Tornadoes in Tokyo

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.

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

1. 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.

2. 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.

3. 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.

4. 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.

5. JEF481 to 94 m/s

   Roofing peels or drops away from the large canopies of factories and warehouses over a wide area.

6. 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.

7. 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.

8. 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.

1. F2, 八丈町, TokyoJanuary 17, 1964F2, 7.5 km (4.7 mi)
2. F2, 大田区, TokyoOctober 14, 1965F2, 4.0 km (2.5 mi)
3. F2, 大田区, TokyoSeptember 30, 2004F2, 1.5 km (0.9 mi)
4. F2, 大田区または世田谷区, TokyoAugust 21, 1965F2, 200 m (219 yd)
5. F2, 大島町, TokyoFebruary 15, 1975F2
6. F1, 町田市, TokyoSeptember 10, 2001F1, 7.0 km (4.3 mi)
7. F1, 八丈町, TokyoNovember 17, 1997F1, 5.0 km (3.1 mi)
8. F1, 大島町, TokyoOctober 7, 2002F1, 1.6 km (1.0 mi)
9. F1, 三宅島三宅村, TokyoNovember 15, 1975F1, 1.0 km (0.6 mi)
10. F1, 大島町, TokyoDecember 25, 2000F1, 1.0 km (0.6 mi)

Warnings in force in Japan nowThe forecast in TokyoThe live radar over Tokyo

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.

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.