May 2019 could be historic month for tornadoes after unprecedented twister streak finally ends at 13 days
After nearly two weeks, Mother nature finally gave the nation a reprieve on Thursday by ending an unprecedented tornado streak at 13 days. On each of those days, weather officials logged at least 8 tornado reports per day across the U.S.
The streak reached 11 days on Monday night when a flurry of tornadoes ripped through Indiana and Ohio, including an EF4 twister that struck Dayton, Ohio, causing significant damage to local communities. The next night, a destructive tornado, also an EF4, ripped through Linwood, Kansas. These are just a few of the massive tornadoes that have touched down recently in the country and extended the streak to almost the two-week mark. Tuesday was day 12, eclipsing the old record of 11, which ended on June 7, 1980.
As of Friday, the National Weather Service’s Storm Prediction Center (NWS SPC) logged 26 preliminary tornado reports on Tuesday. While these reports do not represent confirmed tornadoes, they do suggest that the record for consecutive days on which at least eight tornadoes touched down would be broken once the official totals are in.
That number extended to 13 days as 41 preliminary tornadoes were reported during Wednesday's severe weather event.
On Thursday, only two preliminary tornadoes were reported, bringing the remarkable streak to a welcome end. One of these tornadoes was confirmed by the NWS in Howard County, Maryland.
“The official record uses observed, confirmed tornadoes, and we are still dealing with preliminary tornado counts for the current stretch,” Dr. Patrick Marsh, a warning coordination meteorologist at the SPC, said in an email to AccuWeather.
Marsh told The New York Times that "we are flirting in uncharted territory. Typically, you’d see a break of a day or two in between these long stretches, but we’re just not getting that right now.”
Marsh told AccuWeather he chose eight tornadoes per day because that is the minimum number of tornado local storm reports (LSRs) issued on any given day during this stretch. If the benchmark were set to 10 tornadoes, the 1980 streak would hold.
“If you want to use number of consecutive days with any confirmed tornado, that is 70 straight days, with July 1, 1991, being the last day in that stretch with a tornado,” Marsh said.
Tornado reports have exploded this year after a couple years of low activity. As of Friday, the last day of May, the SPC has reported 1,008 tornadoes (preliminary) so far this year.
This month could end up with the most tornado reports of any recorded May, which is typically the most active month in terms of tornado activity.
“Looking at the data, before this month, May 2015 had the most tornado reports in any May with 414,” AccuWeather Senior Meteorologist Kristina Pydynowski said. "However, the current number of 516 is preliminary and it could be a little less after the season when the SPC will sort through the data for an actual total."
“Regardless, this May will be one of the top two most active tornado Mays (most likely No. 1) on record,” Pydynowski said.
The NWS reports that 38 people have died in 10 tornadoes in the United States this year, up from 10 fatalities in 2018. Seven of those deaths from this year's tornadoes have occurred in May. The majority of confirmed tornadoes this May are less intense, rated as EF0, EF1 and EF2s on the Enhanced Fujita Scale, but there have been a couple of very powerful twisters.
One of the strongest confirmed tornadoes this year was an EF4 tornado that killed 23 people in Lee County, Alabama, in early March. On Wednesday afternoon, the NWS officially rated the tornado that obliterated Linwood, Kansas, an EF4 storm with top wind speeds of 170 mph. No fatalities were reported in Linwood. A third EF4 tornado occurred in Dayton, Ohio, during the overnight hours of May 27.
Pydynowski added that there may be an increase in the number of tornado reports in recent years due to more people being out in the field and reporting tornadoes. There is a theory discussed among meteorologists that social media use may also play a role in this upward trend in tornado reports.
However, Marsh said that he does not feel comfortable “saying much about any trend owing to social media.”
According to Marsh, the nation just finished a stretch of well below normal tornado activity and had a corresponding decrease in the number of tornado LSRs. Thus, showing that LSRs are a relatively accurate indication of tornado activity, despite the potential inflation in the number of tornado reports due to more frequent observation and reporting.
About a decade ago, some preliminary work found that to approximate the number of observed tornadoes based on LSRs, one should multiply the LSR count by 0.85, Marsh said.
The recent uptick in tornado activity may be linked to a very volatile weather pattern across the U.S., with a large dip in the jet stream bringing unusually cool weather in the Southwest.
“At the same time, high pressure strengthened and was responsible for the record heat in the South,” Pydynowski said. “Storms riding the jet stream kept emerging from the Southwest and onto the Plains, clashing with warm and humid air and sparking the onslaught of the severe weather.”
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