Storm is a very strong wind within a large scale weather system, a depression. The area within a depression where storm force prevails is called the storm field. Storm is defined as wind with a force of 9 or more on the Beaufort scale. This means that the average speed of the wind reaches a speed of at least 75 km/h for 10 minutes. If the wind speed is at least 90 km/h on average over 10 minutes, then this is referred to as a severe storm, wind force 10. An average speed of 103 km/h is referred to as a very severe storm, wind force 11. This entry is included in the table for the Netherlands. from at least 100 km/h.
Wind gusts or gusts
Wind is never constant and contains periods in which the speed can be considerably higher. During gusts, the speeds of a storm are generally a few tens of km/h higher. However, gusts are short-lived and therefore cannot be named according to the Beaufort scale, which is based on average wind speeds.
Storm in the language
The term "storm" can also be used metaphorically, for example in the saying "Whoever sows wind will reap storm." Or, "this is a storm in a teacup" (it's not about anything).
Breezy winds with peaks of ≥56 knots (>28 m/s, >100 km/h).
In the winter half year, the criterion of ≥65 knots (>33 m/s, > 120 km/h) also applies in the coastal strip.
Location: at least two of the five coastal stations (Vlissingen, Hoek van Holland, IJmuiden, Den Helder, Terschelling) or inland over an area at least the size of the standard area of 50 × 50 km, or a coherent band with a length of 50 km .
This is the criterion per entry of the weather alarm that came into effect on February 1, 2010.
Origin of a storm
Storms can occur all year round in the Netherlands and Belgium, but the chance of a major storm that rages for a long time is greatest in the period from October to March. The temperature differences between the northern and southern parts of the northern hemisphere are then greatest, which means that the air pressure differences are also large and active depressions arise. Once the atmosphere is restless, a strong westerly air current at an altitude of 9 to 10 kilometers in the atmosphere (jet stream) can reach our shores one storm depression after another. Stormy weather can sometimes occur for two weeks in a row.
How heavy a storm becomes is not so much dependent on the air pressure that reaches the depression in the center of the storm, but is mainly determined by the magnitude of the air pressure differences in the vicinity of that center. A low barometer reading will therefore not always lead to a storm. With a rapid change in air pressure, the wind usually increases considerably. The area with the greatest pressure differences and the strongest winds is usually southwest or west of the storm depression. The heaviest storms in the Netherlands and Belgium are therefore caused by depressions that cross the North Sea. If the core of the depression moves just south, the wind field will also pass south and the south-westerly storm will not pass. Due to a small change in course of the depression, the storm could miss the Netherlands or Belgium at the last minute. Such a change or an increase in storm often only becomes apparent at the last minute. The meteorologists therefore closely monitor the developments of a storm and adjust the weather forecasts if there is reason to do so.
A north-westerly storm is extra dangerous in Flanders, the Netherlands and northern Germany because it pushes up the water in the North Sea.
The combination of a northwesterly storm with a spring tide has been responsible for several major floods in the Netherlands. These included:
the second Saint Elizabeth's flood (1421)
the storm surge of 1682
the dramatic Christmas flood of 1717
the flood of 1953. When the