GBDNA / Shortwaves

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Upper Level Cyclonic Systems

A shortwave is the smallest type of upper level disturbances in the synoptic scale. These impulses are also the fastest moving at the 500MB level, at least until encountering blocking features and amplification trends aloft. Energy tends to be distributed in a linear fashion, accounting for precipitation being limited to a narrow stretch in the cold and overrunning sectors of the cyclone (although convective displays can and do occur close to the frontal structure). Distortion of the 500MB height contours is usually in a flattened “U” signature embedded within the westerlies. An example of this type of disturbance can be found in association with the February 3 1976 Arctic outbreak in the U.S., where two distinct impulses are found rotating through a mean trough complex.

In a few situations, the upper system may be quite intense, displaying a closed core about a small geographic area. These cyclones are termed mega-shortwaves, and are in essence major storms confined to a more compact coverage. A classic case was the February 19 1979 “President’s Day Storm” which buried sections of the Virginias and Mid-Atlantic states with as much as three feet of snow.

"A Guide to Baroclinic Disturbances" is © 2007 by Larry Cosgrove.
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