By Kevin Byrne, AccuWeather staff writer
October 06, 2018, 11:46:36 AM EDT
Tuesday’s severe weather outbreak in the Northeast produced an unusually high number of tornadoes in Pennsylvania.
A total of 13 tornadoes have been confirmed across Pennsylvania as more storm surveys were completed this week. At least 18 tornadoes have been reported in the Northeast overall in the region, according to the Storm Prediction Center (SPC).
The intensity of the tornadoes ranged in scale from EF0 to EF2. Some of the worst damage was reported in the northwestern part of the Pennsylvania where an EF2 tornado caused significant damage to a nursing home and duplex in Conneautville.
Despite the extensive outbreak, no fatalities were reported, although there was at least one injury.
(Photo/National Weather Service)
Pennsylvania’s tornado outbreak is even more surprising when compared to Oklahoma, a state located in Tornado Alley. There have been 13 reported tornadoes in Oklahoma as of Oct. 4, far below the yearly average of 56. Sixty-two tornadoes were confirmed in the state in 2017.
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Of course, there are several months left in 2018 and fall does bring a secondary peak of severe weather, so the threat for severe thunderstorms that can produce tornadoes has not completely diminished.
Overall, Pennsylvania has 17 tornado reports thus far in 2018. There were 26 confirmed tornadoes in 2017 statewide. A yearly average for the state is 15, according to the SPC.
There were several atmospheric factors at play for the severe thunderstorms that unfolded in Pennsylvania, according to AccuWeather Meteorologist Brett Rossio.
Very strong winds were present high above the ground due to to a strong piece of energy in the atmosphere. These high winds are a necessary ingredient for tornado development, Rossio stated. The second ingredient was a very unstable air mass that developed ahead of this wave of energy. Temperatures surged well into the 70s ahead of this disturbance while temperatures high above the ground become rather cold, he explained.
"When this occurs, the air mass becomes highly unstable and severe thunderstorms developed. Many of these storms began rotating due to very strong winds aloft, as well as the variation in wind direction between the surface and upper levels of the atmosphere," Rossio said.
In terms of the lack of activity for tornadoes this year in the Sooner State, a big factor was the chilly spring that the state experienced.
"Climatologically, April and May are the most active months for tornadoes," Rossio said. Temperatures started out far too low with temperatures generally running 2-4 degrees below normal across much of Oklahoma during those months."
Another factor that resulted in a dip in tornado numbers this year is the overall storm track.
"The far cooler air was a result of a persistent Canadian storm track driving chilly Canadian clipper-type systems into the Plains. The ideal storm track is a more westerly-southwesterly storm track that can lift a more subtropical air mass northward from the Gulf of Mexico," Rossio said.
The first confirmed tornado in Oklahoma did not occur until May 1. Even though the state has seen fewer tornadoes, a few still have produced damaging impacts,including an EF1 near Chouteau, Oklahoma, in August.
The record for lowest number of tornadoes in Oklahoma in a year is 16 back in 2014.
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