Greensburg, KS EF5 Tornado of May 4, 2007


According to NOAA’s National Centers for Environmental Information (NCEI), “a destructive tornado, the first 5 rating on the new Enhanced-Fujita Scale and the first 5 classification since May 3, 1999 when an F5 tornado ripped through Moore, Oklahoma occurred on this day. There were 16 tornadoes during about a four hour period, one a little over 2 miles wide! Two of the tornadoes existed for over 1 hour as they churned up the ground, leveling homes and causing fatalities along their path. Miraculously, on 13 people perished, 11 in Greensburg – a miracle because over 90 percent of the town of Greensburg was literately wiped off the face of the earth. Another round of tornadoes occurred the following day across generally the same area. Nearly 250 pivot irrigation sprinklers were damaged or destroyed during the 2 day outbreak. Due to the number of sprinklers involved and the lack of replacements, some farmers would be out of service for over 1 year” (2019).

The Forecast

Figure 1. Storm Prediction Center’s (SPC) 1630Z Day 1 convective outlook on May 4, 2007. Top left panel showing moderate risk of severe thunderstorms, top right panel showing tornado probability, bottom left panel showing damaging wind probability and bottom right panel showing large hail probability (SPC, 2007).

Figure 1 depicts the Storm Prediction Center’s (SPC) day 1 convective outlook, showing a moderate risk of severe thunderstorms with a 15% hatched probability of tornadoes on May 4, 2007. Figure 2 depicts a close-up of the tornado probability at 1630Z. In Figure 2, we see a a 15% hatched probability from southwestern Kansas into extreme eastern Colorado.

Figure 2. SPC Day 1 tornado probability issued at 1626Z on May 4, 2007. Graphic depicts probability of tornado within 25 miles of a point within the outlined area. Hatched area depicts 10% or greater probability of EF2-EF5 tornadoes within 25 miles of any given point within hatched area (SPC, 2007).

The synoptic pattern on the morning of May 4th was typical of spring in the southern Plains of the United States. Figure 3 depicts an upper-level trough ejecting in the Pacific Northwest. According to the SPC (2007) at 1651Z:

“A POWERFUL UPPER TROUGH IS DEVELOPING OVER THE INTERIOR PORTIONS OF THE WESTERN U.S. THIS SYSTEM IS FORECAST TO MOVE EASTWARD AND BEGIN AFFECTING THE CENTRAL AND NORTHERN PLAINS BY THIS AFTERNOON AND EVENING. STRONG WESTERLY WINDS ALOFT WILL SPREAD ACROSS THE SOUTHERN ROCKIES TODAY…WHILE A SURFACE LOW DEEPENS VICINITY OF THE SOUTHEAST COLORADO/SOUTHWESTERN KANSAS AREA. INCREASINGLY STRONG AND GUSTY SOUTHERLY LOW LEVEL WINDS ACROSS THE HIGH PLAINS WILL TRANSPORT RICH GULF MOISTURE NORTHWARD…WITH DEWPOINTS IN THE MID TO UPPER 60S EXPECTED AS FAR NORTH AS WESTERN KANSAS. STRONG DAYTIME HEATING AND RATHER COOL TEMPERATURES ALOFT WILL RESULT IN AN EXTREMELY UNSTABLE AIR MASS FROM PARTS OF NEBRASKA INTO WESTERN OKLAHOMA AND THE EASTERN TEXAS PANHANDLE. THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER EASTERN COLORADO AND WESTERN KANSAS BY LATE AFTERNOON…SPREADING NORTHEASTWARD INTO PARTS OF NEBRASKA DURING THE EVENING”.

Figure 3. 500mb chart at 1200Z on May 4, 2007 showing geopotential height contours, pressure center and observations (SPC, 2019 modified by Francis Lavigne-Theriault, 2019).

The situation at the surface was also typical of the southern Plains in spring. A dryline was seen advancing east-northeastward throughout the day. Figure 4 depicts the dryline at 1:00 pm CDT on May 4th in the Texas panhandle and western Texas.

Figure 4. Surface analysis at 1800Z on May 4, 2007 depicting a dryline (in orange), surface station plots, mean sea-level pressure (MSLP) contours and pressure centers (WPC, 2017).

By 4:00 pm CDT, the dryline was extending into southwestern Kansas and sitting just west of Greensburg, KS (Figure 5).

Figure 5. Surface analysis at 2100Z on May 4, 2007 depicting a dryline (in orange), surface station plots, mean sea-level pressure (MSLP) contours, pressure centers and location of Greensburg (WPC, 2017, modified by Francis Lavigne-Theriault, 2019).

Below are vertical profiles of the atmospheric conditions at Dodge City, KS, which is roughly 45 minutes west of Greensburg. The sounding on the left (12Z), shows that the atmosphere had a substantial “lid” or “cap” at 850mb with southerly winds at the surface. The sounding on the right at 7:00 pm CDT (00Z) shows a completely different story with an uncapped atmosphere around Greensburg.

  • 12Z sounding Dodge City, KS
  • 00Z sounding Dodge City, KS

The Tornado

At 2:53 pm CDT, the SPC issued a mesoscale discussion reading:

“TRENDS ARE BEING CLOSELY MONITORED FOR SIGNS OF CONVECTIVE INITIATION. ALTHOUGH TIMING IS STILL A BIT UNCERTAIN…ONE OR MORE TORNADO WATCHES WILL PROBABLY BE REQUIRED LATE THIS AFTERNOON”.

Figure 6. Mesoscale discussion #0685 issued at 2:53 pm CDT showing area of potential supercell development, low pressure center, cold front and dryline (SPC, 2007).

At the time of this mesoscale discussion, the SPC (2007) mentioned that the mixed-layer convective available potential energy (MLCAPE) was in the 3000-4000 J/kg range, which indicates a very unstable air mass.

Figure 7. Tornado watch #227 issued by the Storm Prediction Center at 6:15 pm CDT on May 4, 2007 (SPC, 2007).

At 6:15 pm CDT, the SPC in Norman, OK issued tornado watch 227 for western and central Kansas, western and northern Oklahoma and the eastern Texas panhandle and northwest Texas (Figure7). The tornado watch read:

“WIDELY SCATTERED STORMS/SUPERCELLS POSSIBLE IN VERY UNSTABLE AIR MASS ALONG SLOWLY RETREATING DRY LINE THIS EVENING. STRENGTHENING ASCENT/WIND FIELD ASSOCIATED WITH APPROACHING FOUR CORNERS UPPER TROUGH MAY ENHANCE TORNADO POTENTIAL AFTER DARK AS LLJ INCREASES TO AROUND 50 KTS” (SPC, 2007).

According to Bluestein (2009), left-splitting cells were the dominant mode of convection for the day until around 0030-0100 UTC (7:30 pm – 8:00 pm CDT), after which cell splitting was no longer observed. It took about one hour for the Greensburg storm to become tornadic and at 0127 UTC (8:27 pm CDT), a weak cyclonic signature was observed on Doppler radar, which can be associated with the first tornado observed on this storm. Figure 8 depicts all the associated tornadoes generated by this supercell storm.

Figure 8. Storm damage tracks from five tornadoes in Kansas on May 4, 2007. Beginning and end times are estimated in CDT from Dodge City, KS WSR-88D radar signatures and correlation with damage paths. Tornado “5” being the Greensburg EF5 tornado (Bluestein, 2009).

After a 30 minute interval of cyclic tornado production (Figure 8), the Greensburg EF5 tornado formed at 9:03 pm CDT (NOAA’s NCEI, 2019) and struck Greensburg roughly 50 minutes later (Bluestein, 2009). Below is a depiction of radar reflectivity (left) and radar velocity (right) as the intense tornadic circulation went over Greensburg, KS.

Below is the NOAA Weather Radio audio archive of the tornado warning issued for Greensburg, KS on May 4, 2007 (source unknown).

NOAA Weather Radio of Greensburg, KS tornado warning on May 4, 2007 (source unknown).

Below is a Doppler radar loop of the supercell that produced the Greensburg EF5 tornado.

Doppler radar loop of Greensburg Storm on May 4, 2007 (SPC, 2019).

Tornado Aftermath

Below is a comparison of downtown Greensburg before and after the EF5 tornado (NWS Dodge City, KS, 2012):

  • Downtown Greensburg before tornado
  • Downtown Greensburg one year after tornado

Scientific Breakthrough from “Greensburg Storm”

Figure
Figure 9. The Greensburg tornado of May 4, 2007 from 29 km southwest of Greensburg looking north-northeastward at 0234 UTC, when damage path was at least 1.5 km wide (Tanamachi & al., 2012).

According to Tanamachi, Bluestein, Houser, Frasier and Hardwick (2012), data were collected in the “Greensburg storm” by the University of Massachusetts X-band, mobile, polarimetric Doppler radar for an astounding 70 minutes, where 10 tornadoes were detected. This mobile Doppler radar data set is one of only a few documenting an EF5 tornado and the supercell’s transition from short-track, cyclic tornado production to long-track tornado production.

Figure 10. UMass X-Pol (a) uncalibrated equivalent reflectivity (in dBZe), (b) aliased velocity (in m s−1), (c) dealiased and edited velocity (in m s−1), (d) differential reflectivity (in dB), and (e) copolar cross-correlation coefficient (unitless) at 0229 UTC. All data are from an elevation angle of 3.1° except for (e), where 4.1° data are shown because 3.1° data were contaminated by beam blockage. The scans intersect the tornado at an altitude of 1.9 km AGL [2.5 km AGL in (e)]. At this time, the damage track of the mature Greensburg tornado was 2.5 km wide, and (c) shows the same Doppler velocity data after manual dealiasing and some editing. Range rings are 15 km apart; spokes are 30° apart (Tanamachi et al., 2012).

According to Tanamachi et al. (2012), the structure of the Greensburg supercell’s hook changed considerably throughout the UMass X-Pol deployment. Figure 11 depicts the evolution of the “hook echo” of the Greensburg storm.

Figure 11. Evolution of hook echo of Greensburg storm in UMass X-Pol (left) uncalibrated equivalent reflectivity (in dBZ) and dealiased Doppler velocity (in ms^-1) on the right on May 4, 2007. (a)–(d) indicates early tornado production stage with numerous small, short-lived vortices, (c),(d) the transition to a single, long-track tornado production phase, (e),(f) the developing phase of the Greensburg tornado, and (g)–(j) the mature Greensburg tornado with two satellite tornadoes, one of which is anticyclonic (Tanamachi et al., 2012).

At 0139 UTC (8:39 pm CDT), a maximum of four simultaneous radar velocity signatures were detected by the UMass X-Pol (Figure 11. c,d), representing several different tornadoes at varying stages of their life-cycle (Tanamachi et al., 2012).

Recap

According to Bluestein (2009), during the evening of May 4, 2007, a large, powerful tornado devastated Greensburg, KS. The “Greensburg Storm” cyclically produced tornadoes for about 30 minutes before producing a large, long-lived tornado. According to NOAA’s NCEI’s storm event database (2019), a large EF5 tornado developed at 9:03 pm CDT on May 4, 2007 north of County Line Road in Kiowa County in Kansas. The tornado travelled north-northeastward for 25.8 miles with a maximum width of 3000 yards (1.7 miles wide). As the tornado moved north, it struck the town of Greensburg with estimated 205 mph winds, where it caused 11 fatalities, 63 injuries and $250 million dollars in property damage. After destroying over 90% of Greensburg, including 961 homes and businesses, the tornado moved northwest and did a complete loop before ending north of The Yellow Brick Road (Figure 12) at 10:05 pm CDT.

Figure 12. The Greensburg, KS EF5 tornado path of May 4, 2007 (NWS Dodge City, KS, 2008).

According to Bluestein (2009), other tornadoes, some also significant, tracked across portions of southern Kansas, but fortunately did not strike any heavily populated areas and did not inflict damage as extensive as that inflicted at Greensburg.

Figure 13. Sister tornadoes east of Greensburg, KS on May 4, 2007 (C. Dan Robinson, n.d.).

Sources

NOAA’s National Centers for Environmental Information. (2019). Storm Events Database. Retrieved from: https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=35937

NOAA’s National Weather Service Storm Prediction Center. (2007). Severe Weather Event: May 04, 2007. Retrieved from: https://www.spc.noaa.gov/exper/archive/event.php?date=20070504

NOAA’s National Weather Service Storm Prediction Center. (2019). Surface and Upper Air Maps. Retrieved from: https://www.spc.noaa.gov/obswx/maps/

NWS Weather Prediction Center. (2017). WPC’s Surface Analysis Archive. Retrieved from: https://www.wpc.ncep.noaa.gov/archives/web_pages/sfc/sfc_archive.php

National Weather Service Dodge City, Kansas. (2012). Greensburg – Five years after EF-5 tornado. Retrieved from: https://www.weather.gov/ddc/greensburgfiveyear

NOAA’s Storm Prediciton Center. (2019). U.S. Tornado Outbreak Interface. Retrieved from: https://www.spc.noaa.gov/exper/outbreaks/#

Tanamachi, R.L., H.B. Bluestein, J.B. Houser, S.J. Frasier, and K.M. Hardwick, 2012: Mobile, X-band, Polarimetric Doppler Radar Observations of the 4 May 2007 Greensburg, Kansas, Tornadic Supercell.Mon. Wea. Rev.,140, 2103–2125, https://doi.org/10.1175/MWR-D-11-00142.1

Bluestein, H.B., 2009: The Formation and Early Evolution of the Greensburg, Kansas, Tornadic Supercell on 4 May 2007.Wea. Forecasting,24, 899–920, https://doi.org/10.1175/2009WAF2222206.1

National Weather Service Dodge City, Kansas. (2008). The Rebuilding of Greensburg – one year later [PDF]. Retrieved from: https://www.weather.gov/media/ddc/Greensburg_1year_later.pdf

Stormtrack. (n.d.). May 4, 2007: Greensburg, Kansas and Arnett, Oklahoma tornadoes. Retrieved from: https://stormtrack.org/weather-library/storm-chasing-event-archive/2007-events/may-4-2007-greensburg-kansas-and-arnett-oklahoma-tornadoes/

National Centers for Environmental Information reports:

This killer tornado started in Comanche county and crossed into Kiowa county at 2003 CST / 2103 CDT. It curved north then northwest before making a complete loop northwest of Greensburg. Thus, the path was 25.8 miles.

This tornado destroyed nearly 95 percent of the town of Greensburg and despite adequate warning, unfortunately took the life of 11 people, some that were in basements. First responders arriving on the scene requested three refrigerated refer trucks thinking there would be hundreds of fatalities. It also destroyed a dozen homes and a church south of Greensburg but did not cause injury. In all, 961 homes and businesses were destroyed, 216 received major damage and 307 received minor damage.

As the tornado was dissipating it turned northwest, west, south and then back east making a loop. This was documented on both high resolution doppler radar and through the ground survey. Also as the tornado was dissipating a new circulation quickly grew northeast of town.

Several oil storage tanks were destroyed causing an environmental concern. In the town of Greensburg, hazardous material was strewn everywhere. As of July 26th, the debris was still not fully cleaned up. Two landfills were filled with debris from the town and this was even as most was burned. Hundreds of thousands of dump truck loads were taken out. It was estimated that approximately 400,000 cubic yards of debris was removed. The major highway running through town was closed for 1 full month.

At one time there were over 150 law enforcement officers (from all over the country) present. Military was called in for debris removal and rebuilding.

Damage of insured losses exceeded $150 million, but including un-insured losses, was roughly 250 million dollars.

**** NOTE **** The 11th victim passed away on September 19th, 2007 after a long battle with a head injury sustained during the tornado.

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