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On the relation between North American winter precipitation and storm tracks
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Two regions of interest were identified for their largest values of storm track intensity, one towards the east and the other towards the west of North America. In both regions local diagnostics reveal an eastward-propagating wave with an average longitudinal extension of about 90 degrees. The upstream NNW-SSE tilt of the wave mirrors its downstream counterpart, which increases with the wave's evolution. The energy builds upstream, maximizing over North America on the early stages and displaces eastward over the Atlantic Ocean where its energy dissipates. This wave pattern leaves a signature in surface precipitation that resembles that of the low-level vorticity. For the western region, the precipitation pattern follows the northern edge of the 200mb storm track as it propagates eastward, flowing up to the northwestern part of North America and down the Rocky Mountains, downstream of which the wave's propagation appears to stall and its energy dissipate. The precipitation has a bow-like shape over the northwestern part of the continent mimicking the shape of the storm track's flow pattern in this area. For the eastern region, the precipitation pattern quickly develops into a wave-like shape with an average longitudinal extension of 50 degrees, strengthening upstream until it moves from the continent into the Atlantic Ocean. The precipitation pattern is in agreement with the zonal path of the 200mb storm track, narrowing as it approaches the eastern coast of North America and propagating eastward over the ocean.