WDXS31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 25S (KARIM) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.1S 90.7E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 363 NM WEST OF COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
MEDIUM SIZED SYSTEM WITH FLARING DEEP CENTRAL CONVECTION WITH EQUALLY
DEEP RAIN BANDS WRAPPING IN MOSTLY FROM ALL QUADRANTS. STRONG 
NORTHERLY UPPER LEVEL WINDS ARE ENHANCING ROBUST POLEWARD OUTFLOW AS
EVIDENCED BY SOUTHWARD STRIATIONS IN THE CIRRUS CANOPY. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED LOW
LEVEL CIRCULATION CENTER IN THE 081509Z ASCAT AMBIGUITY PRODUCT.
THE INITIAL INTENSITY OF 60KTS PLACED WITH MEDIUM CONFIDENCE BASED 
ON THE HIGH END OF PGTW AND ADT DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM:  WESTERN PERIPHERY OF A WEAK
NEAR-EQUATORIAL RIDGE TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   CIMSS ADT: 63 KTS AT 081515Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TC KARIM WILL CONTINUE ON ITS CURRENT
SOUTH-SOUTHEASTWARD TRACK UNDER THE NER. AFTER TAU 48, 
A BUILDING SUBTROPICAL RIDGE FROM THE SOUTHWEST WILL COMPETE 
FOR STEERING AND FORCE A COUNTER-CLOCKWISE
LOOPING MOTION. THE MARGINAL ENVIRONMENT WILL, AT BEST, MAINTAIN
THE CURRENT INTENSITY OF 60KTS UP TO TAU 24. AFTERWARD, INCREASING
VWS, INFLUX OF COOL DRY AIR, THEN COOLING SST WILL GRADUALLY ERODE
THE SYSTEM TO DISSIPATION BY TAU 96. 


MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT
WITH THE TRACK FORECAST. HOWEVER, GIVEN THE UNCERTAINTY IN THE
STORM MOTION DURING THE TRANSITION IN THE STEERING MECHANISM AFTER
TAU 48, THERE IS ONLY MEDIUM CONFIDENCE IN THE JTWC TRACK FORECAST
THAT IS LAID CLOSE TO THE CONSENSUS.


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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