How many tornadoes does Japan get a year?

The Japan Meteorological Agency has confirmed about twenty-five a year since it began investigating every severe local wind in 2007. Earlier counts are lower because less was investigated, not because fewer tornadoes happened: from 1961 to 1990 the database holds only events that met a severity threshold.

What is the JEF scale?

The Japanese Enhanced Fujita scale, used by the Japan Meteorological Agency since 1 April 2016. It rebuilt the Fujita scale for Japanese construction, with 31 damage indicators instead of the Fujita scale's nine, and defines each class by a three-second gust: JEF0 is 25 to 38 m/s and JEF5 is 95 m/s and above. Events before April 2016 are rated on the Fujita scale instead.

What is the strongest tornado recorded in Japan?

No tornado in Japan has been rated above 3 on either scale. The deadliest was the F3 that struck Saroma, Hokkaido on 7 November 2006 and killed nine people.

Does this archive include downbursts?

No. The Japan Meteorological Agency keeps one database of severe local winds and classifies each event, and only the events it classified as tornadoes are listed here. Downbursts, gust fronts, dust whirls and events the survey could not classify are counted on the country page and left out of the archive.

Tornadoes

Tornadoes in Japan

1,576 tornadoes have been confirmed in Japan since 1961, out of every severe local wind the Japan Meteorological Agency has investigated. They killed 35 people and injured 2,390. 131 were rated F2 or JEF2 and above; no tornado in Japan has ever been rated above 3.

What this record holds, and what it leaves out

The Japan Meteorological Agency keeps one database of severe local winds, not a tornado database. It classifies every event it investigates, and only the 1,576 it classified as tornadoes are listed here. The other 1,335 events in the same file are downbursts, gust fronts, dust whirls, and events whose cause the survey could not settle:

What the survey called it	Events
Unidentified	877
Downburst, microburst included	120
Tornado or funnel cloud	109
Downburst or gust front	95
Dust whirl or eddy	83
Gust front	37
Tornado or downburst	11
Other	3

Two of those classes name a tornado as one of two possibilities, "tornado or downburst" and "tornado or funnel cloud". They are left out on purpose: a tornado archive that counts maybes as tornadoes reports a number nobody else will get from the same file.

How complete this is

The database begins in 1961, but it is not evenly filled. From 2007 the Japan Meteorological Agency records every severe local wind it confirms, and it did the same from 1991 to 2006. For 1961 to 1990 it collected only events that met a threshold: an estimated Fujita rating of 2 or more, a death, twenty injuries, five buildings destroyed or twenty half destroyed, plus whatever weaker events turned up in the search. So a rise in the yearly count through the record is mostly a rise in what was looked for.

The rating scales

Tracks are drawn in the color of the rating.

The Fujita scale, to 31 March 2016

Events up to 31 March 2016 are rated on the Fujita scale, which estimates a wind speed from the damage. The Japan Meteorological Agency publishes it in meters a second, over an averaging time that shortens as the scale climbs. Wind speeds and the damage they describe are the Japan Meteorological Agency’s; the averaging time is in brackets. The English wording is ours.

F017 to 32 m/s (about a 15-second mean)
Weak structures such as television aerials are knocked over. Small branches break and shallow-rooted trees lean. A building other than a house may be damaged.
F133 to 49 m/s (about a 10-second mean)
Roof tiles fly and window glass breaks. Plastic greenhouses are badly damaged. Weak-rooted trees fall and strong ones snap at the trunk. A car on the road is blown off it by the crosswind.
F250 to 69 m/s (about a 7-second mean)
Roofs are torn off houses and weak buildings other than houses collapse. Large trees fall or are twisted apart. Cars are blown off the road and trains can be derailed.
F370 to 92 m/s (about a 5-second mean)
Walls are pushed in and houses collapse. Buildings other than houses break up and scatter, steel-framed ones included. Trains are overturned and cars lifted and thrown. Most large forest trees snap or fall, some are pulled out.
F493 to 116 m/s (about a 4-second mean)
Houses break up and scatter, and weak buildings other than houses are blown away without a trace. Steel frames are flattened. Trains are blown away and cars fly tens of meters. Objects of a tonne and more fall out of the sky.
F5117 to 142 m/s (about a 3-second mean)
Houses are blown away leaving nothing, and standing trees are stripped of their bark. Cars and trains are lifted and flown far from where they stood. Objects of several tonnes fall out of nowhere.
Below F0
The survey confirmed a tornado but found damage too slight for the bottom of the scale, so it is recorded as below it rather than as unrated.
Unrated
The survey recorded a tornado but could not put a number on it, most often because nothing it passed carried a rating the scale can be read from.

The Japanese Enhanced Fujita scale, from 1 April 2016

From 1 April 2016 the Japan Meteorological Agency rates severe local winds on the Japanese Enhanced Fujita scale, which it built to fit Japanese construction. A class is assigned by matching what was damaged, and how badly, against 31 damage indicators, so a survey lands on a narrower wind range than the Fujita scale allowed. Wind speeds are three-second gusts. The damage listed is the representative damage JMA gives for each class, in our English.

JEF025 to 38 m/s
Visible damage to a wooden house and windows broken by flying debris. Roofing lifts or peels off over a small area. Greenhouse sheeting peels away and pipe frames deform or collapse. Garden sheds move or tip over, vending machines fall, unreinforced concrete block walls part-collapse, branches 2 to 8 cm thick break.
JEF139 to 52 m/s
Roofing on a wooden house lifts or peels off over a wide area and the eaves or roof boarding break up. Plastic greenhouse frames deform or collapse across whole districts. Light and compact cars are rolled over, a train in normal service is blown off the rails, sign posts lean or fall, reinforced block walls fail, trees are uprooted and conifers snap.
JEF253 to 66 m/s
The upper structure of a wooden house deforms and the walls crack or distort; roof trusses break up and fly. Roofing lifts and flies off a steel-framed warehouse. Vans and large vehicles roll over, reinforced concrete power poles snap, carports lean or collapse, broad-leaved trees snap at the trunk, gravestones topple.
JEF367 to 80 m/s
The upper structure of a wooden house deforms badly or collapses. Steel-framed prefabricated houses lose eaves, roof boarding or wall cladding. Balcony railings on reinforced concrete apartment blocks deform over a wide area. Roofing peels from the large canopies of factories and warehouses, and asphalt is lifted and thrown.
JEF481 to 94 m/s
Roofing peels or drops away from the large canopies of factories and warehouses over a wide area.
JEF595 m/s and above
The upper structure of steel-framed prefabricated houses and steel warehouses deforms badly or collapses. Balcony railings on reinforced concrete apartment blocks deform badly or fall away.
Below JEF0
The survey confirmed a tornado but found damage too slight for the bottom of the scale, so it is recorded as below it rather than as unrated.
Unrated
The survey recorded a tornado but could not put a number on it, most often because nothing it passed carried a rating the scale can be read from.

By prefecture

Every prefecture with a tornado in the record. Each one has a page of its own, with every year and every tornado.

Prefecture	Tornadoes	Deaths	Injuries	Rated 2 and above
Okinawa	216	1	124	13
Hokkaido	174	10	50	13
Niigata	98		21	1
Kochi	78		47	4
Kagoshima	74	4	58	4
Akita	74		13	1
Miyazaki	71	3	421	15
Shizuoka	63	1	153	12
Chiba	56	6	170	11
Ishikawa	54		13	1
Tokyo	46		48	5
Ibaraki	39	5	229	4
Nagasaki	36	1	6	1
Saitama	31	1	127	4
Yamagata	31		6	1
Aichi	29	2	583	7
Mie	29		8
Wakayama	29		29	1
Fukui	27	1	9
Shimane	25		5	2
Tottori	25
Toyama	24		2	1
Fukuoka	23		17	3
Aomori	23		12	1
Miyagi	18		11	1
Tochigi	18		49	5
Kumamoto	17		10	1
Kanagawa	16		48	1
Gifu	15		4	2
Saga	13		52	1
Yamaguchi	12		16	3
Fukushima	11		4	1
Gunma	10		25	3
Iwate	9		3	1
Hyogo	9		2
Ehime	7
Kagawa	7		3
Oita	6			2
Kyoto	6
Yamanashi	5
Okayama	5		3	3
Nagano	4
Tokushima	4
Shiga	4		8	1
Hiroshima	2		1	1
Nara	2
Osaka	1

The deadliest

The strongest

The longest paths

The widest

The most damaging

Houses destroyed outright, as the survey counted them. The Japan Meteorological Agency records buildings rather than money.

Every year

Nearby

Warnings in force in Japan now The forecast in Japan The live radar over Japan

What this means

Ratings are the survey’s, read off the damage rather than measured. Counts rise sharply through the record because what the Japan Meteorological Agency investigated widened twice, in 1991 and in 2007, not because tornadoes became more frequent. The rating scale is above.

Sources

Source: Japan Meteorological Agency website.Japan Meteorological Agency, database of tornadoes and other severe local winds.Prepared by WeatherOverTime from the Japan Meteorological Agency’s data: the events were filtered to tornadoes, the coordinates converted from degrees, minutes and seconds, the totals and rankings computed here, and the place names, scale descriptions and every sentence on this page translated or written by us. It is not a publication of the Japan Meteorological Agency.

What is here

The record: The Japan Meteorological Agency's database of tornadoes and other severe local winds, back to 1961, of which the events JMA classified as tornadoes get a page each, with index pages by prefecture and by year.
Two scales: The Fujita scale to 31 March 2016 and the Japanese Enhanced Fujita scale after it. Each rating is shown on the scale it was assigned on, in the wind speeds JMA publishes for that scale, rather than converted to the American one.
What JMA records: The path and its width, how long the tornado was on the ground, how fast and in which direction it moved, the wind the survey estimated, the weather situation it formed in, the casualties, and the houses and other buildings destroyed, half destroyed and partly damaged.

The US archive · The Canadian archive · Warnings in Japan · The Japanese forecast

The Fujita scale, to 31 March 2016

The Japanese Enhanced Fujita scale, from 1 April 2016

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