WDPN32 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (BOLAVEN) WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.2N 145.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 90 NM NORTH OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 15W (BOLAVEN) SHOWING PERSISTENT CONVECTION IN A CENTRAL
DENSE OVERCAST (CDO) REGION, INTERMITTENTLY FLARING OVER AN OBSCURED 
LOW LEVEL CIRCULATION CENTER (LLCC). OVER THE PAST SIX HOURS, THE
SYSTEM HAS GROWN MUCH MORE SYMMETRICAL AND HAS BECOME LESS TILTED
THROUGH THE ATMOSPHERE, BETTER ALIGNING THE MIDDLE AND UPPER LEVELS
WITH THE LLCC. SPIRAL BANDS OF DEEP CONVECTION CONTINUE TO DISPLAY
OVERSHOOTING CLOUD TOPS, EXTENDING OUTWARD UP TO 405NM RADIALLY
FROM THE LLCC. A 100600Z ATMOSPHERIC SOUNDING FROM GUAM
INTERNATIONAL AIRPORT (PGUM) REPORTED 50KTS AT THE 850MB LEVEL AND
A VERY MOIST ENVIRONMENT OTHER THAN THE 850MB TO 600MB LAYER 
REFLECTING AN AVERAGE RELATIVE HUMIDITY VALUE AROUND 70 PERCENT. 
STATION WINDS FROM SAIPAN INTERNATIONAL AIRPORT (PGSN) AT 100642Z 
REPORTED EASTERLY WINDS SUSTAINED AT 48KTS WITH GUSTS UP TO 68KTS. TO 
THE SOUTH OF THE LLCC, PGUM STATION OBSERVATIONS OF 101107Z
REPORTED 32KTS WESTERLY SUSTAINED WINDS WITH GUSTS UP TO 43KTS.
MAXIMUM OBSERVED RADAR VELOCITY OF 96KTS WAS OBSERVED IN THE SYSTEMS 
SOUTHEAST QUADRANT AT 14,000 FEET. THE INITIAL POSITION IS PLACED WITH 
HIGH CONFIDENCE BASED ON A GUAM WEATHER RADAR FIX AT 101130Z. THE 
INITIAL INTENSITY OF 70 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED 
ON SUBJECTIVE DVORAK INTENSITY ESTIMATES AND CIMSS OBJECTIVE INTENSITY 
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SAR DATA AND SYNOPTIC OBSERVATIONS

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 77 KTS AT 101200Z
   CIMSS AIDT: 77 KTS AT 101200Z
   CIMSS DPRINT: 78KTS AT 101200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 15W IS LIKELY TO CONTINUE STEPPING NORTHWARD 
AND WESTWARD IN DISTINCT INTERVALS AS THE VORTEX CONTINUES TO 
SYMMETRIZE AND WILL GENERALLY TRACK NORTH-NORTHWESTWARD OVER THE NEXT 
12 HOURS. AS THE STR EXTENSION TO THE NORTH CONTINUES TO PROPAGATE 
EASTWARD, TY 15W WILL SLOW DOWN TO A TRACK SPEED OF AROUND 8KTS AND 
ROUND THE RIDGE AXIS BETWEEN TAU 24 AND TAU 36. AFTER ROUNDING THE 
RIDGE TY 15W IS ANTICIPATED TO RAPIDLY PICK UP THE PACE AND ACCELERATE 
TO THE NORTHEAST ALONG THE TIGHT GRADIENT BETWEEN THE STR TO THE EAST 
AND DEEP TROUGH TO THE NORTHWEST. WITH VERTICAL WIND SHEAR AT BAY AND 
THE ENVIRONMENTAL CONDITIONS VERY FAVORABLE, TY 15W IS LIKELY TO 
UNDERGO RAPID INTENSIFICATION THROUGH TAU 48 UNTIL PEAK INTENSITY IS 
REACHED PRIOR TO TAU 72. FOLLOWING ROUNDING THE STR AXIS, TY 15W IS 
FORECAST TO TRACK GENERALLY NORTHEASTWARD THROUGH TAU 120. TY 15W WILL 
BEGIN EXTRATROPICAL TRANSITION (ETT) BY TAU 120 AS IT MOVES NORTH OF 
THE 26C ISOTHERM AND COMES IN PHASE WITH A 500MB TROUGH AND EMBEDS
UNDER A 200MB JET MAX. THE TRACK FORECAST CONFIDENCE IS HIGH
THROUGH TAU 72 AND MEDIUM THEREAFTER. THE INTENSITY FORECAST
CONFIDENCE IS MEDIUM THROUGH TAU 72 AND LOW THEREAFTER.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT TY 15W WILL TRACK GENERALLY NORTH-NORTHWEST, ROUND
THE STR AXIS BETWEEN TAU 24 AND TAU 36, AND THEN GRADUALLY TURN TO
A NORTHEASTWARD TRACK BY TAU 48 AND MAINTAIN THROUGH TAU 120. 
HOWEVER, THERE EXISTS PROMINENT UNCERTAINTY IN BOTH TRACK SPEED AND
MOTION BETWEEN JTWC CONSENSUS MEMBERS, NAMELY THE GFS AND ECMWF 
SOLUTIONS. AS SUCH, A CROSS-TRACK SPREAD OF 86NM AND ALONG-TRACK 
SPREAD OF 155NM IS PRESENT BY TAU 72. THIS SPREAD COMPOUNDS BY TAU 
120, WITH A CROSS-TRACK SPREAD OF 352NM AND AN ALONG-TRACK SPREAD OF 
512NM. THE ALONG-TRACK SPREAD HAS IMPROVED SINCE THE PREVIOUS WARNING, 
BUT STILL YIELDS FAIR UNCERTAINTY AFTER TAU 72.

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