Twisters are a rarity in the Pacific Northwest
Geography plays a big part in why we don’t have the devastating tornadoes found in Midwest
Those who live in the Northwest, especially the inland portion, will often tell you how they feel fortunate not to have to deal with many of the phenomenon’s Mother Nature deals out in the form of hurricanes, ice storms and of course tornadoes.
The latter of course recently has come to the forefront following the deadly events in Moore, Okla. where an F5 twister cut a miles-long swath through the Oklahoma City suburb, killing 24, injuring 300 with damage claims that could hit $5 billion according to some estimates.
While rare, the Northwest is not immune.
“Tornadoes are a worldwide phenomenon,” Eastern Washington University geography and meteorology professor Dr. Bob Quinn said just days after the disaster in Moore.
The only places that don’t get them are the immediate tropics within 10 degrees of the Equator and the Arctic and sub-Arctic regions, he said.
“On the other hand the tornado capital of the world is the United States,” Quinn said. “And the tornado capital of the United States has a bunch of different names, Tornado Alley and all that good stuff is basically the Great Plains.”
More specifically, Quinn said, is the area around Texas, Oklahoma and Kansas that often have the most severe tornadoes. “But severe tornadoes can happen anywhere,” Quinn said. “Any given tornado and in any given place can be a nasty one.”
Even in the Northwest as was the case Friday, July 31, 1987 in Edmonton, Alberta where the F4 “Black Friday” tornado cut a 25-mile path across the provincial capital killing 27 and causing a half-billion in damage. Or the April 5, 1972 twister that ravaged Vancouver, Wash. Its nine-mile path left six people dead.
According to thetornadoproject.com Spokane County has recorded nine tornadoes, the last, April 6, 1994. No deaths have ever occurred.
“Why is that,” Quinn asked that the Midwest is such a tornado hot bed? “Nowhere else on earth do you have the peculiar geography of the Great Plains,” he explained. “You have a source of really warm, moist air out of the south in the Gulf of Mexico.”
That moist air drifts up from the south to meet the colder, more dry air from the Rocky Mountains. Cold air over warm moist air creates the perfect mix he explained. The warm and moist air wants to rise; cold, dry air wants to fall and “You trigger violent overturning in the atmosphere,” Quinn said.
Some of the deadliest tornadoes accompany cyclones in the Indian Ocean, specifically the Bay of Bengal off of Bangladesh.
Mortality is so high in these regions because tens of millions of people live at 5-10 feet above sea level. Such weather events produce thunderstorms, which in turn can produce tornadoes and the most severe in terms of death toll are in Bangladesh, Quinn said his data showed.
So while the conditions which produce such storms are in the waters off Asia, they are different than those in North America, “What it really says is whatever the mechanism is for producing a thunderstorm, they can occasionally produce a tornado,” Quinn said.
Which brings the discussion to the Northwest and why there are so few tornadoes, despite what appears to be somewhat similar geography.
“All 50 states have recorded tornadoes, including Alaska and Hawaii,” Quinn said. “The place that has the least tornadoes – and the average is 800-1,000 a year in the U.S., Texas averaging about 100 – is the Pacific Northwest.”
The state of Washington averages about one to two a year, he said, and even that is a statistical anomaly. “What really happens is you end up with two years with none and then in the right condition in spring, May or June, you get three of them reported in a day.”
The difference maker here in the Northwest is that we have predominantly warm, dry air at the surface. The moisture comes form upper level levels off the Pacific Ocean.
“In May or June, sometimes in the summer and rarely in the fall we can generate a line of thunderstorms, but they are upper level thunderstorms; their bases are up at 9,000 to 12,000 feet,” Quinn said.
So if a tornado is generated it tends to be of the “long, skinny, ropy variety that has to come all the way down and touch the ground,” and only then becomes a tornado, Quinn explained.
“They’re still a tornado but when they touch down they’re not these monster half-mile-wide 250-miles-an-hour wind guys,” Quinn said. Generally they are of the F1 variety on the Fujita Scale that rates storms 1-5 in increasing severity.
Quinn dispelled the wives tale about tornadoes never striking the same place twice. Moore, in fact has been his be three devastating tornadoes since 1999.
“Why would anybody live there,” is one of the questions most asked. “Because it’s home; this is part of life living here,” Quinn said.
Paul Delaney can be reached at firstname.lastname@example.org.