WDXS31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07S (BAKUNG) WARNING 
NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1S 92.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 241 NM WEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 07S (BAKUNG) HAS EXPERIENCED SOME WEAKENING
OVER THE PAST SIX HOURS WITH A MUCH MORE COMPACT AREA OF CONVECTION
AND INCREASING TILT AS DEPICTED VIA ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI). ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS A WARMING TREND IN CLOUD TOP TEMPERATURES. A 170341Z
ASCAT PASS CORROBORATES THESE OBSERVATIONS WITH A TIGHT CIRCULATION
AND 45 KT WIND BARBS ON THE QUALITY CONTROLLED PRODUCT. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON  AGENCY FIXES AND
ASCAT DATA. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE PREVIOUSLY MENTIONED 170341Z ASCAT
ACCOUNTING FOR LOW BIAS.

INITIAL WIND RADII BASIS: A 170341Z METOP-C ASCAT SCATTEROMETER
DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING BETWEEN RIDGING TO
THE SOUTHEAST AND SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 50 KTS AT 170730Z
   CIMSS ADT: 53 KTS AT 170530Z
   CIMSS AIDT: 40 KTS AT 170730Z
   CIMSS D-MINT: 51 KTS AT 170744Z
   CIMSS D-PRINT: 55 KTS AT 170530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE 07S HAS CEASED RAPID
INTENSIFICATION AND IS DISPLAYING SIGNS OF SLOW WEAKENING WHICH
SHOULD CONTINUE AT LEAST FOR THE NEXT 12 HRS. AFTERWARDS MORE RAPID
WEAKENING WILL TAKE PLACE AS THE VORTEX BECOMES FURTHER DECOUPLED
WHILE THE SYSTEM CONTINUES TO TRACK THROUGH AN AREA OF MODERATE TO
HIGH VERTICAL WIND SHEAR WITH DRY AIR WRAPPING IN FROM THE WESTERN
SIDE OF THE VORTEX. GUIDANCE REMAINS AHEAD OF REALITY WITH 07S
STILL TRACKING WEST SOUTHWESTWARD WHICH WOULD DELAY THE EFFECTS OF
DRY AIR ENTRAINMENT AND DECOUPLING OF THE VORTEX. MAJORITY OF THE
NUMERICAL MODELS CONTINUE TO INSIST ON THE SHALLOWING OF THE VORTEX
WITHIN THE NEXT 12-24 HOURS, RESULTING IN A NORTHWESTWARD TRACK
DRIVEN BY A PREDOMINANTLY SOUTHEASTERLY LOW-LEVEL FLOW.

MODEL DISCUSSION: A LARGE CROSS TRACK SPREAD AMONG MODEL GUIDANCE
REMAINS WITH GEFS, UKMO, AND GFS LEADING A GROUPING THAT DEPICTS A
MORE NORTHWEST TRACK. IN CONTRAST THE ECMWF ENSEMBLE REMAINS MORE
CENTERED WITH DETERMINISTIC ECMWF AND NAVGEM SHOWING NORTH
NORTHEAST MOVEMENT. THE JTWC TRACK FORECAST REMAINS SLOWER THAN AND
SLIGHTLY EAST OF THE MULTI-MODEL CONSENSUS, DUE TO UNCERTAINTY IN
REGARD TO THE ENVIRONMENTAL STEERING FLOW. INTENSITY GUIDANCE IS
SPREAD UP TO 15 KTS WITH GFS DEPICTING A QUICKER DOWNWARD TREND.
THE JTWC INTENSITY FORECAST IS SLIGHTLY ABOVE THE MULTI-MODEL
CONSENSUS FOR THE FIRST 24 HOURS ACCOUNTING FOR TC 07S POTENTIALLY
RESISTING THE DECOUPLING PROCESS IN THE NEAR TERM.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   INTENSITY 00-72 HR: MEDIUM//
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