WDPN31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 31W (KALMAEGI) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.0N 130.1E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 323 NM WEST-NORTHWEST OF KAYANGEL
   MOVEMENT PAST 6 HOURS: WESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 31W MAINTAINING TWO DISTINCT LOBES OF DEEP CONVECTION,
HOWEVER, THE SOUTHEASTERN LOBE THAT IS DIRECTLY OVER THE LOW-LEVEL
CIRCULATION CENTER (LLCC) HAS BECOME THE DOMINANT AREA OF DEEP
CONVECTION. THE NORTHWESTERN LOBE HAS BEGUN TO THIN AND STRETCH
NORTHEASTWARD, REESTABLISHING STRONG POLEWARD DEEP CONVECTION. THE
ENVIRONMENT REMAINS HIGHLY FAVORABLE FOR CONTINUED INTENSIFICATION,
AND 31W IS ASSESSED TO BE UNDERGOING RAPID INTENSIFICATION (RI). A
021710Z 37GHZ AMSR2 MICROWAVE IMAGE REVEALS A HIGHLY COMPACT CENTER
AND A DISTINCT MICROWAVE EYE. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE AFOREMENTIONED 021710Z 37GHZ MICROWAVE
IMAGE. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE CIMSS OBJECTIVE INTENSITY ESTIMATES AND THE
AGENCY DVORAK FIXES LIST BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMBINED STEERING INFLUENCE OF A LARGE
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST AND A SECOND,
SMALLER STR CENTERED WEST OF THE LUZON STRAIT.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T4.0 - 65 KTS
   CIMSS SATCON: 60 KTS AT 021910Z
   CIMSS ADT: 64 KTS AT 021910Z
   CIMSS AIDT: 59 KTS AT 021910Z
   CIMSS D-MINT: 31 KTS AT 021910Z
   CIMSS D-PRINT: 50 KTS AT 021910Z

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

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: TS 31W (KALMAEGI) IS FORECAST TO DIP SLIGHTLY
SOUTH AND TRACK WEST-SOUTHWESTWARD AFTER IT TRANSITIONS STEERING
RIDGES AND BEGINS TO TRACK ALONG THE SOUTHEASTERN PERIPHERY OF THE
STR TO ITS NORTHWEST. 31W WILL MAINTAIN A WEST-SOUTHWESTWARD TRACK
UNTIL LANDFALL IN SOUTHERN LEYTE AROUND TAU 48. AFTER TAU 48, THE
STEERING STR WILL SHIFT NORTHEASTWARD, CAUSING 31W TO ASSUME A
NORTHWESTWARD TRACK AS IT ROUNDS THE SOUTHERN PERIPHERY OF THE STR.
31W WILL TRACK NORTHWESTWARD FOR THE REMAINDER OF THE FORECAST
PERIOD, WITH LANDFALL IN SOUTHERN VIETNAM FORECAST TO OCCUR JUST
AFTER TAU 96. 31W WILL BEGIN TO RAPIDLY DETERIORATE AFTER LANDFALL,
LEADING TO DISSIPATION AFTER TAU 120. REGARDING INTENSITY, KALMAEGI
IS CURRENTLY UNDERGOING RI, WHICH IS FORECAST TO CONTINUE UNTIL
LANDFALL IN LEYTE. AS A RESULT, A PEAK INTENSITY GREATER THAN 80
KTS MAY OCCUR BETWEEN TAU 12-24 -- JUST PRIOR TO LANDFALL -- WHICH
IS NOT REFLECTED IN THE FORECAST POINTS. 31W WILL WEAKEN DUE TO 
TERRAIN INTERACTION WHILE IT TRACKS THROUGH THE CENTRAL PHILIPPINES 
AND IS FORECAST TO BE AT ITS WEAKEST POINT JUST BEFORE REEMERGENCE 
INTO THE SULU SEA AROUND TAU 36. THE SULU AND SOUTH CHINA SEAS ARE
HIGHLY FAVORABLE FOR ADDITIONAL INTENSIFICATION, WITH FAVORABLE
VERTICAL WIND SHEAR, WARM SEA SURFACE TEMPERATURES, AND GOOD
DIVERGENCE ALOFT, SUPPORTIVE TO KALMAEGI QUICKLY REGAINING STRENGTH.
31W WILL REACH A SECOND PEAK JUST PRIOR TO LANDFALL IN VIETNAM
AROUND TAU 96. DISSIPATION WILL OCCUR OUTSIDE THE FORECAST PERIOD,
THOUGH 31W WILL QUICKLY DETERIORATE OVER THE MOUNTAINOUS TERRAIN OF 
SOUTHEAST ASIA.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THAT 31W WILL MAKE LANDFALL IN LEYTE BEFORE CURVING
NORTHWESTWARD AND TRACKING JUST NORTH OF PALAWAN. MODELS ARE IN
SLIGHT DISAGREEMENT OVER WHERE 31W WILL MAKE LANDFALL IN VIETNAM,
CONTRIBUTING TO AN APPROXIMATE 200NM CROSS-TRACK SPREAD AT
LANDFALL. DUE TO THE TOPOGRAPHIC SHAPE OF VIETNAM, THE CROSS-TRACK
SPREAD ALSO SLIGHTLY IMPACTS WHEN MODELS PREDICT LANDFALL, WITH
SOUTHERN MODELS PREDICTING LANDFALL SOONER THAN NORTHERN MODELS. AS
A RESULT, THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE
FROM TAU 0-72 AND MEDIUM CONFIDENCE FROM TAU 72-120. RELIABLE
INTENSITY GUIDANCE IS IN STRONG AGREEMENT THAT 31W WILL CONTINUE TO
INTENSIFY THROUGH LANDFALL; HOWEVER, MODELS DISAGREE ON THE
WEAKENING TREND WHILE 31W IS OVER THE PHILIPPINES, CAUSING AN
INTENSITY RANGE OF 55 KTS TO 85 KTS AT TAU 36. THE DISAGREEMENT
OVER WEAKENING BETWEEN TAU 24-36 CAUSES VARIATION IN THE RATE OF
REINTENSIFICATION IN THE SOUTH CHINA SEA, AND THEREFORE THE SECOND
PEAK INTENSITY BEFORE TERMINAL LANDFALL. AS A RESULT, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE OVERALL.

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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