Summary of Albert Clippers

1. These storms form to the lee of the Canadian Rockies, primarily in the province of Alberta. As shown by Thomas and Martin (2007), the average cyclogenesis region is in northern Alberta and usually appears around 36 hours after the circulation breaks off from the Aleutian Low.

2. Clippers are represented in the upper air by short wave troughs. Because of the predominant long wave pattern in the winter, namely ridge in the western U.S., trough in the east, the short waves travel from northwest to southeast, “clipping” the U.S.-Canadian border. Being associate with short waves, they are fast movers, in accordance with the Rossby wave equation.

3. There is no large water source within close range of an Alberta Clipper at formation and while it is moving southeastward toward the Great Lakes. Therefore precipitation is not intense, although these storms can be large in area and have a large area of light (usually) snow. See #6, below.

4. Being short waves in a long wave trough over the eastern U.S., a characteristic of Alberta Clippers is the incursion of an Arctic Air mass after the storm passes.

5. Alberta Clippers are more common than either of the other two storm types, namely Nor’easters and Colorado Hookers.

6. Once a Clipper reaches the Great Lakes, it does obtain an increased amount of water vapor, i.e., it becomes “Lake-enhanced.” Precipitation, usually in the form of snow can be heavy for stations around the Great Lakes, especially on their lee sides.

7. The usual track of an Alberta Clipper is to follow the long wave trough and that normally takes them into eastern Canada. However, sometimes the long wave amplitude is so large that the Clipper tracks off the northeast coast or even the mid-Atlantic coast. When they do that, the usual conservation of Potential Vorticity mechanism can transform the storm into a coastal cyclone, a.k.a, Nor’easter. This is not common but watch out for it. The coastal storm will usually form north of the normal cyclogenesis region.