WDXS33 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 23S (HONDE) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.0S 45.8E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 420 NM SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 23S (HONDE) WITH A BROAD BANDING EYE CURRENTLY SOUTH OF
MADAGASCAR. ENVIRONMENTAL ANALYSIS INDICATES THAT 23S IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD
OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (26-27
C) SEA SURFACE TEMPERATURES OFFSET BY THE PRESENCE OF DRY AIR ALONG
THE WESTERN PERIPHERY OF THE SYSTEM. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON SHORT EXTRAPOLATION FROM A 011638Z
ISS COWVR 34 GHZ MICROWAVE IMAGE REVEALING THE DEFINED MICROWAVE
EYE FEATURE. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON AGENCY DVORAK AND OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW. THE INTENSITY IS PLACED LOWER THAN WHAT
AGENCY DVORAK ESTIMATES WOULD SUGGEST DUE TO RECENT SCATTEROMETRY
REVEALING A WEAKER WIND FIELD, LIKELY DUE TO THE BROAD NATURE OF
THE VORTEX. INITIAL WIND RADII ARE ASSESSED WITH HIGH CONFIDENCE
BASED ON A 011859Z METOP-B ASCAT IMAGE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: PLACED WITHIN A COMPETING STEERING
PATTERN WITH AUBTROPICAL RIDGE (STR) PLACED TO BOTH THE EAST AND
WEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   FMEE: T4.5 - 77 KTS
   CIMSS SATCON: 52 KTS AT 011611Z
   CIMSS ADT: 41 KTS AT 011800Z
   CIMSS AIDT: 63 KTS AT 011800Z
   CIMSS DPRINT: 58 KTS AT 011800Z
   CIMSS DMINT: 65 KTS AT 011604Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR OVER THE WESTERN PERIPHERY OF THE SYSTEM

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 23S IS FORECAST TO MEANDER EASTWARD THROUGH
TAU 24, AS IT CONTINUES TO BE PLACED WITHIN THE COMPETING STEERING
PATTERN. AFTER TAU 24, THE STR TO THE EAST WILL BECOME THE PRIMARY
STEERING MECHANISM AND WILL DRIVE THE SYSTEM SOUTHWARD AS A RESULT.
23S WILL THEN CONTINUE ON A SOUTHWARD TRACK TROUGH TAU 72 WITH
INCREASING TRACK SPEEDS AS IT BEGINS EXTRATROPICAL TRANSITION.
AFTER TAU 72, THE SYSTEM WILL TURN SOUTHEASTWARD AS IT ROUNDS THE
RIDGE AXIS AND FURTHER ACCELERATES. EXTRATROPICAL TRANSITION IS
FORECAST TO COMPLETE NEAR TAU 96, AS THE SYSTEM BECOMES EMBEDDED
WITHIN THE BAROCLINIC ZONE WITH A BROADENING WIND FIELD. REGARDING
INTENSITY, 23S IS FORECAST TO MAINTAIN INTENSITY THROUGH TAU 48, AS
THE ENVIRONMENT REMAINS SIMILAR. THE MAIN HINDRANCE WILL CONTINUE
TO BE THE DRY AIR TO THE WEST. AFTER TAU 48, VERTICAL WIND SHEAR
WILL BEGIN TO RISE AND SEA SURFACE TEMPERATURES WILL DROP, CAUSING
WEAKENING. 23S IS FORECAST TO BE AROUND 50 KTS AS IT COMPLETES
EXTRATROPICAL TRANSITION.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT THROUGH TAU 72, WITH THE EXCEPTION OF NAVGEM. CROSS-TRACK
SPREAD AT TAU 72 IS 58 NM WITH MINIMAL ALONG-TRACK SPREAD. AFTER
TAU 72, ALONG-TRACK SPREAD BEGINS TO INCREASE AS THE VORTEX QUICKLY
ACCELERATES. THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE
THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE
OVERALL AGREES ON A STEADY INTENSITY THROUGH TAU 48 WITH WEAKENING
THEREAFTER. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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