F2 tornado, 千葉市, Chiba, August 31, 1971

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)this tornado

   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.

Rating

F2 on the Fujita scale

Date

August 31, 1971

Time

09:00 JST

Prefecture

Chiba

Municipality, as recorded

千葉市

Path length

2.5 km (1.6 mi)

Path width

100 m (109 yd)

On the ground

5 minutes

Direction of travel

toward the northeast (045 degrees)

Where it began

On land

Weather situation

Typhoon

Deaths

1

Injuries

16

Touchdown point

35.621, 140.084

Lift-off point

35.639, 140.090

Record number

1971083108

The Japan Meteorological Agency records buildings rather than money, in the three degrees Japanese disaster reporting uses. The figures are what local authorities gave the survey and may differ from the final tally.

The live radar over the trackThe forecast for Chiba, 4 km awayEvery 1971 tornado in ChibaEvery tornado in ChibaWarnings in force in Japan now

5 more were confirmed in Japan that day.

The Japan Meteorological Agency publishes the survey’s findings and not its working, so there is no narrative, no damage-point survey and no warning archive behind this page the way there is on an American tornado’s. What the database records is above, in full.

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.