The Alabama Climate Report

Brought to you by the Office of the Alabama

Volume 6, Number 12 September 2016

How many ways are there to measure heat discomfort? When we're talking about weather in Alabama, that isn't necessarily a rhetorical question.

One measure that has been discussed quite a bit recently is the number of days when the temperature hits 90° or more. It was a hotter than normal summer, and the heat continued through September. In Montgomery, for instance, there were 27 September days when the temperature hit 90° or more.

Add that to all the other 90° days starting in May, and Montgomery has enjoyed a grand total of 119 days this year that hit or exceeded the 90° mark. That includes a 91° day on Monday!

But that isn't a record. That would probably have come in 1954, when the capital saw 127 days of temperatures 90° or above.

The Southeast Regional Climate Center says a normal year in Montgomery (for the past half century) would get only 78 days of 90° heat. But that half century mark misses many of the hottest years in the state's climate record.

The SRCC website gives us 90° norms for four cities, and we can compare that to this year's results:

City 2016 Normal
Birmingham 96 days 60 days
Huntsville 105 53
Mobile 90 77
Montgomery 119 78

Other cities and their 2016 hot day tallies include:

City 2016
Dothan 107
Anniston 100
Tuscaloosa 96
Muscle Shl. 93

Looking back at some of the hottest hot seasons in the state climate record, you would have to include 1954: 127 90° days in Montgomery, 110 in Huntsville, 107 in Birmingham and 102 in Muscle Shoals.

It was also toasty in 1925, when Muscle Shoals hit 90° on 128 days, Huntsville 117 times, Birmingham 110 times and Montgomery 104.

To get back to our rhetorical question, when measuring discomfort you might also consider a station's average high temperature for a month. Montgomery saw 27 days of 90° or hotter temperatures in September 2016, but the average high was less than 94.5°.

You can compare that to Birmingham's September in 1925, when the monthly average high temperature was 97.5°. Or July 1902 in Decatur, when the average high temperature for all of July was 98.13°.

You might also look at the extremes. Montgomery hit 100° (on the nose) only three times this year, while Birmingham nudged up to 100° only once, in late June. While there have been some years when no station in Alabama hit the 100° mark, there also have been times when stations saw 100°+ for more than a week at a time.

So, yes, it has been hot since late May, and more often hot than is normal even during an Alabama summer. While it has been persistently hot, my native Alabama associates note that it hasn't really been miserable this year. And while they aren't as reliable as real data, I suppose memory and your individual tolerance for heat are two other ways of measuring discomfort.

As is most often the case, hot weather is in part a function of drought. Sunlight will do one of two things when it hits the surface. It will evaporate water, which cools the atmosphere, or it will be converted to heat energy. This summer much of Alabama saw little rain and an abundance of heat energy.

Several stations around the state reported their driest Septembers on record, including:

City 09/16 rain Old record Date
Auburn  0.14"  0.36"           1919
Decatur 0.09" 0.11" 1901
Huntsville 0.47" 0.48" 1998
Russellville 0.06" 0.34" 1999
Valley Head 0.52" 0.77" 1960

By comparison, Fairhope had slightly more rain than normal in September — 6.34" — and an average temperature that was exactly its norm for September.

On an unrelated note, we are all keeping an eye on hurricane Matthew. If it stays out at sea (as expected), Thursday will mark the 4,000th day since the last major (category 3 or stronger) hurricane hit the continental U.S. As the official 2016 hurricane season nears an end, every day that passes sets a new record for the longest gap between major hurricanes.

With a few cooler nights under our belts it is time to start looking ahead to brisk autumn nights and cold winter days. We are getting conflicting data regarding the forecast for this winter. The wooley bear caterpillar report indicates a warmer than normal winter upcoming, while persimmons seem to point to cold and snow.

I will wait to see how high the spider web index goes before making up my mind.

NOAA, on the other hand, is predicting a neutral winter in which there is neither an El Niño Pacific Ocean warming event nor a La Niña Pacific Ocean cooling event.

Without the guiding atmospheric circulations caused by those events, winter weather in Alabama is more likely prone to significant swings. That includes very cold episodes. In fact, 11 of the past 12 times Arctic weather penetrated all the way into Florida came during neutral winters.

- John Christy