Author Topic: Tornadoes Derecho taking shape in midwest!  (Read 2866 times)

0 Members and 1 Guest are viewing this topic.

australiasevereweather

  • Guest
Tornadoes Derecho taking shape in midwest!
« on: 06 August 2009, 10:00:12 AM »
Derecho taking shape in midwest!
         



An  intense line of thunderstorms is screaming across the state of Illinois at this  time, leaving numerous severe wind reports in it's wake. Trees and power poles  have been taken down in both Iowa and Illinois, and structural damage has been  reported from McDonough County, Illinois.

         

http://67.225.179.1/component/content/article/1-latest-news/1001-derecho-taking-shape-in-midwest
« Last Edit: 06 August 2009, 10:16:14 AM by Jimmy Deguara »

Offline Jimmy Deguara

  • Australian and Tornado Alley storm chaser
  • Administrator
  • Wedge tornado F5
  • *
  • Posts: 2,218
  • Gender: Male
  • Storm Chaser since 1993, Tornado Alley 2001
    • Australia Severe Weather
Re: Tornadoes Derecho taking shape in midwest!
« Reply #1 on: 06 August 2009, 10:17:54 AM »
How defined is the bow in the radar image - you can imagine the change in shear along the gust front! I wonder if any book-end vorticies occurred along this derecho event.

Regards,

Jimmy Deguara
-------------------------------------
Australian Severe Weather
www.australiasevereweather.com

Australian Thunderbolt Tours
www.thunderbolttours.com

Phone  0408 020468  (International :  61  2  408 020468)

Offline Colin Maitland

  • Barrel tornado F4
  • *
  • Posts: 614
  • Gender: Male
Re: Tornadoes Derecho taking shape in midwest!
« Reply #2 on: 06 August 2009, 11:00:48 AM »
Jimmy, would this derecho event be classified as a "progressive" derecho or "serial" derecho? I have been reading about them but some times it doesnt fully sink in until someone can say this is_________ ( whatever) ,then you start to understand a bit better. ( I dont think it is hybrid, but now I have said that I'll be wrong)

Thanks
Col

Late edit, I forgot to say that I was tending towards "progressive" if I have read it right
« Last Edit: 06 August 2009, 11:30:10 AM by coltan »

Offline Jimmy Deguara

  • Australian and Tornado Alley storm chaser
  • Administrator
  • Wedge tornado F5
  • *
  • Posts: 2,218
  • Gender: Male
  • Storm Chaser since 1993, Tornado Alley 2001
    • Australia Severe Weather
Re: Tornadoes Derecho taking shape in midwest!
« Reply #3 on: 06 August 2009, 02:21:57 PM »
Coltan,

Can you look further in your reading and let me know:) I know it is a Derecho and I have seen two of them whilst in the United States but they are not too uncommon - however they cause massive damage! Some are very spectacular!

Regards,

Jimmy Deguara
-------------------------------------
Australian Severe Weather
www.australiasevereweather.com

Australian Thunderbolt Tours
www.thunderbolttours.com

Phone  0408 020468  (International :  61  2  408 020468)

Offline Colin Maitland

  • Barrel tornado F4
  • *
  • Posts: 614
  • Gender: Male
Re: Tornadoes Derecho taking shape in midwest!
« Reply #4 on: 07 August 2009, 01:25:41 AM »

The sight I was reading mostly from is  http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm

Jimmy, this is some of the information that I was reading, but I am a bit stumped, ( in reality it probably doesnt matter, just the fact that it is a derecho is bad enough, I am probably getting myself tied up to technically)

TYPES OF DERECHOS

Are there different kinds of derechos?
There are three types of derechos. One type is called a "serial" derecho and is produced by multiple bow echoes embedded in an extensive squall line (typically many hundreds of miles long) that sweeps across a very large area, both wide and long. This type of derecho is typically associated with a strong, migrating, low pressure system. An example of serial derecho with a very extensive squall line and with embedded smaller scale bow echoes is the one that affected Florida, Cuba, and adjacent portions of the Gulf of Mexico, the Caribbean Sea, and the Atlantic Ocean on March 12-13, 1993.

The second type of derecho is called a "progressive" derecho and it is associated with a relatively short line of thunderstorms (typically from 40 miles to 250 miles in length) which may at times take the shape of a single bow echo, particularly in the early stages of development. In some cases, the width of the progressive derecho and its associated bow echo system remain relatively narrow even though they may travel for hundreds of miles. An example of this is the "Boundary Waters-Canadian Derecho" which occurred on July 4-5, 1999. In other cases, the progressive derecho and associated bow echo system may start out relatively small with a narrow path. However, with time the bow echo system and progressive derecho grow in scale, and they may exceed 250 miles in width towards the middle and latter portions of their path. Initially, the line of thunderstorms may start out as a single bow echo, but as it evolves, it becomes a short squall line, typically with more than one bow echo segment. An example of such development occurred with the "I-94 Derecho" on July 19, 1983 and the evolution can be observed on Fig. 2 of that case page. The progressive derecho is often associated with a weak low pressure system but it may travel for many hundreds of miles along a path that is relatively narrow compared with the path of a serial derecho.

The third type of derecho is "hybrid" and may have mixed characteristics of both a "progressive" and a "serial" nature. For example, the "Southern Great Lake Derecho of May 30-31, 1998 was associated with a strong migrating low pressure system. However, the derecho path and the associated bow echo system had many characteristics of a progressive derecho event.

Thanks

Col