Spirit of MalvernREAD ONLINE
Now is time for severe-weather awarenessPublished March 2, 2014 at 12:00 a.m.
Their tools are barometers, balloons saddled with high-tech gadgetry and Doppler radars. The functions of such items are as familiar to them as is our use of cutlery at a dinner table boasting steaks and baked potatoes. The people who utilize this equipment are the meteorologists of the National Weather Service, an agency of the National Oceanic and Atmospheric Administration.
One member of this front-line force against severe weather is John Robinson, the warning coordination meteorologist for the North Little Rock NWS office, the hub for severe-weather forecasting for most of Arkansas’ 75 counties.
Robinson has been with the weather service for nearly four decades, having started to work there just one month after his college graduation. All but 11 months of his NWS career have been spent at the North Little Rock (formerly Little Rock) location, so he is very familiar with the weather patterns that are commonplace in The Natural State.
He remembers tornado outbreaks like the ones that occurred on March 1, 1997, the day of the Arkadelphia tornado; Jan. 21, 1999, when 52 tornadoes developed in only eight hours, the biggest outbreak ever in the state; Dec. 24, 1982, the Christmas Eve tornadoes that brought the second round of severe storms that month; and Feb. 5, 2008, when one tornado stayed on the ground for roughly 122 miles, making it the longest-track tornado in state history.
Recently, Robinson sent out an email to media outlets across the state. The purpose of the email was to serve notice that today through Saturday will be observed as Severe Weather Awareness Week, both in Arkansas and nationally. Those dates roughly coincide with the beginning of Arkansas’ severe-weather season.
“March, April and May are the most likely months for tornadoes in Arkansas,” Robinson said. “About two years out of three, we have a secondary severe-weather season, usually in November or December. However, tornadoes have occurred in every month in Arkansas. August is our least-likely month for tornadoes.”
When a severe-weather event is unfolding, the NWS monitors the atmospheric conditions using various methods. If a severe-weather watch is warranted, the NWS’ Storm Prediction Center in Norman, Okla., will issue either a severe-thunderstorm watch or a tornado watch.
“A watch means that conditions are becoming favorable for severe weather,” Robinson said. “SPC’s goal is to issue the first watch of the day about two hours before severe weather begins.”
Before that watch occurs, Robinson explained, the SPC will conduct a conference call with all the NWS offices in the targeted watch area. Discussions will center on a variety of topics, including whether a watch is warranted, whether it should be for severe thunderstorms or tornadoes and which counties to include in any resulting watches.
For instance, the SPC will go with a tornado watch over a severe-thunderstorm watch if the expectations are for at least two or more tornadoes to occur, Robinson said.
“The local NWS offices, like ours, are responsible for issuing the warnings,” Robinson said. “A warning means that, based on what we are seeing on radar or the reports that we are getting, severe weather has a high probability of occurrence.”
Over his 39.5 years with NWS, Robinson noted, there have been several changes in the agency, particularly with regard to technological advances.
“When I first started with NWS, we had an old black-and-white radar,” he said. “Back in those days, only about 10 to 15 percent of tornadoes had a warning in effect before they touched down. Most of the time, the warning was not issued until a report was received that a tornado was occurring. Now, our success rate in having a warning in effect before a tornado touches down is in the 85 to 90 percent range.”
More advancements are on the horizon, said Robinson, who mentioned phased array radar as the next step for the NWS.
“[The phased array radar] gathers data much more quickly than the current Doppler radar. In the phased array radar, the beams are sent out electronically — the radar dish does not have to rotate mechanically,” he said, adding that the new type of radar is in the testing phase in Norman and will probably be deployed to NWS offices in 10 to 15 years.
While Arkansas is on the eastern edge of an area known as Tornado Alley, some meteorological professionals have dubbed Arkansas and much of the Mid-South and Southeast to be Fatality Alley because of the area’s high occurrence of nighttime tornadoes that lead to deaths.
Whether that moniker is warranted or not, weather watchers have also noted that Arkansas’ terrain seems to act like a smaller version of the Great Plains that have earned that Tornado Alley title.
Robinson explained this phenomenon by noting that “many of Arkansas’ tornadoes tend to occur on a southwest to northeast line across the state because this is the dividing line between the hilly terrain to the northwest and the flat terrain to the southeast. Thus, that dividing line is somewhat like a path of least resistance because of the terrain.”
The paths of Interstate 30 and U.S. 67/167 were constructed on comparatively flat ground along the edge of those hills — a cost-cutting move. Since “almost two-thirds of Arkansas’ tornadoes travel from southwest to northeast,” as Robinson explained, their most common path is going to be one “roughly paralleling I-30 and U.S. 67/167.”
Of course, tornadoes are not the only form of severe weather to visit Arkansas. There are severe thunderstorms that bring hail, lightning and high winds, and there are floods and flash floods.
Robinson said his concerns for these other forms of severe weather lie in how people respond to such events.
“I know a lot of people think they don’t need to react to severe thunderstorm warnings,” Robinson said, “but when we issue one, we are expecting winds of at least 58 mph and/or hail at least 1 inch in diameter. In other words, we are expecting a dangerous storm that can blow windows out of a house, blow a car off the road, etc.”
The NWS meteorologist then offered an example of a man who lost his life in Arkansas last year when a street sign blew into his vehicle. That happened because of severe-thunderstorm winds, not because of a tornado.
“Also last year, we had two tornado fatalities in the state but six fatalities due to flash-flooding,” he said. Those flooding fatalities, Robinson explained, often come with nighttime or early-morning events, either when people are sleeping or because gauging water depth is harder in low-light conditions.
While statistics on lightning deaths are scant by comparison to those resulting from tornadoes, storms or flooding, Robinson said, “The important thing to remember … is that if someone is struck by lightning and survives (and most people do survive, by the way), there is a very high probability that they will suffer lasting effects for the rest of their lives.”
When it comes to severe weather, Robinson ultimately offered the following advice.
“Keep up with where the warnings are. When we get out and talk to people after tornadoes, it is truly amazing how many people will have no idea at all that a warning was in effect (sometimes the number approaches 50 percent). Unfortunately, I can point to quite a number of cases where people lost their lives when they didn’t hear the warnings.”
Robinson pointed out the paradox because of the myriad ways that people can now receive warnings — radio, television, NOAA weather radio, smartphones, social media, subscription services. However, he said that most of rural Arkansas, like when he first arrived here in 1974, is still reliant only on television.
However, 30 years ago, those tall antennas on everyone’s houses received only local stations. Now, satellite and cable services coming to those homes offer many channels, with only a few that might offer local weather warnings.
For more advice on staying safe during severe weather, Robinson suggested that people visit www.nws.noaa.gov/osbrochures/ttl.pdf.
Arkansas floods 411
Tornadoes are the headline grabbers among severe-weather events but are not the deadliest form of severe weather on average. Nationally, tornadoes annually claim 60 to 65 lives and cause 1,500 injuries. That ranks twisters just ahead of lightning, which is responsible for an average of 55 to 60 fatalities and 400 injuries annually. Meanwhile, flash-flooding and flooding result in more than 90 fatalities per year.
Lightning can be deceptive. If outdoors and close enough to a thunderstorm to hear the thunder, a person is close enough to be struck by lightning — even from nonsevere thunderstorms. Most lightning occurs within 10 miles of the parent storm, but lightning can strike as far as 50 miles away.
The deadliest flood in Arkansas’ recent history occurred in the predawn hours of June 11, 2010, when more than 6 inches of rain fell at the Albert Pike Recreation Area along the Little Missouri River in southwest Arkansas, pushing the river higher by more than 20 feet in only three hours. The flash flooding claimed 20 lives.
Called The Great Flood of 1927 by many historians, the 1927 spring flood that inundated Arkansas and other Mississippi River Valley states is one of the most severe flooding events in weather history. At one time, 6,600 square miles of Arkansas — roughly 36 of the state’s 75 counties — were under water with depths of up to 30 feet.
Severe flood events visited the state again in 1937 and 1945. The 1927 and 1937 floods combined heavy rains in Arkansas with above-normal precipitation and snow melt coming down the Mississippi River. The 1945 event, however, saw devastation more from the former cause than the latter, with portions of west, west-central, northwest and north-central Arkansas recording 2 to 3 feet or more of rain in only three months (February through April).
— Information courtesy of the National Weather Service
Arkansas tornadoes 411
There were nine weather-related deaths in Arkansas during 2013. Only two were caused by tornadoes, with one coming from thunderstorm winds and six occurring because of flooding or flash-flooding.
The severe weather activity in Arkansas in 2013 was about average based on the number of tornadoes. The state saw 34 confirmed twisters, while the average is 33 per year.
Severe weather in Arkansas can be highly variable from year to year. The state has reported as few as 18 tornadoes and as many as 81 per year in the past six years.
The peak months for severe weather in Arkansas are generally considered to be March through May. A study of the number of tornadoes occurring in the state between 1971 and 2000 showed May and April, in that order, to be the worst two months for tornadoes. November was third during that time span.
While spring is considered severe-weather season in Arkansas, severe weather can occur anytime throughout the year. In fact, there is a secondary peak in severe weather activity in December through February. During those three months, more than 330 tornadoes have been recorded since 1950.
The busiest year on record for tornadoes in Arkansas was 1999. There were 107 tornadoes reported and confirmed that year.
The Enhanced Fujita Scale (formerly the Fujita Scale) is used to classify tornadoes in regard to their wind speed. This scale ranges from EF0 (wind speeds of 65 to 85 mph) to EF5 (201 to 240 mph or more).
The more destructive tornadoes, EF3 through EF5, are often spawned by supercell thunderstorms that develop in an isolated manner. The entire storm may spin to create these larger twisters.
The most destructive tornado event in Arkansas’ recent history occurred on March 1, 1997, when 16 tornadoes struck Arkansas and left 25 people dead. Two F4 tornadoes tracked through parts of southwest and central Arkansas, with major damage and deaths in and around the cities of Arkadelphia and Benton.
The deadliest tornado outbreak in Arkansas was on March 21, 1952, when 111 people were killed. Communities such as Bald Knob, Judsonia and Cotton Plant were among the hardest-hit. There were 17 tornadoes that day, with 12 of them being killers.
The only known F5 tornado ever to hit Arkansas occurred on April 10, 1929. It tracked from south of Batesville into the Black River bottoms of Jackson County and on to the north of Centerville. The storm killed 23 people and injured 59 more while destroying about 40 homes and 36 barns.
The longest-track tornado in Arkansas weather history occurred on Feb. 5, 2008, when an EF4 tornado traveled roughly 122 miles through seven counties (Yell, Pope, Conway, Van Buren, Stone, Izard and Sharp). The tornado killed 12 people, injured at least 140 more and damaged or destroyed nearly 900 homes and 100 businesses. Severe damage was noted in Clinton and Atkins.
— Information courtesy of the National Weather Service
Zoned Editions Editor James K. Joslin can be reached at 501-399-3693 or email@example.com.