WDPN32 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (BOLAVEN)     
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.0N 153.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 541 NM EAST-SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SLOWLY
CONSOLIDATING LOW-LEVEL CIRCULATION WITH A BROAD, WEAKLY DEFINED
CENTER. A 071811Z SSMIS 91 GHZ COLOR COMPOSITE MICROWAVE IMAGE SHOWS
CONVECTIVE BANDING AND THE BULK OF THE ASSOCIATED DEEP CONVECTION 
DISPLACED TO THE NORTH AND WEST OF AN ELONGATED CENTER. A 071513Z 
AMSR2 WINDSPEED IMAGE INDICATES GALE-FORCE WINDS ASSOCIATED WITH THE 
DEEP CONVECTION AND A WEAKER WIND BAND TO THE SOUTH, WITH AN 
ELONGATED AREA OF LIGHT CORE WINDS ORIENTED EAST-WEST. CONSEQUENTLY, 
THERE IS LOW CONFIDENCE IN THE INITIAL POSITION. SIGNIFICANT 
RELOCATIONS OF THE INITIAL POSITION ARE VERY POSSIBLE OVER THE NEXT 
DAY, WHICH COULD LEAD TO SHIFTS IN THE FORECAST TRACK. THE INITIAL 
INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
PGTW AND KNES DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: AMSR2 WINDSPEED IMAGE.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 34 KTS AT 071533Z
   CIMSS ADT: 47 KTS AT 071730Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: ALTHOUGH TS 15W IS CONSOLIDATING SLOWLY NOW,
ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR STEADY DEVELOPMENT
THROUGH TAU 36 AS THE SYSTEM TRACKS WEST-NORTHWESTWARD. ANIMATED
WATER VAPOR IMAGERY INDICATES EXPANDING POLEWARD OUTFLOW JUST
BEGINNING TO LINK UP WITH THE WESTERLY FLOW OVER THE SOUTH AND 
SOUTHWEST PERIPHERY OF A TUTT CELL LOCATED NEAR 20N 158E. AFTER TAU 
36, ROBUST POLEWARD OUTFLOW INTO THE TUTT ENHANCED BY JET-STRENGTH
WESTERLIES WILL LEAD TO A PERIOD OF RAPID OR NEAR-RAPID 
INTENSIFICATION. CONSEQUENTLY, TS 15W SHOULD NOT BE UNDERESTIMATED
AS IT TRACKS TOWARD AND OVER THE GUAM REGION WITH PEAK INTENSITY
VALUES INCRESING FROM 75 KNOTS AT TAU 48 TO 100 KNOTS AT TAU 72.
ADDITIONAL INTENSIFICATION WILL OCCUR AFTER TAU 72 AS THE SYSTEM
RECURVES NORTHWARD TOWARD A BREAK IN THE STR, WITH ENHANCED
POLEWARD OUTFLOW INTO A MIDLATITUDE SHORTWAVE TROUGH.     

MODEL DISCUSSION: AS EMPHASIZED EARLIER, THERE IS UNCERTAINTY IN
THE INITIAL POSITION AT LEAST OVER THE NEXT DAY AND FAIR AGREEMENT
IN THE DETERMINISTIC GUIDANCE, THUS THERE IS MEDIUM CONFIDENCE IN
THE JTWC TRACK FORECAST. THE 071200Z GEFS AND EPS ENSEMBLES ALSO
INDICATE A LARGE SPREAD IN SOLUTIONS FROM JUST SOUTH OF GUAM TO
ABOUT 18N LATITUDE. RELIABLE INTENSITY GUIDANCE SUPPORTS THE JTWC
INTENSITY FORECAST WITH MEDIUM CONFIDENCE WITH THE HAFS-A AND
COAMPS-TC (NAVGEM AND GFS VERSIONS) ALL INDICATING RAPID
INTENSIFICATION AFTER TAU 48. ADDITIONALLY, RAPID INTENSIFICATION 
GUIDANCE HAS TRIGGERED REFLECTING THE VERY FAVORABLE ENVIRONMENT 
FORECAST TO EVOLVE IN THE NEXT DAY OR SO. THE 071200Z COAMPS-TC 
INTENSITY PROBABILITY IMAGE ALSO PROVIDES EXCELLENT SUPPORT FOR RAPID 
INTENSIFICATION AFTER TAU 40 WITH PROBABILITIES JUMPING AS HIGH AS 85 
PERCENT FROM TAU 66 TO TAU 90. 

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