WDXS31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 25S (KARIM) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.7S 89.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 510 NM WEST-NORTHWEST OF THE COCOS
ISLANDS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED,
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FLARING
CONVECTION OVER THE CENTER AND PERSISTENT, CURVED DEEP CONVECTIVE
BANDING OVER THE WESTERN PERIPHERY. A 070722Z ATMS 88.2GHZ
MICROWAVE IMAGE SHOWS THE BULK OF THE DEEP CONVECTIVE BANDING OVER
THE WESTERN SEMICIRCLE WITH SHALLOW BANDING WRAPPING INTO THE LLCC.
ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE WITH LOW TO
MODERATE EASTERLY VERTICAL WIND SHEAR HINDERING CONVECTIVE
DEVELOPMENT OVER THE EASTERN SEMICIRCLE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE MSI. THE INITIAL INTENSITY
OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON RECENT ASCAT
DATA (070347Z ASCAT-C) AND THE FMEE DVORAK ESTIMATE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   FMEE: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 25S WILL TRACK SLOWLY POLEWARD ALONG THE
WESTERN PERIPHERY OF THE NER THROUGH TAU 48 WITH GRADUAL
INTENSIFICATION TO A PEAK OF 60 KNOTS BY TAU 48. AFTER TAU 48, THE
SYSTEM WILL ACCELERATE POLEWARD AS IT TRACKS WITHIN THE ENHANCED
FLOW BETWEEN A BROAD MIDLATITUDE TROUGH AND A SUBTROPICAL RIDGE TO
THE EAST. RAPID WEAKENING WILL OCCUR AS THE SYSTEM ENCOUNTERS
INCREASING VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT. AFTER TAU
96, THE SYSTEM WILL WEAKEN AND STALL AS IT ENCOUNTERS A STRONG HIGH
BUILDING TO THE SOUTH EFFECTIVELY BLOCKING FURTHER POLEWARD MOTION.
TC 25S SHOULD DISSIPATE BY TAU 120 WITH THE REMNANTS TRACKING BACK
TOWARD THE EQUATOR UNDER THE LOW-LEVEL SOUTHEASTERLY FLOW
ASSOCIATED WITH THE AFOREMENTIONED HIGH.   

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH DRIVES THE
SYSTEM THROUGH THE STRONG HIGH, NUMERICAL MODEL GUIDANCE SUPPORTS
THE TRACK FORECAST WITH MEDIUM CONFIDENCE. THE 070000Z ECMWF
ENSEMBLE (EPS) ALSO SUPPORTS THE JTWC FORECAST TRACK AND SHOWS THE
BULK OF THE SOLUTIONS EITHER STALLING AND DISSIPATING TC 25S OR 
TRACKING THE REMNANTS WESTWARD UNDER THE LOW-LEVEL FLOW. RELIABLE 
INTENSITY GUIDANCE ALSO IS IN FAIR AGREEMENT WITH PEAK INTENSITIES 
RANGING FROM 50 TO 63 KNOTS. THE JTWC INTENSITY FORECAST IS PLACED 
ABOVE THE INTENSITY CONSENSUS (ICNW) BUT IS CLOSE TO THE HWRF 
SOLUTION.    

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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