LtMarvel
07-11-2009, 01:22 AM
So after the Superman festival, my family drove back to Missouri via an alternate route. We drove across route 13 through Carbondale. I started to notice a pattern: utility poles were down and signs were damaged (one programmable sign was tilted and now said "Ouch!"). Stopped at Arby's for lunch. I asked, and the worker said it was an inland hurricane (and you should have seen it before they cleaned the mess up!).
After checking out some Youtube vids (http://www.youtube.com/watch?v=EGJmOeDEBtw&feature=related), I went to the National Weather Service Site (http://http://www.crh.noaa.gov/pah/?n=southildamage). (Check out the pictures at the bottom!) They said the May 8 event was probably a Derecho. (ABC News just did a story on Derecho the week before!)
Anyway, I can see why the local girl called it an inland hurricane: Check out the eye!
http://www.crh.noaa.gov/images/pah/may8_2009/web_050809eye.jpg
And the NWS has a data map showing top wind speeds (Metropolis is right across from Puducah)...
http://www.crh.noaa.gov/images/pah/fxc/may8wind.png
They don't know for sure what the storm was.
What was it?
First, we may want to start out with what it was not. It was not an inland hurricane, although it may have felt like one. A hurricane is tropical in nature, this system that we experienced was convective. It was not a large tornado. Although there were several small tornadoes embedded within the widespread damaging winds.
The storm system is classified as a Derecho. If you want to learn more about derechos, there is a nice web site put together by the Storm Prediction Center. (http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm) This derecho would probably be determined to be a progressive derecho (http://www.spc.noaa.gov/misc/AbtDerechos/derechosqlns.htm#progressive)
However, this was not your typical derecho. Often on these types of systems in the northern hemisphere, a bookend vortex, or comma head develops on the north side of the system. The comma head usually acts like a large paddle wheel on a boat and helps to focus strong winds in behind the bowing squall line. A large portion of the damaging winds occurred on the southwest and southern end of the comma head.
Although it is still under study, it appears that at least some of the tornadoes in this case occurred with the comma head. This is not unusual, in fact research work in the 1980s documented a case of a derecho that moved through central Illinois in which tornadoes were associated with the comma head.
The system that moved through on May 8 had an unusually large bookend vortex. Numerical simulations completed in the early 1990s and some observational studies documented commahead vortexes were on average 12 nm in diameter. The comma head on the May 8th storm was 30 to 40 nm in diameter. In fact, this is the largest bookend vortex that some experts have seen in their careers. This will be the subject of more in-depth research for years to come.Bold emphasis mine...
After checking out some Youtube vids (http://www.youtube.com/watch?v=EGJmOeDEBtw&feature=related), I went to the National Weather Service Site (http://http://www.crh.noaa.gov/pah/?n=southildamage). (Check out the pictures at the bottom!) They said the May 8 event was probably a Derecho. (ABC News just did a story on Derecho the week before!)
Anyway, I can see why the local girl called it an inland hurricane: Check out the eye!
http://www.crh.noaa.gov/images/pah/may8_2009/web_050809eye.jpg
And the NWS has a data map showing top wind speeds (Metropolis is right across from Puducah)...
http://www.crh.noaa.gov/images/pah/fxc/may8wind.png
They don't know for sure what the storm was.
What was it?
First, we may want to start out with what it was not. It was not an inland hurricane, although it may have felt like one. A hurricane is tropical in nature, this system that we experienced was convective. It was not a large tornado. Although there were several small tornadoes embedded within the widespread damaging winds.
The storm system is classified as a Derecho. If you want to learn more about derechos, there is a nice web site put together by the Storm Prediction Center. (http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm) This derecho would probably be determined to be a progressive derecho (http://www.spc.noaa.gov/misc/AbtDerechos/derechosqlns.htm#progressive)
However, this was not your typical derecho. Often on these types of systems in the northern hemisphere, a bookend vortex, or comma head develops on the north side of the system. The comma head usually acts like a large paddle wheel on a boat and helps to focus strong winds in behind the bowing squall line. A large portion of the damaging winds occurred on the southwest and southern end of the comma head.
Although it is still under study, it appears that at least some of the tornadoes in this case occurred with the comma head. This is not unusual, in fact research work in the 1980s documented a case of a derecho that moved through central Illinois in which tornadoes were associated with the comma head.
The system that moved through on May 8 had an unusually large bookend vortex. Numerical simulations completed in the early 1990s and some observational studies documented commahead vortexes were on average 12 nm in diameter. The comma head on the May 8th storm was 30 to 40 nm in diameter. In fact, this is the largest bookend vortex that some experts have seen in their careers. This will be the subject of more in-depth research for years to come.Bold emphasis mine...