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Home Blogs Eye to the Sky Eye to the Sky: What's driving this surplus of sunshine and heat?

Eye to the Sky: What’s driving this surplus of sunshine and heat?

Summer has arrived early in the Cumberlands.

Not too early. Memorial Day weekend is traditionally when many homeowners open their pools and start hosting more outdoors festivities, and we’re knocking on the door of the holiday weekend.

But it’s a little early in the year for us to be this dry and this hot. The National Weather Service at Morristown is actually publishing graphics about heat awareness this week — in late May! That’s rare.

Remember when the top weather story around here was rain? Rain, rain, and more rain. It was an endless, tiresome pattern…but that is history.

Believe it or not, 2019 is still the wettest year-to-date on record in Oneida as of May 23. We’ve received 33.12 inches of rain this year, which is just ahead of the 32.37 inches of rain we had received by this point in 1975. Unless a rogue thunderstorm develops over the next few days, it’s likely we’ll lose that status (at least temporarily) by the end of the month next week. By May 31 in 1975, 33.44 inches of rain had fallen. But we’ll still be a full 10 inches above normal; the average rainfall through May 31 is 23.04 inches.

But meteorological spring is about to end with two of three months featuring below-average rainfall — though just barely. We currently have 3.69 inches of rain for May, and are likely to finish there. That’s slightly below the average of 3.95 inches for the month. And, in March we received 4.29 inches of rain, slightly below the average of 5.10 inches for the month. April actually featured a rainfall surplus, at 5.74 inches. The average is 4.30 inches. For spring as a whole, we’ve received 13.72 inches of rain, which is slightly above normal (13.35 inches). But by the time meteorological spring ends next week, we’ll probably still be at 13.72 inches of rain, while the average will have risen to 14.75 inches.

All of that is just a statistical way of saying that while we started out the year very wet, we’ve suddenly gotten very dry. And after a true spring — we didn’t jump straight from winter to summer this year as we seem to be doing more and more in recent years — summer has definitely arrived. We’ve had no precipitation in Oneida since a quarter of an inch of rain fell last Friday. The last significant rain we had was May 11-12, when just under two inches fell across a two-day period. Heat indices are near 90 or above on a daily basis this week, and that heat will continue through the Memorial Day weekend.

So what’s the culprit? A heat ridge that is persisting across the Southeast.

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A heat ridge is merely summer vernacular for an upper level ridge that parks itself over the region. A ridge, in meteorological terms, is an area of high atmospheric pressure. When it develops and becomes stationary over the region, it pumps in lots of warm subtropical temps and keeps storm tracks well to our north. Cold fronts that might typically bring rain and slightly cooler temps to our region fizzle out as they approach the region.

If you remember the extremely hot late-summer in 2007, that was caused by a persistent southeast ridge, exacerbated by the extreme drought that had depleted the topsoil of its moisture (allowing it to fully absorb the sun’s rays and make us even hotter). If you remember the heat wave in July 2012 — the last time we hit 100 degrees in Oneida — that was also caused by a heat ridge.

Fortunately, we’re still in late May, and we have plenty of soil moisture, so the heat isn’t as extreme as it might otherwise be if one of these death ridges set up in late July or August.

This ridge is going to stay in place for about another week, before it finally starts to move east next Wednesday. That will allow for a cold front to approach our region. And while we do have slight chances of showers each day (20 percent or less) through the weekend, next Wednesday may bring a slight increase in rain chances, along with cooler temperatures.

However, if you’re looking for appreciable rainfall, that isn’t showing up on models until the first of June! It’s hard to believe that after all the rain we had from September 1 all the way into April, gardeners are having to water their plants and many of us will be breaking out sprinklers for the lawn before we even get into the heart of summer.

So how long will this pattern last? Despite the temporary reprieve next week, it looks as though above-normal temperatures and below-average precipitation will continue through the first half of June, though it might not be quite as exaggerated as it’s been this week.

The summer forecast from the NWS’s Climate Prediction Center calls for an equal chance of above-average or below-average temps, with persistent troughing (a cause of cooler weather) in the Plains states and the best chances for excessive heat contained along the East Coast, along with slight chances for above-average precipitation.

Eye to the Sky is a weather blog by Independent Herald editor Ben Garrett. Garrett is a weather enthusiast who has long blogged about interesting weather on his personal website. He is not a professional forecaster or a meteorologist and information on this blog should not be considered a substitute for forecasts, advisories or other products from the National Weather Service.
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Ben Garrett
Ben Garrett is Independent Herald editor. Contact him at bgarrett@ihoneida.com. Follow him on Twitter, @benwgarrett.
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