WDPN31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8N 143.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 197 NM NORTHWEST OF SAIPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 12W (KROSA) WITH AN INCREASINGLY OBSCURED LOW-LEVEL
CIRCULATION CENTER (LLCC) AS CONVECTIVE STRUCTURES HAVE STARTED
DEVELOPING IN CLOSE PROXIMITY TO THE SYSTEMS IMMEDIATE SOUTHERN
FLANK. WITH THAT BEING SAID, MUCH OF THE NORTHERN AND WESTERN
QUADRANTS REMAIN FREE OF ANY DEEP CONVECTION DUE TO CONTINUED
ENHANCED WIND SHEAR VALUES, RANGING FROM 25-30 KTS AND RELATIVELY
LOW MID-LEVEL RELATIVE HUMIDITY. ALOFT, MODERATE EQUATORWARD
OUTFLOW HAS CONTINUED AND REMAINS EVIDENT THROUGH ANIMATED WATER
VAPOR IMAGERY, HOWEVER, THE SYSTEM STILL LACKS A WELL-FORMED
SUPPORTIVE UPPER-LEVEL OUTFLOW CHANNEL. WITH REGARD TO THE
ENVIRONMENTAL ANALYSIS, HIGH VERTICAL WIND SHEAR (VWS) BETWEEN
25-30 KTS CONTINUES TO OFFSET WARM SEA SURFACE TEMPERATURES BETWEEN
29-30 C AND THE AFOREMENTIONED OUTFLOW ALOFT. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON A RECENT 25119Z METOP C
ASCAT IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE SAME ASCAT IMAGE. SUBJECTIVE AGENCY DVORAK FIXES RANGE
BETWEEN 35-45 KTS, WHILE OBJECTIVE CIMSS ESTIMATES TREND LOWER,
FROM 29-39 KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: BUILDING SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 39 KTS AT 251300Z
   CIMSS ADT: 33 KTS AT 251300Z
   CIMSS AIDT: 35 KTS AT 251300Z
   CIMSS D-MINT: 29 KTS AT 250344Z
   CIMSS D-PRINT: 32 KTS AT 251300Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 12W IS FORECASTED TO TRACK TO THE NORTH AND
NORTH NORTH-EAST OVER THE INITIAL 72 HOURS OF THE FORECAST PERIOD
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE LOCATED
DIRECTLY TO THE EAST. AFTER TAU 72, THE WEAKENING RIDGE WILL BEGIN
ALLOWING THE SYSTEM TO BEGIN ITS GENERALLY NORTHEASTWARD TRACK
UNTIL THE END OF THE FORECAST PERIOD. DURING THAT SAME TIME, A
SOUTHWEST TO NORTHEAST ORIENTED BELT OF ENHANCED SOUTHWESTERLY
WINDS WILL AID IN THE INITIAL APPROACH NORTHEASTWARD UNTIL TAU 120.
WITH REGARD TO INTENSITY, TS 12W IS FORECASTED TO STEADILY
INTENSIFY TO 60 KTS OVER THE NEXT 48 HOURS AS VWS DECREASES TO LESS
THAN 20 KTS. AFTER TAU 48, A SLIGHT WEAKENING PHASE TO 55 KTS IS
EXPECTED AS DRY AIR WRAPS CYCLONICALLY AROUND THE CENTRAL VORTEX
FROM THE WEST UNTIL TAU 96. FOLLOWING TAU 96, TS KROSA IS FORECAST
TO RE-MOISTEN WHILE ALSO GAINING A VIGOROUS POLEWARD OUTFLOW
CHANNEL ALOFT TO THE NORTHEAST, ALLOWING FOR REINTENSIFICATION TO
65 KTS BY TAU 120. WHILE THIS IS HAPPENING, VWS IS EXPECTED TO
SHARPLY DECLINE TO BELOW 10 KTS, AS THE SYSTEM BECOMES COMPLETELY
VERTICALLY ALIGNED.

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION (NWP) TRACK GUIDANCE
HAS CONTINUED TO IMPROVE OVER THE LAST SIX HOURS, INDICATING A
CROSS-TRACK SPREAD OF 132 NM BY TAU 72. FOLLOWING TAU 72, THE
CROSS-TRACK SPREAD HAS ALSO BECOME MORE ALIGNED AS ALL AVAILABLE
MODEL TRACK SOLUTIONS NOW ILLUSTRATE A NORTHEASTWARD TRACK AFTER
TAU 72. OF NOTE, THE GFS DETERMINISTIC SOLUTION CONTINUES TO
CHARACTERIZE A QUICKER NORTHWARD AND NORTHEASTWARD TRACK THAN THE
JTWC MULTI-MODEL CONSENSUS. THE JTWC TRACK FORECAST IS ALIGNED
CLOSELY WITH THE CONSENSUS SOLUTION. WITH REGARD TO INTENSITY, MOST
INTENSITY CONSENSUS MEMBERS SHOW A STEADY INCREASE IN INTENSITY
THROUGHOUT THE NEXT 48 HOURS. HAFS-A AND COAMPS-TC ARE EXPECTING A
SHARPER INCREASE TO 75-85 KTS DURING THE SAME PERIOD, HOWEVER,
ALIGN CLOSELY WITH AN EXPECTED PERSISTENT PHASE OF 55-60 KTS
BETWEEN TAU 48 AND TAU 96. FOLLOWING TAU 96, ALL INTENSITY
SOLUTIONS ILLUSTRATE A REINTENSIFICATION PHASE UNTIL THE END OF THE
FORECAST PERIOD. THE JTWC INTENSITY FORECAST REMAINS ALIGNED WITH
THE MULTI-MODEL CONSENSUS, LENDING MEDIUM CONFIDENCE TO THE INITIAL
72 HOURS, BECOMING LOW THEREAFTER. OF NOTE, COAMPS-TC EPS HAS
STARTED INDICATING A MODERATE INTENSIFICATION PHASE BETWEEN TAU 78
AND TAU 120.

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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