What are downbursts and how do they affect an area on the ground?

A tornado is a powerful updraft with intense winds that spiral inward. A downburst is the exact opposite. A downburst occurs when hail or large raindrops fall into dry air and melt or evaporate, cooling the air very abruptly and intensely. This quickly cooled air becomes much heavier than it was a few moments before, since cold air is denser and heavier than warm air. This pillar of cold air plunges towards the ground, literally falling under its own weight, and flows out of the bottom of the thundercloud.

In 1985 the Delta Airlines flight 191 was arriving at the Dallas Fort Worth International Airport. The evening the plane was approaching DFW there was a strong thunderstorm moving through the area. As the plane approached at a low altitude a downburst caused a microburst. Because of the microburst the plane was pushed downward and caused the plane crash. The debris was thown onto highway 114 and killed many people on the highway. 135 people were killed and 27 people survived but they were all injured.

What causes straight line winds and how

can you recognize them on a radar?

Staright line winds a basicaly a downburst. They are caused by significantly rain cooled air that, after hitting ground level spreads out in all directions producing strong winds. Straight line winds are also know as thundergusts and hurricanes on the prairuie. The winds can be as strong as a tornado. Straight line winds are produced in the downdraft momentum of the downdraft region of the thunderstorm. Whenever there is a strong updraft or downdraft the storm starts producing straight line winds.

     The picture above is a photo of a radar screen. Along the front of the storm line you can see a light blue line and then a green line in front of the yellow area. If in front of the main storm is a skinny light blue line, that means there are straight line winds along the line. The most intense part of the storm is red so the straight line winds occur before the intense section of the storm.

     

How do microbursts form in a thunderstorm?

A microburst is a strong downdraft, which causes an outburst of damaging winds that are forced outward near the ground. Many times a microburst is mistaken as a tornado. Microburst and tornadoes are sometimes confused because microbursts can send winds outwards at speeds up to 168 miles per hour, and can travel for about 2.5 miles. A microburst can cause the same amount of damage as an EF 4 tornado. An EF4 tornado makes roofs fly off houses, through cars and level small houses.

In order for microburst to form a downburst forms first. The downburst develops as the downdraft (strong downward current) moves toward the ground. As soon as the downdraft reaches the ground the highest winds are observed. Then during the outburst stage the wind curls as cold air from the downburst moves away from the point of impact with the ground. After the outburst stage the cushion stage begins. The winds start curling more and the winds begin to accelerate along the ground and then slows because of friction. The cushion stage is where the microburst occurs.

On May 2, 2009 a strong thunderstorm was passing over the Dallas Cowboys practice bubble. A microburst occurred ad collapsed the practice bubble. There were 70 people inside the bubble at the time it collapsed and 12 were injured and taken to the hospital.

Pictures

Pictures

Cowboy's Bubble collapsed because of a microburst

Downburst Diagram

Straight Line Winds Diagram

Diagrams of Microbursts

Downburst photo