TIME Environment

From ‘Gale’ to ‘Inconceivable,’ Ranking Tornado Strength

Ranking tornado strength
Deadly tornadoes devastated the town of Vilonia, Arkansas on Apr. 27 Mark Wilson/Getty Images

As tornadoes blast across the southeastern U.S., a look at how officials gauge just how powerful a killer twister is

Tornado season began with a crash in the southeastern U.S. this week, where dozens of twisters ripped across Mississippi, Arkansas and Alabama. At least 29 people have died in the storms — and with more tornadoes forecast as the weather system moves further east, that number will almost certainly rise.

It’s the suddenness of tornadoes, as much as their power, that accounts for the lives they take. Meteorologists can forecast when and where storms that can produce tornadoes will appear, but they can rarely give residents more than 15 minutes of warning before a twister touches down. Unlike hurricanes, which meteorologists can now track days in advance with increasing precision, tornadoes remain stubbornly unpredictable, although forecasters at the National Oceanic and Atmospheric Administration (NOAA) are working on ways to extend that warning time.

That unpredictability also makes it harder to assess the destructive power of a tornado in real time. Hurricane categories are based on sustained wind speeds in a storm—a Category 1 storm would have sustained winds 74-95 mph (119-153 kph), while a Category 5 storm would have sustained winds of over 157 mph (252 kmh) (“Sustained wind speeds” means the average wind speed in a storm over 10 minutes). The damage a hurricane can cause doesn’t always conform completely to categories. Superstorm Sandy, for instance, wasn’t even a Category 1 hurricane by the time it made landfall in New Jersey, but still caused more than $60 billion in damage, largely due to the size of its storm surge. But more wind generally means more danger—just ask the people of New Orleans, hit by Category 5 Hurricane Katrina in 2005.

Tornado strength is assessed on a different and slower scale, after the twisters have struck. When tornadoes occur, National Weather Service (NWS) officials are dispatched to survey the damage. They also reconstruct tornadoes’ life cycles, where they touched down—and how strong they were. Tornadoes are ranked on the Enhanced Fujita (EF) Scale, developed by a Japanese-American meteorologist who, not coincidentally, got his start studying the damage caused by the atomic bomb in Hiroshima. The original Fujita scale was based primarily on the damage a tornado did, with wind speed estimated after the fact. The scale ranked tornadoes from a F0 (Gale) to an F5 (Incredible), with an unofficial F6 category that would require winds in excess of 318 mph and which goes by the name Inconceivable—accurate, since no F6 tornadoes have ever been recorded.

The Enhanced Fujita scale was adopted in 2007. It was designed to more accurately reflect the actual damage a tornado had done on the ground. The EF scale uses 28 different damage indicators, ranging from small barns to hardwood trees to shopping malls—and each of those indicators is assessed based on several different points of possible damage. A shopping mall could range from damage that is just barely visible to complete destruction of some or all of the building. There’s a large database of how strong a tornado needs to be to cause certain kinds of structural damage, so meteorologists are able to use the final damage report to go back and estimate the tornado’s wind speed at the time of touchdown. The categories range from EF0—with three-second wind gusts of 65-85 mph (104-137 kph)—to EF5, with three second gusts over 200 mph (321 kph).

We won’t know the full strength of this week’s multiple tornadoes until NWS surveyors have had a chance to measure the damage on-site. But there has already been a pair of EF3 twisters this year, striking Arkansas and North Carolina on Apr. 27, and those tornadoes may be upgraded as full damage assessments are carried out. 2014 had been shaping up to be a quiet year for tornadoes—Apr. 27 marked the end of a string of 159 days without an EF3 or above tornado, and there had been only 93 tornado reports this year through Apr. 24. That changed this week—there were 87 tornado reports on Apr. 28 alone. And while no tornado that’s hit yet looks to be as strong as the EF5 twister that devastated Moore, Oklahoma last year, the season is far from done.

TIME weather

WATCH: Weatherman Interrupts Live Broadcast to Evacuate Newsroom During Tornado

When a tornado touched down in his studio’s hometown of Tupelo, Mississippi, WTVA Chief Meteorologist Matt Laubhan stayed on his toes and led a newsroom evacuation in the middle of a live broadcast.

“This is a tornado ripping through the city of Tupelo as we speak, and this could be deadly,” Laubhan says in the clip. Then he points to an area off-camera and shouts, “Basement. Now.”

Shortly after the frantic newscast, the station tweeted, “We are safe here.”

Devastating storms have been ravaging the southern U.S. for the past three days. The violent weather has killed more than 30 people, destroyed homes and businesses and left thousands without power. Officials say 11 were killed in Mississippi on Monday alone.

TIME weather

Photos: Tornadoes Tear Through the South

Several tornados have ripped through the south, including Arkansas, Mississippi and Alabama, adding additional lives to the death toll

TIME weather

Swarm of Tornadoes Tears Across the South

Constance Lambert embraces her dog after finding it alive when returning to her destroyed home in Tupelo, Miss., April 28, 2014.
Constance Lambert embraces her dog after finding it alive when returning to her destroyed home in Tupelo, Miss., April 28, 2014. Brad Vest—AP

Dozens of twisters across Mississippi, Alabama and Tennessee pushed the death toll from this week's storms to at least 35 as the system moves east

Updated 4:58 p.m. ET

At least 16 people were killed Monday as deadly tornadoes ripped through sections of Alabama, Mississippi and Tennessee, bringing the death toll for the storm system that hit the Midwest earlier in the week to 35.

The dangerous weather was headed toward Georgia early Tuesday, after having flattened buildings in towns throughout the region, and Governor Nathan Deal has declared a state of emergency.

“For about 30 seconds, it was unbelievable,” said Mississippi state Sen. Giles Ward, whose Louisville home was destroyed in the storm while he huddled in a bathroom with his wife, four kids and dog. “It’s about as awful as anything we’ve gone through.”

The storm system rumbling east across the country has slammed a huge swath of territory with dangerous weather, from Iowa south to Oklahoma and into Arkansas, which alone saw 15 deaths. An estimated 11 tornadoes hit the central U.S. Sunday and 25 ravaged the South Monday, according to a preliminary count from the National Weather Service Storm Prediction Center.

The storm reserved its most severe weather for Mississippi and Alabama. At least 45 injuries and six deaths were reported in Winston County, Miss., on Monday. One was a woman who died in the day care center she operated in Louisville, though it remained unclear if there were children in the center when the storm hit.

In Tupelo, Miss., every building in a two-block area was damaged when a tornado ravaged the town of about 35,000. Limestone County, Ala., suffered severe damage in the storm, which knocked out power to nearly 12,000 and killed two when a twister hit a trailer park in the small community of Coxey.

Power was out for tens of thousands of customers in the region and road crews worked to clear debris from streets Tuesday, the Associated Press reports.

[AP]

 

TIME weather

Tornadoes Trample Swath of South, Midwest

A U.S. flag sticks out the window of a damaged hot rod car in a suburban area after a tornado near Vilonia, Arkansas April 28, 2014 Carlo Allegri—Reuters

Dozens of twisters across Mississippi and Alabama pushed the death toll from this week's storms to at least 28 as rescuers search for survivors

Tornadoes have torn through the Deep South in the wake of two days of severe weather in the Midwest, killing nine and bringing the tornado-season death toll so far to at least 27.

At least five tornadoes touched down in Mississippi on Monday evening, claiming seven lives, while authorities in Alabama reported that at least two people were dead in Limestome County in the wake of several powerful spring storm cells. The severe winds have downed trees, leading to local power outages, and reportedly also destroyed a trailer park.

A tornado struck Tupelo, Miss., at around 2:45 p.m. on Monday, causing multiple injuries, the Weather Channel reports, though none were expected to be fatal.

A widespread tornado watch was put into effect across the Midwest and South on Monday night. Ohio, Iowa, Tennessee and parts of Missouri are at risk of severe weather.

The fresh spate of tornadoes comes after 18 were killed across three states on Sunday as a result of severe weather. The worst may not be over yet either: the Weather Channel reports that flooding, heavy rain and thunderstorms are expected to continue into Wednesday.

[Weather Channel]

 

TIME weather

At Least 16 Dead as Tornadoes Cut Through Midwest

Search and rescue teams are scouring the rubble in Arkansas and Oklahoma after the year's worst tornado outbreak yet left at least 16 people dead across three states and caused widespread destruction of property

Updated 1:26 p.m. ET

Tornadoes tore through the American Midwest and South on Sunday, killing at least 18 people in three states—14 in central Arkansas, one in Oklahoma in a cyclone’s wake and one in Iowa.

Authorities are reporting that a tornado touched down 10 miles west of the Arkansas state capital Little Rock, causing widespread devastation in the suburban communities of Mayflower and Vilonia. Authorities initially said 16 people had died in Arkansas but later revised that to 14 because two people were counted twice, the Associated Press reports.

“What I am seeing, it is a lot of damage. I’ve been listening to the rescue folks. They’re saying people have to be extracted from vehicles,” Vilonia Mayor James Firestone told CNN. “It looks pretty bad. From what I understand, there has been a subdivision that’s been leveled.”

The tornado was reportedly on and off the ground for a total of 80 miles, cutting large swaths of destruction to the west and north of Little Rock.

“It sounded like a constant rolling, roaring sound,” Mayflower resident Becky Naylor told the Associated Press. “Trees were really bending, and the light poles were actually shaking and moving. That’s before we shut the door, and we’ve only shut the door to the storm cellar two times.”

Just two hours before the tornado touched down in Arkansas, another cyclone unleashed havoc farther to the west in the tiny town of in Quapaw, Okla., where one resident died and six were injured.

Tornadoes were sighted in Nebraska, Iowa and Missouri throughout Sunday as heavy storm cells ripped across the Great Plains.

Meteorologists are forecasting that severe weather, including tornadoes, hail and heavy winds could continue to pound the Midwest and Southeast throughout the beginning of the week. According to the Weather Channel, conditions are ripe for more tornadoes from east Texas across large swaths of the Plains up into Illinois.

[CNN]

TIME weather

Severe Storms, Tornados Forecast Across Large Swath of U.S.

A storm chaser photographer looks at thunderstorms supercells pass through areas in Vinson, Oklahoma
A storm chaser photographer looks at thunderstorms supercells passing through areas in Vinson, Oklahoma late April 23, 2014. The thunder storms on were a precursor of what's forecast for this coming weekend. Gene Blevins—Reuters

Meteorologists at the National Weather Service issued warnings about severe weather this weekend across Kansas, Oklahoma, Nebraska and Texas. Local residents were urged to prepare for hail, thunderstorms and tornadoes

Updated 4:08pm ET

Multiple tornados and severe thunderstorms are forecast this weekend from Nebraska to Texas, in what could be the worst severe weather event of the season so far.

The storms are expected to begin late Saturday and could last into the night before spreading to other areas, according to AccuWeather.com.

Multiple tornados had already touched down in eastern North Carolina by Saturday afternoon, sending 16 people to the emergency room so far and destroying or damaging 200 homes, CBS News reports.

“South-central Kansas to west-central Oklahoma would be in an elevated risk area for severe weather Saturday evening,” meteorologist Scott Breit said. The storms could then move in the direction of Omaha, Neb., Wichita, Kan., Oklahoma City, and Dallas later at night.

Sunday could see more tornados and strong hail lasting into the evening as well, according to National Weather Service’s Storm Prediction Center. It warned that Saturday’s storms would be severe, but “isolated and scattered.”

The relatively tame severe weather season so far makes the upcoming inclement weather a particular source of worry. “A reason for extra concern this weekend is that tornadoes have been nearly non-existent so far and people tend to forget what they have learned from year to year,” said Accuweather senior vice president Mike Smith.

[AccuWeather.com]

TIME nature

Washington State Mudslide Death Toll Rises to 39

Washington State Communities Continue To Deal With Aftermath Of Massive Mudslide
People hold candles during a vigil for mudslide victims at the Darrington Community Center on April 5, 2014 in Darrington, Wa. David Ryder—Getty Images

The Washington State mudslide has claimed 39 victims, according to the Snohomish County Medical Examiner's Office. Seven people remain missing

The Washington State mudslide has claimed 39 victims, according to the most recent count by the Snohomish County Medical Examiner’s Office.

Agency officials have positively identified 36 of the 39 people killed in the March 22 slide, the Seattle Times reports.

Seven people remain missing after the devastating mudslide struck the small riverside neighborhood of Oso in Snohomish County on March 22.

[Seattle Times]

TIME Chile

11 Dead in Chile Forest Fire

And at least 500 homes have been destroyed in the port city of Valparaiso, Chile

TIME Earthquake

Tsunami Warning Issued After Solomon Islands Quake

The 7.5 earthquake occurred 69 miles south of Kirakira on the Solomon Islands Sunday morning, according to the U.S. Geological Survey. The tremors could lead to a violent tsunami, warned the Pacific Tsunami Warning Center

The Pacific Tsunami Warning Center has issued a tsunami warning for the Solomon Islands, Vanuatu and Papa New Guinea after a magnitude 7.5 earthquake shook the Pacific.

The earthquake occurred 69 miles south of Kirakira on the Solomon Islands Sunday morning, according to the U.S. Geological Survey. It was initially categorized a magnitude 7.7 before being revised down to a 7.5.

The tremors could lead to a violent tsunami, warned the Pacific Tsunami Warning Center. Authorities in the region were advised to take action.

“An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicenter within minutes to hours,” warned the PTWC.

An 8.0 magnitude earthquake in February 2013 set off a tsunami that killed at least five people in a remote part of the Solomon Islands, Al Jazeera reported at the time.

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