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Henry Lind's Weather Watch
by Henry Lind

Weather Watch

A Daily Gazette news blog
Weather events in our region and why they happen
 

What’s in a name?

By Henry Lind
Monday, February 17, 2014

It seems we can’t catch a break this winter with nonstop snow events happening every few days. Many observe that a weekly frequency of notable storms is more common, but recently we have not had a week’s respite to figure out where to put the latest contribution to the white landscape. This is described as an “active” weather pattern by meteorologists -- the activity is due to the jet stream shifting frequently rather than remaining in the same general location across the country. A simple explanation of the jet is the result of warm tropical air moving into colder regions, but taking a right turn due to the spinning of the earth. Thus it flows from west to east in our northern hemisphere.

Of course, nothing is that simple and the jet stream is rarely straight west to east, but wiggles for a variety of reasons. If it is somewhat straight and a storm develops to our west in Canada then we call that an Alberta Clipper. Clippers are named not only for their place of origin, but also to reflect the fact that they are fairly fast moving storms. They do not generally have a great deal of moisture and the snowfall is light. Should the jet sag south toward the Gulf of Mexico before it arrives at the east coast and a low pressure system develops, then lots of moisture will be picked up from the Gulf and the storm will be more intense. As these systems slowly travel up the east coast the wind direction on the ground will be from the northeast, and that is how they are known. In New England where a certain letter is rarely pronounced they may be referred to as No’theast.

Blizzard conditions are defined without regard to the origin of the storm or its track but rather specifics with respect to a three hour period of sustained wind speeds over 35 mph, and snow or blowing snow, which reduces visibility to less than one quarter mile. This weekend while we experienced a clipper event, blizzard conditions were the case on the New England coastline.

Another phenomenon which produces snow in the lee of large bodies of water is called Lake Effect or Ocean Effect. These are not organized low pressure systems but once again are based on temperature differences. Wind over open waters of the lakes will cause moisture to be absorbed into the air. When that air is cooled traveling over land, the moisture is forced out and drops to the ground as snow. As the Great Lakes are finally becoming frozen this is less common now, but it has been a substantial part of weather events so far this winter, even affecting the lower Mohawk Valley.

A little understanding of how the next layer of white arrives in our back yard might not make clearing a path easier, but it could give us something to think about while we finish the chore.

 
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