Monday, October 06, 2008
Weather columnist Kevin Myatt: Why the valley's wind wails in winter but whispers in summer
Kevin Myatt is The Roanoke Times' weather columnist.
kevin.myatt
@roanoke.com
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Weather with Kevin Myatt
Recent columns
- We got graupel, but not on official record
- Moisture could get caught up in cold blast
- Forecast for Weather Journal: Partly print, with frequent Internet
- Column archive
Read the Weather Journal blog
- Sprinkles or flurries possible Tuesday, but maybe something bigger for the weekend?
- For now, it looks like a quiet, mostly mild week ahead for SW Virginia
- Coldest morning of winter so far likely across much of Southwest Virginia; Tuesday precipitation looking doubtful
- Weather Journal blog
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During a lull in our weather last month, I solicited questions from readers on my roanoke.com blog.
With the weather looking quiet for several days, I will use some of these short weather updates on Mondays and Wednesdays to answer a few of those questions.
Reader question: Why is the Roanoke Valley windier in the winter than in the summer?
The primary reason we experience more wind in winter than summer is the location of the jet stream. The jet stream is a fast-moving river of air several miles above us that, roughly speaking, divides colder polar air to the north and warmer subtropical air to the south. The jet stream is the primary mover of weather systems such as low-pressure systems and cold fronts.
In summer, as the Northern Hemisphere warms, the jet stream retreats to Canada. As a result, we tend to have more stagnant air masses with weaker fronts and low-pressure systems. From fall to spring, the jet stream moves farther south as the hemisphere cools. During that time, more dynamic storm systems and cold fronts are pushed by the jet stream across the United States, and these usually have more wind.
Under certain circumstances, some of those high-level winds can be pulled to near the surface. When the jet stream is nearby -- as it is more likely to be in cooler months -- there are much stronger winds aloft that are available to be pulled down.
