Warm Pacific may have led to near-record tornado month
By
Adriana Navarro, AccuWeather staff writer
Updated Oct 29, 2021 8:35 PM EDT
The contiguous United States has seen a near-record number of tornadoes spawn this October -- and the reason may stem from an "unusual event" that occurred in the Pacific Ocean.
If it's felt like October 2021 has seen an unusual amount of tornadoes across the nation, it's because it has. As of Oct. 20, the U.S. had seen 85 tornadoes in the month, placing it in the top 10 Octobers with the highest number of tornadoes since 1950. Since that date, AccuWeather meteorologists estimate that at least a dozen tornadoes have been reported, bringing the total close to 100. The year 2018 holds the record with the highest number of confirmed tornadoes in October at 123, followed by 117 in October of 2001.
A second peak of severe weather season generally occurs during the autumn as the seasons change, like in the spring as the weather transitions from colder to warmer. But, as AccuWeather Senior Meteorologist and head of Long-Range U.S. Forecast Paul Pastelok said, this secondary peak was a bit "unusual."
From Oct. 1 to Oct. 20, 2021, the contiguous U.S. saw roughly 85 tornadoes, 20 of which were in Oklahoma. (National Weather Service/Storm Prediction Center)
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"We went into this fall, and it stayed pretty warm across most of the nation. And, in fact, in the middle of October, we had record warmth across the Great Lakes and Canada," Pastelok said. That warmth stuck around in the region for a week or two, setting up a scenario more akin to warm spring weather with cold fronts rolling in rather than the reverse.
"The situation was not that far off from an April forecast," Pastelok said. "So when you just kind of switch the seasons, we were kind of set up for this."
A tornado tore through Interstate 10 in Orange County, Texas, on Oct. 27. (Mary Phan via Storyful)
The formula for severe weather consists of strong, upper-level winds, generally out of the west or northwest, combining with a warm, moist atmosphere in the lower levels.
This time around, something else was a big help. North of the Hawaiian islands, a warm body of water surged in size over the past couple of months. At the same time, storms cooled the waters near the Gulf of Alaska in the Northeast Pacific.
"That caused a big contrast in the sea-surface waters, and that had an impact on the atmospheric conditions over top," Pastelok explained. "You get high pressure forming to the south, low pressure to the north, and in between, when it gets up into the upper levels of the atmosphere, you get strong winds."
The winds continued to pick up, contributing to a strong jet stream that aimed at the northwestern coast of California. But the energy didn't stop there. It endured the journey across the Rockies, losing moisture, perhaps, but continuing eastward.
"And that ran into an area of the country that was all blocked up between all that warmth -- high pressure in Canada, upper-level lows moving into the east -- and everything converged starting in the Plains and then moved to the Midwest and Ohio Valley," Pastelok said. "So a lot of things came together."
Aerial footage shows damage in Purdin, Missouri, outside of St. Louis, that was caused by a tornado that swept through the area on Oct. 24. (SevereStudios/John Humphress)
In addition to this setup, water temperatures in the Gulf of Mexico were running above normal, providing the moisture needed that converged with the upper-level energy needed to create severe weather.
Oklahoma, in particular, was hit by the setup, having recorded at least 20 tornadoes for the entire month compared to only 13 for all of the other months this year combined, according to the National Weather Service Storm Prediction Center.
"The tornado count beat out the rest of the year, which is very unusual for an area that's so used to getting tornadoes in the spring and summer months," Pastelok said of the flurry of October tornado activity in Oklahoma. He acknowledged that this was still preliminary data but said it's still likely that October had more tornadoes than the rest of the months combined.
While the weather pattern created an unusual scenario for October, Pastelok stressed that severe weather could occur at any time of the year, despite there being two defined severe weather seasons.
For the latest weather news check back on AccuWeather.com. Watch the AccuWeather Network on DIRECTV, Frontier, Spectrum, fuboTV, Philo, and Verizon Fios. AccuWeather Now is now available on your preferred streaming platform.
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News / Severe Weather
Warm Pacific may have led to near-record tornado month
By Adriana Navarro, AccuWeather staff writer
Updated Oct 29, 2021 8:35 PM EDT
The contiguous United States has seen a near-record number of tornadoes spawn this October -- and the reason may stem from an "unusual event" that occurred in the Pacific Ocean.
If it's felt like October 2021 has seen an unusual amount of tornadoes across the nation, it's because it has. As of Oct. 20, the U.S. had seen 85 tornadoes in the month, placing it in the top 10 Octobers with the highest number of tornadoes since 1950. Since that date, AccuWeather meteorologists estimate that at least a dozen tornadoes have been reported, bringing the total close to 100. The year 2018 holds the record with the highest number of confirmed tornadoes in October at 123, followed by 117 in October of 2001.
A second peak of severe weather season generally occurs during the autumn as the seasons change, like in the spring as the weather transitions from colder to warmer. But, as AccuWeather Senior Meteorologist and head of Long-Range U.S. Forecast Paul Pastelok said, this secondary peak was a bit "unusual."
From Oct. 1 to Oct. 20, 2021, the contiguous U.S. saw roughly 85 tornadoes, 20 of which were in Oklahoma. (National Weather Service/Storm Prediction Center)
CLICK HERE FOR THE FREE ACCUWEATHER APP
"We went into this fall, and it stayed pretty warm across most of the nation. And, in fact, in the middle of October, we had record warmth across the Great Lakes and Canada," Pastelok said. That warmth stuck around in the region for a week or two, setting up a scenario more akin to warm spring weather with cold fronts rolling in rather than the reverse.
"The situation was not that far off from an April forecast," Pastelok said. "So when you just kind of switch the seasons, we were kind of set up for this."
A tornado tore through Interstate 10 in Orange County, Texas, on Oct. 27. (Mary Phan via Storyful)
The formula for severe weather consists of strong, upper-level winds, generally out of the west or northwest, combining with a warm, moist atmosphere in the lower levels.
This time around, something else was a big help. North of the Hawaiian islands, a warm body of water surged in size over the past couple of months. At the same time, storms cooled the waters near the Gulf of Alaska in the Northeast Pacific.
"That caused a big contrast in the sea-surface waters, and that had an impact on the atmospheric conditions over top," Pastelok explained. "You get high pressure forming to the south, low pressure to the north, and in between, when it gets up into the upper levels of the atmosphere, you get strong winds."
The winds continued to pick up, contributing to a strong jet stream that aimed at the northwestern coast of California. But the energy didn't stop there. It endured the journey across the Rockies, losing moisture, perhaps, but continuing eastward.
"And that ran into an area of the country that was all blocked up between all that warmth -- high pressure in Canada, upper-level lows moving into the east -- and everything converged starting in the Plains and then moved to the Midwest and Ohio Valley," Pastelok said. "So a lot of things came together."
Aerial footage shows damage in Purdin, Missouri, outside of St. Louis, that was caused by a tornado that swept through the area on Oct. 24. (SevereStudios/John Humphress)
In addition to this setup, water temperatures in the Gulf of Mexico were running above normal, providing the moisture needed that converged with the upper-level energy needed to create severe weather.
Oklahoma, in particular, was hit by the setup, having recorded at least 20 tornadoes for the entire month compared to only 13 for all of the other months this year combined, according to the National Weather Service Storm Prediction Center.
"The tornado count beat out the rest of the year, which is very unusual for an area that's so used to getting tornadoes in the spring and summer months," Pastelok said of the flurry of October tornado activity in Oklahoma. He acknowledged that this was still preliminary data but said it's still likely that October had more tornadoes than the rest of the months combined.
While the weather pattern created an unusual scenario for October, Pastelok stressed that severe weather could occur at any time of the year, despite there being two defined severe weather seasons.
In other news:
For the latest weather news check back on AccuWeather.com. Watch the AccuWeather Network on DIRECTV, Frontier, Spectrum, fuboTV, Philo, and Verizon Fios. AccuWeather Now is now available on your preferred streaming platform.
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