Wednesday, July 11, 2012
Pictures of the recent storm June 29, 2012 Derecho photo by Samuel Shea, shelf cloud from the developing derecho in Chicago on June 29, 2012 taken in Woodridge, a western suburb of Chicago. Image Credit: NWS Meteorologist Samuel Shea, and used here with his permission. To see a larger version of this picture, click here.
Radar graphics of the derecho as it rolled over Maryland, Washington DC, and Virginia. Click on these to view larger version.
The screenshots above were taken from radar gifs from the CIMSS Satelite Blog Derecho moving southeastward from the Midwest to the East Coast
. There are a number of graphics and animated gifs there that you can view to watch the storm develop and roll over us. Photos there are in the public domain, but all credit
goes to the Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin – Madison, USA.
For even more detailed images, see the graphics and videos of the June 29 storm at EarthSky
. You'll find another dramatic photo at the NASA Earth Observatory
, with a description of what a derecho is, and why this one was so powerful and devastating:
The storm was what meteorologists call a derecho. Deriving its name from the Spanish term for “straight ahead,” derecho storms generally blow in one direction. They do not swirl like tornadoes, but they can cause tornado-style damage. The U.S. National Oceanic and Atmospheric Administration (NOAA) reported that the wind gusts in the June 29 derecho rivaled those of an EF-1 tornado.
The June 29 derecho occurred along the boundary of two air masses. In the north, the air was stable and dry. In the south, the air was unstable and moist. And hot. The Capital Weather Gang reported that, before the derecho began, areas affected by the southern air mass were facing record-high temperatures—109 degrees Fahrenheit (43 degrees Celsius) in Nashville, Tennessee, and Columbia, South Carolina; and 104 degrees (40 degrees Celsius) in Washington, DC. This hot, humid air provided fuel for the windstorm, which pulled the air skyward, then returned it in violent downdrafts.
Derechos have occurred before, and were actually given their name in the late nineteenth century. They occur most often in the Midwestern and Great Lakes regions of the United States, between May and July. To qualify as a derecho, a storm must cause damage over 240 miles (400 kilometers) and pack wind gusts of at least 58 miles (93 kilometers) per hour. The June 29 derecho damage extended over a much greater length, and the storm brought wind gusts of more than 90 miles (145 kilometers) per hour. The June 29 storm did not just qualify as a derecho. It was, according to the Capital Weather Gang, “one of the most destructive complexes of thunderstorms in memory.”
The NOAA-NWS-NCEP Storm Prediction Center web site has a Derecho Information page, including the July 1995 derechos, one of which leveled over five million trees in Minnesota. There is a lot of information on the Derecho Information page, including excellent graphics that demonstrate how a derecho works.
There are a number of weather related websites filled with useful information. One of my favorites is not one that follows the daily weather, but that follows cloud formations, The Cloud Appreciation Society, and particularly their Photo Gallery. They feature a photo of the month, and a place to submit your own photo. My favorite is just browsing through the photo slide shows. The photo collection comes from submissions from around the entire world.
These days the library collection includes the internet. If you need help finding information on the internet, be sure to ask your public librarian. We have lots of experience and training in how to look and especially important, where to look to find answers.