Weather Explainers

There Are Two Types Of 'Lows' Meteorologists Talk About. Here's How They Create Your Weather.

Two Different Lows That Drive The Weather

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You've probably heard meteorologists mention low pressure, but did you know there are two different types that can generate the weather where you live?

While both can produce anything from snow and rain to thunderstorms, one of them also helps hurricanes generate their powerful winds.

Next we'll dive into a little meteorology 101 highlighting key points about the two types: surface lows and upper lows.

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Surface Lows

Surface low-pressure system example. The white lines are isobars, which are lines of equal surface pressure.

This is the most commonly mentioned low-pressure system, and as their name implies, they are located near the Earth's surface where we live.
They typically have fronts attached to them, with a cold front extending south of the low and a warm front extending to its east. Winds circulating around the low are in a counterclockwise motion in the Northern Hemisphere.
Their strength can vary from weak to intense and is measured using barometric pressure, where lower pressures indicate a stronger system. One type of intense surface low-pressure system you might have heard of before is a "bomb cyclone".
Surface lows in combination with their fronts create lift in the atmosphere, which means when there is sufficient moisture they can produce a variety of precipitation types from rain and snow to thunderstorms. Stronger surface lows also produce windier conditions.
You'll often see multiple circular lines surrounding a surface low on weather maps, as shown above. These are lines of equal pressure called isobars. Stronger and windier lows typically have more numerous isobars surrounding them.

Shown is a model example from Hurricane Milton in October 2024. The white lines are isobars surrounding its center of surface low pressure.

Hurricanes are a type of surface low-pressure system, but the are not associated with fronts. The most intense hurricanes are the strongest surface lows on Earth. The lowest pressure in a hurricane is always found at its center, or in its eye. In general, a lower pressure means a more intense hurricane in terms of its winds and overall destructive potential.

Upper-Level Lows

Upper-level low-pressure system example.

As the name implies, these lows are located in the upper portion of the atmosphere, generally about 15,000 feet and higher. You might hear a meteorologist call it an "upper low", for short.
Upper lows are strongest in the mid-to-upper atmosphere, but they can also have a weaker signature near the Earth's surface.
They often form when a deep, southward plunge of the jet stream pinches off to form a pocket of cold air aloft with a counterclockwise circulation. That circulation usually shows up in vivid detail when viewed with satellite imagery.
Sometimes these upper lows become completely detached from the jet stream and move slowly for days at a time before weakening.
Since upper lows produce a lifting motion in the atmosphere like surface lows do, they contribute to cloud cover, snow, rain and thunderstorms when they overlap with sufficient moisture.
Slow-moving upper lows have historically produced serious flooding rainfall and heavy snow events. That's because their sluggish motion can allow precipitation to affect the same area for an extended period of time.

Chris Dolce has been a senior meteorologist with weather.com for over 10 years after beginning his career with The Weather Channel in the early 2000s.