application to heavy rainfall kyouda masayuki numerical prediction division, japan meteorological...
TRANSCRIPT
Application to Heavy Rainfall
経田 正幸KYOUDA Masayuki
Numerical Prediction Division, Japan Meteorological Agency
9th THORPEX GIFS-TIGGE Working Group meetingGeneva, WMO Headquarters
31 August – 2 September, 2011
Contents• Information for severe weather preparation at
JMA– Early warning information– EPS product
• TC-related heavy rainfall– Case study – Typhoon Fitow (T0709)
• Model output and its calibration– Calibrated precipitation– Calibration method
• Conclusion and suggestion
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Information for Severe Weather Preparation at JMA
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Information for Severe Weather Preparation
• Warning, advisory and bulletin services for severe weather– If hazardous weather conditions are expected, JMA delivers a variety of plain
messages including warnings, advisories and bulletins to the general public and disaster prevention authorities so that appropriate measures can be taken to mitigate possible hazards.
– Bulletins provide information to supplement warnings and advisories.
• Early warning information– Five-day track forecast in Typhoon bulletins
http://www.jma.go.jp/en/typh/typh5.html– Storm, heavy rain, and high waves for the next few days in
bulletin services– Extreme weather as a kind of seasonal forecast
Issued every Tuesday and Friday when a high probability (30% or more) of very high or very low seven-day averaged temperature is predicted in the week starting from five to eight days ahead of the date of announcement
http://www.jma.go.jp/en/soukei/ 4
EPS product for early warning information
• Guidance for early warning information– Currently based on JMA EPS
• It is important to update on schedule.• Our own EPS product is easy to work especially for operational use.
– Limited use of Multi-center/TIGGE products• Others’ EPS/NWPS outputs are used for reference.• Multi-center’s and ECMWF-EPS’s track are used in TC warning process.• Ensemble TC tracks are available at the Numerical Typhoon Prediction
Web site operated by RSMC Tokyo – Typhoon Center in JMA.
• EPS plan in the near future and the next– Expected in step with forecast operation’s plan
• To increase the resolution of the both EPSs’ model from TL319L60 to TL479L100• To conduct One-week EPS from once a day to twice a day although the forecast
ensemble size is reduced by about half• To increase the ensemble size of Typhoon EPS from 11 to 25• To extend the forecast range of One-week EPS up to two weeks• To introduce “Reforecasting”
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JMA Numerical Typhoon Prediction Web site- for the NMHSs of ESCAP/WMO Typhoon Committee
Members -
Ensemble TC tracks are available on the Numerical Typhoon Prediction Web site.
•Multi-center TC tracks•TC tracks derived from Typhoon EPS
6-hourly update products up to 132 hours aheadPlan to increase the ensemble size up to 25
Daily update productsup to 9 days ahead
Plan to conduct the EPS twice a day although the ensemble size is cut
Update cycle, now and in the future
12UTC 18UTC 00UTC 06UTC 12UTC
New and timely EPS products are now available in TC warning process.
TC-related Heavy Rainfall
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Case study - Typhoon Fitow (T0709)
Black solid line : Observed track
Weather Chart :
at 00 UTC on 6th September
Typhoon Fitow made landfall in Honshu, the main island of Japan, at about 15UTC on 6th September.
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3-day accumulated precipitation
683mm651mm
690mm
荒川
多摩川
烏川
入間川
相模川
Heavy rainfall associated with Typhoon Fitow
The 3-day accumulated rainfall in mountain region located in the western part of Tokyo exceeded 500 mm and the water level of the Tama River running through Tokyo Metropolitan area exceeded dangerous level.
Red and blue lines represent to issue flood warning and no warning, respectively.
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Initial time is 12UTC 2 September.
Ensemble forecastup to 9 days ahead
9 月 1 日 09 時2 日 09 時
3 日 09 時4 日 09 時予報円
5 日 09 時予報円
6 日 09 時予報円
3-Day Track Forecastin Typhoon Bulletins
at 00UTCon 3 September
The landfall probability on Japan depended on the timing of recurvature.
Typhoon track forecasts of Typhoon Fitow before recurvature
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Plume diagram for an upriver district
Initial time is 12UTC 2 September.
In order to explore the use of medium-range NWP output to TC forecasting, it is essential to have an accurate grasp of forecast uncertainties of high-impact weather events controlled by the Typhoon motion, especially whether or not Typhoon will approach. 12
Worst-case scenario (1)Initial time is 12UTC 2 September.
Western trackwith landfall
Representative track up to 6 days ahead
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Worst-case scenario (2)Initial time is 12UTC 3 September.
Western trackwith landfall
Representative track up to 5 days ahead
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Model Output and Its Calibration
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Model output and its calibration
• Operational global EPS/NWP model– Not easy to predict precious amounts or even
the order of strong rainfalls• Underestimation of orographic rainfall (ex. Fitow)
• Statistical post-processing– employed routinely to reduce the systematic
errors of JMA NWP model• Calibration is essential to detect whether the forecasted
rainfall amount exceeds warning level or not, although the observed data are limited.
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Typhoon Ma-on bringing heavy rainfall
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Initial time is 12UTC 18 July 2011.
Ensemble TC track up to 4 days ahead
Based on rain gauge data during19th July 2011
In Umaji Village of Kochi Prefecture, 851.5 mm of rainfall
fell on 19th July (local time), ranking high in Japan’s one-day
precipitation.
One-day rainfall amount
The analyzed TC central pressure was 980 hPa and an analyzed
maximum wind speed near TC center was 80 kt.
Calibrated precipitationCalibrated data
Observed gridded data used in the calibration
Three-hour accumulated rainfall from 21UTC 18th July 2011
Underestimation of antecedent rainfall amount over the mountain regions was calibrated due to orographic effect.
Raw data (control run of EPS)
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Calibration method
• Kalman filter– The predictand is “Radar/Raingauge-Analyzed Precipitation”
data which are covered with the Japanese Islands and its surrounding sea area.
– The KF output has a tendency of lower frequency of forecasting severe weather events,
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such as heavy rainfall, than the actual.
• Frequency bias correction– The scheme is applied to
compensate the frequency bias of the KF output. Cumulative frequency
distribution of 7-day accumulated precipitation at Tokyo for July 2002 to June 2003
Blue : EPS model outputRed : Rain gauge
Frequency bias correction forcing
Conclusion and suggestion• JMA makes some guidance based on its own operational
EPS in the early warning operation.– The use and development of Multi-center/TIGGE products are
limited, but Multi-center’s track are used in TC warning process.
• Heavy rainfall forecasting associated with TC is strongly depend on the uncertainty of the TC motion.
– Statistical post-processing is useful to reduce the systematic errors in the operational global EPS model to heavy rainfall.
• To exchange gridded data for ensemble precipitation is expected in the TIGGE-FDP activity.– The rule of its exchange should be clear.
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Thank you for your kind attention.
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