIONALLY, THERE IS STILL SIGNIFICANT CROSS-TRACK
ALONG-TRACK SPREAD FROM BOTH GFS AND ECMWF ENSEMBLE MEMBERS AFTER
TAU 72. THEREFORE, THE JTWC TRACK FORECAST IS PLACED INITIALLY WITH
MEDIUM CONFIDENCE AND WITH LOW CONFIDENCE BY THE END OF THE
FORECAST PERIOD. RELIABLE MODEL INTENSITY GUIDANCE IS IN GOOD
AGREEMENT WITH MOST MEMBERS INDICATING A WEAKENING TREND THROUGH
TAU 48, WHILE HAFS-A AND HWRF CONTINUE TO SHOW A POSSIBILITY OF
STRENGTHENING THROUGH TAU 48. HOWEVER, AFTER TAU 48, ALL MEMBERS
SHOW A MORE STEADY DECLINE THROUGH TAU 120. FOR THIS REASON, THE
JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE.


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