tornadoe

TORNADOES

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DESCRIPTION OF TORNADOES

CONDITIONS OF DEVELOPMENT

CONSEQUENCES

PERIODS AND REGIONS

   - LOCATIONS OF TORNADOES

          In the United States

          In France and Belgium

    - PERIOD OF TORNADOES

PHOTOS AND ANIMATIONS

PERIODS AND REGIONS

LOCATIONS OF TORNADOES

On earth, there are tornadoes in many countries. Their intensity vary by region. Parts of Western Europe are slightly affected by the tornadoes that are generally low intensity. In Australia, which is not spared by the tornadoes, they quickly take the color of sand they suck and causing little damage. The countries of Asia face very high intensity tornadoes (F5). In Africa, there are high intensity tornadoes in tropical regions. South America is less concerned and even though they are not a major plague, tornadoes kill and destroy.

	IN THE UNITED STATES

Tornadoes are found mainly in the central United States. This is by far the most affected countries. The majority of them are found in the region that includes Texas, Oklahoma, Nebraska, Kansas and Missouri. These States are nicknamed the "Tornado Alley". There are between 700 and 1200 per year ! If the United States experience many tornadoes this is that there are favorable conditions for their formation : the meeting of cold and dry air currents from the North Pole with warm, moist air from the Gulf of Mexico.

Distribution of tornadoes in the U.S.A.,
the red part is the "Tornado Alley".
Source NOAA of 1950-1995.

The percentage of tornadoes in USA according to their intensities

	IN FRANCE AND BELGIUM

From 1680 to 1988 France suffered 107 tornadoes, including 13 violent tornadoes (F4 and F5 on the Fujita scale). It is thought that the average number tornadoes each year could be estimated 180 in France. As we can show the table below the number of cases in the first period (1680-1959) shows a significant difference between (49 tornadoes in 280 years) and the second period (29 to 58 years). But that does not mean that the annual number of tornadoes has increased in France. This difference would come from a better collection of information since 1960.

PERIOD	FUJITA SCALE
PERIOD	F1	F3	F4	F5	TOTAL
1680-1959	23	17	8	1	49
1960-1988	27	27	3	1	58
TOTAL	50	44	11	2	107

Inventory of tornadoes in France between 1680 and 1988, according to J. Dessens

Percentage of tornadoes in France from 1680 to 1988 in accordance with their intensities.

Ainsi, la France a connu une quinzaine de tornades de forte puissance (F4 ou F5) depuis 1680, en frappant principalement une bande allant de Bordeaux à Lille en passant par Paris (plus de la moitié) qui est donc la zone la plus à risque, puis il y a le Jura et le Languedoc. Thus, France has been affected by a dozen violent tornadoes (F4 or F5) since 1680, hitting mainly a band from Lille to Bordeaux passing through Paris which is the area most at risk, then there are the Jura and the Languedoc. We observe them with an average frequency of about once every five years. The most common weak tornadoes (F0 or F1) occur on average twice a year by département.

Tornadoes occur in the plains, it is the reason that there are more to
the Northwest and in the Mediterranean and little in southwest,
in the east and in the center of France as we watch this map.

The frequency of tornadoes in France by department

In Belgium the tornadoes are more common than one would think. They act and often go unnoticed when they occur in the countryside. In 1949, of the writings were found and say that the period of 1880 to 1940 there had been 51 tornadoes. From 1982-2000, 62 tornadoes were reported in the press.

PERIODE OF TORNADOES

In the United States, the tornado season is in the spring especially in May. 41,58% of them occur in spring, 39,80% in summer, 11,98% in autumn and only 6,63% in winter. As in Europe more than 80% of tornadoes are observed between 12 hours and 18 hours because these are the hours that correspond to the formation of cumulonimbus and after the tornadoes.

In the Southeastern United States (Gulf of Mexico, Florida) and the East coast, we observed them from August to October, which could have links with the hurricanes. These tornadoes in coastal regions are accompanied by many waterspouts.

Click here to enlarge

Created and updated with the data of NOAA

Tornado season in France and Belgium is without dispute in the summer ! The maximum frequency of tornadoes in Europe are the months of June and August as we show the histogram of the number of monthly tornadoes in France and Belgium. Outside the maximum summer (June-August, with 48 events recorded), the tornadoes are quite properly distributed : 24 in autumn (September-November), 15 in winter (December-February) and 20 in the spring (March to May).

Some tornadoes recorded in Belgium during the 20th century according to the sources of MRI

Some tornadoes recorded in France from 1680 to 1988

As shown in the figure below tornadoes of power (F2 and F3) were observed in all seasons.

In France, tornadoes are especially observable between 16 hours and 17 UTC, and between 18 hours and 19 UTC.During the cold period (November-March), the turbulence occurs primarily around noon. But they occur later in the day, between 16 hours and 19 hours during the warm period from April to October, such as thunderstorms.

The histogram distributions and tornadoes according to hours on the abscissa and
the months on the ordinate. Numbers refer to the Fujita scale (F).
- SR : sunrise,
- SN : Hourly noon
- SS : sunset in Paris.

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