On October 21, 2021, a surprise outbreak of 19 tornadoes ripped across eastern Ohio and Western Pennsylvania. Per NWS Pittsburgh: “A broken line of supercells, which formed along a front, quickly moved through the Ohio River Valley the evening of October 21st and spun off several tornadoes. The number of tornadoes, time of year, and intensity (one long track EF2 tornado) will mark this event as very rare and significant for this region.” Prior to the tornado development, temperatures warmed into the low-mid 60s, and the dewpoints topped out near 60, creating a moderately humid environment. However, other parameters needed for tornadogenesis were pretty low. The CAPE (the energy needed to sustain storms) was extremely low, and storm relatively helicity was meager. These conditions did not suggest that a tornado outbreak was imminent.
Early indications from the Storm Prediction Center (SPC) and models suggested that a squall line with perhaps an isolated supercell or two could produce strong, possibly damaging winds. The SPC had placed the area in the marginal or level 1 out of 5 risk of severe weather at 1300z (9:00 am ET), with the only risk being damaging winds. The forecast remained unchanged with the 1630z update (12:30 pm ET). At 2000z (4:00 pm ET), the SPC had placed a 2% tornado risk over parts of the area, noting, “While the tornado threat is low with these storms, it is non zero and have opted to introduce a 2 percent probability to reflect this potential.” At 4:36 pm, the first tornado developed in Medina County, Ohio, and for the next three and half hours, 18 more twisters would spin up across the area. Just before 7:30 pm, a tornado warning was issued for Washington County (the county I live in) as a supercell had just crossed the PA/WV border. I immediately called my friend Serina, and we went chasing. Our goal was to catch up to the storm at Cannonsburg. We could see power flashes about 2.5 miles to our west as we took the Cannonsburg exit of I-79. The mesocyclone passed directly over us, dropping the final tornado of the outbreak just three miles to our east in Peters Township. The following morning, before heading to Ohio for a Tornado Talk-related trip, I drove through Hopewell Township, where the strongest tornado occurred. I surveyed the first eight miles of the path via ground and about a mile of that with the drone. Time constraints and poor weather (heavy rain started to move in) prevented me from flying the drone over other parts of the path. Over the course of the next ten days, I was able to survey three other tornadoes from this event, two EF1s in Washington County and an EF1 that moved through parts of Beaver and Butler Counties. The Beaver/Butler County Tornado survey was conducted with the NWS, as they wanted me to fly my drone over the path for them. Unless otherwise noted, photos provided throughout the summary were taken by me.
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