Meteorological Conditions Associated with Long-Lasting Shore Parallel Band Events over Lake Michigan

The Great Lakes region most frequently is observed to receive Lake effect (LE) precipitation during the cool seasons from October to March. LE occurs when cold air passes over warm bodies of water, prompting destabilization of the atmosphere and resulting precipitation. A 16-yr cold-season climatology of LE occurrence was developed for Lake Michigan from 2006-2022. A total of 1428 LE days were identified. Of the 1428 LE days identified, 1292 were classified as having wind parallel bands (WPBs), while 527 were classified as having shore parallel bands (SPBs). Of the SPBs, 71 had durations lasting more than 24 hours and were classified as long-lasting SPBs. In general, more long-lasting SPB events occurred in the cooler months of January and February, whereas the warmer months of October and March contained many fewer long-lasting SPB events. When a long-lasting SPB did occur in these warmer months, they tended to have a shorter longevity than those in the heart of the cold season. Further, four variables were examined to determine the spectrum of meteorological conditions associated with helping to sustain the infrequent long-lasting SPB events over Lake Michigan: (i) Lake water to 850-mb temperature difference; (ii) specific humidity (SH); (iii) surface level pressure (SLP); and (iv) wind speed and direction.