It took summer — true summer, anyway — a while to get here, but it doesn’t look like the hot and relatively dry pattern we’re currently in is going to end anytime soon.
Some of you will read that and scoff. “Relatively dry?” What about the flash flooding that some areas experienced on Friday? But compared to where we were at the first week of July, the past week has been quite a change-up. And it’s certainly hotter now than it has been all summer.
June and the first part of July were marked by intermittent cold fronts that kept funneling cooler-than-average temperatures and above-average rainfall into much of Tennessee. But things have flipped in a big way, and what we’re seeing currently is much more reminiscent of a typical summer in East Tennessee — hot and humid, with daily chances for thunderstorms.
Believe it or not, this July is still running a little below-normal in the temperature department. While today’s temps in Oneida have not been recorded by the National Weather Service, the month-to-date is averaging 83.2 degrees for a daily high. The normal for the month of July is 85.5 degrees. That’s mostly due to a cool start to the month, which included a high of just 78 degrees on July 5.
As hot as it’s been, we’ve still only recorded two days above 85 degrees this month — 87 degrees this past Tuesday (July 11) and 88 on Wednesday. That marked just the fifth and sixth days this summer with temperatures above 85 degrees. We’ve still hit 90 degrees only once (June 14).
Speaking of Friday’s flash flooding, it was spotty at best. The official rain gauge in Oneida measured only a tenth of an inch of rainfall on Friday, so we’re still at 3.46 inches for the month — with only a tenth of an inch since July 8. But even if it doesn’t rain another drop this month, we’ll end up well above the average July rainfall total of 2.4 inches.
Okay, so that’s where we’ve been. How about where we’re headed? At one point, and this was just a few days ago, it looked like a cold front would push through the region tonight or tomorrow, resulting in widespread rain coverage. Instead, it looks like most of us will be dry, not just tomorrow but for at least the next week. Isolated thunderstorms are possible almost every day, but most people won’t see rain. Rain chances may build into next weekend, but it still looks like more people will be dry than will be wet.
In fact, the 12z run of the GFS forecast model earlier today depicted just two-tenths of an inch of rain over the next seven days, and less than a half-inch of rain over the next 15 days. The 18z run of the same model this evening was somewhat more wet, but still depicts less than an inch of rain over the next 15 days.
I wouldn’t take those numbers as the gospel. For one, it’s a model run; not a forecast. For another, these low-resolution models are notoriously inaccurate when it comes to depicting convective rainfall totals, and that’s just what typical summer thunderstorms are.
But the bottom line is that we’ve suddenly turned off dry. The National Weather Service is forecasting a 20 percent chance of thunderstorms on Tuesday afternoon and again Wednesday afternoon, but is forecasting sunny skies for Monday, Thursday and Friday. It’s somewhat unusual to see a forecast in the dog days of summer with less than a 20 percent chance of rain three out of five days.
The culprit is a ridge of high pressure that is going to be in place over the eastern U.S. Weather enthusiasts refer to these as “death ridges,” because they often result in hot and dry weather for days on end. The models have been depicting this for quite some time, indicating that while last week was hot, the hottest weather is still on the way.
While the GFS model beats back the ridge enough for an increase in thunderstorm coverage next weekend, the European holds the ridge strong through at least next weekend, which would result in hotter and drier weather.
What happens after that depends on what happens with the ridge. The GFS is hot for this week, depicting highs in the upper 80s each day, and hitting 90 on Friday. But it is even hotter next week, consistently popping temps over 100 degrees even here on the northern Cumberland Plateau.
I wouldn’t count on it being quite that hot. We rarely hit 100 degrees here on the plateau. It’s happened only seven times in Oneida since records-keeping began in the early 1960s. Almost all of those days were in the heat waves of 1980 and 2012.
But the bottom line is that it’s going to be hot. How hot it gets remains to be seen. The GFS keeps popping its hottest temps after truncation — which is about seven days out, when the model’s resolution drops and it becomes less accurate. For example, the model’s 12z run today had a high of about 91 on Sunday, pre-truncation, but then jumped us all the way to 96 on Monday and 101 on Tuesday, post-truncation.
How long the pattern lasts also remains to be seen. The 12z run of the GFS showed signs that things would start to break down right around the end of July. However, the 18z run that followed popped a high temperature of 102 for July 29 and kept us well into the 90s through the end of the run. So for now it’s a waiting game.
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.