Tropical Storm KULAP Advisory 9月28日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (KULAP) WARNING NR
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 31.0N 144.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 343 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONSOLIDATING SYSTEM WITH DEEP CONVECTION WRAPPING INTO A
PERSISTENT CONVECTIVE CLOUD STRUCTURE, WHICH IS OBSCURING A LOW
LEVEL CIRCULATION CENTER (LLCC). ADDITIONALLY, A 271852Z SSMIS
37GHZ DEPICTS FORMATIVE CONVECTIVE BANDING OVER THE NORTHERN
QUADRANT WRAPPING INTO THE LLCC.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON
ANIMATED SHORTWAVE INFRARED SATELLITE IMAGERY, AS WELL AS AN
EARLIER 271121Z METOP-B ASCAT PASS. THE INITIAL INTENSITY IS ALSO
PLACED WITH MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED METOP-B
ASCAT WHICH SHOWS UP TO 50 KNOT WIND BARBS ON THE EASTERN
PERIPHERY. ALONG WITH A BLEND OF THE AUTOMATED DVORAK ESTIMATES
INTENSITIES FROM CMISS ADT OF 49 KNOTS, WHILE SATCON SHOWS UP TO 56
KNOTS IN COMBINATION WITH SUBJECTIVE AGENCY DVORAK INTENSITIES FROM
PGTW T3.0, RJTD T3.5, AND KNES T3.0.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 56 KTS AT 271559Z
   CIMSS ADT: 49 KTS AT 271940Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
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 19W HAS ROUNDED THE RIDGE AXIS OF THE
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST AND HAS
INCREASED ITS TRACK SPEED UP TO 18 KTS TOWARD THE NORTHEAST.
ADDITIONALLY, A DEEP SHORTWAVE TROUGH UPSTREAM OVER NORTHERN CHINA
IS EXPECTED TO ERODE AND WEAKEN THE STR TO THE EAST, WHICH WILL
ULTIMATELY ALLOW 19W TO CONTINUE TO ACCELERATE NORTHEASTWARD.
BETWEEN TAU 24 AND TAU 36, THE SYSTEM WILL INTENSIFY TO A MAXIMUM
 WIND SPEED OF 70 KNOTS, AS STRONG SHEAR IS OFFSET BY VERY STRONG
DIVERGENT POLEWARD OUTFLOW ALOFT. BY TAU 36, AS THE SYSTEM BEGINS
TO INTERACT WITH THE DEEP SHORTWAVE TROUGH, THE SYSTEM WILL ALSO
INDUCE WARM AIR ADVECTION WHICH WILL AMPLIFY AND DEEPEN THE
SHORTWAVE UPPER-LEVEL TROUGH. AS THIS OCCURS THE TROUGH WILL BECOME
NEGATIVELY TILTED WHICH WILL ALLOW 19W TO BEGIN TO UNDERGO
EXTRA-TROPICAL TRANSITION (ETT). BY TAU 48, THE SYSTEM WILL
COMPLETE EXTRA-TROPICAL TRANSITION (ETT) AS IT GAINS FRONTAL
CHARACTERISTICS AND BECOMES A WARM SECLUSION TYPE EXTRA-TROPICAL
LOW, WHILE DECREASING ITS INTENSITY SLIGHTLY DUE TO COOLER SEA
SURFACE TEMPERATURE VALUES (25-26C) AND STRONG VERTICAL WIND SHEAR.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE ARE IN VERY GOOD AGREEMENT
THROUGH
TAU 24, WITH ONLY A 70 NM SPREAD IN MODEL TRACK SOLUTIONS. BY TAU
48, THE MODEL GUIDANCE INCREASES IN UNCERNTANTY WITH A GRADUAL
ALONG-TRACK SPREAD TO 200 NM. THIS IS LIKELY DUE TO HOW NUMERICAL
MODELS
ARE HANDLING LARGE SCALE DEEP SHORTWAVE UPPER LEVEL TROUGHS. BECAUSE
OF THIS, SOME
INTERACTIONS WITH 19W ARE BEHAVING DIFFERENTLY. OVERALL THE JTWC
TRACK FORECAST
IS ASSESSED WITH HIGH CONFIDENCE, WITH THE JTWC TRACK FORECAST
REMAINING CLOSE TO THE MULTI-MODEL CONSENSUS. THE INTENSITY
FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE WITH GFS DECAY SHIPS
(DSHA), HWRF, AND GFS GUIDANCE SHOWING A PEAK OF 70 KNOTS, WITH
CTR1 GUIDANCE ON THE HIGH END UP TO 85 KNOTS. THEREFORE, THE JTWC
INTENSITY FORECAST REMAINS CLOSE TO THE MULTI-MODEL CONSENSUS
THROUGH OUT THE FORECAST PERIOD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
NNNN
NNNN