WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 31W (KALMAEGI) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.8N 135.1E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 164 NM NORTH OF KAYANGEL
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 31W WITH ROBUST RADIAL OUTFLOW AND VIGOROUS CENTRAL
CONVECTION. THE MOST INTENSE CONVECTION IS WRAPPING ALONG THE
NORTHERN AND WESTERN SEMICIRCLES. THE ENVIRONMENT CONTINUES TO BE
HIGHLY FAVORABLE FOR CONTINUED INTENSIFICATION, WITH LOW (5-10 KTS)
VERTICAL WIND SHEAR, VERY WARM (29-30 C) SEA SURFACE TEMPERATURES,
AND STRONG DIVERGENCE ALOFT ENHANCING DEVELOPMENT. THE EQUATORWARD
AND WESTWARD OUTFLOW CHANNELS ARE ENHANCED BY INTERACTION WITH THE
EQUATORIAL TRADE WINDS TO THE SOUTH; THE POLEWARD AND EASTWARD
OUTFLOW IS ENHANCED BY AN UPPER-LEVEL TROUGH TO THE NORTHEAST. THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON A
COMBINATION OF LOW-LEVEL CLOUD BANDING PRESENT IN ANIMATED MSI AND
AGENCY POSITION FIXES. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE CIMSS OBJECTIVE INTENSITY
ESTIMATES AND AGENCY DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   CIMSS SATCON: 39 KTS AT 012320Z
   CIMSS ADT: 47 KTS AT 020200Z
   CIMSS AIDT: 37 KTS AT 020200Z
   CIMSS D-MINT: 31 KTS AT 012140Z
   CIMSS D-PRINT: 39 KTS AT 020200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 31W (KALMAEGI) IS FORECAST TO TRACK
WESTWARD AS IT REMAINS UNDER THE STEERING INFLUENCE OF THE STR
CENTERED TO THE NORTHEAST FOR THE NEXT 48 HOURS. BETWEEN TAU 48-72,
A STR CENTERED OVER THE SOUTH CHINA SEA WILL BUILD AND ASSUME
STEERING INFLUENCE OVER 31W. AS THE STR CONTINUES TO BUILD THROUGH
THE REMAINDER OF THE FORECAST PERIOD, IT WILL SHIFT NORTHEASTWARD,
CAUSING 31W TO CURVE NORTHWESTWARD AND MAINTAIN A NORTHWESTWARD
TRACK THROUGH TAU 120. REGARDING INTENSITY, 31W WILL TRACK THROUGH
A HIGHLY FAVORABLE ENVIRONMENT LEADING UP TO LANDFALL IN THE
PHILIPPINES, CHARACTERIZED BY HIGHLY FAVORABLE VERTICAL WIND SHEAR,
HIGH OCEAN HEAT CONTENT, AND STRONG DIVERGENCE ALOFT. 31W IS FORECAST 
TO UNDERGO RAPID INTENSIFICATION (RI) AND INTENSIFY FROM THE INITIAL
INTENSITY OF 45 KTS TO 95 KTS WITHIN 48 HOURS. TERRAIN INTERACTION
WILL WEAKEN KALMAEGI AS IT CROSSES THROUGH CENTRAL PHILIPPINES; 
HOWEVER, IT IS EXPECTED TO RECOVER QUICKLY AFTER REEMERGING INTO THE 
SOUTH CHINA SEA. 31W WILL LIKELY WEAKEN TO BELOW 80 KTS BETWEEN TAU 
48-72 DUE TO TERRAIN INTERACTION, THOUGH IT IS NOT REFLECTED IN THE 
FORECAST POINTS. KALMAEGI WILL QUICKLY REINTENSIFY OVER THE SOUTH 
CHINA SEA, REACHING A SECOND PEAK OF 105 KTS BETWEEN TAU 96-120 WHILE 
OFF THE COAST OF VIETNAM.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THAT 31W WILL TRACK GENERALLY WESTWARD UNTIL LANDFALL AT
TAU 48. AT WHICH POINT, MODELS BEGIN TO DIVERGE, WITH CROSS-TRACK
SPREAD INCREASING SLIGHTLY DUE TO DISAGREEMENT OVER WHERE 31W WILL
MAKE LANDFALL. ALL MODELS ARE IN AGREEMENT THAT 31W WILL TRACK
NORTHWESTWARD FOR THE LATTER HALF OF THE FORECAST PERIOD. THE JTWC
FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE FROM TAU 0-72 AND
MEDIUM CONFIDENCE FROM TAU 72-120. RELIABLE INTENSITY GUIDANCE IS
IN STRONG AGREEMENT IN RI OCCURRING BETWEEN TAU 0-48. THE MAJORITY
OF JTWC RI GUIDANCE -- INCLUDING, BUT NOT LIMITED TO, RIPA, RIDE,
RICN, FRIA -- ARE SIGNALING A VERY HIGH LIKELIHOOD OF RI. AFTER TAU
48, HOWEVER, MODELS DISAGREE ON THE RATE AT WHICH 31W WILL WEAKEN
WHILE INTERACTING WITH LAND, IN ADDITION TO KALMAEGI'S WEAKEST
INTENSITY. AS A RESULT, THERE IS A LARGE SPREAD IN THE INTENSITY
AND REINTENSIFICATION FOLLOWING REEMERGENCE OVER WATER, INCLUDING
THE PEAK INTENSITY. MODELS AGREE THAT THE WEAKEST INTENSITY WILL
OCCUR AROUND TAU 60 BUT RANGE FROM 55 KTS TO 80 KTS. MODELS ARE
ALSO IN AGREEMENT IN THE TIMING OF THE PEAK INTENSITY AT TAU 96, BUT
PEAK WINDS RANGE FROM 80 KTS TO 115 KTS. CONSEQUENTLY, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH OVERALL HIGH CONFIDENCE FROM
TAU 0-72 AND OVERALL MEDIUM CONFIDENCE FROM TAU 72-120.

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