WDPN31 PGTW 040900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (KALMAEGI) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4N 121.8E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 256 NM SOUTH OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 31W (KALMAEGI) IS STILL RECOVERING FROM ITS TIME OVER
THE CENTRAL PHILIPPINES HAVING TEMPORARILY DECREASED IN INTENSITY
OVER THE PAST 6 HOURS. THE STRUCTURE OF TY KALMAEGI SHOWS SIGNS OF
TIGHTENING AGAIN AS THE CIRCULATION ENTERS THE SULU SEA. MAJOR
CONVECTIVE ACTIVITY IS CURRENTLY FLARING IN THE SOUTHWEST QUADRANT
AS DEPICTED BY ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY.
ENVIRONMENTAL CONDITIONS REFLECT MARGINAL CONDITIONS FOR CONTINUED
DEVELOPMENT WITH STRONG OUTFLOW AND WARM SEA SURFACE TEMPERATURES
(29 C TO 30 C) OFFSET BY UNFAVORABLE VERTICAL WIND SHEAR (25-30
KTS). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
EIR SATELLITE IMAGERY AND AGENCY FIXES. THE INITIAL INTENSITY OF 70
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON OBJECTIVE AID
ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T4.0 - 65 KTS
   CIMSS SATCON: 64 KTS AT 040523Z
   CIMSS ADT: 63 KTS AT 040530Z
   CIMSS AIDT: 66 KTS AT 040530Z
   CIMSS D-MINT: 68 KTS AT 040523Z
   CIMSS D-PRINT: 59 KTS AT 040530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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: TY KALMAEGI WILL CONTINUE TO TRACK WESTWARD
OVER THE SULU SEA UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE TO THE
NORTHEAST. THE SYSTEM WILL STRENGTHEN SLIGHTLY OVER WATER BEFORE
ENCOUNTERING THE NORTHERN PORTION OF PALAWAN, PHILIPPINES.
FOLLOWING LANDFALL OVER PALAWAN AROUND TAU 12, THE SYSTEM WILL
START A NORTHWESTWARD TRACK AS RIDGING OVER THE GULF OF TONKIN
TAKES OVER STEERING. TY KALMAEGI IS FORECAST TO INTENSIFY AGAIN
ENCOUNTERING MARGINALLY FAVORABLE CONDITIONS OVER THE SOUTH CHINA
SEA CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES (29 C TO 30 C)
AND RELATIVELY LOWER VERTICAL WIND SHEAR (20-25 KTS). A PEAK
INTENSITY OF 95 KTS IS FORECAST AROUND TAU 48. BETWEEN TAU 48 AND
72 TY KALMAEGI WILL MAKE LANDFALL SOUTH OF QUY NHON, VIETNAM AND
BEGIN A RAPIDLY WEAKENING TREND FACILITATED BY TOPOGRAPHIC
INTERACTION. THE SYSTEM WILL FULLY DISSIPATE OVER LAND BY TAU 96.

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT ON THE INITIAL
FORECAST TRACK WITH A CROSS-TRACK SPREAD UNDER 80 NM UNTIL TAU 36.
AFTERWARDS THE INTERPOLATED MEMBERS OF NAVGEM FAVOR A MORE
NORTHWESTWARD TRACK TOWARDS DA NANG, VIETNAM. INTERPOLATED ECMWF
MEMBERS PUSH THE TYPHOON SOUTH DEPICTING LANDFALL SOUTH OF TUY HOA,
VIETNAM. THE MULTI-MODEL CONSENSUS KEEPS THE TRACK ONLY SLIGHTLY
NORTHWEST AFTER TRACKING OVER THE NORTHERN PORTION OF PALAWAN AND
DEPICTS LANDFALL TO THE SOUTH OF QUY NHON, VIETNAM. THE JTWC
FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS WIDELY SPREAD (UP TO 40 KNOTS)
WITH GFS DEPICTING A PEAK INTENSITY OF 85 KTS WHILE HAFS-A ALLOWS
FOR FURTHER INTENSIFICATION DEPICTING MAX INTENSITIES OF 110 KTS.
THE JTWC INTENSITY FORECAST IS SLIGHTLY UNDER THE MULTI-MODEL
CONSENSUS UNTIL TAU 48 AND AFTERWARDS REFLECTS THE CONSENSUS. 

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