Greensburg, Kansas EF-5 tornado: May 4, 2007

During the late afternoon hours of May 4, 2007, the atmosphere over western Oklahoma and Kansas had become an ominous mixture of high instability and strong low-level wind shear. A potent upper-level storm system was arriving in the south-central Great Plains of the United States. Though the next day, May 5, had forecasters on edge for the possibility of a major tornado outbreak, the evening of May 4 was thought to be more in question: would any storms form? and, if so, how long would they sustain themselves?
Earlier in the afternoon, an isolated supercell thunderstorm had produced a very photogenic tornado in northwestern Oklahoma, near the town of Arnett, in Ellis County. This tornado was high-based, and well-documented. Though the tornado was violent, visibly lifting whole trees high into the air as it churned viciously across mainly open rangeland, it produced little other damage. But it was, perhaps, a sign that the right combination of things were at work in the atmosphere to make May 4 a memorable day as well.
Later that evening, another supercell storm initiated over Harper County, Oklahoma. With the environment becoming even more supportive of tornadoes near dusk, the storm grew explosively over the next hour as it drifted northward into Kansas. The combination of ingredients was more than sufficient to allow this storm to become a very prolific tornado producer. Its first tornado occurred near the town of Sitka, Kansas, at around 8:30 PM. The storm produced several other tornadoes between Sitka and the town of Protection before the first large, long-tracked tornado of the evening formed northwest of the town of Coldwater. This tornado eventually devastated the small farming community of Greensburg (pop. ~1,300), leaving 95% of the structures damaged or destroyed, and was responsible for 11 deaths. At 1.7 miles wide, and with a path length of nearly 29 miles, the tornado was rated EF-5, the first such designation on the Enhanced Fujita Scale.
As the Greensburg tornado occluded on the northwest side of town, a new, long-tracked tornado began to its northeast. This tornado ultimately grew even larger, reaching a width possibly as much as 2.7 miles near the town of Trousdale. Fortunately, the town was not directly impacted.
Though confirming each tornado proved to be difficult (due to terrain/lack of damage indicators, and a major tornado outbreak occurring over the same areas less than 24 hours later!) this single supercell thunderstorm known as the “Greensburg Storm” produced at least 22 tornadoes over the course of several hours on the evening of May 4, with the last tornadoes lifting near the towns of Holyrood and Ellsworth, Kansas.
For more information, visit the following links:
www.crh.noaa.go...
ams.confex.com...
Storm chasers: David Demko, Don & Nicole Giuliano
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