WDXS31 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (TWENTYNINE) 
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.2S 125.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 299 NM WEST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 29S SLOWING DOWN, WHILE STRUGGLING TO CONSOLIDATE AND
ORGANIZE OVER THE LAST SIX HOURS. INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON A LOW-LEVEL CIRCULATION CENTER (LLCC)
PARTIALLY OBSCURED BY FLARING BURSTS OF CONVECTION OVER THE
SOUTHERN PORTION OF THE SYSTEM. AS THE MID-LEVEL SHEAR IS SLOWLY
SUBSIDING, THE ENVIRONMENTAL CONDITIONS ARE BECOMING MORE
FAVORABLE, WITH WARM (29-30 C) SEA SURFACE TEMPERATURES (SST),
MODERATE POLEWARD OUTFLOW AND MOISTURE AVAILABLE THROUGHOUT THE
VERTICAL COLUMN. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
LOCATED OVER WESTERN AUSTRALIA, AS WELL AS ANOTHER STR TO THE
NORTHEAST OF THE SYSTEM

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 40 KTS AT 122136Z
   CIMSS ADT: 34 KTS AT 122330Z
   CIMSS AIDT: 32 KTS AT 122330Z
   CIMSS D-MINT: 29 KTS AT 122135Z
   CIMSS D-PRINT: 31 KTS AT 130110Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: 15-20 KTS MID-LEVEL SHEAR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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 29S HAS SLOWED DOWN, WITH THE TRANSLATION
SPEEDS OF 3-4 KTS OVER THE LAST 18 HOURS. THEREFORE, OVER THE NEXT
24 TO 36 HOURS, THE SYSTEM IS EXPECTED TO CONTINUE MOVING
SOUTHWESTWARD, PRIMARILY STEERED BY THE STR LOCATED TO THE
NORTHEAST. AFTER THIS PERIOD, STEERING INFLUENCE WILL SHIFT TO A
DEEP-LAYER STR POSITIONED TO THE SOUTH AND OVER WESTERN AUSTRALIA,
GUIDING THE SYSTEM WESTWARD. AROUND 96 HOURS INTO THE FORECAST
PERIOD, A PASSING LONGWAVE TROUGH TO THE SOUTH IS PROJECTED TO
WEAKEN THE RIDGE, CAUSING TC 29S TO SHIFT DIRECTION AND TRACK
SOUTHWARD, THEN SOUTHEASTWARD TOWARD THE AUSTRALIAN COASTLINE. IN
TERMS OF INTENSITY, TC 29S IS EXPECTED TO GRADUALLY CONSOLIDATE,
ORGANIZE, AND STRENGTHEN OVER THE NEXT 36 HOURS. BEYOND THAT POINT,
THE SYSTEM WILL ENCOUNTER EVEN WARMER (30-31 C) WATERS, WHILE OTHER
ENVIRONMENTAL FACTORS WILL REMAIN FAVORABLE FOR CONTINUED
DEVELOPMENT. THIS WILL ALLOW FOR REACHING PEAK SUSTAINED WINDS OF
95-100 KTS BETWEEN TAUS 72 AND 96. AFTER 96 HOURS, AS THE SYSTEM
BEGINS TURNING POLEWARD, CONDITIONS ARE FORECAST TO DETERIORATE.
INCREASING WESTERLY WIND SHEAR AND THE INTRUSION OF DRY AIR INTO
THE CORE OF THE CYCLONE ARE EXPECTED TO WEAKEN THE SYSTEM.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE SHOWS MODERATE
AGREEMENT OVER THE FIRST 72 HOURS. ALL MODELS GENERALLY SUGGEST A
SOUTHWESTWARD MOVEMENT INITIALLY, TRANSITIONING TO A WESTWARD PATH.
THE JTWC SHORT-TERM TRACK FORECAST CLOSELY FOLLOWS THE MULTI-MODEL
CONSENSUS AND IS ASSIGNED MEDIUM CONFIDENCE, BASED ON A CROSS-TRACK
SPREAD OF 140 NM AND AN ALONG-TRACK SPREAD OF 190 NM BY 72 HOURS.
CONFIDENCE IN THE EXTENDED TRACK FORECAST IS LOW DUE TO A
SIGNIFICANT INCREASE IN MODEL GUIDANCE SPREAD. DETERMINISTIC GFS
SHOWS THE FASTEST PROGRESSION, PUSHING THE SYSTEM FURTHER WEST,
WHILE GALWEM PROJECTS A SLOWER MOTION WITH A SUSPICIOUSLY SHARP
U-TURN BETWEEN TAUS 96 AND 120. AS WITH THE TRACK FORECAST,
INTENSITY PREDICTIONS ALSO CARRY MEDIUM CONFIDENCE IN THE NEAR
TERM, DROPPING TO LOW CONFIDENCE BETWEEN 72 AND 120 HOURS. ALL
CONSENSUS MODELS INDICATE GRADUAL BUT STEADY INTENSIFICATION OVER
THE NEXT 48-72 HOURS. BEYOND THAT, THE INTENSITY GUIDANCE DIVERGES,
WITH A SPREAD OF UP TO 85 KTS. HAFS IS THE MOST AGGRESSIVE,
PROJECTING A PEAK INTENSITY OF 145 KTS, WHILE STATISTICAL-DYNAMICAL
MODELS SUGGEST MUCH WEAKER DEVELOPMENT, AROUND 55-60 KTS. THE JTWC
INTENSITY FORECAST ALIGNS WITH THE UPPER END OF THE CONSENSUS,
LEANING TOWARD THE SOLUTIONS OFFERED BY GFS, HWRF, AND HAFS.
ADDITIONALLY, ONE OF THE RAPID INTENSIFICATION (RI) AIDS (NRL
CHIPS-BASED MODEL) TRIGGERED THIS RUN AND INDICATES RI THROUGH TAU
48, WITH THE SYSTEM REACHING 90 BY THAT TIME.

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