June 4th 2005:the lack of an extensive supercell development

[Andrea Griffa]

If someone doesn't remember, June 4th 2005 was the day of the HIAWATHA tornado in Brown County KS.
That day was characterized by an early convective development (21.30 Z) that didn't take to an isolated supercell development; if I remember right SPC outlook showed an high risk of severe thunderstorms for East KS, extreme SE part of NE and, NW MO, and SW Iowa.
Synoptic situation showed a short wave trough on W Nebraska with a strong mid level flow from S-SW on eastern part of Kansas.

http://www.spc.noaa.gov/exper/archive/even...4/500-oa-00.gif

At the ground, there was a low pressure system with the low put down in central Nebraska associated with a cold front extending from S-central NE till central KS and Ok panhandle.

http://www.spc.noaa.gov/exper/archive/even.../hpc-sfc-00.gif

At 21Z convection started in NE Kansas and a tornadic supercell rapidly developed in Brown county and at 21.20 and 21.30 two tornado were in the ground in Hiawatha.

But as rapidly brown county supercell developed, the other supercells in the lines merged and didn't permit an isolated supercell development leading to a bow echo and lewp development.

http://www.spc.noaa.gov/exper/archive/even...50604/rad18.gif

http://www.spc.noaa.gov/exper/archive/even...50604/rad24.gif

So wich are the causes of the lack of the isolated supercell development? As to me they have to be researched in the wind shear and the orientation of the boundary. BL-6km vector is nearly parallel with the orientation of the cold front. Thermodynamic setup was very good for a tornadic outbreak so I don't consider that.
Anyone has got an idea? Let's discuss about the case.

 

[Chris Hayes]

This was my last day of chasing last year, before I headed back to Ohio. I was parked in a parking lot with several other chasers for a couple of hours. In my opinion there was too much forcing or the cap wasn't strong enough. As soon as storms started to fire in SC/SE KS, the entire line let loose. There was only about an hour period of isolated storms. The most intense storm of that day, though it went HP if I remember correctly, was in southern Oklahoma. Day had some potential to be a big tornado day, but didn't deliever.

 

[nickgrillo]

There was way too much lift across much of the warm sector (which initiated rapidly developing storms by 21z). Instability was very strong to extreme (with at least 3000 j/kg mixed-layer CAPE) across most of the warm sector... Given the the very moist boundary layer (with mostly near 70F sfc Tds across eastern KS, ahead of the dryline). Deep-layer shear was pretty favorable for supercell mode, with 0-3km SRH (>150m2/s2) favorable for low-level mesocyclones / tornadoes. I (and quite a few others) felt that southern KS (along the DL) would have been a good place to be... A weak OFB was floating along the southcentral KS/northcentral OK border, which was very slightly increasing the low-level shear (given more backed sfc flow).

I thought the HIGH risk would easily verify, given the likelihood of widespread tornadic storms across northeast KS/northwest MO/southwest IA closer to the warm front. I really liked the southcentral KS area for chasing wise, given less convergence (and slightly stronger CINH) which would have favored more discrete storms. However, throughout the day... Storms continually had a problem becoming rooted, and continually fizzled out (they would show promise, get SVR-warned and blow apart). I was hoping storms would root onto an OFB and sustain themselves long enough to produce a tornado. After sitting and watching storms continually go up, and the updrafts getting chocked off (mushy piles of junk) -- storms began to fire further south along the sc KS/nc OK border region and earned TORs on them. So, we headed south... The storms very quickly merged and became an absolute mess (yet still producing a couple of low-contrast tornadoes, which a few chasers caught).

To sum it up... You had way too much lift for the already weak capping inversion that was in place across KS. If you would have had stronger CINH, then I believe more discrete activity could have formed. I still believed (and hoped) the day would feature discrete activity along the dryline, but it didn't.

<img src=http://www.spc.noaa.gov/exper/archive/events/050604/raobs/OUN_12_obs.gif>

This 12z OUN sounding showed a deep layer of CINH using a mixed-layer parcel, as well as strong instability. Look at the lack of 6km shear (33kts on this sounding -- which is borderline for supercell mode).

<img src=http://www.spc.noaa.gov/exper/archive/events/050604/raobs/TOP_00_obs.gif>

A TOP sounding at 00z shows extreme instability and very little CINH using both mixed-layer and surface-based parcels (this was just ahead of rhe cold front)... The sounding also shows extreme BL-6km vertical shear, as well as strong 0-3km helicity (215m2/s2) -- given the favorable veering flow within the boundary layer (with strongly backed flow near the sfc layer).

<img src=http://www.spc.noaa.gov/exper/archive/events/050604/raobs/OUN_00_obs.gif>

Now, further south at OKC at 00z showed stronger CINH (and instability) using both surface-based and mixed-layer parcels. Low-level shear is notably weaker (as well as slightly weaker, but still quite favorable 6km vertical shear) with a very messy profile between 675-850mb.

Updrafts would constantly go to mush piles on and on across southern KS and were never able to sustain themselves, as the lack in low-level shear resulted in the weaker updrafts (with very few storms containing sustained mesocyclones).

 

[Andrea Griffa]

Originally posted by Chris Hayes
This was my last day of chasing last year, before I headed back to Ohio. I was parked in a parking lot with several other chasers for a couple of hours. In my opinion there was too much forcing or the cap wasn't strong enough. As soon as storms started to fire in SC/SE KS, the entire line let loose. There was only about an hour period of isolated storms. The most intense storm of that day, though it went HP if I remember correctly, was in southern Oklahoma. Day had some potential to be a big tornado day, but didn't deliever.

You could be right. Anyway this is the Tpeka sounding of 12Z; it shows 450J/kg of CIN...00Z sounding, then, shows that cin has been take away.
It's somewhat strange that there was a so rapid erosion of the cap in such few hours...

 

[nickgrillo]

Originally posted by Andrea Griffa+--><div class='quotetop'>QUOTE(Andrea Griffa)</div>

You could be right. Anyway this is the Tpeka sounding of 12Z; it shows 450J/kg of CIN...00Z sounding, then, shows that cin has been take away.
It's somewhat strange that there was a so rapid erosion of the cap in such few hours...][/b]

Those soundings are 12 hours apart... Which is very ample time to erode a capping inversion, given sufficiant conditions to do so. The 12z TOP sounding shows a deep layer of CINH (radiational inversion)... Along with nearly non-existant instability. With time, a forecaster will know that diurnal heating will change these factors. Strong boundary layer heating/moistening increased CAPE (along with mid-level cooling from the approaching shortwave, yielding steep mid-level lapse rates) and eroded the layer of CINH.

<!--QuoteBegin-Chris Hayes
In my opinion there was too much forcing or the cap wasn't strong enough. As soon as storms started to fire in SC/SE KS, the entire line let loose. There was only about an hour period of isolated storms. The most intense storm of that day, though it went HP if I remember correctly, was in southern Oklahoma. Day had some potential to be a big tornado day, but didn't deliever.

It was both... There was way too much forcing and too weak of a capping inversion to begin with. Actually, storms initiated in central KS at first (then convection developed upstream) and deep convection didn't really develop along the dryline in southern KS until 22-23z (much further southward in OK, supercells developed along the dryline about an hour or two prior)

 

[Andrea Griffa]

Originally posted by nickgrillo+--><div class='quotetop'>QUOTE(nickgrillo)</div>

<!--QuoteBegin-Andrea Griffa

You could be right. Anyway this is the Tpeka sounding of 12Z; it shows 450J/kg of CIN...00Z sounding, then, shows that cin has been take away.
It's somewhat strange that there was a so rapid erosion of the cap in such few hours...]

Those soundings are 12 hours apart... Which is very ample time to erode a capping inversion, given sufficiant conditions to do so. The 12z TOP sounding shows a deep layer of CINH (radiational inversion)... Along with nearly non-existant instability. With time, a forecaster will know that diurnal heating will change these factors. Strong boundary layer heating/moistening increased CAPE (along with mid-level cooling from the approaching shortwave, yielding steep mid-level lapse rates) and eroded the layer of CINH.[/b]

I agree with you Nick, when you say that is a radiational inversion but if you see well there's a good nose at 850mb that put in evidence that there was also a moderate low level warm advection that played an important role in doing a moderate capping inversion. That is what I was thinking about. Probably as you say guys, too much low level forcing and strong heating plus a strong moisture advection on the ground easily eroded the capping inversion, giving the start to the convection during the mid-afternoon.

And what about the o-6 km shear vector and the orientation of the boundary?

 

[Bill Doms]

A weak OFB was floating along the southcentral KS/northcentral OK border, which was very slightly increasing the low-level shear (given more backed sfc flow).

Throughout the early afternoon there was also a very subtle OFB evident from NE KS extending into SW IA from the early morning convection. It appeared not to the be the WF or was partially obscured. Either way it still enhanced the backing significantly from Brown county KS into the NW corner of MO. Does anyone happen to have saved vis sat images from say from the 19Z-20Z timeframe? (not enough time to research) Also, there were 18Z launches that day, correct?

At 21Z convection started in NE Kansas and a tornadic supercell rapidly developed in Brown county and at 21.20 and 21.30 two tornado were in the ground in Hiawatha.

Two tornadoes? This is confirmed?

 

[Mike Peregrine]

Does anyone happen to have saved vis sat images from say from the 19Z-20Z timeframe?

Here you go:

A second tornado was confirmed in Pottawatomie Co. as well ... the Topeka summary with damage photos is here:

http://www.crh.noaa.gov/top/events/june042...05/june2005.php

I never saw a photo of the tornado itself, though - and doubt that anyone intercepted it. It was recorded at 5:30 - about an hour after Hiawatha. By the way - this tornado had to have occurred in the storm WEST of the Hiawatha cell (Pottawatomie is the next county west of Jackson), which seems really bizarre to me, since a lot of chasers headed over to that cell - (we can just add this one to the list of bizarre things this day).

 

[Andrea Griffa]

A weak OFB was floating along the southcentral KS/northcentral OK border, which was very slightly increasing the low-level shear (given more backed sfc flow).

Throughout the early afternoon there was also a very subtle OFB evident from NE KS extending into SW IA from the early morning convection. It appeared not to the be the WF or was partially obscured. Either way it still enhanced the backing significantly from Brown county KS into the NW corner of MO. Does anyone happen to have saved vis sat images from say from the 19Z-20Z timeframe? (not enough time to research) Also, there were 18Z launches that day, correct?

At 21Z convection started in NE Kansas and a tornadic supercell rapidly developed in Brown county and at 21.20 and 21.30 two tornado were in the ground in Hiawatha.

Two tornadoes? This is confirmed?

Bill, here is SPC report:


2120 5 S HIAWATHA BROWN KS 3978 9554 CONE TORNADO REPORTED ON THE GROUND... POSSIBLY NEAR THE TOWN OF BAKER. (TOP)

2128 2 ESE HIAWATHA BROWN KS 3984 9550 ***1 INJ*** REPORTS OF A LARGE TORNADO ON THE GROUND NEAR HIAWATHA... DEBRIS CLEARLY VISIBLE... TORNADO HAD BEEN ON THE GROUND FOR 10 TO 12 MINUTES.

 

[Andy Wehrle]

I'm sure Bill is aware of that tornado since he was on it...I believe he was referring to the second tornado since he only saw one. Is this correct, Bill?

http://www.mnwxchaser.com/60405.html

 

[Mike Peregrine]

Andrea - I think those SPC entries were both for the same tornado, actually ... the tornado was on the ground near Baker (which is SW of Hiawatha), up to about 5 mi. south of Hiawatha. The crazy one is the one I mentioned earlier in the county to the west, which I haven't seen anything on apart from the Topeka report.

 

[Andrea Griffa]

Andrea - I think those SPC entries were both for the same tornado, actually ... the tornado was on the ground near Baker (which is SW of Hiawatha), up to about 5 mi. south of Hiawatha. The crazy one is the one I mentioned earlier in the county to the west, which I haven't seen anything on apart from the Topeka report.

Infact it seemed to me a bit strange

 

[Mike Peregrine]

Not that it matters much to the discussion, but the first report was likely the one I called in, as we made the call the moment we could verify the tornado - - - our report was made at the junction of 170th Street and Kestrel Road, which is precisely where Mapquest shows Baker (not even really a town there - ha). The tornado itself was actually north and a bit east of our location at that point.

The later report from south of Hiawatha likely came from highway patrol, though I was never sure about that. There were three patrol cars on the scene by the time the tornado arrived there.

 

[Jeff Snyder]

And what about the o-6 km shear vector and the orientation of the boundary?

Looking at the hodographs from LMN at 18z and 00z, it appears that the deeplayer shear vector appears to be out of the WSW (from sfc to 6km level, which was about 480mb that day). There was a surface trough (don't really want to call it a dryline, as there were mid-upper 60s behind it, with southwesterly winds) that seems to have been oriented NNE to SSW across southern KS and northcentral OK, before turning more to the southwest across central OK (per sfc obs). From my crude calculations, the 0-6km shear vector appears to be 45-50kts from about 245 degrees (or towards about 65 degrees). This is based on a SSE near-surface flow (the surface wind was a little more SE in places, but it veered off the surface, so this is an attempt to average a bit). This would make the deeplayer shear vector about 45 degrees from the convergence boundary / trough (given the slight NNE/SSW orientation), which isn't too bad. Does anyone have a higher-resolution surface map from this day so we can get a more accurate orientation of the convergence source?

 

[Mike Peregrine]

Probably not what you are looking for resolution-wise (Glen Romine may have a better one), but here's the 18z surface chart -

EDIT - here is the page that Glen did for this event ... should be pretty helpful: http://www.atmos.uiuc.edu/~romine/jun04/

Note that the surface trough/convergence axis wasn't firmly established until 21z ... sometime after the Jackson Co. storm produced the first tornado.