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HABYTIME MINI LECTURE 45: STORM RELATIVE WIND

METEOROLOGIST JEFF HABY

The wind “felt” by the storm is called the storm relative wind. An analogy is driving a car 50 miles per hour into a 20 mile per hour wind. The wind sensed by the car is a 70 mile per hour wind. A storm moving into the wind field will result in an addition of the storm motion to the wind interacting with the storm. A storm can move in a different direction as compared to the low level wind when directional shear with height causes the storm to be influenced by the overall wind direction interacting with the storm. For example, winds from 700 to 300 may be strong from the west. While the wind at the surface may be strong from the southeast, the storm motion will be heavily influenced by the west winds aloft.

Storm relative wind is important since it can allow a storm to inject energy and moisture faster than it could otherwise. Strong winds moving into a storm can produce a greater Helicity, stronger convergence and stronger moisture convergence. An increase in heat, moisture and momentum can be supplied to the updraft when the storm relative wind is stronger. The stronger storm relative wind will also enhance speed and direction wind shear which contributes to horizontal vorticity.