It is important to remember, not all damaging thunderstorm winds are tornadic. Thunderstorms are capable of producing equally destructive and life-threatening thunderstorm winds, commonly referred to as straight line winds. In general terms, straight line winds refer to winds that are not associated with rotating winds in a tornadoes. Instead, they move forward along the ground in a straight fashion. The word "derecho" comes from Spanish origin and means "straight ahead". When strong winds exiting a cluster of thunderstorms produce a widespread high wind event, meteorologists sometimes refer to that event as a derecho. The winds associated with derechos blow straight ahead, or are straight line by nature.
Lines of thunderstorms that develop across Texas are capable of producing straight line wind speeds in excess of 100 mph. Winds flowing out of these thunderstorms accelerate ahead of the line of storms along what is termed the gust front.
Downbursts, another type of straight line wind, are strong downdrafts of air in a single thunderstorm that accelerate downward and produce an out-rush of damaging wind on or near the ground.
There are two types of downbursts - microbursts and macrobursts. The microburst is short-lived and of great concern to the aviation community. It produces strong winds in an area less than 2.5 miles in diameter. In contrast, macrobursts are longer-lived and are capable of producing extensive wind damage across areas larger than 2.5 miles in diameter.
Straight line thunderstorm winds occasionally can reach speeds in excess of 100 mph. These types of winds are intense enough to uproot trees and destroy buildings. If these winds occur in conjunction with large hail, even more extreme damage can occur, such as causing holes in the sides and roofs of houses, or destroying crops and other vegetation. Often, because of the widespread and significant nature of resulting damage, many people mistakenly believe they have been in a tornado. In reality, they have experienced a straight line wind event, comparable in strength to a weak tornado. So how can we protect ourselves during straight line wind events?
Identifying the approaching high wind is a first step in this process. As a downburst impacts the ground and the damaging straight line winds begin to spread out, a curled area of dust or rain, referred to as a "dustfoot" or "rainfoot" may be evident. In the curl of a dustfoot or rainfoot, high winds may be occurring. Other indications of straight line winds may include a wall of approaching dust or rain, or the presence of shelf or roll clouds, both associated with thunderstorm outflow. Monitoring weather information from KTRE -TV, ktre.com, and from the NOAA Weather Radio will also help keep you informed of many of the approaching straight line wind events in your area.
Lastly, treat straight line wind events the same as you would an approaching tornado. Seek shelter in a reinforced shelter, on the lowest floor in an interior bathroom or closet, away from all windows. Always cover your head to protect against the impact of flying debris that can injure.
By developing a severe weather safety plan that includes learning how to identify approaching high wind events, knowing how to monitor your local severe weather information, and determining those locations in your home where you can take shelter, you and your family can greatly increase your chances of remaining safe during the times when damaging and life threatening straight line wind events impact your area.
For questions about straight line winds or any other weather information, e-mail firstname.lastname@example.org.