Historic Cold Wave – Initial Report

(Saturday morning lows, courtesy MesoWest)

I say initial because it is not really over yet. Temperatures this week will continue to be below normal, and we have one final, weak cold front that will come through tomorrow before we can really start to warm up. And, warming up may take a while, since 2 to 4 inch soil temperatures are still in the 30s over the northern half of the state, and many ponds are frozen.

Notice the lows on the map above from Saturday. Teens as far south as Biloxi, MS. 20s in Orlando. Freezing temperatures as far south as Sarasota and Lake Okeechobee, FL. 40s in the Florida Keys!

The cold wave that has frozen Alabama for the past 10 days is not unprecedented, but is rare. It will likely wind up, overall, being one of the 10 coldest long-term (more than a week) periods in recorded Alabama history. We have certainly been colder than this before on certain days. The temperature in BHM reached -10 on Feb 13, 1899, and -6 on January 21, 1985. We’ve had 13 days since 1896 with highs in the teens. But, to have bitterly cold temperatures for most of 2 weeks is rare.

Below are the top 20 coldest 7, 10, and 14-day periods in BHM since 1896, by average daily temperature (with overlapping periods removed, using data from AL Office of the State Climatologist).

So far, our coldest 7-day period this year looks like it was the one ending yesterday, with an average temperature of 24.9, tying for 12th. The 10-day period ending yesterday had an average temp of 26.9, already putting it in the top 10. We’ll have to see how the 14-day average ends up once this week is over, but it looks like we’ll wind up in the top 10 there, also. Also notice that many of the colder periods than this one were helped along by snow cover, so this may be some of the coldest air ever in Alabama without snow.

Later this week, we’ll finalize these numbers, and also look at number of days in a row with highs or lows below a certain threshold, and figure a way of “ranking” cold outbreaks.

Category: Pre-November 2010 Posts