WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (KALMAEGI) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1N 117.1E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 273 NM WEST-SOUTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 21 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 31W (KALMAEGI) HAS BEGUN A NORTHWEST TRANSIT ACROSS
THE SOUTH CHINA SEA IMPROVING IN STRUCTURE AND CONVECTIVE ACTIVITY
AS EVIDENCED BY ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY.
THE STRUCTURE OF THE STORM HAS TIGHTENED AND AN EYE FEATURE WILL
LIKELY DEVELOP OVER THE NEXT 6 HOURS. ENVIRONMENTAL CONDITIONS ARE
FAVORABLE WITH WARM SEA SURFACE TEMPERATURES (29 C TO 30 C), GOOD
OUTFLOW, AND LOW VERTICAL WIND SHEAR (10-15 KTS). THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR IMAGERY AND
AGENCY FIXES. THE INITIAL INTENSITY OF 80 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON OBJECTIVE AID ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS SATCON: 73 KTS AT 050504Z
   CIMSS ADT: 82 KTS AT 050530Z
   CIMSS AIDT: 78 KTS AT 050530Z
   CIMSS D-MINT: 88 KTS AT 050504Z
   CIMSS D-PRINT: 71 KTS AT 050530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY KALMAEGI WILL CONTINUE ON ITS NORTHWESTWARD
TRACK UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGING TO THE
NORTHWEST AND NORTHEAST. AS IT TRACKS ACROSS THE WARM WATERS OF THE
SOUTH CHINA SEA WITH LITTLE VERTICAL WIND SHEAR TO INHIBIT IT, THE
SYSTEM WILL BE ABLE TO REACH WIND SPEED MAXIMUM BY TAU 24.
AFTERWARDS TY KALMAEGI WILL BEGIN A SLOW WEAKENING TREND INITIATED
BY HIGHER WIND SHEAR (20-25 KTS) AND AIDED LATER BY TOPOGRAPHIC
INTERACTION AS THE SYSTEM APPROACHES LANDFALL. TY KALMAEGI IS
FORECAST TO MAKE LANDFALL JUST SOUTH OF TAM QUAN, VIETNAM BETWEEN
TAU 24 AND TAU 36. THE SYSTEM WILL FULLY DISSIPATE OVER LAND BY TAU
72.

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT ON THE FORECASTED
TRACK WITH A CROSS-TRACK SPREAD UNDER 70 NM FOR THE ENTIRETY OF THE
FORECAST PERIOD. THE JTWC FORECAST TRACK IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. THE INTENSITY GUIDANCE
SPREAD IS AROUND 50 KTS AS SOME OF THE RAPID INTENSIFICATION MODELS
ARE OFFSET BY LESS AGGRESSIVE HAFS-A AND GFS. THE JTWC INTENSITY
FORECAST IS LAID CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE.  

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: HIGH//
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