Nevada County Picayune and Gurdon Times Newspaper Archive

Area residents trained as weather spotters

With Spring right around the corner, so is severe weather season.

Because of this, the National Weather Service, Shreveport, La. office, held a weather spotter course at the Nevada County Courthouse Thursday, Feb. 9, with about 30 people showing up for the training.

Bill Murrell, with the NWS, gave the PowerPoint presentation, showing those gathered what to look for in times of severe weather. They were also told the best place to be to see the storm.

Weather spotters, he said, are the key during severe weather because radar can only see so much. Because of the Earths curvature, the radar beam continually rises, which makes the lower part of a storm cell invisible to it. This is where spotters come in. They can let the NWS know whats happening with the bottom part of the storm.

Doppler radar, he said, helps and can see more, but is still limited. Doppler radar shows motion both toward and away from the radar and can see rotation within a cloud. Weather spotters are the eyes of the weather service.

In addition, he said, when the NWS issues a watch or warning the response isnt as great as when it can announce severe weather has been reported by a weather spotter.

The NWS and Department of Defense are the only two agencies allowed to have what is known as 10 centimeter radar, which provides better detail and accuracy. The radar used by television weathermen is 5cm radar, which is not as accurate or detailed.

Murrell said when the NWS issues a weather watch, its normally for three to six hours in duration. A warning, which means there is a likelihood of something happening, is for 30-60 minutes.

He explained severe weather as hail 3/4 inch or larger in size and winds 58 miles per hour or greater. Structural damage, Murrell said, begins when winds reach 58 mph. The difference between a tornado and funnel cloud, is a tornado is on the ground and the funnel cloud isnt.

Tornadoes are gauged according to the Fujita scale based on wind speed. This scale runs from F0 to F5. An F0 tornado has winds from 40-72 mph. F1, considered a weak tornado, has winds from 73-112 mph. The F2 is listed as a strong tornado, with wind speed from 113-157 mph. An F3 is a severe tornado, with winds reaching 158-206 mph. The F4 is considered a devastating tornado, with winds from 207-260 mph. The largest of known tornados, the F5, is called an incredible tornado. It has wind speeds from 261-318. There is another level on the Fujita scale, called an F6, which is listed as an inconceivable tornado. According to NWS information, this twister has winds from 319-379 mph. However, the NWS states these winds are unlikely, and if they occurred, they wouldnt be recognizable.

Murrell said there are two main periods for severe storms in the Ark-La-Tex region. The first is March-May, when 52 percent of tornados occur, and April 19-May 20, when 30 percent of tornados are spawned. The second period is, interestingly enough, from the middle of November through the middle of December. Severe weather in this region can happen at any time and with little warning.

Much of the meeting showed how to recognize different activity within a storm cloud, with the spotters to note such things as the wall cloud, where severe weather is generated.

The best place for weather spotters, he said, is East-Southeast from the storm itself. He suggested spotters leave themselves a buffer zone of a mile or two, in case the storm is a right mover, which means it changes direction to the right. Such a move would put the spotter directly in the storms path.

Murrell pointed out the dangers of severe weather, saying the biggest weather killer is flooding  not lightning or tornados. Flooding, he said, is an underrated killer.

Next on the list is lightning. Lightning, he said, gets hotter than the surface of the sun, reaching temperatures of 50,000 degrees Fahrenheit. He gave the formula for determining how close a storm is saying each five seconds from the time lightning strikes to the sound of thunder is a mile.

Hail is another major weather problem, though few people are killed by hail. Murrell said the biggest thing with hail is the amount of property damage it can do.

He pointed out a lot of severe storms in this area occur at night, unlike in the Midwest, when the storms happen during the afternoon hours. This, he said, is due to the afternoon heating and the moisture coming up from the gulf meeting the cooling temperatures as night falls.

He urged everyone to report severe weather, giving the NWSs toll-free number  1-800-551-8338. He said the best way to get the NWS information is via email at www.srh.noaa.gov/shv. The NWS can receive 20 emails a minute, compared to one phone call a minute.