Cool August not a trend for coming winter
Posted August 13, 2014
Updated August 14, 2014
We can forgive you for thinking the first two weeks of August have felt more like September than August. The combination of clouds and rain have resulted in a cool start to the month. In fact, were August to end today, it would be the coolest August on record at RDU in terms of monthly average high and low temperatures going back to 1945. (Note: I’m using “average” here intentionally; the NWS bases normals upon a sliding 30-year window. However, for this analysis, we’ve used data from RDU dating back to the first complete year of data, 1945.)
A cool start to August
Through the first 13 days of August, we’ve averaged 81.7 degrees for highs for the month. That’s closer to the average monthly high for September (81.1) than it is to the next-coldest August on record (82.6 in 1992). We’re running 5.8 degrees below the average monthly high for August from 1945-2013. Low temperatures are nearly average, though, with our 13-day average low in August at 67.5 degrees, almost spot on the average.
When you consider that our temperatures are generally going down in August (the normal high drops 3.3 degrees from August 1st to the 31st), the fact that we’re starting out averaging so much cooler is truly remarkable. That’s a testament to just how much of an influence the clouds and rain, thanks to a pattern much more reminiscent of something we might see in the winter than late summer, can have on our temperatures.
Of course, we still have about three more weeks in August, and with a warming trend in the forecast for the next couple of days, our August 2014 numbers should continue to trend upward. But any month that feels like September – the month I was born and the beginning of my favorite season in North Carolina – will make me happy.
2014 so far
Looking at highs and lows, it has been an interesting year for us here in central North Carolina. As you can see from the plot of monthly average temperatures at RDU, we began the year on a rather cold note, especially in January, when the average low fell in the lowest 25 percent of all Januarys.
March was more consistently cool: Both the average highs and lows fell in the lowest quarter for Marches at RDU.
Then, we flipped a bit of a switch: After a nearly-normal April in both categories, but both May and June were in the warmest 25 percent for both highs and lows. But as you know, things turned very wet and remarkably cooler in July, and we’ve remained that way so far in August.
The natural question is whether this will continue into the winter. As much as we cool-weather fans would like it to, it doesn’t appear likely.
The Climate Prediction Center’s three-month outlook for August, September and October suggests a return to at-or-above-normal temperatures as we end the summer and move into autumn. They expect a developing El Niño – warmer-than-normal waters in the equatorial eastern Pacific – to take shape, affecting our weather for the fall and winter.
It’s worth noting that this El Niño was originally forecast to be a whopper and well underway by now. The three-month outlook will be revised in about a week, and it will be interesting to see if the CPC backs off the above-normal chance of a warmer-than-normal end to summer and beginning of fall.