WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (KALMAEGI) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4N 127.7E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 466 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 31W
(KALMAEGI) WITH A HIGHLY COMPACT CORE AND DEEP CONVECTION TIGHTLY
CIRCLING THE OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). THE
SYSTEM HAS FAILED TO FORM A DEFINED EYE AND IS LIKELY ATTRIBUTED TO
THE MODERATE NORTHEASTERLY SHEAR. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE ANIMATED MSI. THE INITIAL
INTENSITY OF 80 KTS IS ASSESSED WITH LOW CONFIDENCE BASED ON THE
AGENCY DVORAK FIXES ALL AGREEING ON T4.5. HOWEVER, CIMSS INTENSITY
ESTIMATES ARE A BIT LOWER, AROUND THE 65-70 KNOT RANGE. THE INITIAL
INTENSITY IS HEDGED SLIGHTLY HIGHER DUE TO THE COMPACT NATURE OF
THE SYSTEM POTENTIALLY CAUSING UNDERESTIMATION. ENVIRONMENTAL
ANALYSIS INDICATES THAT 31W IS IN A FAVORABLE ENVIRONMENT
CHARACTERIZED BY STRONG POLEWARD AND EQUATORWARD OUTFLOW ALOFT,
MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA
SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF AN ELONGATED
SUBTROPICAL RIDGE (STR) CENTERED NORTHWEST OF LUZON

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 68 KTS AT 030540Z
   CIMSS ADT: 59 KTS AT 030540Z
   CIMSS AIDT: 66 KTS AT 030540Z
   CIMSS D-MINT: 67 KTS AT 030451Z
   CIMSS D-PRINT: 77 KTS AT 030540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 31W IS FORECAST TO TRACK GENERALLY WESTWARD
THROUGH TAU 24, ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE
NORTHWEST. AN INITIAL LANDFALL IS EXPECTED TO OCCUR RIGHT AROUND TAU
12 WITHIN LEYTE. THE SYSTEM WILL THEN TRACK ACROSS THE VISAYAS AND
ENTER THE NORTHERN SULU SEA JUST AFTER TAU 24. FROM TAU 24 ONWARD,
THE TRACK TRAJECTORY IS EXPECTED TO BE MORE NORTHWESTWARD AS THE
SYSTEM ROUNDS TO THE SOUTHWESTERN PERIPHERY OF THE STR. A FINAL
LANDFALL IS FORECAST TO OCCUR AROUND TAU 84 WITHIN CENTRAL VIETNAM.
REGARDING INTENSITY, 31W IS FORECAST TO FURTHER INTENSIFY UP UNTIL
THE TIME OF LANDFALL IN LEYTE. IF THE SYSTEM IS ABLE TO FORM A
DEFINED EYE, THEN A HIGHER INTENSITY COULD OCCUR THAN IS CURRENTLY
FORECAST. AS IT STANDS, AN INTENSITY OF AROUND 85-90 KTS IS
FORECAST FOR LANDFALL. A PERIOD OF SLIGHT WEAKENING THROUGH TAU 24
IS EXPECTED AS THE SYSTEM TRACKS ACROSS THE VISAYAS. AFTER EMERGING
BACK OVER WATER, 31W IS FORECAST TO REINTENSIFY DUE TO STRONG
EQUATORWARD OUTFLOW AND WARM SEA SURFACE TEMPERATURES. AFTER MAKING
LANDFALL IN VIETNAM, RUGGED TERRAIN INTERACTION WILL CAUSE 31W TO
RAPIDLY WEAKEN. COMPLETE DISSIPATION IS FORECAST TO OCCUR NO LATER
THAN TAU 120, WITHIN THAILAND.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE CONTINUES TO BE IN
VERY GOOD AGREEMENT WITH A MERE 50 NM CROSS-TRACK SPREAD AT TAU 72.
THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE
THEREAFTER. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH MODELS
AGREEING ON WEAKENING FROM TAU 12-24, AND THEN REINTENSIFICATION
THROUGH TAU 72. THE PEAK BEFORE LANDFALL IN VIETNAM RANGES FROM 85
KTS (COAMPS-TC) TO 120 KTS (HAFS-A). THE JTWC INTENSITY FORECAST
IS PLACED SLIGHTLY HIGHER THAN CONSENSUS THROUGHOUT THE FORECAST 
PERIOD WITH OVERALL MEDIUM CONFIDENCE. 

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