The Heartland Tornado Outbreak
March 11-12, 2006
Introduction - Background of the Storm
On February 16, a front with moisture finally came through and a line of severe storms broke out east of Kansas City in St. Louis, as well as the southeast and midwest east of St. Louis. On March 9, another such front came through, affecting Oklahoma, Arkansas, Louisiana, Mississippi, and on east. On March 11, severe storms broke out south of Kansas City, with storm reports from southern Missouri, Arkansas, Oklahoma, Illinois, Indiana, and even Wisconsin.
The next day, March 12, was set up with the low on our doorstep (eastern Kansas and western/central Missouri), a southerly moisture flow (south winds bringing in warm Gulf air), the cold front still to our west with a temperature difference in the ballpark of 35-40 degrees F, and a dryline just west of the Kansas City area in Kansas. Other synoptic features in place were a potent upper level trough moving through, plenty of wind shear, and the warm front that went through on Saturday the 11th sitting in central Kansas/central Missouri across the state line. As early as 7:45 am CST on Sunday, a Severe Thunderstorm Watch had been issued for the Kansas City area and south down the state line. I collected all the Convective Outlooks, Mesoscale Discussions, and Severe Thunderstorm and Tornado Watches and Warnings pertinent to the Kansas City area in one document.
Supercell thunderstorms broke out on Sunday in three phases. The morning saw elevated convection with cold surface temperatures in Kansas, with storms also north and northeast of Kansas City. Early afternoon saw the second phase, with supercells firing up along the dryline and moving from far eastern Kansas into Missouri all along the state line. Some of these spawned tornadoes with fatalities reported. But the late afternoon and evening storms proved to be the most severe. Supercells kept erupting along the dryline and working themselves up into tornado-spawning entities throughout the evening until the squall line finally came through with the frontal passage around 10:00-11:00 pm CST (04Z-05Z). You can find the SPC Storm Reports here and a collection of radar images for the evening storm system here, as well as the detailed field analysis report from NWS Pleasant Hill, MO. For the day of March 12, there were 140 tornado reports, 127 wind reports, 402 hail reports, with total storm reports at 669. In the Kansas City area, there were 14 tornadoes confirmed, with 7 F0s, 1 F1, 4 F2s and 2 F3s identified by NWS field analysis. There were 6 fatalities for the KC Metro area alone (1 in the afternoon phase (Sedalia, MO), and 4 in the evening phase (1 in Urich, MO and and 4 in Renick, MO)*. This record outbreak will stand along with the Super Outbreak of April 3-4, 1974.
*Ongoing updates available on SPC Storm Reports page and NWS Pleasant Hill, MO page.
The Late Afternoon/Evening Outbreak and the Cell of
Below are the radar images and corresponding Doppler velocities from the local National Weather Service office in Pleasant Hill, MO. These were captured as the storms were producing wind, rain and lightning all around the area, including our place. There is a radar image missing for 0130Z because this was one of the 3 times that our electricity went out while I was trying to save images. It came back on almost immediately each time, but by then I'd missed the exact time-match window. Notice the large cell in all three radar images (circled) and the corresponding couplet on the Doppler velocity image (circled). You can see a very distinct mesocyclone rotating in that cell.
The first chart (above-left) is 100 mb Mean Parcel CAPE and CIN. CAPE (Convective Available Potential Energy) measures how much potential there is in the entire atmosphere for air parcels to rise rapidly (positive buoyancy). Rising (buoyant) air parcels are necessary for convection, which gives us our building cumulus clouds (including thunderheads, called convective towers). CAPE is measured in joules per kilogram (j/kg). Higher values of CAPE indicate areas with high instability, which helps pave the way for severe storms to develop. On the attached chart, which represents conditions in the first 100 mb of the atmosphere, you can see the CAPE (red contours) values of 2000 and 1500 in the Kansas City area. You could say we were ripe for it, as these are considered high values. The CIN (Convective Inhibition) is the blue shading, with blue values you can barely see. The CIN value of -25 near the state line indicates moderate inhibition of convection, and coupled with the high CAPE, wasn't sufficient to keep storms from forming.
Next (above-right) is the Surface-Based Unstable Lifted Index and Surface-Based CAPE chart. This says surface-based as it represents the values from the surface to 500 mb, which is roughly 18,000 feet. Lifted Index (LI) measures the the temperature of the parcel in relation to its surroundings at 500 mb, which is a factor in its buoyancy. The readings for LI of -6 and -5 in central/western MO by the state line indicate very strong instability (positive buoyancy) with a high potential for severe thunderstorms to erupt. And they did.
The third chart (above-left) is for Surface Theta-E/Advection. Theta is a Greek symbol and along with the E represents Equivalent Potential Temperature, which combines temperature and dew point into one value to determine how warm and moist the air is. Advection is the movement of said air by the winds. Theta-E represents to what extent warm, moist air is present to destabilize the atmosphere. Remember one of the things we had in place on the synoptic scale was a warm flow from the Gulf of Mexico to the south and from the Pacific across Mexico to the southwest. Pacific and Gulf air is warm and moist and brings humid conditions (raised dew points, which we had in the warm sector ahead of the frontal boundary). The higher numbers in green (332 and 334, temperature in Kelvins) show areas of high theta-e air (warm and moist), which sets the stage for afternoon and evening convection (bingo). This was very unstable air! The purple contours and numbers indicate to what extent this air is being brought in by the winds. Note the values of 10 and 15 in the Kansas City area - the contours show that the air has run up against the warm frontal boundary and is pooling there.
The last chart (above-right) is for Deep Layer Moisture Convergence. This is related to dynamic and thermodynamic forcing/lifting on the synoptic scale. Now what does that mean? Moisture converges (the high theta-e blowing in) and the rising air parcels (forcing/lift) take it up into the upper levels of the atmosphere (deep layer), where divergence aloft occurs, setting the stage for storm development. High values (red contours) of moisture convergence reflect a lot of forced ascent of this warm, moist air, which gives the various levels of the atmosphere a lot of moisture to work with. This much convergence at this low level combined with strong vorticity are a couple of variables favorable for tornadoes to form (as long as the large-scale convection keeps developing). However, these are not the only factors that need to be in place for tornado development, other factors being out of the scope of this paper.
Skew-Ts and Hodographs
The red line is the temperature and the green line is the dew point - when they meet through a deep layer, it indicates the atmosphere is saturated, which is favorable for precipitation. The wind barbs at the right show the wind direction and speed at various levels of the atmosphere, and you can see that they do change from the surface up to 500 mb, indicating shear. Sure enough, the hodograph (little circle at the upper left corner) shows the wind plot line veering to the right subtly, which is an indicator of severe weather potential. One thing I want to point out here (on the Skew-T) is the temperature and dew point line rising to the right up to about 890 mb, which indicates an inversion (stability), and the large space between these two lines at 700 mb, which indicates a dry layer (a cap for convection to break through in order for severe storms to form). At 12 noon on the 12th, there was surface saturation but convection had not broken the cap yet (the cap is the top of the inversion). By 6:00 pm, the system had rained out in Topeka, as indicated by the large space (dry air) from the surface to 650 mb - true enough, all the storm activity was ongoing east of Topeka, mostly in southwestern and central Missouri by this time.
The first sounding for 12Z (6:00 am CST) on the 12th shows the setup of the atmosphere for the day's events. This sounding shows upper-level clouds (lines are close at 750 mb) and a dry layer from 760 mb to 800 mb, which is another factor for potential instability. Also, the surface inversion was in place which indicates stability, but the winds were shearing and, along with convection, would likely mix the atmosphere into instability (the winds form eddies that mix the surface air with the upper level air).
Meteograms, or a Map of How the
Day Played Out
Far-Traveling Cell and Hook Echo Cell
Of note is that there was one major cell that formed at the Oklahoma/Kansas border during the afternoon phase of the outbreak (around 5:00 pm CST), which moved through the Clinton and Sedalia areas (east central Missouri, southeast of KC Metro area), spawned a number of separate tornadoes, and kept itself intact until it reached Indiana around sunrise March 13th. This single cell traveled 400-500 miles before it finally dissipated! In comparison, the life-cycle of a single thunderstorm cell is usually about one hour, and this cell stayed intact for roughly 14 hours! Conditions remained favorable for the cell to continue regenerating, as outflow and downshear stayed clear of the updrafts, allowing the storm formation variables to remain intact and the cell to keep feeding on itself. On the 2356Z radar image in the link above, you can see the two large cells off to the northeast - one of those cells is this long-lived cell.
In addition, I was able to capture the radar image and Doppler velocities for a cell in the evening phase of the outbreak that spawned the fatal tornado in Urich, MO. The radar image for 0219Z (8:19 pm CST) below shows a pronounced hook echo and the Doppler velocities radar image beside it shows the mesoscale couplet. This image depicts winds moving away from the radar and winds moving toward the radar, and the couplet is where they are very close together, indicating rotation (mesocyclone). As for a TVS (Tornado Vortex Signature), I think I see one blue dot in the red area, which would indicate very small-scale rotation (twister). I've circled the couplet showing the mesocyclone, which could possibly contain the supposed 'blue dot' TVS. Though a TVS on radar is very rare, this storm was in close proximity to a radar station (Pleasant Hill), increasing the possibility of the signature being apparent on the image.
In the radar image for 0234Z (8:34 pm CST), you can see the cell moving out of Henry County and into Johnson County, Missouri. The fatality in Urich had already occurred by this time, at 0211Z (8:11 pm CST) 3 miles west of Urich in Henry County, MO. A man's house was destroyed and he was thrown out into the field, where he died. This was one of the many sobering occurrences of the day's outbreak, reminding one of how fragile our lives can be on this planet when we're forced to stare down Mother Nature's fury. The fact that in an outbreak of this magnitude there were relatively few fatalities is a testament to the awareness of the public and the advent of technology and science to warn in as timely a manner as possible. We've come a long way since 1974.
In the Classroom the morning after, I posted a report with the preliminary storm reports and coverage from the local National Weather Service office and the local Fox 4 weather team (scroll down to Tuesday, March 14, 2006 (Joe Lauria) and the entry below that one (Casey Curry) for preliminary stats, preliminary tornado location graphic, and tornado pics from Sedalia). In that posting, I mentioned that this outbreak was a record-breaker and would stand along with the Super Outbreak of April 3-4, 1974. By the end of the week, the local National Weather Service office posted a short storm synopsis, and they mentioned the same thing, which made me proud that I had recognized that myself. (The links at the bottom of the 'storm synopsis' page are no longer valid; however, the text and images from these links were copied into the 'local National Weather Service office' link at the beginning of this paragraph.)
However, the storm reports are very sobering. One in particular struck way too close to home. An F3 went through the Pomme de Terre lake area between Pittsburgh and Hermitage (one hour northeast of Springfield, MO), heavily damaging a place called Carson's Corner (7 injuries). Carson's Corner is a little corner at the end of a neighborhood that has a little store, a boat storage facility, a gas station, a curio shop, and I think a little repair place. I can't remember exactly, but this sounds about right - my point is that it's small - literally a corner. The neighborhood is where my mother moved to when she sold our house in Dallas. She's gone now, but I still have relatives in the town of Galmey across the dam and down the road from Carson's Corner, with a house out on the tip of a finger of land jutting between two coves. This F3 came perilously close to their house on its trek to Hermitage. They did a visual of the damage the next day (I called and told them what I read in the storm report), and it was so strange to hear that some of these places were gone. They had to go the long way around because the dam road was blocked due to damage. The tornado didn't damage the neighborhood, only the Carson's Corner area. It gave me the strangest feeling to hear about this - I can't explain it. If I hadn't read the NWS storm report and found the Carson's Corner damage entry, I wouldn't have known this or been able to tell them about it. Saying it made me feel good isn't the right statement, but I was glad that I had this access and ability to research the storm for myself and be able to pass along the knowledge I gleaned from the report. I'm going this weekend to take a first-hand look at the damage. Maybe I can post some pictures here later.
I also liked being able to see on the radar what was coming our way - especially when I could also see it on the horizon at the same time. There's something almost magical about that. Knowing it's coming is invaluable to me. The people around me may be tired of hearing about the weather all the time, but they appreciate me when they need to know what to expect. I wish my mother were here to see what I've accomplished. Every time it would "cloud up" she'd go get the book of state maps that outlined all the counties and cities and we'd watch the weather (Harold Taft, Channel 5, Dallas, Texas, 1960s and 1970s) and determine where the storms were in relation to our house. I'd never really thought of it before, but I guess you could say she fed my interest in meteorology by doing that. I still have that book.
In closing, I'd like to say that I learned a lot from accessing images while the storm was occurring. Real-time field learning is the best way to understand what we're trying to learn. I guess you could call this armchair storm chasing! And of course it's always interesting to live through an historical event (and humbling to survive to tell the story).
NOTE: The Kansas City National Weather Service office posted the official record-breaking totals for tornados in 2006 in Missouri at the end of the year. From there, you will find links at the bottom of the page to the 2006 Climate Summary for the Kansas City, Missouri area, along with the normals and averages in temperature, precipitation and winds. Linked within the summary are the March 12th Tornado Outbreak, the July 11th Deluge, and the November 29th Winter Storm.