Tornado is generated with cumulus cloud and thunder cloud, and atmospheric vortex reaches ground. Big tree that roof of dwelling house is stripped off when tornado is generated falls down and may bring heavy damage, but it occurs when and where, or prediction is the difficult weather phenomenon.
When you obtained information such as hazardous wind watches when black cloud approaches and felt accident of weather, please take action to protect own body in reference to the next thing.
When the following phenomenon is caused, thunder cloud which developed which tornado produces may approach.
・Black cloud approaches, and the outskirts become suddenly dark.
・We hear thunder and can see lightning.
・Cold wind that felt a chill begins to blow.
・Large rain and "hail" begin to fall.
From the Meteorological Agency homepage
Weather information about intense gusts of wind such as tornadoes
In cases that intense gusts of wind such as tornadoes may produce, the next information is announced by the Meteorological Agency.
- Notice-like weather information (from half day of tornado occurrence one day ago)
When the weather phenomenon to be tied to disaster is expected by the development of low pressure, we specify with "intense gusts of wind such as tornadoes" and call for attention.
- Thunderstorm advisory (several hours ago of tornado occurrence)
When damage is expected by outbreak of intense phenomenon (thunderbolt, hail, sudden strong rain, gust of wind) with thunder cloud, thunderstorm advisory is announced. When outbreak of intense gusts of wind such as tornadoes is expected then, we specify with "tornado" in addition matter of the warning text and call for attention.
- Hazardous wind watch (from 0 of tornado occurrence one hour ago)
When it was judged that it was weather condition that intense gusts of wind such as tornadoes are easy to generate, hazardous wind watch is announced. This information right tells that it is weather condition that is easy to be generated of tornado now.
○○The first prefectural hazardous wind watch
We announce △△ Local Meteorological Observatory at 15:26 for Heisei X X six a year 21 days a month
○○In the prefecture, there might be tornado occurrence.
Tornado is generated with thunder cloud. When there is sign that thunder and wind take a sudden turn, and thunder cloud gets closer to, you move in firm building, and please act for ensuring safety.
This information is effective until 16:30 for 21 days.
Example of hazardous wind watch
Action that you should take on announcement of hazardous wind watch
If hazardous wind watch is announced, at firstThe skyWhen we pay attention to state of the , and thunder cloud senses sign to approach, please take the following action as possible.
- We evacuate to firm building nearby.
- We enter shade that can protect the body from scattering thing and lower the body and, without such a building, protect head.
- We do not approach telephone pole, big tree to have possibilities to collapse.
- We do not evacuate to storeroom, garage, prefab house (temporary building).
- We close shutter, window, curtain and are separated from window.
- In the 2-story above-mentioned house, we move to the first-floor cave.
- We move to cave near as possible center of house.
- We enter under strong desk and table and we make the body small and protect head.
- We confirm "the tornado announcement accuracy trendy cast".
- We collect information with TV radios and confirm.
Column Fujita (F) scale
As expression of strength of intense gusts of wind such as tornadoes, Fujita (F) scale may be used. This is standard to estimate the wind velocity such as tornado or downburst (we devise by Dr. Tetsuya Fujita of University of Chicago). Six phases of strength from strongest F5 to F0 is expressed.
In addition, tornadoes F4 or more are not observed in Japan until now.
|F scale||The wind velocity||The situation|
(average of about 15 seconds)
|Structure having weak antennas of TV falls down. Twig is broken, and slight tree of root may incline. Non-dwelling house may be broken.|
(average of about ten seconds)
|Roof tile flies, and glass window is broken. Damage of plastic greenhouse is serious. Weak tree of root falls down, and trunk compromises with strong tree. When running car catches side wind, it is blown down by way.|
(average of about seven seconds)
|Roof of dwelling house is stripped off, and weak non-dwelling house collapses. Big tree falls down and is wrenched off. Car is blown off way, and train may derail.|
(average of about five seconds)
|Wall is pushed down, and dwelling house collapses. Non-dwelling house is scattered in pieces, and even the making of steel frame is destroyed. Train overturns and car is lifted and is transferred. Even Oki of the forest almost compromises, or fall down; lend and may be pulled up.|
(average of about four seconds)
|Dwelling house is scattered in pieces in the area, and weak non-dwelling house is blown off without trace. Even the making of steel frame is collapsed. Train is blown off, and dozens of meters of cars fly in the air. A certain object falls 1 ton or more and is extreme in danger.|
(average of about three seconds)
|Dwelling house is completely blown off, and skin of Tachiki is stripped off. Car, train are lifted and fly and are transferred to terrible place. Object which there are several tons falls out of nowhere.|
(from the Meteorological Agency homepage)
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