Advisories

WDPN33 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (KOGUMA) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.9N 161.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 1210 NM EAST-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY-
EXPOSED LOW-LEVEL CIRCULATION CENTER POSITIONED ON THE NORTHERN EDGE 
OF THE CENTRAL DENSE OVERCAST, WHICH SUPPORTS THE INITIAL POSITION 
WITH HIGH CONFIDENCE. ALTHOUGH VERTICAL WIND SHEAR HAS DECREASED 
SLIGHTLY TO 10-15 KNOTS, NORTHEASTERLY VWS CONTINUES TO HINDER 
POLEWARD OUTFLOW OVER THE NORTHEAST QUADRANT. THE INITIAL INTENSITY IS 
ASSESSED AT 55 KNOTS BASED ON A BLEND OF THE SUBJECTIVE AND OBJECTIVE 
INTENSITY ESTIMATES WITH MEDIUM CONFIDENCE. WIND RADII HAVE BEEN 
ADJUSTED BASED ON A 072200Z ASCAT-B BULLSEYE IMAGE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE NORTH, WEAKENED SLIGHTLY BY TROPICAL STORM 15E
(NOLO) POSITIONED 630NM TO THE NORTH-NORTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   PHFO: T4.0 - 65 KTS
   CIMSS SATCON: 51 KTS AT 072047Z
   CIMSS ADT: 49 KTS AT 072350Z
   CIMSS AIDT: 44 KTS AT 072350Z
   CIMSS D-MINT: 51 KTS AT 072253Z
   CIMSS D-PRINT: 51 KTS AT 080020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 27W IS FORECAST TO TRACK WEST-NORTHWESTWARD
TO NORTHWESTWARD THROUGH TAU 72 ALONG THE SOUTHWEST PERIPHERY OF
THE STR, MAINTAINING A 660-700NM SEPARATION DISTANCE FROM TS 15E
(NOLO) THROUGH TAU 60, WHICH IS WITHIN THE TYPICAL RANGE FOR WEAK
BINARY INTERACTION. ENVIRONMENTAL CONDITIONS ARE FORECAST TO IMPROVE 
QUICKLY WITH DECREASING VWS, WHICH WILL ALLOW TS 27W TO RAPIDLY 
INTENSIFY TO 120 KNOTS BY TAU 60. AFTER TAU 60, TS 27W WILL TURN 
NORTHWESTWARD TO NORTH-NORTHWESTWARD WHILE SLOWING TO ABOUT 6 KNOTS AS 
IT ROUNDS THE WESTERN PERIPHERY OF THE STR. AFTER TAU 72, THE SYSTEM 
WILL GRADUALLY WEAKEN DUE TO INCREASING VWS OF 20-25 KNOTS AND DRY AIR 
ENTRAINMENT OVER THE SOUTHERN PERIPHERY.  

MODEL DISCUSSION: THE PHYSICS-BASED MODELS ARE IN FAIR AGREEMENT
THROUGH TAU 72, WITH A 120NM SPREAD IN THE GUIDANCE, DIVERGING AFTER 
TAU 72 DUE TO UNCERTAINTY IN THE RECURVE LOCATION AND ALONG-TRACK 
SPEEDS. THERE REMAINS VERY LOW POTENTIAL FOR WEAK BINARY INTERACTION. 
THE JTWC FORECAST FAVORS AICN THROUGH TAU 120 AND IS POSITIONED 
SOUTHWEST OF CONW AT TAU 120. ECMI AND EEMI HAVE SLOWED SIGNIFICANTLY 
AND ARE IN BETTER AGREEMENT WITH THE REMAINDER OF THE GUIDANCE. THE 
BULK OF THE AI-BASED AND DETERMINISTIC ENSEMBLE MEMBERS SUPPORT THE 
JTWC TRACK SCENARIO, WITH A FEW MEMBERS INDICATING A SLOW TRACK MOTION 
POSSIBLY DUE TO THE WEAK BINARY INTERACTION IN THE EXTENDED FORECAST 
PERIOD. THERE IS SUBSTANTIAL SUPPORT FOR RAPID INTENSIFICATION (RI), 
WITH THE 071200Z COAMPS-TC (GFS) RUN INDICATING 90 PLUS PERCENT 
PROBABILITY OF RI FROM TAU 06 TO TAU 42. ADDITIONALLY, RI AIDS HAVE
CONSISTENTLY TRIGGERED SUPPORTING THE IMMINENT RI PHASE.     

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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