WDPN32 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (BOLAVEN)      
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.7N 151.5E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 427 NM EAST-SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST DAY, ENVIRONMENTAL CONDITIONS HAVE IMPROVED
SIGNIFICANTLY WITH A ROBUST POLEWARD OUTFLOW CHANNEL INTO THE TUTT
TO THE NORTHEAST AND IMPROVED BROAD EQUATORWARD OUTFLOW NOW EVIDENT
IN ANIMATED WATER VAPOR IMAGERY. ADDITIONALLY, SST VALUES OF 29-30
C COUPLED WITH A POOL OF DEEP WARM WATER ARE AIDING IN THE FORMATION 
OF AN IMPRESSIVE CENTRAL DENSE OVERCAST FEATURE (CLOUD TOP 
TEMPERATURES AS HIGH AS -83 C) OVER THE CONSOLIDATING LOW-LEVEL 
CIRCULATION AS DEPICTED IN ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY. A 081757Z SSMIS 91 GHZ COLOR COMPOSITE MICROWAVE IMAGE 
REVEALS CURVED DEEP CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE 
WRAPPING INTO THE CENTER WITH MULTIPLE, FRAGMENTED BANDS OVER THE 
NORTHERN SEMICIRCLE. THE ONLY LIMITING FACTOR AT THIS TIME IS THE 
ELONGATED, PARTIALLY EXPOSED NATURE OF THE LOW-LEVEL CIRCULATION 
CENTER, WHICH IS POSITIONED JUST NORTHWEST OF THE CORE CONVECTION 
(HOOK FEATURE EVIDENT IN THE SSMIS IMAGE). THUS, THERE IS MEDIUM 
CONFIDENCE IN THE INITIAL POSITION WITH UNCERTAINTY IN THE EXACT 
POSITION. THIS POSITIONAL UNCERTAINTY COULD LEAD TO SLIGHT SHIFTS IN 
THE SHORT-TERM FORECAST TRACK OVER THE NEXT DAY BEFORE THE SYSTEM 
BECOMES MUCH BETTER ORGANIZED. THE INITIAL INTENSITY IS ASSESSED AT 
50 KNOTS WITH MEDIUM CONFIDENCE, WHICH IS WITHIN THE RANGE OF DVORAK 
INTENSITY ESTIMATES. 

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 48 KTS AT 081537Z
   CIMSS ADT: 61 KTS AT 081730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: HIGH OCEAN HEAT CONTENT.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE
FOR STEADY DEVELOPMENT TO 60 KNOTS BY TAU 24 AS THE SYSTEM TRACKS
NORTHWESTWARD. AFTER TAU 24, POLEWARD OUTFLOW IS EXPECTED TO
IMPROVE FURTHER WITH ENHANCED OUTFLOW INTO THE TUTT POSITIONED TO
THE EAST AND INTO THE MIDLATITUDE WESTERLIES. TS 15W WILL CONTINUE
TO TRACK NORTHWESTWARD THROUGH TAU 48 OVER WARM SST AND OVER A POOL 
OF DEEP WARM WATER, WHICH EXTENDS ALONG THE TRACK TO THE NORTHWEST OF
GUAM. AFTER TAU 24, THE UPPER-LEVEL AND LOW-LEVEL WILL BECOME
VERTICALLY ALIGNED, WHICH WILL FAVOR A SUSTAINED PERIOD OF RAPID
INTENSIFICATION (RI) DURING THE SYSTEM'S PASSAGE OVER THE NORTHERN
MARIANAS. PEAK INTENSITY IS FORECAST TO INCREASE FROM 70 KNOTS TO
90 KNOTS DURING THIS PASSAGE. ADDITIONAL RI WILL OCCUR AFTER TAU 48
AS THE SYSTEM RECURVES NORTHWARD TOWARD A BREAK IN THE STR, WITH
ENHANCED POLEWARD OUTFLOW INTO A MIDLATITUDE SHORTWAVE TROUGH.
AFTER TAU 96, TS 15W WILL BEGIN EXTRA-TROPICAL TRANSITION AS IT
BEGINS TO INTERACT WITH THE MIDLATITUDE WESTERLIES AND BAROCLINIC
ZONE.      

MODEL DISCUSSION: DETERMINISTIC GUIDANCE REMAINS IN TIGHT AGREEMENT
WITH A 65 NM TO 75 NM CROSS-TRACK SPREAD IN SOLUTIONS FROM TAU 36
TO TAU 48. ADDITIONALLY, THE MAJORITY OF THE EPS AND GEFS SOLUTIONS
NOW TRACK THE SYSTEM NORTH OF GUAM. IN GENERAL, THE ENSEMBLE
SOLUTIONS SHOW A NARROW SWATH FROM ABOUT 14N TO 16N LATITUDE THUS
THERE IS NOW HIGH CONFIDENCE IN THE JTWC FORECAST TRACK THROUGH TAU
72. THE MESOSCALE MODELS (COAMPS-TC AND HAFS-A) SUPPORT RI AFTER
TAU 24 CONTINUING THROUGH TAU 84 WITH PEAK INTENSITIES OF 120 KNOTS 
(HAFS-A AT TAU 60) TO 145 KNOTS (COAMPS-TC (GFS VERSION) AT TAU 120).
ADDITIONALLY, RAPID INTENSIFICATION GUIDANCE IS TRIGGERED (CONSISTENT 
OVER THE PAST DAY) REFLECTING THE HIGHLY FAVORABLE ENVIRONMENT. THE 
081200Z COAMPS-TC INTENSITY PROBABILITY DATA ALSO PROVIDES EXCELLENT 
SUPPORT FOR RAPID INTENSIFICATION AFTER TAU 24 WITH PROBABILITIES 
PEAKING AT 95 PERCENT FROM TAU 42 TO TAU 66. 

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