The mild trend started when December, January, and February posted above normal temperatures but not to the magnitude in which March did. Were the warm temperature events related? We shall see. I will be addressing this topic in three separate articles to explain the science behind the “Meteorological Madness” in March.
Trying to narrow it down to one particular reason would be nearly impossible. There were various contributing factors that all played a role into the heatwave. Many of which we have already experienced during our very mild winter. According to the Climate Prediction Center, over 7,000 daily record high temperatures were broken during the period between March 1 and March 27. The warmth was not widespread, however. Western Canada, Alaska, eastern Asia, and southeastern Europe experienced rather cold conditions. To keep it from getting too lengthy, I’ll cover 3 main factors leading to the “March Madness”.
We’ll start at the top of the atmosphere and work our way down to the surface. First off, I’ll cover the La Nina/Northern Atlantic Oscillation (NAO) combination. Most people have heard us talk about El Nino/La Nina. This winter and early spring has experienced a La Nina pattern. Basically, this is a cooling of the western South American coastal waters and affects the upper-level wind pattern or jet stream. For the most part, this winter/early spring, the jet stream was far enough north that is trapped most of the cold air in Canada. Coupled with La Nina was a positive Northern Atlantic Oscillation. When this occurs we typically see a ridge build in the east with a trough over pacific west. Combing these two effects we get a low-level jet stream that acts as a conveyor belt and carries warm air northward from the Gulf of Mexico.
At the mid-levels of the atmosphere we witnessed two major weather patterns that dominated the lower 48. On the west side of the Rockies, an anomalously low pressure system brought rain and cool temperatures to the Pacific Northwest. On the east coast, an anomalously high pressure system made for relatively quiet weather in the Plains, Great Lakes, and Ohio Valley region. Think of two gears spinning; the west coast gear spinning counter-clockwise and the east coast gear spinning clockwise. In between these “gears” is where a strong west to east pressure gradient was established, once again developing a strong south to north air-flow.
At the surface, we saw little in the way of precipitation. Now this doesn’t have a direct effect on temperatures but it does help. With a lack of snow on the ground or moist soil the sun’s energy was not reflected back from snow or spent on melting snow. The sun’s energy is than absorbed at the surface and radiated upward. In this case, the surface had the ability to hold on to that heat overnight and get a jump start on the next day.
There are many more variables that are a part of the equation but I could don’t want to bore you all to tears! Numerous records were broken during the month of March, including in the Husker state. I’ll touch on these in my next article.
Meteorologist Tony DeGrand