United States

Tarpocalypse 2012: That's No Derecho, English

July 06, 2012; 12:02 PM

We put up an article with this video of ballplayers trying to keep a tarp on a baseball field in Joliet, Ill., last Friday night.

Some netizens said it was the Super Derecho that caused these high winds, but after investigating it, I have found that it was not. Instead, it was another thunderstorm that developed behind it (by 10 p.m., the derecho was already in Washington, D.C., as shown by the radar in the story). Here's what the storm looked like as it approached town (download radar loop):

This is the velocity shot, showing 50-knot winds at 247 feet (which is close enough to the surface to be accurate, normally radars are looking high into the sky but Joliet is right next to the radar site -- note the "cone of silence" where the radar cannot see above it).

By the way, guess what that pattern of missing data is to the left of the center of the radar? It's the interstates near Chicago, which have been masked out because they have a tendency to show up on radar at night when the beam gets reflected to the ground (and they show up as moving objects, since the vehicles are moving).

There were a number of local storm reports 3-5 miles north of Joliet indicating trees and power poles down, during this time. Also I show a radar loop of the particular storm that struck Joliet. Since the wind hits before it starts raining, it's likely that the outflow boundary, which was slightly ahead of the storm, is what we're seeing here (near the end of the video it starts raining). The highest wind gust in the area was 41 mph at a USGS station, although the Joilet airport also gusted to 38.

And in regards to the Super Derecho, the Amish have opinion on that, English. (reminded me of an old Simpsons episode where Homer accidentally builds an Amish barn: "Tis' surely no pool, English.")

If you want to know more about last week's "Super Derecho" please check out these blogs. The Roanoke and Capital Weather blogs were particularly interesting. The damage caused by this storm, and the wind gusts it produced, were not unlike the 2010 "Land Hurricane / Super Derecho" that I blogged about in May 2010, and we also just had a strong Derecho in Chicago last Summer.

ACCUWEATHER: http://ow.ly/c4dHc (Story) http://ow.ly/c4e0o (Photos)

NASA: http://ow.ly/c4dGg

*This blog erroneously says that the NOAA Derecho Climatology Study ignored East Coast derechos.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com