WDXS31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 25S (KARIM) WARNING 
NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1S 91.1E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 355 NM WEST-SOUTHWEST OF THE COCOS
ISLANDS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A UNIFORM
CENTRAL DENSE OVERCAST (CDO) OBSCURING THE LOW-LEVEL CIRCULATION
CENTER (LLCC), WHICH IS POSITIONED UNDER THE NORTHEASTERN EDGE OF
THE CDO. A 091837Z ATMS 88 GHZ MICROWAVE IMAGE DEPICTS THE BULK OF
THE DEEP CONVECTION IS IN THE EASTERN SEMICIRCLE WITH A PROMINENT
CONVECTIVE BANDING FEATURE TO THE SOUTH. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE OBSCURING CDO AND ATMS
MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH
HIGH CONFIDENCE BASED ON AGENCY DVORAK INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   APRF: T3.5 - 55 KTS
   CIMSS SATCON: 75 KTS AT 091309Z
   CIMSS ADT: 59 KTS AT 091740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT IN THE UPPER-LEVELS

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 25S IS FORECAST TO TRACK SOUTHWARD TO
SOUTH-SOUTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE NEAR
EQUATORIAL RIDGE (NER) THROUGH TAU 24. DUE TO THE MARGINALLY
FAVORABLE ENVIRONMENTAL CONDITIONS THE INTENSITY IS FORECAST TO
REMAIN CONSISTENT THROUGH TAU 12. AFTER TAU 12, THE SYSTEM WILL
TRACK WITHIN THE STEERING FLOW BETWEEN A BROAD UPPER-LEVEL TROUGH
AND A SUBTROPICAL RIDGE POSITIONED TO THE EAST. ENVIRONMENTAL
CONDITIONS SHOULD DEGRADE QUICKLY WITH INCREASING VERTICAL WIND
SHEAR OF 30-40 KNOTS AND INCREASING CONVERGENCE ALOFT ASSOCIATED
WITH THE AFOREMENTIONED UPPER-LEVEL TROUGH. THEREFORE, TC 25S WILL
WEAKEN STEADILY. NEAR TAU 36, A STRONG LOW-LEVEL HIGH WILL BUILD
TO THE SOUTH EFFECTIVELY HALTING POLEWARD TRACK MOTION AND COMMENCING
AN ABRUPT EQUATORWARD TRACK MOTION WITHIN THE LOW-LEVEL SOUTHEASTERLY
FLOW. INTERACTION WITH A WEAK BAROCLINIC ZONE, COOLER SST (25-26C) 
AND SIGNIFICANT ENTRAINMENT OF DRY AIR WILL LEAD TO RAPID 
DISSIPATION 
AS THE REMNANTS ACCELERATE NORTHWESTWARD.        

MODEL DISCUSSION: RELIABLE MODEL GUIDANCE SUPPORTS THE JTWC TRACK
PHILOSOPHY WITH OVERALL MEDIUM CONFIDENCE DUE TO DIFFERENCES IN THE
TIMING AND EXACT TRACK DURING THE STALL AND SHARP EQUATORWARD TRACK
TURN. AFUM AND UEMN UNREALISTICALLY DRIVE THE SYSTEM EASTWARD
THROUGH THE FORECAST PERIOD AGAINST THE ENVIRONMENTAL FLOW. THE
JTWC INTENSITY FORECAST IS INITIALLY PLACED SLIGHTLY ABOVE THE
MODEL GUIDANCE DUE TO THE LINGERING CHANCE OF MINOR INTENSIFICATION
THROUGH TAU 12. 

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