Advisories

WDPN33 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (KOGUMA) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.5N 148.2E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 318 NM WEST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY) 
27W (KOGUMA) RELATIVELY STEADILY TRACKING NORTHWESTWARD, RELATIVELY 
UNCHANGED FROM SEVERAL HOURS PRIOR. THE 102144Z SSMIS MICROWAVE IMAGES 
CONFIRM THE SYSTEM IS BEGINNING A SECOND EYEWALL REPLACEMENT CYCLE 
(ERC), WITH A DRY SLOT FORMING IN THE NORTHWESTERN QUADRANT, ALONG 
WITH A NASCENT OUTER EYEWALL STRETCHING ACROSS THE NORTHERN 
SEMICIRCLE. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT, 
CHARACTERIZED BY LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), BORDERLINE 
(26-27 C) SEA SURFACE TEMPERATURES (SST), MARGINAL (25-50 KJ PER CM 
SQUARED) OCEAN HEAT CONTENT (OHC), AND MODERATE POLEWARD OUTFLOW. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-
DEFINED EYE IN ANIMATED MSI. THE INITIAL INTENSITY OF 115 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE 101953Z RCM-3 SAR WIND 
SPEED DATA. 

INITIAL WIND RADII BASIS: 101953Z SAR DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   CIMSS SATCON: 115 KTS AT 102300Z
   CIMSS ADT: 112 KTS AT 110040Z
   CIMSS AIDT: 116 KTS AT 110040Z
   CIMSS D-PRINT: 115 KTS AT 102300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TY 27W IS FORECAST TO TRACK NORTH-NORTHWESTWARD 
FOR THE NEXT 12 HOURS WHILE IT REMAINS ON THE SOUTHWESTERN PERIPHERY 
OF THE STEERING RIDGE. FOLLOWING TAU 12, 27W WILL CURVE NORTHWARD AS 
IT BEGINS TO ROUND THE STR. KOGUMA IS EXPECTED TO ROUND THE RIDGE AXIS 
JUST BEFORE TAU 24 AND RECURVE TO THE NORTHEAST. 27W WILL MAINTAIN A 
NORTHEASTWARD TRACK FROM TAU 24 THROUGH THE END OF THE FORECAST. 
REGARDING INTENSITY, 27W IS EXPECTED TO STEADILY WEAKEN THROUGH TAU 96 
AS THE ENVIRONMENT BECOMES INCREASINGLY HOSTILE. VWS IS EXPECTED TO 
INCREASE THROUGHOUT THE FORECAST PERIOD, INCREASING FROM 25 KTS AT TAU 
36 TO 60 KTS BY TAU 96. THE HIGH VWS IS EXPECTED TO CAUSE SIGNIFICANT 
DRY AIR ENTRAINMENT. ADDITIONALLY, OHC IS EXPECTED TO DROP TO 0 KJ PER
CM SQUARED AS KOGUMA CROSSES THE 26C ISOTHERM BETWEEN TAU 12-24. 
HOWEVER, THE RATE OF WEAKENING WITHIN THE NEXT 24-36 MAY BE INCREASED 
IF 27W FAILS TO COMPLETE THE ERC BEFORE THE ENVIRONMENT DETERIORATES 
SIGNIFICANTLY. 27W IS EXPECTED TO SKIRT THE EQUATORWARD FRINGES OF THE 
WESTERLIES BETWEEN TAU 72, BEFORE FINALLY BECOMING EMBEDDED IN THE 
FLOW BY TAU 96. AS A RESULT, KOGUMA IS FORECAST TO BEGIN EXTRATROPICAL
TRANSITION BY TAU 72 AND COMPLETE TRANSITION BY TAU 96.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG 
AGREEMENT THROUGH THE DURATION OF THE FORECAST PERIOD, THOUGH NAVGEM, 
GFS, AND GEFS ARE MINOR OUTLIERS. DISCOUNTING THOSE MODELS, THE JTWC 
TRACK FORECAST IS PLACED WITHIN THE TIGHTEST GROUPING OF MODELS WITH 
OVERALL HIGH CONFIDENCE. RELIABLE INTENSITY AIDS ARE IN STRONG 
AGREEMENT IN DEPICTING A STEADY WEAKENING TREND THROUGH TAU 96 AND 
EXTRATROPICAL TRANSITION. HOWEVER, AS DISCUSSED ABOVE, 27W MAY WEAKEN 
FASTER THAN ANTICIPATED SHOULD IT ATTEMPT ANOTHER ERC AND FAIL TO 
COMPLETE THE CYCLE PRIOR TO REACHING UNFAVORABLE ENVIRONMENTAL 
CONDITIONS. AS A RESULT, THE JTWC INTENSITY FORECAST IS IN CLOSE 
ALIGNMENT WITH HAFS-A, COAMPS-TC, AND HWRF WITH OVERALL MEDIUM 
CONFIDENCE.

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