WPAC: TAPAH - Post-Tropical

[Hayabusa]

The name Tapah officially has reached typhoon intensity for the first time

[euro6208]

WDPN31 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
008//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 113 NM
SOUTHWEST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 13 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS CONVECTIVE BANDING WRAPPING INTO A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION (LLC) WITH THE BULK OF THE DEEP
CONVECTION IN THE EASTERN HALF OF THE SYSTEM. THERE IS GOOD
CONFIDENCE IN THE INITIAL POSITION BASED ON THE EIR, A 201726Z AMSR2
89 GHZ MICROWAVE IMAGE, AND IT CLOSELY ALIGNS WITH RJTD RADAR FIXES.
THE INITIAL INTENSITY OF 55 KTS ALIGNS WITH THE PGTW DVORAK FIX
INTENSITY OF T3.5 (55 KTS) AND IS SUPPORTED BY OBSERVATIONS UP TO 55
KTS FROM OBSERVATIONS ON OKINAWA. LOW (10-15 KT) VERTICAL WIND SHEAR
(VWS), GOOD EQUATORWARD AND POLEWARD OUTFLOW, AND WARM (27-28
CELSIUS) SEA SURFACE TEMPERATURE (SST) MAKE THE ENVIRONMENT
SUPPORTIVE OF INTENSIFICATION. TS 18W IS TRACKING POLEWARD ALONG THE
WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. BY TAU 36, TS 18W WILL HAVE ROUNDED THE STR AXIS AND BEGIN
TURNING NORTHEASTWARD. THERE IS A BRIEF PERIOD WHERE THE ENVIRONMENT
WILL SUPPORT SOME INTENSIFICATION BEFORE STRONG VWS, LAND
INTERACTION, AND COOL SST WILL CAUSE GRADUAL WEAKENING. THE
INTENSITY IS EXPECTED TO PEAK AT 65 KTS AS 18W APPROACHES THE
CHANNEL BETWEEN SOUTH KOREA AND JAPAN AROUND TAU 36. BY TAU 48, TS
18W WILL MOVE INTO MID-LATITUDE BAROCLINIC ZONE AND BEGIN
EXTRATROPICAL TRANSITION (ETT). ETT IS EXPECTED TO COMPLETE BY TAU
72 AS THE SYSTEM TRANSITIONS INTO A GALE-FORCE COLD CORE LOW.
NUMERICAL GUIDANCE IS IN STRONG AGREEMENT THROUGH TAU 48. AFTER TAU
48, ALONG-TRACK SPEED DIFFERENCES INCREASE THE SPREAD AMONG THE
MODELS SLIGHTLY. BASED ON STRONG AGREEMENT IN THE FORECAST, THERE IS
GOOD CONFIDENCE IN THE JTWC TRACK FORECAST.//
NNNN

[mrbagyo]

There's probably some mini-swirl inside the big eye

[euro6208]

No upgrade yet. Still 55 knots based on observation from Okinawa.

WDPN31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
009//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 108 NM
WEST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 13 KNOTS (KTS)
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(AMSI) REVEALS CONVECTIVE BANDING, PRIMARILY ON THE EAST, WINDING
INTO A BROAD, PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER. THERE
IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON THE AMSI, RADAR
IMAGERY, AND SURROUNDING OBSERVATIONS. THE INITIAL INTENSITY OF 55
KTS IS ON THE HIGH SIDE OF DVORAK INTENSITY ESTIMATES RANGING FROM
T3.0-T3.5 (45-55 KTS) DUE TO OKINAWA OBSERVATIONS UP TO 55 KTS. THE
ENVIRONMENT, WITH MODERATE (10-15 KT) VERTICAL WIND SHEAR (VWS),
GOOD EQUATORWARD AND POLEWARD OUTFLOW, AND WARM (27-28 CELSIUS) SEA
SURFACE TEMPERATURE (SST), IS SUPPORTIVE OVERALL, HOWEVER, SOME DRY
AIR ENTRAINING INTO AND SUPPRESSING CONVECTION ON THE WESTERN HALF
OF THE SYSTEM IS EXPECTED TO LIMIT FURTHER INTENSIFICATION. TS 18W
IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. AROUND TAU 24, TS 18W WILL HAVE ROUNDED THE STR AXIS AND BEGIN
TURNING NORTHEASTWARD. THERE IS A BRIEF PERIOD WHERE THE ENVIRONMENT
IS MARGINALLY SUPPORTIVE BEFORE STRONG VWS, LAND INTERACTION, AND
COOL SST BEGIN TO CAUSE GRADUAL WEAKENING. BY TAU 48, TS 18W WILL
BECOME ENTRENCHED IN THE MID-LATITUDE BAROCLINIC ZONE AND BEGIN
EXTRATROPICAL TRANSITION (ETT). AFTER COMPLETING ETT (NO LATER THAN
TAU 72), A GALE-FORCE COLD CORE LOW WILL REMAIN. NUMERICAL GUIDANCE
IS IN STRONG AGREEMENT THROUGH TAU 36. AFTER TAU 36, CROSS-TRACK
AGREEMENT REMAINS GOOD BUT ALONG-TRACK DIFFERENCES CAUSE THE SPREAD
AMONG THE MODELS TO INCREASE. BASED ON STRONG AGREEMENT AND SHORT
DURATION OF FORECAST, THERE IS GOOD CONFIDENCE IN THE JTWC TRACK
FORECAST.//
NNNN

[euro6208]

Okinawa seeing gust well over 106 mph.

[1900hurricane]

Obs from the south end of Okinawa (Naha airport and proper) and nearby Kerama seem to support about a 1 minute intensity of 65 kt. It certainly isn't the most picturesque typhoon ever, but at least it isn't Barry levels bad. RMW is clearly huge.

[1900hurricane]

Here's some in motion.

[mrbagyo]

^ that phoon looks terrible.

[Tailspin]

Not real tight on that above loop.But it does look large.


https://imgur.com/pYuPZnL
Roughly 4hrs old nothing above 45KTS on the plot sampled.

[euro6208]

WDPN31 PGTW 210900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
010//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 397 NM
SOUTH-SOUTHWEST OF SASEBO, JAPAN, HAS TRACKED NORTHWARD AT 12
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY REVEALS A CONSOLIDATING SYSTEM WITH A LARGE, 45NM DIAMETER
RAGGED EYE AND EXTENSIVE SPIRAL BANDING OVER THE EASTERN SEMICIRCLE.
A 21/0147Z ASCAT-B IMAGE SHOWS A LARGE, OBLONG CENTER WITH A SWATH
OF 50-60 KNOT WINDS DISPLACED OVER THE EASTERN SEMICIRCLE. SURFACE
OBSERVATIONS FROM OKINAWA INDICATE SUSTAINED 40-50 KNOT WINDS WITH
GUSTS OF 70-80 KNOTS WITHIN THE SPIRAL BANDING. THERE IS GOOD
CONFIDENCE IN THE CURRENT POSITION BASED ON THE EYE FEATURE AND
HOURLY RADAR FIXES. THE 21/0423Z AMSR2 IMAGE SHOWS IMPROVED DEEP
CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION
CENTER. THE CURRENT INTENSITY IS INCREASED SLIGHTLY TO 60 KNOTS,
WHICH IS CONSISTENT WITH THE PGTW DVORAK ESTIMATE OF T4.0 (65 KNOTS)
AND RECENT SURFACE OBSERVATIONS. THE ENVIRONMENT, WITH MODERATE (10-
15 KT) VERTICAL WIND SHEAR (VWS), GOOD EQUATORWARD AND POLEWARD
OUTFLOW, AND WARM (27-28 CELSIUS) SEA SURFACE TEMPERATURE (SST), IS
SUPPORTIVE OVERALL, HOWEVER, SOME DRY AIR ENTRAINING INTO AND
SUPPRESSING CONVECTION ON THE WESTERN HALF OF THE SYSTEM IS EXPECTED
TO LIMIT FURTHER INTENSIFICATION. TS 18W IS TRACKING POLEWARD ALONG
THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. THE 34-KNOT AND 50-KNOT WIND
RADII HAVE BEEN ADJUSTED BASED ON A DETAILED ANALYSIS OF RECENT
ASCAT IMAGERY.
B. AROUND TAU 24, TS 18W WILL HAVE ROUNDED THE STR AXIS AND BEGIN
TURNING NORTHEASTWARD. THERE IS A BRIEF PERIOD WHERE THE ENVIRONMENT
IS MARGINALLY SUPPORTIVE BEFORE STRONG VWS, LAND INTERACTION, AND
COOL SST BEGIN TO CAUSE GRADUAL WEAKENING. BY TAU 24, TS 18W WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE
BAROCLINIC ZONE AND MIDLATITUDE WESTERLIES. AFTER TAU 36, TS 18W
WILL ACCELERATE NORTHEASTWARD AND WILL BECOME EMBEDDED IN THE STRONG
MIDLATITUDE WESTERLIES OVER THE SEA OF JAPAN, COMPLETING ETT BY TAU
48 WITH CLEAR FRONTAL CHARACTERISTICS. AFTER COMPLETING ETT, A GALE-
FORCE COLD CORE LOW WILL REMAIN AND TRACK NORTH OF MISAWA AB.
NUMERICAL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 48. AFTER TAU
48, NUMERICAL GUIDANCE DIVERGES WITH SIGNIFICANT DIFFERENCES IN
TRACK SPEED. OVERALL, THERE IS GOOD CONFIDENCE IN THE JTWC TRACK
FORECAST.//
NNNN

[euro6208]

[1900hurricane]

MetOp-C has a large area of >=50 kt winds on the east side of the circulation. Still think it should be 65 kt (1 minute sustained).

[euro6208]

WDPN31 PGTW 211500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
011//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 348 NM
SOUTHWEST OF SASEBO, JAPAN, HAS TRACKED NORTHWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND
A 210933Z SSMIS 91GHZ MICROWAVE IMAGE DEPICT DEEP CONVECTIVE BANDING
WRAPPING INTO A LARGE, RAGGED EYE. A 211147Z ASCAT-A IMAGE SHOWS A
LARGE, OBLONG CENTER WITH A SWATH OF 50-55 KNOT WINDS DISPLACED OVER
THE EASTERN SEMICIRCLE. THERE IS GOOD CONFIDENCE IN THE CURRENT
POSITION BASED ON THE EYE FEATURE AND RJTD HOURLY RADAR FIXES. THE
CURRENT INTENSITY REMAINS ASSESSED AT 60 KNOTS, WHICH IS CONSISTENT
WITH THE PGTW AND RCTP DVORAK CURRENT INTENSITY ESTIMATES RANGING
FROM 3.5 TO 4.0 (55-65 KNOTS). ENVIRONMENTAL CONDITIONS HAVE
GRADUALLY DEGRADED WITH INCREASING (15-20 KNOTS) VERTICAL WIND SHEAR
(VWS) OFFSET BY IMPROVED POLEWARD OUTFLOW. UPPER-LEVEL ANALYSIS ALSO
INDICATES AN UPPER LOW OVER THE CENTER WITH CONVERGENT FLOW, WHICH
IS HINDERING SIGNIFICANT CONVECTIVE DEVELOPMENT. WARM (27-28
CELSIUS) SEA SURFACE TEMPERATURE (SST) VALUES REMAIN SUPPORTIVE. TS
18W IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. AROUND TAU 24, TS 18W WILL HAVE ROUNDED THE STR AXIS AND BEGIN
TURNING NORTHEASTWARD. THERE IS A BRIEF PERIOD WHERE THE ENVIRONMENT
IS MARGINALLY SUPPORTIVE BEFORE STRONG VWS, LAND INTERACTION, AND
COOL SST BEGIN TO CAUSE GRADUAL WEAKENING. BY TAU 24, TS 18W WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE
BAROCLINIC ZONE AND MIDLATITUDE WESTERLIES. AFTER TAU 36, TS 18W
WILL ACCELERATE NORTHEASTWARD AND WILL BECOME EMBEDDED IN THE STRONG
MIDLATITUDE WESTERLIES OVER THE SEA OF JAPAN, COMPLETING ETT BY TAU
48 WITH CLEAR FRONTAL CHARACTERISTICS. AFTER COMPLETING ETT, A GALE-
FORCE COLD CORE LOW WILL REMAIN AND TRACK NORTH OF MISAWA AB.
NUMERICAL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 48. AFTER TAU
48, NUMERICAL GUIDANCE DIVERGES WITH SIGNIFICANT DIFFERENCES IN
TRACK SPEED. OVERALL, THERE IS GOOD CONFIDENCE IN THE JTWC TRACK
FORECAST.//
NNNN

[Hayabusa]

STS

STS 1917 (Tapah)
Issued at 00:50 UTC, 22 September 2019

<Analysis at 00 UTC, 22 September>
Scale Large
Intensity -
Center position N31°05' (31.1°)
E126°55' (126.9°)
Direction and speed of movement NNE 30 km/h (15 kt)
Central pressure 975 hPa
Maximum sustained wind speed 30 m/s (60 kt)
Maximum wind gust speed 45 m/s (85 kt)
≥ 50 kt wind area SE 200 km (110 NM)
NW 150 km (80 NM)
≥ 30 kt wind area ALL 560 km (300 NM)

[euro6208]

WDPN31 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
012//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 283 NM
SOUTHWEST OF SASEBO, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 12
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS AN EXPANSIVE CLOUD FIELD AND A BROAD EYE-LIKE FEATURE.
THE INITIAL POSITION IS PLACE WITH FAIR CONFIDENCE BASED ON A 211601Z
GMI 37GHZ MICROWAVE IMAGE, WHICH SHOWS THE BROAD NATURE OF THE
SYSTEM. THE INTENSITY OF 60 KNOTS IS HEDGED BETWEEN DVORAK CURRENT
INTENSITY (CI) ESTIMATES OF T4.0 (65 KNOTS) FROM PGTW AND T3.5 (55
KNOTS) FROM KNES. ENVIRONMENTAL ANALYSIS REVEALS THAT TS 18W IS
EXPERIENCING NEUTRAL (15 TO 20 KNOT) VERTICAL WIND SHEAR. TS 18W HAS
A ROBUST POLEWARD OUTFLOW CHANNEL BUT LITTLE TO NO EQUATORWARD
OUTFLOW. SEA SURFACE TEMPERATURES REMAIN FAVORABLE, BETWEEN 27 AND 28
DEGREES CELSIUS. TS 18W IS TRACKING NORTH-NORTHEASTWARD WHILE UNDER
THE INFLUENCE OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. THE AFOREMENTIONED STR WILL REMAIN THE PRIMARY STEERING FEATURE
IN THE SHORT TERM. AS TS 18W TRACKS AROUND THE STR THE TRACK WILL
SHIFT FROM NORTH-NORTHEASTWARD TO NORTHEASTWARD. FAVORABLE SEA
SURFACE TEMPERATURES AND STRONG POLEWARD OUTFLOW OFFSET BY
INCREASING VERTICAL WIND SHEAR WILL ALLOW FOR A GRADUAL DECREASE IN
INTENSITY. AS TS 18W TRACKS AROUND THE STR IT WILL BEGIN TO INTERACT
WITH THE MIDLATITUDE WESTERLIES. INTERACTION WITH THE BAROCLINIC ZONE
WILL CAUSE TS 18W TO BEGIN EXTRATROPICAL TRANSITION (ETT) BY TAU 24
AND COMPLETE ETT BY TAU 36. AFTER ETT, A GALE FORCE WIND FIELD WILL
REMAIN AND RAPIDLY TRACK NORTHEASTWARD. DYNAMIC MODEL GUIDANCE
REMAINS IN GOOD AGREEMENT THROUGH TAU 36 WITH AN INCREASING ALONG-
TRACK SPREAD BY TAU 48. THE JTWC FORECAST TRACK IS PLACED NEAR THE
MULTI-MODEL CONSENSUS. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
NNNN

[Tailspin]

Track data from Hong Kong Observatory:
香港天文台的熱帶氣旋路徑數據：

Date & Time Latitude Longitude
(HKT) Int (deg N) (deg E)
=========== ====== ======== =========
2019091811 TD 21.7 128.9
2019091813 TD 21.8 128.9
2019091814 TD 21.9 129.4
2019091816 TD 21.9 129.4
2019091819 TD 22.0 129.4
2019091820 TD 22.0 129.4
2019091823 TD 22.2 129.2
2019091902 TD 22.2 129.1
2019091903 TD 22.3 129.1
2019091905 TD 22.4 129.1
2019091908 TD 22.5 128.9
2019091909 TD 22.5 128.8
2019091912 TD 22.5 128.6
2019091914 TD 22.5 128.8
2019091916 TD 22.5 128.7
2019091917 TD 22.6 128.7
2019091919 TD 22.7 128.5
2019091920 TS 22.8 128.3
2019091922 TS 22.9 128.3
2019091923 TS 22.9 128.2
2019092002 TS 22.9 127.5
2019092003 TS 22.9 127.3
2019092005 TS 22.8 127.2
2019092008 TS 23.0 127.0
2019092009 TS 23.0 127.0
2019092012 TS 23.1 126.9
2019092014 STS 23.4 126.9
2019092016 STS 23.5 126.7
2019092019 STS 23.6 126.7
2019092020 STS 23.7 126.7
2019092023 STS 24.2 126.5
2019092102 STS 24.9 126.3
2019092103 STS 25.0 126.2
2019092104 STS 25.3 126.2
2019092105 STS 25.4 126.1
2019092108 STS 26.0 125.8
2019092109 STS 26.1 125.8
2019092110 T 26.2 125.8
2019092112 T 26.6 125.8
2019092114 T 27.4 125.6
2019092116 T 27.9 125.6
2019092119 T 28.3 125.7
2019092120 T 28.4 125.7

https://imgur.com/R3UrEef

Not the official agency but interesting look back over for intensity comparisons none the less.

TROPICAL CYCLONE TAPAH
(2019-09-22 02:00:36 UTC)
==========================
HKO:
211800Z 29.6N 126.1E 65KT
(+012H) 32.6N 127.7E ---KT
(+024H) 36.1N 130.9E 57KT
(+036H) 39.9N 135.8E ---KT
(+048H) 43.3N 143.0E ---KT
JTWC:
211800Z 29.6N 126.0E 60KT
(+012H) 32.5N 127.8E 55KT
(+024H) 35.9N 131.1E 50KT
(+036H) 39.5N 136.1E 45KT
(+048H) 43.6N 143.0E 40KT
JMA:
220000Z 31.1N 126.9E 60KT
(+012H) 33.7N 129.1E 60KT
(+024H) 37.8N 133.4E 60KT
(+048H) 45.2N 149.0E 45KT
NMC:
220000Z 30.8N 126.9E 64KT
(+012H) 33.6N 129.0E 54KT
(+024H) 37.4N 132.9E 49KT
(+036H) 40.9N 138.6E 45KT
(+048H) 45.2N 147.8E 39KT
CWB:
211800Z 29.6N 126.1E 58KT
(+012H) 32.6N 127.6E 58KT
(+024H) 35.8N 130.5E 58KT
(+036H) 39.5N 135.2E 54KT
(+048H) 42.8N 141.5E 49KT
KMA:
220000Z 31.0N 126.4E 68KT
(+012H) 34.5N 129.1E 62KT
(+024H) 38.4N 133.9E 56KT

[euro6208]

WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
014//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 94 NM WEST-
SOUTHWEST OF SASEBO, JAPAN, HAS TRACKED NORTHEASTWARD AT 22 KNOTS
OVER THE PAST SIX HOURS. TS 18W HAS COMMENCED EXTRA-TROPICAL
TRANSITION (ETT) AND IS ACCELERATING NORTHEASTWARD WITHIN THE
MIDLATITUDE SOUTHWESTERLIES. ADDITIONALLY, THE SYSTEM HAS A WEAK
FRONTAL STRUCTURE AS EVIDENCED IN SATELLITE IMAGERY AND THE 22/00Z
1000-500MB THICKNESS ANALYSIS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A BROAD, EXPOSED LOW-LEVEL CIRCULATION (LLCC) WITH
DEEP CONVECTION SHEARED OVER THE NORTH AND NORTHEAST QUADRANTS DUE
TO STRONG (30-35 KNOT) SOUTHERLY VERTICAL WIND SHEAR (VWS). ALTHOUGH
BROAD, THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION DUE TO THE
EXPOSED NATURE OF THE LLCC AND RJTD RADAR FIXES. A 220508Z AMSR2
89GHZ COLOR COMPOSITE IMAGE SHOWS A DEFINED LLCC WITH DEEP
CONVECTIVE BANDING PERSISTING OVER THE NORTH QUADRANT. SURFACE
OBSERVATIONS HAVE INCREASED ALONG THE NORTHWEST COAST OF KYUSHU
ISLAND WITH 40-45 KNOT WIND GUSTS REPORTED. THE INITIAL INTENSITY OF
55 KNOTS IS BASED ON A DVORAK CURRENT INTENSITY ESTIMATE OF 3.5 (55
KNOTS) FROM PGTW. ENVIRONMENTAL CONDITIONS ARE GRADUALLY DEGRADING
WITH THE INCREASING VWS AND SLIGHTLY COOLER SST, HOWEVER, POLEWARD
OUTFLOW REMAINS ROBUST. TS 18W IS TRACKING NORTHEASTWARD AS IT
RECURVES AROUND THE NORTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE
(STR) LOCATED TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS 18W WILL CONTINUE TO RECURVE NORTHEASTWARD INTO THE SEA OF
JAPAN WITH INCREASING, HOSTILE VWS EXPECTED AND COOLER SST (LESS
THAN 24C). TS 18W WILL COMPLETE ETT BY TAU 24 AND CONTINUE TO
ACCELERATE NORTHEASTWARD TOWARD HOKKAIDO. THE SYSTEM IS FORECAST TO
REMAIN A STRONG COLD-CORE LOW WITH GALE-FORCE WINDS ANTICIPATED OVER
NORTHERN HONSHU. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
THROUGH TAU 36, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
NNNN

[mrbagyo]

590 frames



Image© KMA

[1900hurricane]

This is over half a day old now, but ASCAT near 12Z still had quite a few 60 kt vectors in there. JTWC was at 55 kt at the time while JMA was 60 kt.

[Hayabusa]

LOW
Issued at 00:50 UTC, 23 September 2019

<Analysis at 00 UTC, 23 September>
Scale -
Intensity -
LOW
Center position N38°00' (38.0°)
E135°00' (135.0°)
Direction and speed of movement NE 65 km/h (35 kt)
Central pressure 992 hPa