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Sedalia, MO tornado May 20, 2010

News Chopper 9 Pilot Johnny Rowlands live streamed tornadogenesis southwest of Sedalia, MO on May 20, 2010 at approximately 6:45 p.m.

Discussion:  A surface area of low pressure was passing near Kansas City, MO and an H7 upper level low was positioned just northwest of the surface low.  A cold front trailed back into southeastern Kansas and northeastern OK from the surface low with a boundary draped along and just south of the the I-70 corridor. 
A bit of sunshine this afternoon allowed temperatures to reach the upper 60’s to lower 70’s and dewpoints were in the low to mid 60’s.  In addition, surface and upper level shear was maximized near the low pressure centers.

As thunderstorms formed, they encountered the boundary and storm relative helicities were enhanced allowing the atmosphere to reach the correct parameters for tornadic thunderstorms.  Once the thunderstorms crossed the boundary, they weakened considerably, thus eliminating the tornado threat.

In addition to the parameters already mentioned, cold air aloft at the 500mb level, crossed over the Johnson and Pettis County areas near the time of peak afternoon heating. 500mb temps were on the order of -13C to -14C. This has similar characteristics to a CC500L tornado event, but I am not versed well enough in this phenomenon to accurately discuss it. Jon Davies has a great paper, which I continue to read over and over, at this link for review:

SPC MesoAnalysis indicated 500 J/kg of CAPE and SRH 0-1 and 0-3 in the 150-200 m^2/s^2 range in the area of the tornadoes this afternoon.  The 0Z/21 SPC Mesoanalysis references are below:

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Tornado Warning Seneca, MO 5-16-10

Just finished a chase from my house.  Got a call from my family in Seneca, MO saying they were under a tornado warning.  When I opened GRlevel sure enough there was a tornado warning. BRV was showing a definite area of rotation just to the NE of Seneca moving SE at 20MPH.  My cousins could see a lowering but could not confirm if it was reaching the ground to the east of Seneca approx. 5 to 7 miles.  Was on the phone with 3 different people telling them the location of the possible tornado and hail core.  There were a few reports of hail but as I write this no reports of wall clouds or rotation on SN. GR never showed MESO’s or TVS’s which surprised me. By the time one of the chasers got to the area the storm had diminished considerably.  I laughed when my cousin said it was sad that they had to call KC to see what their weather was doing! ~ TB

Here are some screen shots from GRLevel3 I took during the “Chase”.


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May 12, 2010 – OK Storm Chase summary

This was probably the most unexpected outcome of the day type chases, since when I woke I was not expecting to chase. It was 2 days after my big bust in Kansas so I really didn’t have the confidence to chase. Around 4pm, I noticed storms had fired to my east and had some great looking updraft structures. I noticed it was a line, but that southern storm looked great visually. After contacting a couple people about the parameters and what the radar looks liked, I decided to leave work @ 5pm, get my equipment, and jet east on I-40. I got to Groom, TX, when the first storm went tornado warned. I thought we were going to miss the show, but the storm near Wellington was looking really good, both visually and on radar. That was our storm, the tail-end charlie. We got to Shamrock, and made a quick decision to dive south to Wellington, then back east to Magnum, then north to be in a decent position. But by the time we got to Wellington, the storm was pretty far away, at least another 30 miles. We got to Magnum, and the storm further east was going insane on radar, but I knew we were a good 30 miles from that storm. My hopes were diminishing. I decided to stay on the furthest south storm, and see what we could get out of it.

I called my buddy Corey Sloan for a quick nowcast and he gave me the good news that we were in some good dynamics. We kept traversing north and east to get ahead of the storm. We were 7 miles south of Elk City on SH-6 about 2 miles south from the SH-6/SH 152 intersection. We saw a clearing in the clouds to our NE, and saw the edge of a nice wall cloud. Just then what looked like a funnel became clear, but we were sure if it was just scud or not. Then we noticed a large dust cloud forming under it, right then I knew it was a tornado. I pulled over, and tried getting as many pics as I could. Unfortunately, the lighting was crap, and I tried getting my tripod set up, but that didn’t help. I still managed to get a couple pics, and after adjusting the contrast, the tornado is very evident. I couldn’t confirm it as a tornado, simply because we were far away and couldn’t tell if it was just scud or if it was rotating. Finally after calling Norman NWS and David Drummond, I could confirm it as a tornado.

After grabbing some quick McD’s in Elk City, we attempted to core punch a couple storm coming out of Hemphill County, TX. We travelled up US 283 to Crawford, OK, but by then the storms had weakened and only got dime sized hail. We called it a day, drove home, and arrived around 1am.

Total miles for this chase: ~366

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UPDATED Sunday 10 a.m. CDT

The storm system is forecasted to eject faster now….this was a concern of mine when I made this forecast Friday night….I mentioned the target area may need to be adjusted 150 to 200 miles further east, and it has materialized.  The atmosphere is poised for a significant weather event Monday afternoon and evening.  Instability and shear profiles create the potential for a very violent environment across the target area.  The Storm Prediction Center has this area highlighted for a moderate risk on their SWODY2 outlook.  Overnight convection and the ability of the atmosphere to recover will be the key to how violent the storms are Monday afternoon and evening. 

I will update my target location tonight and/or tomorrow on the blog as well as

Initial Target Location: Wichita, KS to Muskogee, OK (Additional adjustments will be made as we get closer to the event)  In addition, there appears to be a secondary target shaping up, at least early, from Hays, KS to the NW.

Forecast Discussion: This forecast is based on a blend of the NAM-WRF, GFS, SREF, and ECMWF.

A strong storm system is poised to take aim on the southern and high plains beginning late Sunday and into Monday evening. There will be a marginal/conditional threat for elevated severe thunderstorms Sunday evening across the target area, with large hail the main threat. Overnight convection and any remnant outflow boundaries will need to be nowcasted during the Monday morning forecast. 

The negatively tilted trough will eject into the plains on Monday and the associated areas of low pressure will bring the potential for a significant severe weather event across the southern and high plains during the Monday afternoon and evening time frame.  A strong thermodynamic and kinematic environment will be in place for a few significant, long track tornadoes accompanied by very large hail.  Here is a look at the significant tornado parameter values greater than 5 as progged by the SREF at 0Z/11:

A 100kt jet stream is forecasted over the area with a 90kt jet streak embedded in the flow.  This jet streak is forecasted to be nosing into south central and southeast KS at 0Z/11.  The right entrance region of the jet streak appears to be over north central OK and the left exit region looks to be over southeast KS at 0Z/11.  This strong, upper level flow will create significant divergence aloft and convergance at the surface which will aid in storm growth, maturity, and duration.

A strong mid level shortwave, at the 500mb level, is forecasted to be quickly ejecting into the plains overnight Sunday and into the afternoon hours on Monday.  This mid-level disturbance, accompanied by 70 to 80kt SWLY 500mb winds, will be the triggering mechanism for potentially violent weather across the plains states.  This disturbance is forecasted to be over SC KS by 0Z/11.

A strong southerly flow at the surface and low level jet at 850mb, of 40 to 50 kts, will provide an efficient WAA regime to pump rich Gulf moisture into the region during the day on Monday.  Surface and 925mb dewpoints are forecasted to be in the low to mid 60’s across the target area by Monday afternoon, with some progs showing lower 70’s in south central KS ahead of the dryline.   Moisture depth and quality are indeed not an issue with this setup!

This southerly flow will continue during the day on Monday and continue to provide a very moist and significantly unstable airmass across the region.  SBCAPE values approaching 3000 J/KG and MUCAPE values over 3500 J/kg in the warm sector. 

SREF CAPE values over 2000 J/kg at 0Z/11:

There is moderate capping inversion, which has lessened on the last few model runs, in the target area at the H85 and H8 layer, along with H7 temps in the 5C to 8C range. The CAP may now be in the favor of more discrete supercells during the event.  Nonetheless, I belive the forcing and convergence along the dryline and warm front, along with the convective temperature being realized will quickly erode the CAP and rapid thunderstorm development will occur with the storms quickly becoming supercellular/tornadic.

At the surface a strong and deepening area of low pressure, on the order of 992mb, is forecasted to be in central KS at 0Z/11. This area of low pressure will quickly progress to the east/northeast overnight.  A warm front is forecasted to be draped from south central KS into central Oklahoma putting the target area in the warm sector by Monday afternoon, albeit a very small warm sector.  While a dryline will be setting up from south central KS to the Red River Valley.

Here is a quick look at the surface feature locations from the NAM-WRF, GFS, UKMET and ECMWF for timing comparisons.  The UKMET is indeed the outlier on these models runs.

Surface temperature are forecasted to be in the upper 70’s to lower 80’s. Surface winds are out of the south/southeast and backed in the target area at 20+ kts.  This warm front and dryline will be the focusing mechnsism for severe thunderstorms, some potentially tornadic, during the Monday afternoon and evening time frame.

The GFS and NAM-WRF are showing a THETA-E ridge nosing into SE KS at 0Z/11.

Storms will fire north and east of the warm front , near the triple point, as well east of the dryline late Monday afternoon into the evening hours.  The strong forcing and low level wind shear, overall bulk shear of 60 to 70kts and shear vectors perpindicular the boundaries, should not allow the atmosphere to decouple and keep the storms surface based well after dark.  This indicates the tornado threat may well extend into the overnight hours across the target area before the atmosphere decouples. 

Storm motions could be an issue with forecasted motions being in the 35 to 40kt range:

In addition, midlevel lapse rates on the order of 8C to 9C will promote a large hail threat, with some hail stones being fairly substantial.

Helicity values are very high, with most models forecasting, over 300+ m2/s2 0-1 and 0-3km Helicity values over much of the warm sector Monday afternoon.  EHI values are forecasted to be 4+ in the target area, some model progs are putting EHI’s in the low teens.  These shear values/upper air dynamics have the models progs producing long, curved hodographs with added SRH’s along the attendant warm front in the target area.  Here are the 36 hour NAM-WRF forecasted soundings from Bartlesville, OK and Wichita, KS:


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Yazoo City, MS Tornado: April 24, 2010

Posted by Jesse Risley on April 27, 2010 at 9:43 PM    

The video that I have uploaded here chronicles the monstrous supercell  that struck Yazoo City, Mississippi on Saturday, April 24, 2010.   Convective Addiction compatriots Jesse Risley and Brad Goddard, along  with fellow chaser Kevin Crawmer, intercepted the supercell several  miles to the south of Yazoo City, MS.  At is became apparent that a tornado  of elephantine proportions was enshrouding itself just behind the  curtains of rain wrapping into the southern flank of the cell, our  efforts turned from videographer to diverting oncoming motorists who  were obviously unaware of the dangers that they were about to encounter  as they proceeded northbound on U.S. 49.  Unfortunately, a few of them  encountered the outer flanks of the wedge tornado and sustained  vehicular damage just up the road from our location, though no one was  seriously injured as far as we could tell.

The most disturbing aspect of this entire day was the fact that when we originally entered the community from the north about twenty minutes prior to  the arrival of the tornado, a Tornado Emergency had already been issued by the  NWS office in Jackson, MS several minutes prior to our  arrival on Hwy 49N.  However, it was  business as usual in the community and no sirens appeared to have been  activated at that time.  Witnesses later told us that they heard the sirens very  briefly before the tornado hit (app. 1-2 minutes as best, others said 5-10 minutes).  You can hear  a forecaster from the NWS in the background several minutes into the  videotape reading a live on-air NOAA Weather Radio script of the Tornado  Emergency.

As we entered the community again immediately following the passage of the twister, our efforts quickly turned to  assisting with imminent search and rescue operations, as there were no  emergency personnel on the scene of some of the worst damage that  occurred in the eastern side of the city for 5-10 minutes after our  arrival.  This was likely due more to the extent of damage and road  blockages community-wide than it was a failure on anyone’s (EMS, LE or Fire) part to  respond in a commensurate manner.  In a situation this drastic, the only first responders may very well be ordinary citizens and neighbors.

There is much to be said about the prudence and sanity of chasing HP supercells that are producing strong to violent tornadoes, wrapped in  rain, while moving at hypersonic speeds of 55+ mph, and in the “jungles” of  the Deep South nonetheless.  This is exactly why we positioned ourselves far enough south to ensure that we wouldn’t even be in imminent danger  if the cell took a sudden right turn, yet still allowing respectably  close viewing of the tornado, which was mostly wrapped in rain from our vantage point.

My kudos go out to the fellow chasers who also laid down the chaser hat and worked selflessly for hours with  search and rescue efforts, helping numerous residents that were trapped  in the remnant shambles of a neighborhood forever changed that Saturday  afternoon.

The damage video that I shot isn’t even the tip of the iceberg of  what I saw yesterday, but it does offer a glimpse at the destructive  power of nature.  This was certainly a significant chase day, yet it  will remain my most humble and tragic to date.  Most of the damage footage taken in the more sunnier conditions was shot about 2-3 hours after the passage of the twister, when we were finished helping with search and rescue efforts.  I have only included what I feel is appropriate to share, as this was an emotionally charged atmosphere and some individuals sustained serious injuries as well.

An ongoing damage assessment analysis from the NWS (KJAN) can be found here.

A few radar grabs from GR Level 2 are included below.  They were  provided to us by chaser Jared Thompson of Texas.

A look back at some visual aides from April 24th

The Day 1 Outlook from the SPC is shown below

The EHI is a simple tool that is calculated by combining helicity values and atmospheric instability into  one single unit for determining whether or not a particular environment is ripe for supercell development.  A 0-1 km EHI > 1-2 suggests that significant tornadoes may be possible; the values at 17z are approaching 10 in central MS!

 The Significant Tornado parameter for the fixed layer is a composite index that comprises the 0-6 km bulk wind  difference, 0-1 km SRH, SBCAPE, sbCIN (note no shading), and surface parcel LCL  height. This mesoanalysis version of STP uses fixed layer calculations of  vertical shear, and the surface lifted parcels, as an alternative to the  “effective layer” version of STP.

Note the 300 mb Jet max is approaching 120 kts from the southwest.

 Note the 500 mb winds of 60-80 kts, when combined with the 300 mb jet streak (above)  approaching 120 kts, yielded effective shear magnitudes of 50+ kts.


 Note the 55-65kt low level jet which promoted enlarged hodographs, lending SRH values of between 300 (W. MS) and 700 (NE MS), as noted in the SRH chart down below. At that time, 850 mb dewpoints sat near 14C over western MS.

 Note the southerly winds pooling warm, moist air northward from the Gulf of Mexico, turning increasingly S-SE progressing northward through Mississippi.

 A strong LLJ rendered 0-1 km SRH of between 300-700 m2/s2 over the entire region.

At 16z SFC-1km Vertical Shear is already 60 kts across this region; > 15-20 kts is considered favorable for supercell tornadoes.

Effective bulk shear values of 60-70 kts suggest that supercells are likely (>40 kts is more than sufficient).

It is now evident that the LLJ is promoting higher THETA-E values, noting that any region with an elevated THETA-E corresponds to more significant instability and thus higher SBCAPE indices.

Warming temperatures and increasing low level dewpoints are  increase instability, as CINH erodes.  This is showing elevated THETA-E values over the region.

 At 17z most of Mississippi sits with SBCAPE AOA 2000 J/KG, with CINH eroded, lending an environment primed for severe weather.

Normalized CAPE values sit at 0.15 m/s**2 at 17z, suggested average parcel accelerations.

Note: Greater than 40 m/s**3 is considered high; values sit at 80 just east of where the Yazoo supercell
developed at 17z.

Note that a negatively tilted shortwave trough is beginning to advect ENE from the ARKLATEX region.

The VGP parameter is used to estimate the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft.  Values in excess of 0.20 m/s**2 suggest that tornadoes are more likely; here they are reaching 0.60 m/s**2 near Yazoo City.

The LFC paramater is indicative of the level at which a lifted parcel begins a free acceleration upward to equilibrium.  Tornado potential increases when LFC heights are between 1500-2000m above the surface.  As we can see, STRONG support for tornadogenesis is noted with LFC levels at 1000m.

The LCL Heights are sitting at between 500 and 1000m, lending good support for tornadoes. This is the level at which a lifted partial saturates, and is also used to estimate cloud base heights.

The BRN shear value sits at over 150 m2/s**2 across the entire region.  The BRN Shear is the denominator in the formula for the Bulk Richardson  Number, a ratio of CAPE values to deep layer shear  (6km wind – sfc wind)^2.  This indicates that an incredible amount of shear is present over the area that would soon host a number of tornadic supercells Saturday afternoon.

This chart gives us a glimpse of frontogenesis characteristics as an operational characteristic of kinematics.

Note that SFC-6 km shear is at 68 kts; storm motion is at 233 degrees (SW) and 57 kts!

Jesse L. Risley

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