WDXS31 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 17S (ZELIA) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.5S 118.7E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 48 NM NORTH OF PORT HEDLAND, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A STILL
DISRUPTED INNER CONVECTIVE CORE DUE TO A COMBINATION OF FACTORS. AN
EYEWALL REPLACEMENT CYCLE (ERC) REMAINS IN PROGRESS ACCORDING TO
RADAR IMAGERY FROM PORT HEDLAND, AUSTRALIA, SHOWING A 13 NM EYEWALL
SURROUNDED BY A 33 NM CONCENTRIC SECONDARY EYEWALL, A STRUCTURE
CONSISTENT WITH TEMPORARY WEAKENING. EASTERLY VERTICAL SHEAR OF
15-25 KT PERSISTS, CONTRIBUTING TO THE IRREGULAR SHAPE OF THE INNER
CONVECTIVE CORE IN EIR IMAGERY. THE CYCLONE HAS BEGUN MOVING MORE
QUICKLY OVER THE PAST SIX HOURS TOWARD THE SOUTHEAST, APPEARING TO
MAKE ITS FINAL MOVE TOWARD THE AUSTRALIAN COASTLINE. THE INITIAL
INTENSITY IS HELD AT 115 KT BASED ON A BLEND OF AGENCY DVORAK
INTENSITY ESTIMATES, OBJECTIVE SATELLITE-BASED INTENSITY ESTIMATES
FROM THE UNIVERSITY OF WISCONSIN, AND A 132141Z RCM-2 SAR PASS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER RIDGE OVER NORTHERN
AUSTRALIA AND THE TIMOR SEA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   DEMS: T6.5 - 127 KTS
   APRF: T6.5 - 127 KTS
   CIMSS SATCON: 111 KTS AT 132230Z
   CIMSS ADT: 109 KTS AT 132330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE 17S (ZELIA) APPEARS TO BE
MAKING ITS FINAL MOVE TOWARDS THE VICINITY OF PORT HEDLAND,
AUSTRALIA. DYNAMICAL MODELS ARE IN GOOD AGREEMENT THAT LANDFALL
WILL OCCUR IN UNDER 12 HOURS, AND THE JTWC TRACK FORECAST FOLLOWS
SUIT. THE FORECAST HAS SHIFTED A BIT EASTWARD DUE TO ZELIA'S
EASTWARD JOG OVER THE PAST 12 HOURS, AND NOW PLACES THE LANDFALL
LOCATION JUST EAST OF PORT HEDLAND. HOWEVER, TRACK WOBBLES COMMON
TO EYEWALL REPLACEMENT CYCLE (ERC) EVENTS MAY INFLUENCE THE EXACT
LANDFALL LOCATION. ZELIA IS LIKELY TO EITHER APPROXIMATELY MAINTAIN
ITS CURRENT INTENSITY OR SLIGHTLY REINTENSIFY PRIOR TO LANDFALL,
WITH REINTENSIFICATION BEING MORE LIKELY IF THE ONGOING ERC
COMPLETES WHILE THE CYCLONE IS STILL OVER WATER. HIGH-RESOLUTION
MODEL GUIDANCE SUGGESTS THAT THE FINAL MOVE TOWARDS THE COASTLINE
IS BRINGING ZELIA AWAY FROM THE COLD OCEANIC WAKE THAT DEVELOPED
DUE TO THE STORM'S QUASISTATIONARY MOTION OVER THE PAST 24 HOURS,
AND OVER WARMER COASTAL WATERS THAT COULD SUPPORT SOME
REINTENSIFICATION IF THE INNER CORE STRUCTURE ALLOWS. AFTER
LANDFALL, THE DEEP-LAYER STEERING RIDGE OVER NORTHERN AUSTRALIA
WILL PUSH ZELIA SOUTHWARD, ULTIMATELY DECAYING INLAND OVER WESTERN
AUSTRALIA WITHIN 72 HOURS.

MODEL DISCUSSION: THE JTWC TRACK AND INTENSITY FORECASTS ARE CLOSE
TO THE MULTI-MODEL CONSENSUS, WHICH IS TIGHTLY CLUSTERED IN BOTH
RESPECTS. THE JTWC TRACK FORECAST HAS SHIFTED APPROXIMATELY 20 NM
EAST OF THE PREVIOUS FORECAST.

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