CHICAGO (AP) — An unusually massive line of storms packing
hail, lightning and tree-toppling winds was rolling through the Midwest on
Wednesday and could affect more than one in five Americans from Iowa to
Meteorologists were even warning about the possibility of a weather event
called a derecho (deh-RAY'-choh), which is a storm of strong straight-line
winds spanning at least 240 miles. The storms are also likely to generate
tornadoes and cause power outages that will be followed by oppressive
heat, said Russell Schneider, director of the National Weather Service's
Storm Prediction Center in Norman, Okla.
The weather service issued tornado warnings in several counties in Iowa,
Illinois and Wisconsin. The National Weather Service said a tornado
touched down near Belmond, about 90 miles north of Des Moines, but it
wasn't immediately clear if it caused any damage or injuries.
"We're becoming increasingly concerned that a major severe weather event
will unfold," Schneider said. "The main thing is for folks to monitor
conditions and have a plan for what to do if threatening weather
For the first time this year, the center was using its highest alert level
for parts of Iowa, Illinois, Indiana and Ohio. In Chicago, Wednesday
night's White Sox game against the Toronto Blue Jays was postponed in
anticipation of bad weather and airlines canceled more than 120 flights at
O'Hare International Airport.
The storms were expected to push into northwest Indiana early Wednesday
The Northern Indiana Public Service Co., the region's largest utility,
said it was increasing staff at its customer call center and scheduling
extra work crews to handle any outages.
In Pennsylvania, Pittsburgh was adding public safety and public works
personnel and repositioning some equipment to prepare for possible
flooding or downed trees and wires, the Pittsburgh Post-Gazette reported.
All told, the area the weather service considers to be under heightened
risk of dangerous weather includes 74.7 million people in 19 states.
Tornadoes and a derecho can happen at the same time, but at any given
place Wednesday the straight-line winds are probably more likely.
Straight-line winds lack the rotation that twisters have, but they can
still cause considerable damage as they blow down trees and other objects.
"Be prepared to move away from windows," Schneider said. Listen for
weather warnings and go into a basement, if possible, and get underneath a
study object like a table, he said, if a tornado warning is issued. "You
want to know where your family's at so everyone can get to safety
Last year, a derecho caused at least $1 billion in damage from Chicago to
Washington, killing 13 people and leaving more than 4 million people
without power, according to the weather service. Winds reached nearly 100
mph in some places and in addition to the 13 people who died from downed
trees, an additional 34 people died from the heat wave that followed in
areas without power.
Derechoes, with winds of at least 58 mph, occur about once a year in the
Midwest. Rarer than tornadoes but with weaker winds, derechoes produce
damage over a much wider area.
Wednesday's storm probably won't be as powerful as 2012's historic one,
but it is expected to cause widespread problems, said Bill Bunting,
operations chief at the National Weather Service's Storm Prediction Center
in Norman, Okla.
The storms will move so fast that "by the time you see the dark sky and
distant thunder you may have only minutes to get to safe shelter," Bunting
For Washington, Philadelphia and parts of the Mid-Atlantic the big storm
risk continues and even increases a bit Thursday, according to the weather
The term derecho was coined in 1888, said Ken Pryor, a research
meteorologist at the Center for Satellite Applications and Research at the
National Oceanic and Atmospheric Administration in College Park, Md. The
word is Spanish for "straight ahead" or "direct," Pryor said.
The structure of a derecho-producing storm looks distinctive in radar and
satellite imagery, Pryor said. "The systems are very large and have
signatures that are very extreme," he said. "You get large areas of very
cold cloud tops that you typically wouldn't see with an ordinary
thunderstorm complex. The storms take on a comma or a bow shape that's