Yes We Call it "The Streak"
Posted January 3, 2010
Not "The Streak" Ray Stevens sang about in his early '70s song about running in the buff, of course, but day after day of unseasonably cold weather. As you all have experienced by now, we've had a seriously cold arctic airmass build into the central and eastern U.S. in the days since the new year started, bringing us a high of 32 at RDU on Saturday despite sunshine, and wind chills in the single digits early on Sunday. As far as we can see right now, it appears we'll remain on the low side of normal right through our 7-day forecast and potentially at least a few days beyond that.
There are various ways to measure how impressive a cold snap may be, for example by whether it produces a lot of new records for coldest low or high temperatures, or how average temperatures for the month stack up against historical records. We'll have to wait until the end of January to get a good sense of how this cold spell ranks among the big ones, but one quick assessment that Greg suggested recently was to see how many days in a row our average daily temperature fell below some threshold indicating a very cold day for these parts.
As an example, we noticed that several days in our forecast for the week ahead fell between 25 and 30 degrees for a daily mean (Saturday 2 Jan was the start of the cold snap, and featured a mean temperature of 27 degrees - this meant enough hours below freezing to get a good "fountain mountain" ice buildup going on the fountain outside our studios!).
I checked our 7-day against that criteria and saw that we were forecasting 4 straight days with an average of 30 or lower, and would only be a little above that on Wednesday if our forecast verifies closely. A check of historical records using some neat tools hosted by some of NOAA's Regional Climate Centers showed that the last time we went 4 days in a row that cold was Jan 1-4, 2002, or eight years ago. If we end up staying a little cooler Wednesday and stretch this "streak" to 5 days, that would be the first such streak in almost ten years, dating back to Jan 25-29, 2000 (yes, associated with the "big snow" of that season).
For now, it appears unlikely we'll add a sixth straight day on Thursday, but if that were to happen it would be the first time since Jan 1994. The longest stretch of consecutive days averaging 30 or lower for RDU is nine, which happened in the extremely cold month of January 1977.