The Transition Season: Dangers of High Winds
This is the time of year Mother Nature tries to balance out the warmer spring days with strong fronts that bring episodes of cold, Arctic air. The end result is usually strong winds that can cause major headaches. What you know about how strong winds develop can help protect you and your property.
Frontal systems are one of the driving forces behind spring wind storms. Thunderstorms tend to develop along a cold front and race in the direction the front is advancing. When the storms grow to a height in the atmosphere where they tap the fast-moving jet stream, they can produce what are known as straight-line winds. These thunderstorm gusts can exceed 100 mph and cause significant damage.
Two examples of such storms are downbursts, which are thunderstorms that produced localized wind gusts that can exceed 100 mph and derechos, which is a long-lived line of storms that produces wind damage across more than 240 miles of real estate and contain gusts exceeding 58 mph. Derechos are most common late in the spring through August. Downbursts and derechos often trigger the issuance of Severe Thunderstorm Watches and Warnings.
Even in a cold front’s wake and after the thunderstorms have passed, gusty winds can wreak havoc. The reason---strong low-pressure systems in spring produce a significant pressure change, which triggers gusty winds. These winds are most prominent in the Mountain West and Plains where gusts are strong enough to blow semi-trucks and buses off the road.
Wind Advisories and High Wind Warnings are issued ahead of these types of large-scale wind events. In the Southwest where the top layer of the soil is prone to blowing around in high winds, Dust Storm Warnings are issued when visibility is expected to be reduced to one-half mile or less and winds are expected to exceed 30 mph.
One particular type of Southwest dust storm isn’t associated with a large wind event but rather thunderstorms. A haboob occurs when the air pouring out of a thunderstorm sweeps up dust along its path. It forms suddenly without advanced warning and can be visible as a wall of dust and debris miles long and thousands of feet high. This type of dust storm only lasts a few minutes.
In the event of an approaching haboob, a motorist should safely pull off the road and set the emergency brake. If it’s not safe to pull off the road, slow down, turn on headlights, honk the horn occasionally so cars approaching who have limited visibility due to the dust can at least hear your car. It’s best to use the center line as a guide to help drive through the storm.
Post-frontal winds in spring are typically associated with very low humidity and can cause dry brush to catch fire with the smallest spark. A wind storm that moves over an area where a wildfire is already burning can easily help it expand in size. In this event, a Fire Weather Watch would be issued up to 3 days in advance of the winds and a Red Flag Warning within 24 hours of the expected high winds.
The coast is also vulnerable to high wind disruptions. Specifically, the Northwest Coast and the East Coast are known for spring systems that pack gusty winds. The immediate coastline, including the beaches, are most susceptible to property damage and even coastal flooding as wind coming off the water inundates low-lying spots adjacent to the shore. Although much less common by late March into April, a strong enough East Coast storm, known as a Nor’easter can even produce blizzard conditions across the interior Appalachians into interior New England.
Mountains act as a catalyst for an acceleration of wind. As mentioned earlier, the pressure difference along a frontal system is a large driver of gusty winds. As these winds sweep down a mountain range, such as the Rockies, the air warms and accelerates. An example of this is a Chinook Wind that occurs when wind sweeps down the Rockies into the Plains. Gusts exceeding 40 mph are common in Chinook winds and temperatures can warm significantly, quickly melting any snow that may have been on the ground following a storm system.
Not to be outdone, spring is the tail end of the Santa Ana wind season in southern California. These winds occur when a strong high pressure moves into the Great Basin, usually following a cold front. A strong east wind accelerates down the mountain passages and through the canyons of southern California in a Santa Ana event. These winds are known for producing hot weather, major property damage and bring a sharp increase in wildfire risk due to the dry nature of the airmass.
Knowing the dangers and hot spots for gusty winds in the spring will hopefully help keep you, your car and property better protected in the event of rapidly changing skies.
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Story Image: A cherry tree seen blowing in the wind. (Courtesy of Wikimedia Commons)
