Tropical Storm PAKHAR Advisory 12月12日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (PAKHAR) WARNING NR
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 19.2N 128.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 439 NM SOUTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) DEPICTS
PERSISTENT DEEP CONVECTION WRAPPING INTO A LOW-LEVEL CIRCULATION
CENTER (LLCC). TROPICAL STORM PAKHAR IS CONTINUING TO INTENSIFY
WITH CLOUD TOP TEMPERATURES REMAINING VASTLY IN THE -70C RANGE
WITH A SMALL SHORT BURST OF OVERSHOOTING TOPS REACHING -90C. DURING
THE SAME TIME OF SATELLITE IMAGE AT 111710Z, A NEW MEASURE CAME IN
FROM CIMSS ADT INCREASING INTENSITY TO 51KTS. AT 111732Z RECENT GMI
89GHZ AND 37GHZ IMAGES HELPED PLACE THE INITIAL POSITION WITH HIGH
CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE AND IS HEDGED BETWEEN MULTIPLE AGENCIES FIXES, WHICH
ARE LISTED BELOW. A REGION OF STRONG VERTICAL WIND SHEAR (VWS) LIES
DIRECTLY TO THE NORTH OF THE SYSTEM WITH CURRENT ANALYSIS
INDICATING A MODERATE (20-25 KNOTS) RANGE, IMPACTING THE NORTHERN
SECTOR OF THE SYSTEM. RADIAL OUTFLOW REMAINS DIRECTLY ABOVE THE
SYSTEM, ALONG WITH WARM (28C-29C) SEA SURFACE TEMPERATURES.
INITIAL WIND RADII BASIS: PERSISTENCE.
CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED WELL TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 47 KTS AT 111737Z
   CIMSS ADT: 51 KTS AT 111740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 29W WILL MOST LIKELY REACH ITS MAX
INTENSITY DURING THE NEXT 12 HOURS. BETWEEN TAUS 12 AND 24, PAKHAR
WILL BEGIN ENCOUNTERING A MUCH STRONGER REGION OF VWS TO THE NORTH.
TS 29W WILL REMAIN ON THE NORTHEAST TRACK FOR THE NEXT 24 HOURS.
HOWEVER, BY TAU 24 THE TRACK WILL START SHIFTING SIGNIFICANTLY TO
THE SOUTH AND SOUTHWEST DUE TO THE STRONG STR TO THE NORTHEAST. AT
THIS TIME, TS 29W WILL ALSO BEGIN ENCOUNTERING HIGHER SHEAR AND THE
UPPER-LEVEL CIRCULATION WILL START DECOUPLING FROM THE LLCC. WHEN
THE DECOUPLING BEGINS, THE SYSTEM WILL ALSO START ENCOUNTERING AN
INFLUX OF LOW AND MID-LEVEL DRY AIR, WHICH APPEARS TO ENGULF THE
SYSTEM THROUGH THE NEXT 36 HOURS. THE OVERALL LOW-LEVEL TRACK
MOTION TO THE NORTHEAST WILL ALSO SEIZE, AND THE LLCC WILL THEN BE
STEERED TO THE SOUTH-SOUTHWEST BY THE LOWER-LEVEL FLOW
PREDOMINATELY COMING FROM THE NORTH-NORTHEAST. THE SHARP TURN BACK
SOUTH WILL ULTIMATELY END THE SYSTEM BY TAU 48 IF NOT SOONER.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE FROM THE DETERMINISTIC
TRACK GUIDANCE ARE ALL INDICATING A SHARP TURN. HOWEVER, THE EXACT
TIMING AND SHARPNESS OF THE TURN VARY GREATLY BETWEEN EACH OF
THE MODELS. THE SHARPEST TURN APPEARS FROM THE GFS SOLUTION TURNING
AT TAU 12 AND NEARS THE POINT OF ITS CURRENT 00Z POSITION BY TAU
24WITH ONLY A 38NM SEPARATION. THE ECMWF INTERPOLATED TRACK MAKES
THE TURN WELL AFTER TAU 24 AND DOES NOT INDICATES A MORE GRADUAL
TURN TO THE SOUTHEAST. THE JTWC FORECAST REMAINS CONSISTENT WITH
THE PREVIOUS FORECAST AND LIES JUST OUTSIDE AND POLEWARD OF THE
MAIN MODEL CONSENSUS TRACK WITH LOW CONFIDENCE. INTENSITY GUIDANCE
REMAINS MIXED, WITH THE PEAK INTENSITY REMAINING NEAR 50 KNOTS
BASED ON THE MOST CURRENT TREND. THEREFORE, THE JTWC INTENSITY
FORECAST IS SET WITH MEDIUM CONFIDENCE DUE TO THE TREND
REMAINING THE SAME.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM//
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