WASHINGTON (AP) — Everything had to come together just perfectly to create the killer tornado in Moore, Okla.: wind speed, moisture in the air, temperature and timing. And when they did, the awesome energy released over that city dwarfed the power of the atomic bomb that leveled Hiroshima.
On Tuesday, the National Weather Service gave it the top-of-the-scale rating of EF5 for wind speed and breadth, and severity of damage. Wind speeds were estimated at between 200 and 210 mph.
To get such an uncommon storm to form is “a bit of a Goldilocks problem,” said Pennsylvania State University meteorology professor Paul Markowski. “Everything has to be just right.”
For example, there must be humidity for a tornado to form, but too much can cut the storm off. The same goes with the cold air in a downdraft: Too much can be a storm-killer.
“Everything was ready for explosive development yesterday,” said Colorado State University meteorology professor Russ Schumacher, who was in Oklahoma launching airborne devices that measured the energy, moisture and wind speeds. “It all just unleashed on that one area.”
Several meteorologists contacted by The Associated Press used real time measurements, some made by Schumacher, to calculate the energy released during the storm’s 40-minute life span. Their estimates ranged from 8 times to more than 600 times the power of the Hiroshima bomb, with more experts at the high end. Their calculations were based on energy measured in the air and then multiplied over the size and duration of the storm.
An EF5 tornado has the most violent winds on Earth, more powerful than a hurricane. The strongest winds ever measured were the 302 mph reading, measured by radar, during the EF5 tornado that struck Moore on May 3, 1999, according to Jeff Masters, meteorology director at the Weather Underground.
Still, when it comes to weather events, scientists usually know more about and can better predict hurricanes, winter storms, heat waves and other big events.
That’s because even though a tornado like the one that struck Moore was 1.3 miles wide, with a path of 17 miles long, in meteorological terms it was small, hard to track, rare and even harder to study.
“This phenomenon can be so deadly you would think that something that catastrophic, that severe would lend itself to understanding,” said Adam Houston, meteorology professor at the University of Nebraska, Lincoln. “But we’re fighting the inherent unpredictability of these small-scale phenomena.”
Unlike hurricanes, which forecasters can fly through in planes and monitor with buoys and weather stations, usually over a period of days, tornadoes form quickly and normally last only a matter of minutes.
Still, the conditions needed to form such a violent and devastating tornado were there and forecasters knew it, warning five days in advance that something big could happen, Brooks said.
By Monday morning, forecasters at the National Weather Center knew “that any storm that formed in that environment had the potential to be a strong to violent tornado,” he said.
“Tornadoes are perhaps the most difficult things to connect to climate change of any extreme,” said NASA climate scientist Tony Del Genio. “Because we still don’t understand all the factors required to get a tornado.”