Derecho?

[Chad Cowan]

A SEPARATE AREA OF WIND DAMAGE SUGGESTIVE OF WINDS OF 80 TO 100 MPH WAS FOUND IN THE 4000 BLOCK OF NORTH SHERIDAN IN THE WRIGLEYVILLE AREA WITH EXTENSIVE TREE DAMAGE AND SEVERAL UPROOTED TREES IN THIS AREA[/COLOR]

I posted this in the 8/23 DISC thread, but for those who didn't see it, I went to this area and did a damage survey. I was amazed by the size of the trees that were blown over and snapped in half. I did notice that the largest area of trees that were uprooted were on the southern edge of the cemetery and were blown over to the north. Yet, two of the largest downed trees in different areas were blown down to the east.

I think that the 80-100 mph estimate from the LOT damage survey may be overdoing it a bit. The ground in this area is extremely saturated, having received over 10 inches of rain this month (which allows for lesser wind speeds to uproot trees) and I did note some significant rotting in the damaged trees. Nonetheless, I do believe this event qualifies as a derecho due to the widespread nature of the event. I think everyone will agree that the term derecho is used too loosely and that a more detailed definition is needed.

 

[Andrew Sorce]

Heres a link to an amazing Derecho that I experienced during my first week of college. I was majoring in meteorology so it was a perfect primer to my studies. Its a decent read...enjoy.

http://www.spc.noaa.gov/misc/AbtDerechos/casepages/sep71998page.htm

 

[Brandon Sullivan]

Yep. Im gonna agree with most everyone, it was definitely a derecho.

 

[Andrew Pritchard]

Yep. Im gonna agree with most everyone, it was definitely a derecho.

Yep? Care to add why? Or just because that team is winning?

Well, Brandon convinced me, I'm on the "yes" side now.

I suppose I'm still just somewhat on the fence with this event. Without a clear cut standard no one will be changing sides or anything. By what the SPC page defines, I suppose it would be one. But their definition basically covers any bow echo or squall line that develops and produces severe level winds. I think if you go by the generally accepted "idea" of a derecho, it does not. I've seen the photos and heard the reports, yes, this bow echo produced significant wind events. Yes, it crossed a portion (though small) of three different states. But still, (and maybe I'm just beating a dead horse) I just don't think it was a jaw dropping event. It quickly crossed a 200 mile or so path and was done in several hours producing patchy significant wind damage. Before I start putting this event up there with the best I'd still like to have seen the event last several hours more (as Darin I believe it was said, derechos are generally those events that can last half a day or more) and often the entire segment produces significant winds, not patchy areas of enhanced wind damage.

When I envision a derecho, I envision it blowing EVERYTHING down, not just "well such and such city had estimates of 80-100 mph!"

 

[Darin Kaiser]

Just a quick link from the NWS in Lincoln concerning straight line wind damage that was determined as a fast moving microburst.
http://www.crh.noaa.gov/crnews/display_story.php?wfo=ilx&storyid=9927&source=0

 

[Rich Thompson]

In response to a question from another forum (from Chad C?):

IMHO, the only reason to worry about labeling an event a "derecho" is *if* that category of storms suggests something meteorologically meaningful about the storm system in question. Does calling the 8/23 event a "derecho" tell us anything about the event, other than some arbitrary definitions w.r.t. wind damage reports? It's my personal opinion that the derecho definition is getting stretched on the low end, such that more and more events qualify as derechoes. In other words, a "derecho" doesn't mean the same thing to me that it used to mean. I can say the same for an "outbreak" or a "wedge" tornado.

Rich T.

 

[Kevin Bowman]

sorry for bumping an old thread but found this when going through data on this storm

300pm Day 1 Convective outlook
MIDWEST...
ORGANIZED BOW ECHOES HAVE ALREADY PRODUCED WIND GUSTS OF 80-100 MPH ACROSS PARTS OF NRN IL. THIS ACTIVITY WAS ALONG THE LEADING EDGE OF COMPACT MID LEVEL IMPULSE AND ASSOCIATED WIND MAX OF 40-60KT. VISIBLE IMAGERY DEPICTS INTENSE SURFACE HEATING ONGOING AHEAD OF THE SEVERE STORMS WITH AN AXIS OF VERY UNSTABLE AIR OVER NRN IND...SRN LOWER MI AND WRN OH. GIVEN ONGOING STORM ORGANIZATION AND INTENSITY...AND SUPPORTIVE UPPER FORCING...DERECHO EVENT ACROSS THE UPPER MIDWEST APPEARS LIKELY TO CONTINUE THROUGH THE REMAINDER OF
THE DAY. ACTIVITY SHOULD BEGIN TO GRADUALLY SUBSIDE IN INTENSITY AS STORMS MOVE TOWARD SWRN ONTARIO AND THE ERN GREAT LAKES AREAS THROUGH LATE EVENING.

the big thing is "appears likely to continue", as in its already happening and not forecast to happen.

most of the metro area was hit 30 minutes after this day 1 was issued

 

[MatthewCarman]

Here is a idea, call the Derechos that are realy bad and last more than 24 hours Super Derechos. That way people might still think they are a rare line of destructive storms and then we could still use the term Derecho for a line of storms not as destructive and for strong Bowecho's that could be considered a Derecho.

Just my thoughts on the topic.

 

[Tomas Pucik]

Why super derechoes?

There are sets of conditions, that convective windstorm must fulfill ( I will not state them, as is is easy to look them up on the internet ) to be refered to as derecho. I think that derecho is a name that anyone relates to a very damaging event.

Btw, very little number of derechoes can last more than one day. Actually, as stated by Wakimoto, most of derechoes last around 9 hours and observed duration times were between 2.3 to 20 hours.
So anything lasting longer would be probably very, very rare.

Also, in case of progressive derecho, it is possible to have series of downburst in ONE bow echo segment to actually deal most or all of the wind damage that occurs with derecho.