Summer does a slow fade out

Published 7:00 am Saturday, August 25, 2018

By Skip Rigney

This week I noticed a slight yellow tinge to the leaves on my sycamore trees. On a black gum tree, I saw a few red leaves had appeared in the canopy of green. To my annoyance, I saw love bugs floating through the air. And, it’s obvious that it stays dark longer in the morning and dusk falls earlier in the evening than a month ago.

All these are signs that summer has passed its prime and is slowly waning. As an additional reminder that we are beginning a seasonal transition, a front moved through the area on Wednesday. Meteorologists labeled it a cool front.

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That moniker made sense to the people to our north. Corinth in the far northeast corner of the state cooled down to 59 degrees on Thursday morning.

By the time northerly winds had pushed the air mass into south Mississippi, the term “cool” front was an overstatement. There was no longer much difference in temperature ahead of and behind the front. But for those keenly attuned to changes in humidity, the post-frontal air mass did bring some slight relief from the summer muggies.

Dew point temperatures, which are a measure of how humid the air is, dropped from the summery middle 70s down into the upper 60s.

Drier air heats and cools more quickly than more humid air, so lower humidities allowed cooler mornings than we’ve seen in a while. The Poplarville Experiment Station recorded 66 degrees on Thursday and Friday mornings.

Although the signs of summer’s end are becoming more numerous, there is no need to unpack your sweaters just yet. Computer weather models indicate a return to a typical summer pattern for most of the next two weeks. The Bermuda High Pressure system, a dominant player in our summer weather, is predicted to be anchored over the western Atlantic with its elongated western side nosing into the Gulf of Mexico. The clockwise circulation of winds around the high will cause winds to blow gently onshore from the Gulf.

That translates into warm and humid with a chance of mainly afternoon showers and thunderstorms. Sound familiar?

One feature of late summer is an increased threat of hurricanes for the northern Gulf Coast. Although the Atlantic hurricane season officially runs from June through November, the statistical peak of our season is from mid-August through September.

Tropical cyclones occur this time of year in the Pacific as well. Hurricane Lane has grabbed the weather headlines this week as it threatened the Hawaiian Islands, which is a relatively rare occurrence.  Despite weakening, Lane brought torrential rains to the steep volcanic slopes of the islands, causing severe flooding. 

Meanwhile, the tropical Atlantic, Caribbean, and Gulf of Mexico remain unusually quiet.

Sea surface temperatures in the eastern tropical Atlantic continue to be abnormally cool, and dry air covers much of the central tropical Atlantic. Both of these factors tend to suppress tropical cyclone development.

Nevertheless, it is a good bet that the National Hurricane Center in Miami will see an increase in their workload over the next two weeks as we head toward the historical peak of the Atlantic season on September 10th.