WDPN31 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (KALMAEGI) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.3N 110.6E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 210 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 31W
(KALMAEGI) WITH A FILLING EYE AND WARMING CLOUD TOPS AS IT QUICKLY
APPROACHES CENTRAL VIETNAM. THE DEGRADATION IS LIKELY DUE TO AN
INCREASE IN NORTHEASTERLY VERTICAL WIND SHEAR ACTING ON THE SYSTEM.
HOWEVER, A 060609Z AMSR2 37 GHZ MICROWAVE IMAGE REVEALED THAT THE
CORE OF THE SYSTEM REMAINS WELL-DEFINED WITH A STRONG MICROWAVE EYE
FEATURE AT THE LOWER LEVELS. ENVIRONMENTAL ANALYSIS INDICATES A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE
EQUATORWARD OUTFLOW, MODERATE TO HIGH (20-25 KTS) VERTICAL WIND
SHEAR, AND WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED
AMSR2 IMAGE AND ANIMATED MSI. THE INITIAL INTENSITY OF 110 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SLIGHTLY LOWER END OF
THE AGENCY DVORAK FIXES AND OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE FROM THE 060241Z METOP-C
ASCAT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE POSITIONED TO THE NORTH-NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   DEMS: T6.0 - 115 KTS
   CIMSS SATCON: 114 KTS AT 060537Z
   CIMSS ADT: 124 KTS AT 060600Z
   CIMSS AIDT: 117 KTS AT 060600Z
   CIMSS D-MINT: 116 KTS AT 060611Z
   CIMSS D-PRINT: 112 KTS AT 060600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE 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: 31W IS FORECAST TO MAKE LANDFALL IN THE NEXT
FEW HOURS NEAR QUY NHON. 31W WILL THEN CONTINUE ON A
WEST-NORTHWESTWARD TRACK THROUGH TAU 24 INTO NORTHERN CAMBODIA AND
SOUTHERN LAOS. TERRAIN INTERACTION WILL RAPIDLY DETERIORATE THE
VORTEX WITH COMPLETE DISSIPATION FORECAST TO OCCUR NEAR TAU 24
WITHIN EASTERN THAILAND. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH A 65 NM CROSS-TRACK SPREAD AT TAU 24. THE JTWC TRACK
FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE ALL AGREES ON RAPID WEAKENING
THROUGHOUT THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS
PLACED WITH MEDIUM CONFIDENCE DUE TO INHERENT UNCERTAINTIES
REGARDING THE EXACT WEAKENING TREND THAT OCCURS.

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