WDPN32 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (BOLAVEN) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.3N 145.5E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 21 NM NORTHEAST OF ROTA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
15W (BOLAVEN) SHOWING PERSISTENT CONVECTION IN A CENTRAL DENSE
OVERCAST (CDO) REGION, INTERMITTENTLY FLARING SOUTH OF THE MOSTLY
OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC). SPIRAL BANDS OF DEEP
CONVECTION EXHIBIT OVERSHOOTING CLOUD TOPS AND GREAT RADIAL EXTENT, UP 
TO 380NM NORTHEAST OF THE LLCC. A 100600Z ATMOSPHERIC SOUNDING FROM 
GUAM INTERNATIONAL AIRPORT (PGUM) REPORTED 35KTS AT THE 850MB LEVEL 
AND A MOIST ENVIRONMENT OTHER THAN THE 850MB TO 640MB LAYER REFLECTING 
RELATIVE HUMIDITY VALUES AROUND 80 PERCENT. STATION WINDS FROM SAIPAN 
INTERNATIONAL AIRPORT (PGSN) AT 100554Z REPORTED EASTERLY WINDS 
SUSTAINED AT 36KTS WITH GUSTS UP TO 52KTS. TO THE SOUTHWEST OF THE 
LLCC, PGUM STATION OBSERVATIONS OF 100627Z REPORTED 32KTS WESTERLY 
SUSTAINED WINDS WITH GUSTS UP TO 40KTS. AS OF 100600Z, THE SYSTEM HAD 
NOT YET REACHED THE CLOSEST POINT OF APPROACH TO THE MARIANAS ISLANDS. 
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A RADAR 
FIX AT 100530Z. THE INITIAL INTENSITY OF 70 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON GREAT ALIGNMENT BETWEEN MULTIPLE SUBJECTIVE
DVORAK INTENSITY ESTIMATES AND CIMSS OBJECTIVE INTENSITY ESTIMATES
LISTED BELOW. UNFORTUNATELY, RADAR VELOCITY COULD NOT BE EXAMINED
FOR THE AFOREMENTIONED RADAR FIX DUE TO LACK OF DATA AT THIS
LOCATION (BLANKED OUT CIRCLE ALONG GATE INTERVAL).  HOWEVER, A
RADAR VELOCITY OF 69KTS IS OBSERVED WHERE THERE IS DATA NEAREST THE 
FIX (WITHIN 10NM).

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 66 KTS AT 100600Z
   CIMSS ADT: 67 KTS AT 100600Z

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: HIGH
   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 TRACKING SOMEWHAT
ERRATICALLY, STEPPING NORTH AND WEST IN DISTINCT INTERVALS AS THE
VORTEX CONTINUES TO SYMMETRIZE, BUT WILL GENERALLY TRACK
NORTHWESTWARD OVER THE NEXT 12 HOURS. AS THE STR TO THE NORTH
RAPIDLY RE-CENTERS TO THE NORTHEAST AND THE WESTERN EXTENSION OF
THE RIDGE RAPIDLY ERODES AHEAD OF AN APPROACHING DEEP-LAYER TROUGH,
TY 15W WILL SLOW DOWN TO A TRACK SPEED OF AROUND 9KTS AND ROUND THE
RIDGE AXIS NEAR TAU 36. AFTER ROUNDING THE RIDGE TY 15W WILL
RAPIDLY PICK UP THE PACE AND SHOOT OFF TO THE NORTHEAST ALONG THE
TIGHT GRADIENT BETWEEN THE STR TO THE EAST AND DEEP TROUGH TO THE 
NORTHWEST. VERTICAL WIND SHEAR HAS GENTLY EASED AND WEAKENED, WHICH IN 
TIME WILL ALLOW THE VORTEX TO FURTHER SYMMETRIZE. ONCE FURTHER 
CONSOLIDATED, NEAR TAU 12, THE SYSTEM IS LIKELY TO TAP INTO A HIGHLY 
FAVORABLE ENVIRONMENT AND UNDERGO RAPID INTENSIFICATION THROUGH TAU 48 
UNTIL THE 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.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT TY 15W WILL TRACK GENERALLY NORTH-NORTHWEST, ROUND THE 
STR AXIS NEAR 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 DETERMINISTIC SOLUTION AND THE ECMWF 
ENSEMBLE MEAN SOLUTION.  BETWEEN THE TWO NAMED, A CROSS-TRACK SPREAD 
OF 69NM AND ALONG-TRACK SPREAD OF 158NM IS PRESENT BY TAU 72. THIS 
SPREAD BECOMES EXACERBATED BY TAU 120, WITH A CROSS-TRACK SPREAD OF 
330NM AND AN ALONG-TRACK SPREAD OF 740NM.  DESPITE THE DISAGREEMENT, 
THE REMAINING CONSENSUS MEMBERS REFLECT GOOD AGREEMENT OVERALL,
CONTRIBUTING TO THE TRACK FORECAST CONFIDENCE OF HIGH THROUGH TAU
72 AND MEDIUM THEREAFTER. THE INTENSITY FORECAST CONFIDENCE IS
MEDIUM THROUGH TAU 72 AND LOW THEREAFTER.

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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