Milder and drier weather returns

Published 7:00 am Saturday, February 20, 2021

By Skip Rigney

After a cold week the weather pendulum will swing back to a milder position in the days ahead. Temperatures are forecast to press the 70 degree mark by mid-week.

This past Tuesday and Wednesday were the coldest February 16th and 17th in Pearl River County in many years as temperatures dropped to near or below 20 degrees in many locations. New records were set on February 16th in Gulfport (22 degrees), and on February 16th and 17th in Slidell (22 and 23 degrees), and Hattiesburg (18 and 20 degrees).

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It could have been even colder. Just ask folks in Texas. For example, Conroe, Texas, 40 miles from Houston, is no further north than us, only a few miles further from the Gulf, and has average temperatures in mid-February very similar to ours. Conroe’s low Tuesday morning was 9 degrees.

Add enough moisture and rising motion in the atmosphere above the cold dome of surface air and you have a recipe for a major winter mess. Ice, sleet, and snow hit states from Texas to Maine, including much of Mississippi, twice this past week.

What caused such a cold air mass to move south from the arctic? As with any weather system, multiple factors were at play, but one likely culprit was a rapid warming in the upper atmosphere above the Arctic back in early January. Scientists are just beginning to understand these sudden stratospheric warmings (SSWs), which happen about six out of every ten winters.

SSWs disrupt the usual wind pattern in the upper polar atmosphere. Sometimes the disruption works its way downward to mid-levels of the atmosphere. When that happens, the normal west-to-east wind pattern at those lower altitudes, which has come to be known as the polar vortex, can become unstable and push large surges of arctic air southward.

Fortunately, the wind flow pattern in the middle and upper levels across the Northern Hemisphere appears to be shifting into a different mode. The door between us and the polar north will still swing open from time to time over the next few weeks, but at least it won’t be stuck open.

After a mild day tomorrow, another cold front is expected to pass through Sunday night. Temperatures behind the front will fall back into the 30s Monday night, but a warming trend on Tuesday and Wednesday, along with sunny skies, will provide a reminder that spring is right around the corner.

If we define typical temperatures as those that occur about two-thirds of the time based on the historical record, typical daily lows in Pearl River County for the last week in February range from 33 to 53 degrees. Typical daily highs usually range from 55 to 75 degrees. It looks like the forecast temperatures for the upcoming week, unlike this past week, will fall into the typical range.

As for rainfall, so far this month most areas in the county have already picked up an amount equal to or exceeding the normal amount of five to six inches for February. The upcoming week should allow the saturated ground to dry out a little. Despite a few showers in the area Sunday night and again Thursday and Friday, the National Weather Service predicts less than one-tenth of an inch of rain for the county through Friday.