What would happen if you moved your hands in opposite directions? The pencil would rotate. Imagine you hold a pencil between your two hands. It’s a turning of the winds or a change in their speed with height. That part of the atmosphere is known as the Ekman layer.ĭue to the change in wind speed with height, there also can be friction between different layers of moving air. Air passing over this lowest kilometer (0.6 mile) or so to the ground “feels” the effects of surface drag. Trees, houses, cars and everything else serve as obstacles to the wind. But near the ground, air masses can encounter all sorts of things. In the air well above us, there’s little to slow down rushing pockets of air. When such strong winds hit land, they slow a bit. And as that eyewall moves across a site, the storm’s winds can explode within a matter of seconds. Whirling fury may neighbor quiet zonesĪ typical hurricane eyewall tends to be about 16 kilometers (10 miles) thick. Their winds also blow in many different directions. (They do that by scanning those clouds with Doppler weather radar.)īut eyewalls don’t just produce winds with epic speed. Scientists can actually gauge whether a storm is strengthening by probing how electrified its clouds are. That’s why eyewalls only spit out sporadic bolts when a storm is intensifying - when more air is moving in the upwards direction rather than around and around. In order to spark lightning, there need to be lots of straight-up-and-down rising motion. So while they reach the height of typical thunderstorms - 10 to 12 kilometers (6.2 to 7.5 miles) - the rising motion isn’t quite as strong, given that they’re circling like a merry-go-round. Parcels of air swirl slantwise into the storm, inward from all directions. National Weather Service, GR2 Analyst, M. Instead, the air plumes only blossom upwards thanks to extra-chilly air aloft. That means there is no real forcing mechanism to move the air sideways. Such storms form from vertical instabilities. Scientists refer to hurricanes are barotropic (Bear-oh-TROH-pik). Those conditions can serve to fuel quickly rising storm clouds. Warm sea surface temperatures and fairly unstable air are major ingredients in the recipe for a hurricane.
That’s one surefire sign that the air is unstable. This can create a localized plume of rising air known as an updraft. When the air near the ground is extra warm, it will rise up to pierce through some of the cooler air above.
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That’s why ice crystals may grow outside of windows of a cloud-level airplane - even when it’s a hot summer day at ground level. The atmosphere naturally cools the farther away you rise from the planet’s surface. Unstable air - turbulence and rising motion - is key to building and strengthening hurricanes. Their unstable winds can even spawn tornadoes by the dozens.
Their clouds can dump a meter (upwards of 3 feet) of rain - or more - on inland communities. When their direction is right, these can sweep destructive storm surges inland across coastlines. That’s saying a lot, because even the outer regions of hurricanes combine Mother Nature’s wildest weather. Explainer: Winds and where they come from
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