| ROANOKE WEATHER |  |
|
 |
Current Conditions: Partly Cloudy
Temperature: 78°F Wind: From the SW at 6 mph Relative Humidity: 64% |
Extended Forecast Driving Conditions Vacation Planner Weather Alerts Air Quality |
 |
SUN Scattered Thunderstorms 66°F...82°F |
 |
MON Isolated Thunderstorms 67°F...86°F |
|
TUE Partly Cloudy 69°F...89°F |
Latest entries from the Weather Journal blog
About Kevin
Kevin Myatt grew up in Arkansas to the tune of tornado sirens and the rhythm of hailstones, aspiring to be a meteorologist before his studies and career were turned to journalism instead. Though he often chases storms, he prefers living in the cooler, more tranquil weather of the Blue Ridge. He moved to Roanoke in 1999 to take a job on the copy desk of The Roanoke Times; writing headlines and editing copy is his principal work for the newspaper today.
Each May, Kevin assists Pulaski County High School / Virginia Tech meteorology instructor Dave Carroll in leading college and high school students to the Plains to observe severe weather firsthand. The accounts of many of his storm chases can be found here on the storm chasing page of his weather blog on roanoke.com.
Kevin was an editor for "Hurricanes and the Middle Atlantic States," a book written by D.C.-area weather enthusiast Rick Schwartz and published by Blue Diamond Books that documents hurricanes striking the mid-Atlantic states since colonial times.
The Weather Journal column began in 2003 and appears on Friday's Virginia section front in The Roanoke Times. The Weather Journal blog began in 2006 and follows weather day-by-day between the larger columns.
Mountains put a twist on twister potential
By Kevin Myatt
The Roanoke Times
Do the mountains protect Southwest Virginia from tornadoes?
It's sort of a trick question.
The answer is no, and yes.
First, the "no" part. If the atmosphere is set up exactly how it needs to be to produce a long-lived supercell thunderstorm with a tornado, that tornado isn't necessarily going to bounce off a ridge and skip over the next valley.
There are numerous examples of tornadoes crossing rugged terrain unimpeded. On Feb. 5, a tornado stayed on the ground for more than 100 miles through hills and hollows in the Ozarks of Arkansas, landscape comparable to that of southern West Virginia. A tornado has been observed on a 12,000-foot summit in the Sierras, and a large, violent twister at about 10,000 feet once shredded forests while crossing the Continental Divide near Yellowstone National Park.
So, in the specific case of a tornado that's already occurring, there should be no expectation that the nearby mountain ridge will protect you.
But in the general sense that Southwest Virginia gets fewer tornadoes than flatter areas to our east and west, the answer is yes, the mountains do factor into reducing our tornado risk.
The Appalachians often serve as a barrier between surface air masses. When warm, moist Gulf of Mexico air is streaming northeastward on the western side of the mountains, cooler, drier air is sometimes trapped east of the mountains. Even very strong storms moving across the mountains may weaken as they enter cooler, more stable air.
It is rare for a strong surface low pressure system to move right up the spine of the Appalachians. Storm systems usually track on one side of the mountains or the other. Those that move west of the mountains take much of their instability, moisture and wind energy with them into the Ohio Valley, while those moving to the east carry those prime tornado ingredients closer to the coast.
On a more local level, the placement of mountain ridges can disrupt the strong flow of air into a developing storm that is needed for it to rotate and make it more likely to produce a tornado.
But, sometimes, the atmospheric setup can become so primed that it overcomes all these factors. Destructive tornadoes in Roanoke in 1974 and Bedford in 2002 are prime examples, as well as the 1929 Rye Cove tornado that killed 12 students and a teacher at a rural mountain school.
There are just enough exceptions to pay attention to tornado safety rules.
Weather Journal appears Fridays, with short updates on Mondays and Wednesdays.
Conditions and Storms
- Latest storm warnings and radar from the National Weather Service in Blacksburg
- Ski slopes -- in season, of course
- Road conditions
- Tropical storm updates - 24/7
- Chasing the Wind - On the road in Tornado Alley
