WPAC: TAPAH - Post-Tropical

[Hayabusa]

18W EIGHTEEN 190919 0000 22.5N 128.7E WPAC 25 999

[Hayabusa]

[euro6208]

WDPN31 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN)
WARNING NR 001//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 18W (EIGHTEEN), LOCATED APPROXIMATELY 245
NM SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED
NORTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY INDICATES THE CENTRAL CONVECTION
REMAINS SHEARED SOUTHWESTWARD OF AN EXPOSED LOW LEVEL CIRCULATION
(LLC). THE ASSOCIATED CONVECTION HAS BEEN FLARING BUT HAS NOW BEGUN
TO BUILD OVER THE LLC. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE WELL DEFINED LLC IN THE ABOVE ANIMATION AND
CONCENTRIC WITH AGENCY FIXES. THE INITIAL INTENSITY IS BASED ON THE
DVORAK ESTIMATES OF T1.5/25KTS FROM PGTW AND RJTD AND IS CONSISTENT
WITH
RECENT ASCAT PASSES. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS
SPLIT UNDER STRONG (25-30KT) NORTHEASTERLY VERTICAL WIND SHEAR (VWS)
ON THE SOUTHERN HALF (OVER THE CONVECTION) AND LIGHT (10-15KT) VWS ON
THE NORTHERN HALF. THE VWS, HOWEVER, IS OFFSET BY STRONG EQUATORWARD
OUTFLOW. SEA SURFACE TEMPERATURES IN THE AREA REMAIN CONDUCIVE AT
29-30C. TD 18W IS IN A COL BETWEEN THE SUBTROPICAL RIDGE (STR) TO THE
NORTHWEST AND THE STR TO THE NORTHEAST AND REMAINS QUASI-STATIONARY.
3. FORECAST REASONING.
A. THIS IS THE FIRST WARNING ON THIS SYSTEM AND ESTABLISHES THE
FORECAST PHILOSOPHY.
B. TD 18W WILL BEGIN TO SLOWLY TRACK NORTHWESTWARD AS THE STR
BECOMES THE PREDOMINANT STEERING MECHANISM. AFTER TAU 24, IT WILL
TURN MORE POLEWARD AS IT ROUNDS THE STR AXIS, CRESTING IT NEAR TAU
48. AFTERWARD, THE TD WILL TRACK MORE NORTH-NORTHEASTWARD ON THE
POLEWARD SIDE OF THE STR. BY TAU 72, THE CYCLONE WILL BE IN THE EAST
CHINA SEA JUST SOUTH OF CHEJU ISLAND, SOUTH KOREA. THE VWS WILL
BECOME MORE FAVORABLE AS THE SYSTEM TRACKS POLEWARD, ENHANCING
GRADUAL INTENSIFICATION TO A PEAK OF 55KTS BY TAU 72, AIDED BY
ENHANCED POLEWARD OUTFLOW ASSOCIATED WITH THE PREVAILING WESTERLIES.
NUMERICAL MODELS HAVE COME INTO BETTER AGREEMENT WITH EGRR ON THE
LEFT MARGIN OF THE ENVELOPE THAT SPREADS OUT TO 260NM BY TAU 72.
HOWEVER, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST
DUE TO THE UNCERTAINTY IN THE INITIAL STORM MOTION.
C. AFTER TAU 72, TD 18W WILL ENTER THE SEA OF JAPAN (SOJ) AND
ACCELERATE NORTHEASTWARD, CROSSING THE TSUGARU STRAIT AND RETURNING
BACK INTO THE PACIFIC OCEAN JUST SOUTH OF HOKKAIDO, JAPAN, BY TAU
120. INCREASING VWS AND COOLING SSTS IN THE SOJ WILL GRADUALLY ERODE
THE SYSTEM AND BY TAU 120, REDUCE IT TO 30KTS. CONCURRENTLY, THE
SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION BY TAU 72 AS IT GETS
EMBEDDED IN THE BAROCLINIC ZONE. NUMERICAL MODELS ARE ALSO IN GENERAL
AGREEMENT BUT SPREADS OUT TO OVER 500NM BY TAU 120, LENDING LOW
CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
NNNN

[1900hurricane]

About time it organized enough for classification. Only took it half a month. I was getting worried that we'd run up on 95W again first! : P

[euro6208]

Time for this to develop and move away. Make room for others.

[euro6208]

[Hayabusa]

Finally named after 2 weeks since being tagged as an invest

TS 1917 (Tapah)
Issued at 07:10 UTC, 19 September 2019

<Analysis at 06 UTC, 19 September>
Scale Large
Intensity -
Center position N22°25' (22.4°)
E128°35' (128.6°)
Direction and speed of movement WNW Slow
Central pressure 994 hPa
Maximum sustained wind speed 18 m/s (35 kt)
Maximum wind gust speed 25 m/s (50 kt)
≥ 30 kt wind area ALL 500 km (270 NM)

[doomhaMwx]

Intensification into a minimal typhoon as it approaches western Mainland Japan and South Korea doesn't seem to be out of the question.

[euro6208]

WDPN31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN)
WARNING NR 002//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 18W (EIGHTEEN), LOCATED APPROXIMATELY 256
NM SOUTH OF KADENA AB, OKINAWA, JAPAN HAS TRACKED WESTWARD AT 01
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS AN EXPOSED LOW LEVEL CIRCULATION (LLC) WITH CONVECTION
LOCATED TO THE NORTHEAST AND SOME SHEARED TO THE SOUTHWEST. DUE TO
THE WELL-DEFINED LLC, THERE IS HIGH CONFIDENCE IN THE INITIAL
POSITION. THE INITIAL INTENSITY OF 30 KTS IS BASED ON MULTI-AGENCY
DVORAK ESTIMATES OF T1.5 (PGTW) AND T2.0 (RJTD) AS WELL AS A 190049Z
METOP-B ASCAT PASS DISPLAYING SMALL AREAS OF 30-35 KT WINDS AROUND
THE LLC. UPPER LEVEL ANALYSIS INDICATES THAT THE SYSTEM REMAINS SPLIT
UNDER STRONG (25-30KT) NORTHEASTERLY VERTICAL WIND SHEAR (VWS) TO THE
EAST AND LIGHT (10-15KT) VWS ON THE WESTERN PERIPHERY OF THE SYSTEM.
HOWEVER, STRONG EQUATORWARD OUTFLOW OFFSETS THE VWS. SEA SURFACE
TEMPERATURE (SST) REMAINS HIGH AT 29-30C. TD 18W IS IN A COL BETWEEN
THE SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AND THE STR TO THE
NORTHEAST AND REMAINS QUASI-STATIONARY.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. AS THE STR BECOMES THE PREDOMINANT STEERING MECHANISM, TD 18W
WILL BEGIN TO SLOWLY TRACK NORTHWESTWARD. BETWEEN TAU 24 AND 36, IT
WILL SHIFT TO A MORE POLEWARD TRACK AS IT ROUNDS THE STR AXIS. AFTER
CRESTING THE STR, TD 18W WILL TRACK MORE NORTH-NORTHEASTWARD ON THE
POLEWARD SIDE OF THE STR. THE VWS WILL BECOME MORE FAVORABLE AS THE
SYSTEM TRACKS POLEWARD, ENHANCING GRADUAL INTENSIFICATION TO A PEAK
OF 55 KTS BY TAU 48, AIDED BY ENHANCED POLEWARD OUTFLOW ASSOCIATED
WITH THE PREVAILING WESTERLIES. BY TAU 72, THE CYCLONE WILL BE JUST
EAST OF CHEJU ISLAND, SOUTH KOREA, BEGINNING TO INTERACT WITH LAND.
MODEL GUIDANCE HAS CONTINUED TO COME INTO BETTER AGREEMENT AS
CROSS-TRACK VARIATION DECREASES TO A SPREAD OF 160 NM BY TAU 72.
HOWEVER, THERE REMAINS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST DUE TO THE UNCERTAINTY IN THE INITIAL STORM MOTION AND
SPEED.
C. AFTER TAU 72, TD 18W WILL ENTER THE SEA OF JAPAN (SOJ) AND
ACCELERATE NORTHEASTWARD, RETURNING BACK INTO THE PACIFIC OCEAN JUST
AFTER TRANSITING ACROSS HOKKAIDO, JAPAN, BY TAU 120. TD 18W WILL
GRADUALLY ERODE AS IT TRANSITS THROUGH THE SOJ AS IT ENCOUNTERS
INCREASING VWS AND COOLING SST. AS THIS OCCURS, THE SYSTEM WILL ALSO
UNDERGO EXTRA-TROPICAL TRANSITION (BEGINNING BETWEEN TAU 72 AND 96)
AS IT BECOMES EMBEDDED IN THE BAROCLINIC ZONE, COMPLETING
EXTRA-TROPICAL TRANSITION BY TAU 120. NUMERICAL MODELS ARE IN GENERAL
AGREEMENT BUT SPREADS OUT TO OVER 400 NM BY TAU 120, LENDING LOW
CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
NNNN

[Hayabusa]

[euro6208]

18W EIGHTEEN 190919 1200 23.0N 128.1E WPAC 40 990

Up to 40 knots.

[euro6208]

WDPN31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH)
WARNING NR 003//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 211 NM
SOUTH OF KADENA AB, OKINAWA, JAPAN HAS TRACKED NORTHWESTWARD AT 08
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
IMAGERY SHOWS CONVECTIVE BANDING WRAPPING INTO AN EXPOSED LOW LEVEL
CIRCULATION (LLC) WITH ASSOCIATED CONVECTION LOCATED TO THE SOUTH.
DUE TO THE WELL-DEFINED LLC, THERE IS HIGH CONFIDENCE IN THE INITIAL
POSITION. A 191201Z METOP-B ASCAT PASS SHOWING AN AREA OF 40 KTS
WINDS, DVORAK ESTIMATE OF T2.0/30KTS (RJTD), AND DISTANT WIND
OBSERVATIONS OF 32 KTS AT SHIMOJI SHIMA ISLAND (RORS) SUPPORT THE
INITIAL INTENSITY OF 40 KTS. UPPER LEVEL ANALYSIS INDICATES THAT THE
SYSTEM IS UNDER AN AREA OF LOW TO MODERATE (10-20 KTS) VERTICAL WIND
SHEAR (VWS) WITH REGIONS OF HIGH VWS LOCATED TO THE WEST AND EAST OF
THE CONVECTION. THE STRONG EQUATORWARD OUTFLOW AND HIGH (29-30
CELSIUS) SEA SURFACE TEMPERATURE (SST) ENHANCE INTENSIFICATION AS TS
18W TRACKS NORTHWESTWARD. TS 18W REMAINS LOCATED IN A COL BETWEEN A
SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AND A STR TO THE NORTHEAST
WHICH SERVE AS THE PRIMARY STEERING MECHANISMS FOR THE SYSTEM.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS 18W WILL CONTINUE TO TRACK NORTHWESTWARD FOR THE NEXT 12 TO
24 HOURS, INTENSIFYING TO A PEAK INTENSITY OF 60KTS AT TAU 12. AT TAU
24, THE SYSTEM WILL SHIFT POLEWARD AS IT ROUNDS THE STR AXIS. TS 18W
WILL RETAIN ITS INTENSITY AS IT CRESTS THE STR AND INTERACTS WITH THE
PREVAILING WESTERLIES, TRACKING BETWEEN CHEJU ISLAND AND SASEBO,
JAPAN AROUND TAU 72 WHEN INCREASING LAND INTERACTION WILL BEGIN TO
ERODE THE SYSTEM. AT THIS TIME, THE SYSTEM WILL BEGIN TO ACCELERATE
TO THE NORTHEAST AS IT ENCOUNTERS TROUGHING TO THE NORTH, PULLING THE
SYSTEM INTO THE SEA OF JAPAN (SOJ). NUMERICAL GUIDANCE IS IN GOOD
AGREEMENT AT EARLY TAUS WITH CROSS-TRACK SPREAD INCREASING TO 185 NM
BETWEEN THE OUTLIERS UKMET AND ECMWF BY TAU 72. DUE TO THIS
UNCERTAINTY, THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.
C. AFTER TAU 72, TS 18W BEGINS TO ENCOUNTER INCREASING VWS AND
COOLING SST, GRADUALLY WEAKENING THE SYSTEM. TS 18W WILL TRACK ACROSS
HOKKAIDO, JAPAN AND EXIT BACK OVER THE PACIFIC AS IT UNDERGOES
EXTRA-TROPICAL TRANSITION (ETT). ETT WILL BEGIN BETWEEN TAU 72 AND
96, FULLY COMPLETING THE TRANSITION BY TAU 120. AT TAU 120, THE
GENERAL AGREEMENT BETWEEN NUMERICAL MODELS REACHES A SPREAD OF 400
NM, LENDING LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC TRACK
FORECAST.//
NNNN

[euro6208]

40 knots looks good. WIsh JTWC relied on ASCAT more often.

[euro6208]

WDPN31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
004//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 213 NM
SOUTH OF KADENA AB, OKINAWA, JAPAN HAS TRACKED NORTHWESTWARD AT 08
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) IMAGERY SHOWS CONVECTIVE BANDING WRAPPING INTO A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION (LLC) WITH ASSOCIATED CONVECTION
PREDOMINANTLY LOCATED TO THE SOUTH AND SOUTHEAST. OVER THE LAST SIX
HOURS, THE SYSTEM HAS STAGNATED IN DEVELOPMENT SHOWING NO SIGN OF
STRUCTURAL IMPROVEMENT. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON EXTRAPOLATION FROM A 191307Z METOP-C ASCAT IMAGE
AND THE PARTIALLY EXPOSED LLCC IN THE IR LOOP. THE INITIAL INTENSITY
OF 40 KNOTS IS BASED ON PERSISTENCE FROM THE AFOREMENTIONED ASCAT
IMAGE DUE TO THE APPARENT STAGNATION OF DEVELOPMENT. UPPER LEVEL
ANALYSIS INDICATES THAT THE SYSTEM IS UNDER AN AREA OF LOW TO
MODERATE (10-20 KTS) VERTICAL WIND SHEAR (VWS) AND IS SUPPORTED BY
STRONG EQUATORWARD OUTFLOW AND HIGH (29-30 CELSIUS) SEA SURFACE
TEMPERATURE (SST). TS 18W REMAINS LOCATED IN A COL BETWEEN A
SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AND A STR TO THE NORTHEAST.
THE STR TO THE NORTHEAST HAS BEGUN TO BUILD AND IS TAKING OVER AS
THE PRIMARY STEERING MECHANISMS FOR THE SYSTEM.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS 18W WILL CONTINUE TO TRACK NORTHWESTWARD FOR THE NEXT 12 TO
24 HOURS AS IT BEGINS TO RECURVE AROUND THE STR TO THE NORTHEAST.
THE SYSTEM WILL STEADILY INTENSIFY, REACHING A PEAK OF 60 KNOTS BY
TAU 36 AS IT ROUNDS THE RIDGE AXIS. BY TAU 48, 18W WILL BE TRACKING
TO THE NORTHEAST, PASSING BETWEEN CHEJU ISLAND AND SASEBO, JAPAN
BEFORE TAU 72. AS TAPAH TRACKS THROUGH THE KOREAN STRAIT, LAND
INTERACTION WILL BEGIN TO WEAKEN THE SYSTEM, A TREND THAT WILL
PERSIST FOR THE DURATION OF THE FORECAST. ALSO, AROUND THIS TIME,
INTERACTION WITH A PASSING MID-LATITUDE TROUGH WILL BEGIN THE
EXTRATROPICAL TRANSITION. NUMERICAL GUIDANCE IS IN STRONG AGREEMENT
THROUGH THIS PORTION OF THE FORECAST LENDING HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK.
C. AFTER TAU 72, TS 18W BEGINS TO ENCOUNTER AN INCREASINGLY
UNFAVORABLE ENVIRONMENT AS VWS INCREASES AND SSTS DECREASE. THE
SYSTEM WILL CONTINUE TO WEAKEN AS IT TRACKS THROUGH THIS UNFAVORABLE
ENVIRONMENT AND BECOMES EMBEDDED IN THE PASSING MID-LATITUDE TROUGH.
TS 18W WILL MAKE LANDFALL AS AN EXTRATROPICAL CYCLONE OVER SOUTHERN
HOKKAIDO AROUND TAU 96 BEFORE EXITING BACK INTO THE PACIFIC OCEAN.
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH ONLY A 170NM SPREAD AT
TAU 96, LENDING OVERALL HIGH CONFIDENCE IN THE JTWC FORECAST
TRACK.//
NNNN

[euro6208]

Now forecast to become a typhoon.



WDPN31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
005//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 218 NM
SOUTH OF KADENA AB, OKINAWA, JAPAN HAS TRACKED NORTHWESTWARD AT 06
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) SHOWS DEEP CONVECTIVE BANDING WRAPPING INTO
A BROAD, PARTIALLY EXPOSED LOW LEVEL CIRCULATION (LLC). THE SYSTEM
HAS EXTENSIVE DEEP CONVECTION IN THE SOUTH AND SOUTHEAST THAT AT
TIMES APPEARS TO WRAP INTO THE EASTERN AND NORTHERN QUADRANTS BUT
FAILS TO PERSIST. OVER THE LAST SIX HOURS, THE SYSTEM HAS SHOWN
MODEST IMPROVEMENTS IN BOTH CONVECTION AND STRUCTURE. THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON A 192229Z 37GHZ
SSMIS MICROWAVE IMAGE THAT SHOWS CONVECTIVE BANDING WRAPPING INTO A
BROAD (90NM) CIRCULATION CENTER. THE INITIAL INTENSITY OF 45 KNOTS
IS BASED ON EARLIER ASCAT IMAGES AND ADJUSTED FOR THE IMPROVEMENTS
IN STRUCTURE. THE INTENSITY IS ABOVE THE PGTW AND RJTD DVORAK FIX
ESTIMATES OF T2.0 (30KTS) DUE TO THE BROAD NATURE OF THE SYSTEM
CAUSING ERRONEOUSLY LOW DVORAK ESTIMATES. UPPER LEVEL ANALYSIS
INDICATES THAT THE WESTERN SIDE OF THE SYSTEM IS IN AN AREA OF LOW
TO MODERATE (10-20 KTS) VERTICAL WIND SHEAR WHILE THE EASTERN SIDE
OF THE SYSTEM IS IN AN AREA OF MODERATE TO HIGH (15-30 KTS). THE
GENERALLY UNFAVORABLE VERTICAL WIND SHEAR IS OFFSET BY STRONG
EQUATORWARD OUTFLOW AND HIGH (29-30 CELSIUS) SEA SURFACE
TEMPERATURES (SST) IN THE REGION. TS 18W IS TRACKING WEST-NORTHWEST
BETWEEN A SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AND A STR TO THE
NORTHEAST. THE STR TO THE NORTHEAST HAS BEGUN TO BUILD AND IS TAKING
OVER AS THE PRIMARY STEERING MECHANISM FOR THE SYSTEM.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS 18W IS FORECAST TO TURN MORE NORTHWESTWARD AS IT BEGINS TO
RECURVE AROUND THE STR TO THE NORTHEAST. THE SYSTEM WILL STEADILY
INTENSIFY AS IT RECURVES; REACHING 60 KNOTS AS IT ROUNDS THE RIDGE
AXIS BY TAU 36. THE PEAK INTENSITY WILL OCCUR SHORTLY AFTER AS AN
APPROACHING MID-LATITUDE TROUGH BRIEFLY ENHANCES POLEWARD OUTFLOW,
ALLOWING ANOTHER BRIEF PERIOD OF INTENSIFICATION TO A PEAK OF 65
KNOTS. THEREAFTER, INCREASING VERTICAL WIND SHEAR FROM THE TROUGH
WILL BEGIN TO WEAKEN THE SYSTEM AND CAUSE THE SYSTEM TO BEGIN
EXTRATROPICAL TRANSITION. BY TAU 48, 18W WILL BE TRACKING TO THE
NORTHEAST, PASSING BETWEEN CHEJU ISLAND AND SASEBO, JAPAN BEFORE TAU
72. AS TAPAH TRACKS THROUGH THE KOREAN STRAIT, LAND INTERACTION WILL
CONTINUE TO WEAKEN THE SYSTEM. THE WEAKENING TREND WILL PERSIST FOR
THE DURATION OF THE FORECAST. NUMERICAL GUIDANCE IS IN STRONG
AGREEMENT THROUGH THIS PORTION OF THE FORECAST LENDING HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK.
C. AFTER TAU 72, TS 18W BEGINS TO ENCOUNTER AN INCREASINGLY
UNFAVORABLE ENVIRONMENT AS VERTICAL WIND SHEAR REMAINS STRONG AND
SSTS CONTINUE TO DECREASE. THE SYSTEM WILL CONTINUE TO WEAKEN AS IT
TRACKS THROUGH THIS UNFAVORABLE ENVIRONMENT IN THE SEA OF JAPAN AND
BECOMES EMBEDDED IN THE PASSING MID-LATITUDE TROUGH. TS 18W WILL
MAKE LANDFALL AS AN EXTRATROPICAL CYCLONE OVER SOUTHERN HOKKAIDO
AFTER TAU 84 BEFORE EXITING BACK INTO THE PACIFIC OCEAN AROUND TAU
96. MODEL GUIDANCE BEGINS TO SPREAD AFTER TAU 72; HOWEVER, IT
REMAINS IN GENERALLY GOOD AGREEMENT THROUGH TAU 96. DUE TO THE GOOD
AGREEMENT IN MODEL GUIDANCE THERE IS OVERALL HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK.//
NNNN

[euro6208]

HWRF peaks between South Korea and Japan.

[euro6208]

WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
006//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 210 NM
SOUTH-SOUTHWEST OF KADENA AB, OKINAWA, JAPAN HAS TRACKED
NORTHWESTWARD AT 03 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS DEEP CONVECTIVE BANDING
WRAPPING INTO A BROAD, PARTIALLY EXPOSED LOW LEVEL CIRCULATION (LLC).
THE LLC APPEARS TO HAVE AN ELONGATED SHAPE AND IS ROTATING
END-OVER-END, CAUSING POSITIONAL UNCERTAINTY AS PORTIONS OF THIS
CIRCULATION ARE OCCLUDED BY THE DEEP CONVECTION EXTENDING TO THE
SOUTH AND SOUTHEAST. THE INITIAL POSITION IS PLACED WITH FAIR
CONFIDENCE BASED ON A 200517Z AMSR 89 GHZ MICROWAVE IMAGE DISPLAYING
CONVECTION WRAPPING INTO THE BROAD LLC. THE INITIAL INTENSITY OF 50
KNOTS IS BASED ON THE 200133Z METOP-C ASCAT PASS DEPICTING A BROAD,
CLOSED CIRCULATION WITH AN AREA OF 45-50 KT WINDS EXTENDING TO THE
EAST OF THE LLC. THIS INTENSITY IS ABOVE THE PGTW/RJTD/RTCP DVORAK
ESTIMATES OF T3.0 (45 KTS) DUE TO THE BROAD NATURE OF THE SYSTEM
CAUSING LOW DVORAK ESTIMATES. UPPER LEVEL ANALYSIS SHOWS THAT TS 18W
IS UNDER AN AREA OF FAVORABLE (10-20 KTS) VERTICAL WIND SHEAR (VWS)
WITH THE EASTERN AND SOUTHEASTERN EXTENSION OF THE SYSTEM
EXPERIENCING MODERATE TO HIGH (15-25 KTS) VWS. THE SYSTEM REMAINS IN
AN AREA OF WARM (28-29 CELSIUS) SEA SURFACE TEMPERATURES AND
MAINTAINS STRONG EQUATORWARD OUTFLOW TO OFFSET THE VWS. TS 18W IS
TRACKING NORTHWEST UNDER THE STEERING INFLUENCE OF A SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS 18W IS FORECAST TO TURN TO A NORTH-NORTHWESTWARD TRACK AS IT
RECURVES AROUND THE STR TO THE NORTHEAST. DURING THIS PORTION OF THE
TRACK, THE SYSTEM WILL STEADILY INTENSIFY, REACHING ITS PEAK
INTENSITY OF 65 KNOTS BY TAU 24. TS 18W WILL ROUND THE RIDGE AXIS BY
TAU 36, MAINTAINING INTENSITY THROUGH TAU 48, JUST SOUTHEAST OF CHEJU
ISLAND, AS AN APPROACHING MID-LATITUDE TROUGH BRIEFLY ENHANCES
POLEWARD OUTFLOW. THERE IS SOME UNCERTAINTY IN THE TIMING OF THE
ARRIVAL OF THE MID-LATITUDE TROUGH, WITH NAVGEM AND GFS SHOWING
ARRIVAL AROUND TAU 48 WHILE ECMWF SHOWS INTERACTION AT TAU 60. AS THE
TROUGH ARRIVES, INCREASING VWS WILL BEGIN TO ERODE THE SYSTEM AS IT
TRACKS NORTHEAST THROUGH THE KOREAN STRAIT AND INTO THE SEA OF JAPAN
WHILE TS 18W BEGINS TO UNDERGO EXTRATROPICAL TRANSITION (ETT).
ADDITIONALLY, LAND INTERACTION WILL CONTINUE TO WEAKEN THE SYSTEM
THROUGH TAU 72. NUMERICAL GUIDANCE IS IN STRONG AGREEMENT THROUGH
THIS PORTION OF THE FORECAST, SUPPORTING HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.
C. AFTER TAU 72, TS 18W WILL ENCOUNTER AN INCREASINGLY UNFAVORABLE
ENVIRONMENT WITH COOLING SST AND HIGH VWS, CONTINUALLY WEAKENING THE
SYSTEM AS IT TRACKS NORTHEAST ACROSS THE SEA OF JAPAN AND BECOMES
EMBEDDED IN THE PASSING MID-LATITUDE TROUGH. TS 18W WILL TRANSITION
INTO AN EXTRATROPICAL CYCLONE PRIOR TO MAKING LANDFALL IN HOKKAIDO.
TS 18W WILL THEN EXIT BACK OVER THE PACIFIC OCEAN AT TAU 96. THERE IS
FAIR ALONG- AND CROSS-TRACK SPREAD IN THE MODELS BEGINNING AFTER TAU
72, HOWEVER, THE GENERAL GUIDANCE IS IN AGREEMENT, LENDING TO OVERALL
HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

[NotoSans]

 https://twitter.com/philipslau681/status/1175135254182449152

[Hayabusa]

TY

TY 1917 (Tapah)
Issued at 21:45 UTC, 20 September 2019

<Analysis at 21 UTC, 20 September>
Scale Large
Intensity -
Center position N25°30' (25.5°)
E126°10' (126.2°)
Direction and speed of movement NNW 25 km/h (14 kt)
Central pressure 970 hPa
Maximum sustained wind speed 35 m/s (65 kt)
Maximum wind gust speed 50 m/s (95 kt)
≥ 50 kt wind area E 240 km (130 NM)
W 170 km (90 NM)
≥ 30 kt wind area ALL 650 km (350 NM)

[Hayabusa]

Shifted towards SK