COLUMBUS (WCMH)–Our record warm April in central Ohio gave way to a late March throwback–temperature you would expect around the first day of spring, not typically in early May.
The big picture is controlled by the polar jet stream, which represents a narrow corridor of fast-moving winds that push weather systems and large air masses along for the ride. The jet stream at our latitude normally varies from a prevailing westerly flow to a occasionally a more high-amplitude north-south pattern through the seasons, especially in the colder months.
This week, a peculiar slow-moving flow currently features six large waves (wave number 6) atmospheric configuration, which is balky and creates extreme weather in places where the flow is highly contorted. For example, cold air is flowing all the way south from northern Canada to the Deep South, while warm air is pumped northward on the opposite side of the wave into Greenland and the Canadian Maritimes.
Six waves are aligned across the entire Northern Hemisphere, separated by several thousand miles, when normally there might be four or five such loops. Standing waves in the jet stream are not unlike when a streamflow is diverted by a rock formation Weather systems tend to remain stuck due to this form of global wave resonance for days on end.
The result based upon a big longwave low-pressure trough in the East, is unseasonably cold and unsettled weather through the first week of May, culminating in frost Monday morning in rural areas of Ohio, and a few snowflakes in the interior Northeast.