Chicago Area Derecho Events

[Chicago Storm]

I was recently reading back on one of the NWS LOT weather event write-ups on the 8/23/07 derecho. It mentioned derecho/QCLS related meso vorticies and the impact they have on increasing significant high wind and tornado potential. So with that in mind I decided to look into more of the derecho events that have occured in the area over the past several years, to see if they also featured numerous meso vorticies as the significant derecho in 8/23/07 did.

The first event I will decided to take a look at was the derecho on 8/4/08.

Environment:

A non-severe MCS pushed through the CWA during the morning-early afternoon hours which kept destabilization in check for the time. Clouds rapidly eroded allowing for rapid destabilization to occur. Initiation quickly took place in NE. Iowa around 20z as a disturbance pushed into Central Wisconsin. Some mode was initially multicell/linear, but transitioned to HP cell...before transitioning to linear as it pushed through the CWA. The environment ahead of the line featured high cape, decent deep layer shear, and was high in moisture content. MLCAPE values were up around 6000 J/KG, deep layer shear of 40kt+, PWAT's around 2.00", and SRH of around 200. There was also a nice Theta-E axis in the area, which the storms moved southeast along. The derecho composite (16) and Craven/Brooks Sig Severe (created using a combo of MLCAPE & deep layer shear) were very high...showing the significant potential. A second cluster of storms developed around midnight near Chicago. This cluster grew upscale into an MCS, which pushed southeast. A third MCS moved into the South-Central portion of the CWA during the early morning hours on the 5th.

Derecho/Meso Vorticies:

As the developing derecho moved into the far western portion of the LOT CWA there were already two clear meso vorticies, MV1 and MV2. MV1 was one of the longer lasting and stronger MV's with this event, though there was a lack of wind reports with it due to the rural areas it moved through. As the derecho progressed through the rest of the CWA there were numerous other MV's. MV2, 3, 6, 8, 9, 10, and 11 were all relativily short lived and most of which were fairly weak too. MV4 and MV5 were two more longer tracked and stronger MV's, with MV5 being the strongest of the two. MV5 went on to produce 3 tornadoes (EF-0, EF-1, EF-2) , localized intense swaths of significant damaging winds (Griffith, IN and vicinity), and a more concentrated area of severe wind reports. MV7 was also a fairly significant and produced two EF-1 tornadoes, localized intense wind damage, and a more concentrated area of wind reports...as MV5 did. MV12 was decent while over the area, but intensified as it pushed towards the lake shore and moved out over the lake. A 94mph wind gust was reported just offshore from Chicago associated with this MV. In addition to the meso vorticies, a few more things to note with this event were the strong RIJ, nice bookend vortex, and the amount of lightning that occured.

The below map shows MV tracks and wind(blue), sig wind(black), and tornado(red) reports:

The second cluster of storms to form developed on the backside of the main derecho's cold pool This cluster lacked severe reports given the main derecho's impact ont he atmosphere, but there were a few reports. There were also a few MV's with this complex, along with a few embedded supercell structures at the start. the Mv's were fairly weak and short in track.

The below map shows MV tracks and severe wind reports:

The third MCS moved in from N. Missouri/S. Iowa during the early morning hours. Several severe wind reports were logged, most of which were near MV tracks. There were two long tracked MV's, MV6 and 7. In addition to being long tracked, they were both quite defined from time to time. There was actually significant wind damage in Watseka associated with MV7, per LOT surveys. Most of the other MV's were fairly short lived and weak.

The below map shows MV tracks and severe wind reports:

As you can see by the maps and other information, there is without a doubt a correlation in between meso vorticies and an increased threat of significant wind damage and/or tornadoes in derecho/QCLS situations. This stands as the second derecho event to feature this in the Chicago area (8/23/07). Other events from the past few years will be looked at a posted in this thread.

[Thundersnow12]

very nicely done. I think this event ranks up near #1 for most of them that I can remember. Also another thing about this day that we have both talked about before but a bit OT, is how fast we destabilized after the morning convection.

Will be looking into 7/11 over the next few days when I get some free time.

[Chicago Storm]

The next event I decided to look into was the 6/19/09 high wind/derecho event.

Environment:

Leading up to the event, there were several severe MCS's that pushed throuh the previous night and into the morning of this day. Across the CWA, clouds and precip quickly moved out during the late morning to around mid day allowing fro destabilization to occur. Across the IA/MO/IL area another high CAPE, high deep layer shear, and high moisture content environment existed. The environment featured CAPE values in the 4000-6000 J/KG range, deep layer shear of 40-60kts, nice Theta-E advection, PWATS over 2.00", and 0-1km SRH around 200. Development quickly occured in two areas ahead of a disturbance moving through the Central Plains. The first area was in East-Central Missouri and the second was near the cold front in SE. Iowa/NW. Missouri. Both areas of convection eventually grew upscale into widespread damaging wind producing MCS's. Both MCS's ended up pushing into the CWA during the same time period, which lead to an unorganized mess across the area. What was the E. Missouri MCS entered the CWA from the southwest and eventually weakened across the heart of the area. The second stronger and more developed bowing MCS that developed along the weak cold front out west raced eastward into the area. A nice line of storms developed in WAA wing fashion that extended northeast out to SE,. Wisconsin. Several embedded cells within this line of convection featured meso's/rotation. Eventually this MCS also weakened into a mess of convection in the area, which pushed eastward.

Derecho/Meso Vorticies:

There were numerous meso vorticies with this event, most of which were associated with the line of storms that developed ahead of the Iowa MCS, from the northeast DVN CWA up into SE. Wisconsin. Most of these vorticies were fairly weak/shallow, short lived, and elevated. The most significant MV's were MV9, 18, and 19. While they were more intense, the intensity was short lived and the tracks were also fairly short. MV9 actually produced ended up producing an EF-1 tornado near Route 14 in Woodstock. Four other meso vorticies occured across the far southern portion of the CWA, associated with more discrete cells within the other MCS that pushed into the area form E. Missouri. As you can see on the MV tracks/damage reports map, most of the wind damage/high wind reports were not associated with any clear meso vorticies. Two factors probably lead to this...The first being the fact that most of the MV's were weak/shallow across the northern portion of the CWA in the WAA wing and the second being a messy convective pattern across the CWA given both MCS's were pushing through the area at the same time. Given how well developed the bowing MCS pushing in from Iowa was and the environment in the area, it's quite possible the threat would have been higher if the second MCS from Missouri had not existed.

The below map shows MV tracks, wind(blue, and tornado(red) reports:

[kab2791]

Wow, awesome thread. Great analysis Joe.

[Chicago Storm]

6/18/10....

Environment:

A non-severe MCS rolled through the entire CWA prior to 7AM. Clearing took place allowing for several hours of destabilization before the mid/late afternoon derecho. Another cluster of storms develops in Nebraska during the pre-dawn hours. This cluster quickly grew upscale into a bowing MCS and raced eastward. Along the way the MCS developed a well defined MCV and was producing damaing winds across Iowa, with a target on the CWA for after 1PM. Ahead of the MCS, the environment featured CAPE values of 3000-5000 J/KG, deep layer shear of 40-50kts, nice Theta-E advection, PWATS around 2.00". The complex moved through the area producing numerous severe wind/hail reports. After it passed, a second line of storms developed from NE. Iowa down into South-Central Iowa. This line quickly grew upscale into an bowing MCS, which races ESE across the CWA. Wind/hail reports with this line were limited due to the elevated nature of the convection thanks to the initial MCS.

Derecho/Meso Vorticies:

MV1 featured the longest track and was well defined on several occasions. MV13 was rather short in length, but also was well defined for a time. The same can be said about MV8, 9, 10, 14, and one or two more. The others were relativily weak and shallow. As you can see on the tracks/reports map, several wind reports were near the MV's. There is also a nice concentraion of wind reports across the central portion of the CWA where no MV's were visible. This area featured more of an outflow wind threat, ahead of the actual line of storms. This is the third derecho in the CWA to feature a higher impact near MV's.

The below map shows MV tracks, wind(blue), sig wind(black), and tornado(red) reports with the derecho/inital MCS:

The second MCS also featured several MV's. Any severe potential with this MCS was limitaed due to the atmospheric impacts from the first derecho, thus only a few severe wind reports were logged. Even with that, there were a few reports near MV tracks. Most of the MV's in this case were weak/shallow and a bit elevated.

The below map shows MV tracks and severe wind/tornado reports with the second MCS later in the evening:

[Chicago Storm]

6/23/10...

Environment:

Several severe MCS's pushed through during the night and into the morning hours. Precip and clouds stuck around across ther northern portion of the CWA into the afternoon. This set up a boundary between I-80 and I-88. Along and south of this area, the environment was really able to recover from prior convection. CAPE values jumped up to 3000-5000 J/KG, deep layer shear was 50kt+, 0-1km SRH or 100-200, and a high derecho and Craven/Brooks Sig Severe composite indicies. PWATS also increased to around 2.00". As the front and associated forcing pushed into the region, development occurd in E. Iowa and NE. Missouri. Discrete cells eventually developed along I-88 in N. Illinois too. some of these discrete cells had nice rotation and were tor warned. Eventually, the actvity in to the west in E. Iowa pushed in, and everything organized into an derecho which raced east across the CWA and beyond.

Derecho/Meso Vorticies:

As with many of the events looked at thus far, this event featured numerous meso vorticies. The most notable were MV2, 4, 8, and 19. The most significant and long track was MV2. It originated with one of the inital discrete cells and was sustained along the leading edge of the line across the entire CWA. This MV was well defined during most of its journey and helped produce significant damage and an EF-1 tornado near Matteson. MV4 also initially started out with a discrete cell before being maintained with the line. It also produced areas of significant damage. MV8 was also initially was a product of a discrete cell and produced significant damage in localized areas. MV9 developed along the line and produced localized significant damage (Most of the reports with MV19 occured in the IWX CWA). Most of the other MV's were fairly short in length, but were defined for a time. As you can see by looking at the MV tracks and wind/tornado reports map below, most of the wind reports were concentrated near the stronger/long track MV's (MV2, 4, and 8).

The below map shows MV tracks, wind(blue), sig wind(black), and tornado(red) reports:

[Thundersnow12]

6/23/10...

My buddy and I were on this storm just east of Amboy looking into at and it was quite elevated and never good get sfc based. Still a nice HP and went on to produce to crazy wind along 30.

[Hoosier]

Try 8/24/1998. I'm not sure what it was like in terms of mesovorticies but it was a pretty good wind event.

[Chicago Storm]

My buddy and I were on this storm just east of Amboy looking into at and it was quite elevated and never good get sfc based. Still a nice HP and went on to produce to crazy wind along 30.

I was on the cell that pushed into De Kalb Co.

It had a lowering for a time, before the damaging wind threat took over.

[Chicago Storm]

Try 8/24/1998. I'm not sure what it was like in terms of mesovorticies but it was a pretty good wind event.

I'll look into it. Hopefully full radar data is avaliable.

Thus far the following events have been covered

6/23/07 (LOT write-up)

8/4/08

6/19/09

6/18/10

6/23/10

Next in line will probably be...

5/30/04

8/3/04

8/2/06

7/11/11

8/24/98

9/21/10 (maybe)

With these added, pretty much all of the significant events in the 2000's would be taken care of.

[Hoosier]

I'll look into it. Hopefully full radar data is avaliable.

Thus far the following events have been covered

6/23/07 (LOT write-up)

8/4/08

6/19/09

6/18/10

6/23/10

Next in line will probably be...

5/30/04

8/3/04

8/2/06

8/24/98

9/21/10 (maybe)

With these added, pretty much all of the significant events in the 2000's would be taken care of.

Might want to look into 5/18/2000 also.

[Thundersnow12]

Next in line will probably be...

5/30/04

8/3/04

8/2/06

8/24/98

9/21/10 (maybe)

5/30/04 was a big ole high risk with a ton of svr reports I believe, like 900 maybe? 8/2/06 started in central KS and made it all the way up to here, and the one in 2004 was a MDT risk? all going off memory here lol

[Hoosier]

5/30/04 was a big ole high risk with a ton of svr reports I believe, like 900 maybe? 8/2/06 started in central KS and made it all the way up to here, and the one in 2004 was a MDT risk? all going off memory here lol

5/30/04 is probably among my top 5 memorable severe weather days on these boards. The large area that had favorable ingredients for tornadoes was really quite scary.

[Chicago Storm]

Might want to look into 5/18/2000 also.

That's one of the many events on my "If I get a chance" list...though it is near the top of that list.

[Chicago Storm]

5/30/04 was a big ole high risk with a ton of svr reports I believe, like 900 maybe? 8/2/06 started in central KS and made it all the way up to here, and the one in 2004 was a MDT risk? all going off memory here lol

All correct.

[Chicago Storm]

5/30/04 is probably among my top 5 memorable severe weather days on these boards. The large area that had favorable ingredients for tornadoes was really quite scary.

Nice line of discrete supercells from near Peoria to Rensselaer.

Already picked out at least 10 MV's looking at the loop off of KLOT.

[Hoosier]

Nice line of discrete supercells from near Peoria to Rensselaer.

Already picked out at least 10 MV's looking at the loop off of KLOT.

Yeah things got going early that day. IIRC there was a line that moved across northern IL during the morning. Then a break with another round in the late afternoon/early evening.

And wow, this tor area is even larger than I thought.

1630z outlook

20z outlook

[Thundersnow12]

Nice line of discrete supercells from near Peoria to Rensselaer.

Already picked out at least 10 MV's looking at the loop off of KLOT.

wanna fwd me that email so it saves me the time of going to get the data for that day? lol will pm you my email.

[Thundersnow12]

Yeah things got going early that day. IIRC there was a line that moved across northern IL during the morning. Then a break with another round in the late afternoon/early evening.

And wow, this tor area is even larger than I thought.

20z outlook

you should see the UA/sfc hand analyzed maps my friend did, pretty damn cool.

[Hoosier]

you should see the UA/sfc hand analyzed maps my friend did, pretty damn cool.

Although it happened before the era of the SPC 4-8 day outlook, it was one of those events that was fairly apparent from several days out. I can't remember what specific models had on specific runs but you just knew there was going to be trouble with an unseasonably strong system like that. Storm mode got messy during the evening...I have wondered what might've happened if that process was delayed a bit.

[Thundersnow12]

I wont ruin what Joe will put up for 5/30/04 but im doing a bit of a radar analysis of that afternoon/evening now and its pretty darn cool, between the few supercells that go up out ahead of the line from north of BMI and head into northwest IN. And then the line itself that munches the two furthest western supercells near PNT and then little cells go up in waa wing type fashion that just get sucked into the line along with a good amount of meso vorts up in northern IL.

Anyone with the time should def download the data from this day.

[Chicago Storm]

5/30/04...

Environment:

Meso analysis not avaliable prior to 2005. Refer to 12 and 0z soundings from ILX below...

12z ILX

0z ILX

Event:

The map will pretty much speak for itself....

This was another event that featured a severe MCS during the morning hours. Precip/cloud cover actually stuck around into the early afternoon across the estern portion of the CWA. Back to the west, discrete cells quickly developed from SE. Iowa down into C. Missouri. This activity grew upscale into a few line segments and raced northeast into the CWA. At the same time, other discrete cell developed from C. Illinois eastward into C. Indiana. These cells were eventually overtaken by the main line segments.

There were a large amount of meso vorticies with this event. About 5 or so across the southern portion of the CWA were associated with discrete supercells. Many of the MV's were long track and well defined. The most notable were MV's 1, 2, 3, 4, 8, 11, 12, 15, 16, and 21. Not only were they all long track, but they were very well defined alost the entire time they existed and featured most of the severe wx report concentration. MV4 (discrete cell) produced a tornado southwest of Dwight. MV21 produced 2 tornadoes in Livingston Co. MV 24 and 30 both produced possible tornadoes in far W. Indiana. Just about all of the wind and tornadoes reports occured near an MV track.

The below map shows MV tracks and wind/tornado reports:

[hm8]

Great thread.

Obviously we can see that there's usually a correlation between mesovorticies and a higher sig. wind threat. My question is why? Clearly the rotation would increase the tornado threat, by why would it increase the chance for straight-line winds?

[A-L-E-K]

Thanks for putting this together, in fact bookmarked and foldered for future ref.

[Thundersnow12]

this might be a bit harder with more events but something fun to do, Joe..but maybe we could put together a thread of analysis of tornadic supercells in northern IL from the last the 16 years (as far back as NCDC data goes)

The hard part would be finding good events that we don't know about.

[tornadotony]

this might be a bit harder with more events but something fun to do, Joe..but maybe we could put together a thread of analysis of tornadic supercells in northern IL from the last the 16 years (as far back as NCDC data goes)

The hard part would be finding good events that we don't know about.

I'd be willing to assist in this also...

[Thundersnow12]

I'd be willing to assist in this also...

Alright sweetness, was gonna send you a PM. This would be fun to do. I only know of a few events in the mid-late 90's so analyzing more would be a blast.

[Chicago Storm]

this might be a bit harder with more events but something fun to do, Joe..but maybe we could put together a thread of analysis of tornadic supercells in northern IL from the last the 16 years (as far back as NCDC data goes)

The hard part would be finding good events that we don't know about.

I'd be willing to assist in this also...

I'd be in on that.

[Chicago Storm]

8/3/04...

Environment:

Meso analysis not avaliable. Refer to 0z soundings from DVN and ILX below...

0z DVN

0z ILX

Event:

A severe MCS pushed southwest of the CWA during the morning hours. As for the main event, it developed in two parts. Part one developed during the morning across C. South dakota and the second piece around Omaha during the afternoon. Both areas raced eastward during the day producing widespread and sig severe wind reports along the way. Both MCS's merged as they entered the CWA, producing a ood amount of reports across the area.

As of meso vorticies, this event had few compared to other events looked at thus far. The most notable were MV's 1, 4, 5, and 8. MV1 almost tracked across the entire CWA and was fairly well defined for a time. MV4 became well defined out over Lake Michigan. As for wind reports, they were fairly scattered across the area with about half located near MV's. The other MV's were fairly weak and short lived. Also of note was the nice bookend vortex on the north end this MCS as it pushed through the DVN CWA.

The below map shows MV tracks and severe wind reports:

[Chicago Storm]

8/2-3/06...

Environment:

Some meso analysis is missing...So refer to 0z DVN and ILX soundings below...

0z DVN

0z ILX

Event:

Prior to the main event late on the 2nd/early on the 3rd, a broken line of scattered severe storms moved through the area ahead of a cold front during the evening on the 2nd. The main event developed in Kansas and quickly gew upscale into a bowing MCS. This complex raced northeast into the CWA after 3AM on the 3rd. Some of the storms from the evening were still ongoing at the time the main MCS was moving through.

As for meso vorticies, there were a few... All of the MV's were fairly weak and most were short in track (excluding MV1 and 2). MV6 was acually the most interesting out of the bunch. After it weakened a small and somewhat enhanced area of velocities/downburst winds rolled from the endpoint of it's track ENE through Yorkville and into N. Will Co, which is where the greatest concentration of wind reports was located.

The below map shows Mv tracks and severe wind reports: