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JMA best track data

Kenji KISHIMOTO Forecast Division Japan Meteorological Agency. JMA best track data. Introduction JMA Dvorak analysis Summary. Contents. Introduction JMA Dvorak analysis Summary. Contents. Center position Central pressure Maximum winds (10 minute averages) 50-knot wind radius

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JMA best track data

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  1. Kenji KISHIMOTO Forecast Division Japan Meteorological Agency JMA best track data

  2. Introduction • JMA Dvorak analysis • Summary Contents

  3. Introduction • JMA Dvorak analysis • Summary Contents

  4. Center position • Central pressure • Maximum winds (10 minute averages) • 50-knot wind radius • 30-knot wind radius Parameters JMA best track data starts from 1951 and adds wind data from 1977.

  5. Process Dvorak analysis system TC analysis system Weather chart analysis system

  6. Process Almost all TCs generate and reach the peak intensity over the sea where there is few surface observation. Best track intensity are mainly based on Dvorak analysis after termination of aircraft observations in 1987. Percentages at each 5-degree square (1573 TCs from 1951 to 2010 in WNP) Peak intensity position Tropical storm formation position 1.0% 2.0% 3.0% 4.0%

  7. Introduction • JMA Dvorak analysis • Summary Contents

  8. JMA Dvorak analysis JMA rule (1) Kobatable (2) landfall rule CI number T number Dvorak (1984) EIR method

  9. History of JMA Dvorak analysis

  10. Koba table Koba H., T. Hagiwara, S. Osano and S. Akashi, 1991: Relationships between CI Number and Minimum Sea Level Pressure/ Maximum Wind Speed of Tropical Cyclones., Geophysical Magazine, Vol.44, No.1, 15-25.

  11. Koba Table The Koba table is based on comparison between JMA best track data during the reconnaissance period and reanalysis CI numbers. JMA best track data with JMA Dvorak ensure consistency with ones during the reconnaissance period. Maximum winds Central pressure

  12. Limitation of Dvorak analysis Kamahoriet al. (2006) found that, based on RSMC-Tokyo best track dataset, there was a substantial decrease in the number of TC days for intense typhoons over the WNP between the periods 1977-1990 and 1991-2004. However, this result differed from the one using the JTWC dataset which showed an increasing trend in the number of TC days for intense typhoons. Difference in best tracks of JTWC and RSMC-Tokyo from 1977 to the present (in satellite observation era)

  13. Limitation of Dvorak analysis MSW estimation from Dvorak analysis provide the mean value corresponding to CI numbers, which makes it unsuitable to detect intense typhoons. Aircraft observations can detect more intense typhoons.

  14. Verification

  15. Verification Observations at Japanese southern islands: MSLPs and maximum winds (10 minute averages) Aircraft observations during T-PARC and ITOP: MSLPs and SFMR maximum winds in Vortex messages

  16. Verification The accuracy of SFMR estimation has large uncertainty especially in case of strong winds. SFMR wind (m/s) dropsonde(m/s) SFMR-dropwindsonde comparison with the best fit Havel, Patrick J, 2009: Surface wind field analysis of tropical cyclone during TCS-08: Relative impacts of aircraft and remotely-sensed observations, Naval Postgraduate School, Sept, 2009, 76pp

  17. Introduction • JMA Dvorak analysis • Summary Contents

  18. JMA best track data ensure consistency between before and after the termination of the aircraft observation, except the following. • The change from aircraft observation to satellite estimation apparently brings decreasing trend in the frequency of intense typhoons. Summary

  19. How to access the data http://www.jma.go.jp/jma/jma-eng/jma-center/rsmc-hp-pub-eg/RSMC_HP.htm

  20. Thank you for your kind attention!!

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