Wednesday, August 21, 2019

Downburst! Close Call at Reagan National Yesterday

This dramatic video of a commercial airliner doing a missed approach at Reagan National at 5:27pm EDT yesterday was taken by Dave Statter (@STATter911).

The photo (below) is of the rain curtain associated with the downburst at it approached Reagan National Airport. In a downburst, high winds begin as the rain arrives. Trees were toppled minutes before it hit the ground at Anacostia about two minutes before this screen capture.

Dave's video (above) depicts the missed approach. The jet (circled) is making final approach to Runway 19. The leading edge of the downburst is beginning to move across the runways.
click to enlarge
The plane was about to land. Two other planes are waiting to takeoff at the end of the runway.

The plane, now inside the downburst, makes a missed approach and starts to climb out.

The plane is now behind the building in the background. I enhanced the contrast of the rain. 
The arrows show the wind flow. Wind shear is a rapid change in wind direction and/or wind speed. That was certainly the case here. Trying to land in those strong, shifting winds could have led to a catastrophe. Downburst winds flow down from the thunderstorm and then spread out near the ground. The wind shear was so strong, the rain flowed upward and made the tell-tale "curl" at the downburst's leading edge.

The plane was safely on its way. The crew made an excellent decision not to land.

Here is the wind data from the Terminal Doppler Weather Radar at the time of the missed approach. "R" is Reagan National. The downburst winds were moving across the runways as the missed approach occurred.
There were actually two downbursts. One near Anacostia and a second (that would turn into a violent downburst) was just striking the ground near Suitland.

FYI: Here is the violent downburst at Suitland at 5:33pm. There was at least 80 knots of wind shear.
The downburst at Reagan was weakening. This image is from the Reagan Terminal Doppler Weather Radar, one of the essential elements of the downburst warning system for aviation.

On July 2, the Washington Post's Capital Weather Gang published an article I authored pertaining to the 25th anniversary of the last downburst-related commercial airliner crash and how meteorologists worked to put an end to those tragedies. I don't know whether the crew received a wind shear alert or whether their training was the basis for their missed approach. Regardless, the system worked yesterday and everyone was safe.

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