WDPN31 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KOINU) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.4N 130.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 630 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
STEADILY GROWING CENTRAL DENSE OVERCAST (CDO) FEATURE THAT IS
OBSCURING THE LLCC BENEATH. A 300901Z SSMIS 91GHZ MICROWAVE IMAGE
REVEALS BETTER ORGANIZED LOW LEVEL CLOUD LINES AND A SINGLE
DOMINANT CONVECTIVE BAND WRAPPING AROUND THE SOUTHERN SEMICIRCLE. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR AND
SSMIS IMAGERY. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON AUTOMATED INTENSITY ESTIMATES FROM CIMSS
(ADT, AIDT, DPRINT) INDICATING 36-40KTS WHILE DVORAK INTENSITY
ESTIMATES LAG SLIGHTLY BEHIND.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 300830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 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: TS 14W (KOINU) IS FORECAST TO CONTINUE ON A
NORTH-NORTHWESTERLY HEADING AS THE STEERING RIDGE TO THE NORTHEAST
CONTINUES TO BREAK DOWN. BY TAU 48 HOWEVER, THIS RIDGE BUILDS BACK
WESTWARD AND FORCES 14W TOWARDS THE SOUTHERN TIP OF TAIWAN AND INTO
THE VERY NORTHERN REGION OF THE SOUTH CHINA SEA THROUGH THE
FORECAST PERIOD. IN TERMS OF INTENSITY, VERTICAL WIND SHEAR (VWS)
REMAINS THE PRIMARY LIMITING FORCE PREVENTING CONSIDERABLE
INTENSIFICATION. AS EVIDENCED BY THE GROWING CDO, THE SYSTEM IS
IMPROVING ITS VERTICAL ALIGNMENT AND CORE STRUCTURE EVER MORE
RAPIDLY. IF THIS TREND CONTINUES OVER THE NEXT 36 HOURS, THE SYSTEM
WILL CONTINUE TO INTENSIFY, EVENTUALLY REACHING 70KTS BY TAU 36. BY
TAU 48, THE CHANCES FOR RAPID INTENSIFICATION MAY INCREASE, AS THE
SYSTEM CROSSES THE 20TH PARALLEL. GFS IS INDICATING THAT 14W MAY
TAP INTO VIGOROUS DUAL CHANNEL OUTFLOW, BOTH POLEWARD AND
EQUATORWARD WHICH WHEN COUPLED WITH DECREASED VWS AND WARM (30C)
SSTS, WILL QUICKLY INTENSIFY 14W TO AROUND 95KTS BY TAU 72. IN THE
EXTENDED TRACK FORECAST, AS THE SYSTEM PASSES THE SOUTHERN TIP OF
TAIWAN, THE VIGOROUS OUTFLOW ALOFT IS GENERALLY LOST, RESULTING IN
A SLIGHTLY REDUCED INTENSIFICATION TREND THROUGH THE FORECAST
PERIOD AND A RESULTANT PEAK INTENSITY OF 110KTS BY TAU 120.  

MODEL DISCUSSION: WITH THE EXCEPTION OF NVGM, NUMERICAL MODELS ARE
IN FAIR AGREEMENT INITIALLY WITH TWO GROUPINGS BECOMING EVIDENT
BEYOND TAU 24. ECMWF AND THEIR ENSEMBLE TAKE A MORE DRAMATIC TURN
WESTWARD AFTER TAU 24, RESULTING IN A CENTERLINE TRANSIT OF THE
LUZON STRAITS INTO THE SOUTH CHINA SEA. THE REMAINING GUIDANCE
TRENDS SLIGHTLY MORE POLEWARD AND TOWARD SOUTHERN TAIWAN. THE KEY
DIFFERENCE WITH ECMWF IS THE STR TO THE NORTHEAST BUILDS BACK MUCH
FASTER AND ALONG ITS NORTHERN FLANK PREVENTING A MORE POLEWARD
TRACK. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED WITH
OVERALL MEDIUM CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS IN
FAIR AGREEMENT THROUGH TAU 48 WITH ALL MEMBERS INCLUDING SEVERAL
RAPID INTENSIFICATION (RI) AIDS INDICATING A STEADY INTENSIFICATION
TREND. AFTER TAU 48, DECAY-SHIPS BEGINS TO WEAKEN THE SYSTEM WHILE
COAMPS-TC AND HWRF SURGE TO WELL OVER 100KTS. THIS DISSONANCE
RESULTS IN A NEARLY 100KT DIFFERENCE IN INTENSITY BY TAU 120. BASED
ON THE IMPROVING ENVIRONMENT AND OTHER FACTORS MENTIONED ABOVE, THE
JTWC INTENSITY FORECAST IS PLACED ABOVE THE MULTI-MODEL CONSENSUS
BUT BELOW THE AFOREMENTIONED MOST AGGRESSIVE MEMBERS. THESE
PLACEMENTS ARE MADE INITIALLY WITH MEDIUM CONFIDENCE AND WITH LOW
CONFIDENCE THEREAFTER.   

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