kenji kishimoto forecast division japan meteorological agency
TRANSCRIPT
JMA BEST TRACK DATA
Kenji KISHIMOTO Forecast Division
Japan Meteorological Agency
CONTENTS
Introduction JMA Dvorak analysis Summary
CONTENTS
Introduction JMA Dvorak analysis Summary
PARAMETERS
Center position Central pressure Maximum winds (10 minute averages) 50-knot wind radius 30-knot wind radius
JMA best track data starts from 1951 and adds wind data from 1977.
PROCESSDvorak analysis system
TC analysis systemWeather chart analysis
system
Almost all TCs generate and reach the peak intensity over the sea where there is few surface observation.
Tropical storm formation position Peak intensity position
1.0% 2.0% 3.0% 4.0%
Percentages at each 5-degree square (1573 TCs from 1951 to 2010 in WNP)
Best track intensity are mainly based on Dvorak analysis after termination of aircraft observations in 1987.
PROCESS
CONTENTS
Introduction JMA Dvorak analysis Summary
JMA DVORAK ANALYSIS
Dvorak (1984) EIR method
JMA rule(1) Koba table
(2) landfall ruleCI numberT number
HISTORY OF JMA DVORAK ANALYSIS
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.
KOBA TABLE
Central pressure Maximum winds
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.
LIMITATION OF DVORAK ANALYSIS
Kamahori et 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 overthe WNP between the periods 1977-1990 and 1991-2004. However, this result differed fromthe 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)
MSW estimation from Dvorak analysis provide the mean value corresponding to CI numbers, which makes it unsuitable to detect intense typhoons.
LIMITATION OF DVORAK ANALYSIS
Aircraft observations can detect more intense typhoons.
VERIFICATION
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
VERIFICATION
SFMR-dropwindsonde comparison with the best fit
SFMR wind (m/s)
dropsonde (m/s)
The accuracy of SFMR estimation has large uncertainty especially in case of strong winds.
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
CONTENTS
Introduction JMA Dvorak analysis Summary
SUMMARY
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.
HOW TO ACCESS THE DATAhttp://www.jma.go.jp/jma/jma-eng/jma-center/rsmc-hp-pub-eg/RSMC_HP.htm
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