Last year, the Navigator did a series of stories about deicing solutions. This winter we are focusing on weather systems. Our purpose is to help you understand what the meteorologists mean when they talk about an Alberta Clipper, the troposphere, dew points and how they all work together to create a winter storm. Weather.com has an entire glossary section on their website explaining winter weather, which will be referenced often along with other notable weather related pages in our upcoming series. Our plan is to condense the information and make it understandable to everyone.
Our first story explains how a winter storm forms.
As you probably know, the jet stream is a current of air around 20,000 feet above the ground that affects the weather. The position of the jet stream is quite influential when it comes to temperatures, wind, and the path in which a storm travels. Technically, weather.com describes it as “an area of strong winds concentrated in a relatively narrow band in the upper troposphere of the middle latitude and subtropical regions of the Northern and Southern Hemispheres… The troposphere is the lowest layer of the atmosphere located between the earth’s surface to approximately 11 miles into the atmosphere.” Temperatures usually drop as altitude increases in the troposphere.
More simply, the jet stream separates the warm air from the cold air. During winter when the jet stream dips down into the lower third of the U.S., low pressure increases as the cold polar air replaces the usually warmer tropical air. Air always moves from areas of high pressure to areas of low pressure, and due to the Coriolis Effect, the winds turn as they move, thereby causing a cyclone. In the Northern Hemisphere, winds circulate counterclockwise around areas of low pressure.
Next time, we will discuss the different types of storms that occur based on where the jet stream is located. For now, we will discuss the basics that are needed to form a winter storm.
In addition to the jet stream pulling enough cold air to lower the temperatures to freezing or below, an air disturbance needs enough warm, moist air (which is usually pulled from the Gulf of Mexico, the North Atlantic Ocean, or Pacific Ocean) to be able to produce frozen precipitation.
As The Weather Channel explains, “The intensity of a storm depends upon several items, such as the strength and positioning of the jet stream and associated upper air disturbances, the related strength of the horizontal temperature gradients, and the availability of moisture.”
Finally, the type of front that is advancing will have an effect on the clouds, winds, and temperature. When a warm front pushes its way into the cold mass, the lighter, less dense warm air lifts over the cold air causing the clouds to become thicker and lower in the sky. When a cold front pushes its way into a warm mass of air, the heavier, denser cold air must lift and push the warm air out of the way. This causes gusty winds and a sharp drop in temperature as it makes its way through.
