Weather and weather system

Low-pressure weather systems = depressions or cyclones. They are meteorological phenomena characterised by an area where the atmospheric pressure is lower than the surrounding regions. These low-pressure systems often form in the Atlantic, then move eastwards and are responsible for unstable weather. Low-pressure systems are associated with various types of weather conditions, including clouds, precipitation, and wind. A low-pressure system has lower pressure at its centre than the areas around it.

On weather maps, a low-pressure system is labelled with red L. They are often represented by isobars, which are lines connecting points of equal atmospheric pressure. Where isobars are closer together, the pressure gradient is greater, and conditions are windier.

High-pressure weather systems = anticyclones. Meteorological phenomena characterised by an area where atmospheric pressure is higher than the surrounding regions. As the cold air sinks, it warms up, which means it can hold more water, so there is no cloud formation or rain. Highs are associated with calm, dry and bright conditions.

On a weather map, you may notice a blue H, denoting the location of a high-pressure system. When analysing a weather map, meteorologists pay close attention to the location, size and movement of high-pressure systems, because they can have a significant impact on local and regional weather conditions. The interaction between high- and low-pressure systems can influence the development of weather fronts, which can lead to changes in weather conditions.

The weather front is a transition zone between two different air masses at the Earth’s surface. The fronts move over a few days guided by the direction of the current winds.

Warm air front : The warmer air mass pushes the cold air mass. But the process happens more slowly than cold fronts because it is more difficult to push the cold air which is denser.

Cold air front : is formed when a cold air mass quickly pushes a warmer air mass towards the troposphere.

Stationary fronts : is developed when cold or warm fronts stop moving. There are two air masses who push against each other, but neither is powerful enough to lift the other.

Occluded fronts : is when the cold and warm fronts follow each other. The occluded fronts are made at low pressure.

A hurricane is a rotating meso-scale (ie. smaller than an usual low-pressure system) low-pressure system born from two separated kinds of storms : the tropical storms, with winds under 63kph (39mph) and the tropical cyclones with winds over 63kph (39mph). As hurricanes may occur up to 12 times a year in the Atlantic Basin alone, they are actively watvh upon by weather institutes .

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Above 119kph, it can be rated on the Saffir-Simpson scale, using the one-minute-average wind speed 10 meters above the sea surface. Each step stands for a certain amount of damage that can be dealt by the storm in a certain wind span.

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Fun fact : the name of the storm vary along with the place it was born : Hurricane in the Atlantic Basin; Typhoon in the North Pacific and Cyclone anywhere else.

A tornado is a small-diameter column of rotating air developed within a convective cloud and in contact with the ground that can generate winds up to 500kph. Tornadoes most often occur in association with thunderstorms during the spring and summer in the mid-latitudes of both the Northern and Southern Hemispheres.

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Like hurricanes, tornadoes are rated on a scale : the Fujita Scale, they are rated from 0 to 5 accordingly to both their wind speed and damaged caused. As they was bias, the original Fujita Scale was later replaced by the Enhanced Fujita Scale.

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In absolute number, the United States has the most tornadoes but also the most violent ones, but they can happen in Europe too, England has the highest spatial concentration but they are far weaker than those of the United States. France is also one of the countries that records the most tornadoes in Europe, especially in its northern part.

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The blizzard is a North ice wind which goes along with a snowstorm. It happens in the middle altitude and the poles. It takes place in winter when the jet stream goes to the South. Also, when the North cold air mass meets a tropical warm air mass. And that creates violent winds which can form a storm.

For example: December 2022 in the East of North America.

A thunderstorm is a type of weather characterized by lightning and the loud sound of thunder. These storms usually happen with big, tall clouds called cumulonimbus clouds.

Thunderstorms can happen alone, in groups, or in lines, and they can cause dangerous weather conditions like heavy rain, floods, strong winds, and sometimes tornadoes.

Thunderstorms often come with quick changes in air pressure and temperature and can form quickly, making them a common and risky natural event in many places around the world.

A cumulonimbus is a type of cloud with significant vertical extent that is often associated with severe weather phenomena.

These clouds are typically characterised by a dark, flat base and an anvil-shaped top that can spread out horizontally over long distances.

Cumulonimbus clouds are responsible for the formation of various weather phenomena such as heavy rain, hail, lightning, thunder, and occasionally even tornadoes. They usually form in unstable environments where warm, moist air rises rapidly, cools, and condenses into massive thunderstorm clouds. These clouds are often associated with hazardous weather conditions and can cause significant damage when they develop into severe storms.