WDXS31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (TWENTYNINE) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.8S 124.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 336 NM NORTH-NORTHEAST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 29S WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND VOID OF ANY DEEP CONVECTION. A 130509Z AMSR2 89 GHZ
MICROWAVE IMAGE REVEALED THE LOW-LEVEL CLOUD LINES WRAPPING INTO
THE CENTER WITH NO ASSOCIATED CONVECTION. THE SYSTEM HAS CONTINUED
TO FAIL TO ORGANIZE LIKELY ATTRIBUTED TO THE PERSISTENT MID-LEVEL
SHEAR DISALLOWING VERTICAL STRUCTURALIZATION. AS THE SYSTEM
TRANSITIONS FROM THE DIURNAL MINIMUM, CONVECTION COULD BEGIN TO
BUILD BACK OVER THE SYSTEM, ALLOWING FOR MORE DEVELOPMENT.
ENVIRONMENTAL ANALYSIS INDICATES THAT 29S REMAINS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD AND
EQUATORWARD OUTFLOW, LOW (5-10 KTS) DEEP LAYER SHEAR, AND WARM
(29-30 C) SEA SURFACE TEMPERATURES. THESE PARAMETERS ARE OFFSET BY
SOME SLIGHT DRY AIR ENTRAINMENT ALONG THE NORTHERN PERIPHERY OF THE
SYSTEM AND THE MODERATE (15-20 KTS) MID-LEVEL SHEAR. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MENTIONED
AMSR2 MICROWAVE IMAGE SHOWING THE LLCC. THE INITIAL INTENSITY OF 35
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK
AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) CENTERED OVER WESTERN AUSTRALIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 36 KTS AT 130630Z
   CIMSS ADT: 39 KTS AT 130600Z
   CIMSS AIDT: 32 KTS AT 130600Z
   CIMSS DPRINT: 27 KTS AT 130600Z
   CIMSS DMINT: 26 KTS AT 130509Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT AND MODERATE MID-LEVEL
SHEAR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 IS FORECAST TO TRACK WEST-SOUTHWESTWARD
ALONG THE NORTHERN PERIPHERY OF THE STR TO THE SOUTH THROUGH TAU
24. NEAR TAU 24, THE STR OVER WESTERN AUSTRALIA IS EXPECTED TO
PROPAGATE EASTWARD AND THEN AN EXTENSION OF RIDGING FROM THE WEST
WILL JUT UNDERNEATH THE SYSTEM AND DRIVE IT MORE WESTWARD THROUGH
TAU 72. NEAR TAU 72, AN INCOMING LONG WAVE TROUGH WILL BREAK DOWN
THE RIDGE AND CAUSE 29S TO SLOW AND BEGIN A SHARP TURN TOWARD THE
SOUTH TO SOUTHEAST. REGARDING INTENSITY, 29S IS FORECAST TO
MARGINALLY INTENSIFY OVER THE NEXT 24 HOURS DUE TO THE MID-LEVEL
SHEAR. AFTER TAU 24, THE SHEAR IS EXPECTED TO WEAKEN AND ALLOW 29S
TO FURTHER INTENSIFY. A PEAK OF 90 KTS IS CURRENTLY FORECAST TO
OCCUR AT TAU 72, THOUGH IF HAFS-A IS RIGHT, IT COULD BE HIGHER.
AFTER TAU 72, WESTERLY SHEAR AND DRY AIR ENTRAINMENT WILL QUICKLY
RISE DUE TO THE LONG WAVE TROUGH INTERACTING WITH THE SYSTEM. AS A
RESULT, A RAPID WEAKENING TREND WILL ENSUE THROUGH THE REMAINDER OF
THE FORECAST PERIOD AS THE SYSTEM IS DECAPITATED AND SHEARED APART.


MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH A 98 NM CROSS-TRACK SPREAD. AFTER TAU
72, MODELS BEGIN TO DIVERGE. GFS CONTINUES TO BE THE MODEL THAT
TRACKS THE VORTEX THE FURTHEST WEST BEFORE TURNING POLEWARD WHILE
ECMWF HAS THE VORTEX MAKE A SHARP EASTWARD TURN AFTER TAU 96. THE
JTWC TRACK FORECAST IS PLACED CLOSER TO THE ECMWF TRACKERS AFTER
TAU 72. GUIDANCE LENDS HIGH CONFIDENCE TO THE TRACK FORECAST
THROUGH TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE
CONTINUES TO BE IN VERY POOR AGREEMENT, PARTICULARLY REGARDING THE
PEAK INTENSITY OF THE SYSTEM. HAFS-A HAS BEEN SET ON A PEAK OF
AROUND 155 KTS WHILE HWRF DEPICTS A PEAK OF 120 KTS. GFS HAS A PEAK
OF AROUND 90 KTS AND COAMPS-TC 70 KTS. THE JTWC INTENSITY PEAK IS
PLACED CLOSE TO THE MULTI-MODEL CONSENSUS OF 85-90 KTS AT TAU 72.
GFS HAS NOT BEEN INITIALIZING WELL REGARDING THE INTENSITY OF THE
SYSTEM AND SUGGESTS AN INTENSITY OF AROUND 80 KTS AT TAU 36 WHILE
ALL OTHER MODELS ARE LOWER AT 50-60 KTS AT THAT TIME. INTENSITIES
ARE PLACED SLIGHTLY BELOW CONSENSUS THROUGH TAU 36 TO OFFSET GFS.
OVERALL, THERE IS LOW CONFIDENCE IN THE INTENSITY FORECAST
THROUGHOUT THE FORECAST PERIOD.

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