I cannot understand for the life of me the idea of low pressure vs high pressure in the atmosphere. Example: hurricane Milton has one of the lowest pressures ever recorded. Tried watching videos, reading, etc. Seems counterintuitive that low pressure = bad weather and high pressure = good weather?
In: Physics
The hurricane acts like an air pump, pushing air, creating high pressure where the air is going and leaving low pressure behind. As the hurricane loses energy and the storm dissipates, the pumping action dies and the pressure imbalance does away.
Low pressure pulls clouds and moisture towards a location, we say there’s a low pressure system moving in. Means clouds and likely rain.
A high pressure system is the opposite, it pushes clouds and moisture away so you end up with more sunshine.
By saying Milton has the lowest pressure means it’s bringing or pulling in a lot of moisture, which means heavy rains.
Low pressure air is warm, High pressure air is cold.
When you have warmer air, it can hold on to more evaporated water. More evaporated water in the air (humidity) makes it easier for rain clouds to form. Warm air also has a tendency to rise above cold air, which carries the humidity upwards allowing it to cool and form clouds. It takes time for cooler air to fill the space left by the warm air rising, so you get a low pressure area.
Cold air doesn’t like to have very much evaporated water in it. Less water in the air means less cloud formation, especially since cold air likes to sink towards the ground. This sinking air causes a high pressure area since it takes time for the air to spread out.
Hurricanes turn everything up to 11, and lower pressure in the eye of the storm means the air is warmer and evaporating more water to add to the strength of the storm.
Hope that helps.
Low pressure air is warm air. Warm air ascends into the sky like steam from a pot of boiling water. The ocean heats the air and it soars into the sky. As warm air goes up, other air blows in to replace it. The air blowing up and blowing in make it very windy.
High pressure air is like putting a lid on the pot of boiling water. The air is trapped and doesn’t blow around.
The atmosphere consists of blobs of high pressure air moving and bumping into each other. Each of the blobs has a center where the pressure is highest, and as you move towards the edge of the blobs the pressure goes down. It is lowest at the boundaries between blobs. It is the interaction of these blobs, which have different temperature and humidity profiles, along their low pressure boundaries which usually causes our more dramatic weather events. At their centers, the blobs are pretty stable so we see calmer weather there.
Low pressure means that the density of the air is lower there, and that air is rushing inwards and upwards to fill that spot. As air rushes in and upwards, it brings in wind as well as water vapor, which condenses and then forms rain and storms. This vacuum can also create a vicious feedback loop. The air closer to the ground is typically warmer, and it cools off as it ascends, which creates even more condensation and creates convection in the stronger storms as this cooled air moves away at high altitudes and begins to sink, causing more warm air to fill its place.
High pressure is the opposite. Air is moving outwards and downwards. While this can create high winds too, they aren’t usually as strong and rarely produce any sort of weather as cool dry air is being pushed downwards where its typically warmer.
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