Friday, December 2, 2011

December, the onset of winter.

November was a little warmer than normal and, as has been typical for the past two years, a drier than normal month. The average temperature was 62.6, 0.8 degrees above normal. Rainfall was 1.15", 0.88" below normal. Rainfall was 57% of normal.

Despite that, a daily rainfall record was set on November 23, with 0.73". The old record was not much, 0.09" in 1977. That was the only record of any kind set in November.

December is usually a little wetter than November, rainfall increasing to 2.62" from 2.03", or 30%. Let's hope we have a wet December to close out the year!

December has falling temperatures through the month, but not in an intuitive way. During the first week of December average temperatures fall the fastest of the year, not in October or November as you might expect. December 4th has the greatest temperature fall of any day of the year, with a fall of 0.45 degrees. December 5th and 12th are in second place with a daily fall of 0.4 degrees. No other days have a fall of 0.4 degrees or more. There is also a pause in the temperature fall from December 15-18. On December 1, the average high is 66.5 and by December 31 the average high has fallen to 60.4, a fall of 6.1 degrees. On December 1 the average low is 49.7, which falls to 43.7 by December 31, a fall of 6.0 degrees.

On December 7, St. Simons Island tied its record high of 79. This record was originally set in 1971.

On December 7-8, at my home the temperature dropped 39.7°F from high to low. This ties the greatest temperature change in 24 hours or less since I started observations in November 2003.


The forecast discussion from the Jacksonville National Weather Service Office is linked here.


The weather observations for the last 72 hours at Malcom-McKinnon airport on St. Simons Island are here.



Date..............actual..............normal................departure.............notes

Dec 1...........37.2 / 60.6.......49.7 / 66.5............-9.2
Dec 2...........41.4 / 62.2.......49.5 / 66.3............-6.2
Dec 3...........41.9 / 63.9.......49.2 / 66.0............-4.7
Dec 4...........58.8 / 67.3.......48.6 / 65.7...........+5.9
Dec 5...........57.4 / 74.5.......48.2 / 65.3...........+9.2
Dec 6...........58.1 / 71.2.......47.9 / 65.1...........+8.1
Dec 7...........41.5 / 76.6.......47.7 / 64.8...........+2.8..............0.04" rain...sustained wind 28 mph gust to 45 mph
Dec 8...........36.9 / 55.0.......47.4 / 64.5...........-10.0.............39.7°F drop from high to low
Dec 9...........44.8 / 62.8.......47.1 / 64.2............-1.8
Dec 10.........51.4 / 56.5.......46.9 / 64.0............-1.5
Dec 11.........52.7 / 56.7.......46.6 / 63.7............-0.4
Dec 12.........46.4 / 54.7.......46.2 / 63.3............-4.2..............1.22" rain
Dec 13.........48.4 / 62.1.......45.9 / 62.9...........+0.8
Dec 14.........49.5 / 66.4.......45.7 / 62.7...........+3.7
Dec 15.........52.3 / 71.4.......45.5 / 62.6...........+7.8
Dec 16.........52.9 / 70.9.......45.5 / 62.4...........+7.9
Dec 17.........47.8 / 69.8.......45.5 / 62.4...........+4.8...............0.01" rain
Dec 18.........39.4 / 58.5.......45.6 / 62.3............-5.0
Dec 19.........45.3 / 68.0.......45.5 / 62.2...........+2.8
Dec 20.........54.5 / 71.4.......45.5 / 62.0...........+9.2
Dec 21.........59.9 / 70.9.......45.4 / 61.9..........+11.7
Dec 22.........61.0 / 72.9.......45.2 / 61.7..........+13.5
Dec 23.........61.9 / 72.3.......45.1 / 61.6..........+13.7..............0.01" rain
Dec 24.........52.9 / 64.8.......45.0 / 61.5...........+5.6
Dec 25.........56.3 / 67.5.......44.9 / 61.4...........+8.7...............0.01" rain
Dec 26.........51.6 / 60.6.......44.7 / 61.3...........+2.6
Dec 27.........47.8 / 65.7.......44.5 / 61.1...........+3.9...............0.35" rain
Dec 28.........41.0 / 58.5.......44.3 / 60.9............-2.8
Dec 29.........40.6 / 59.4.......44.1 / 60.7............-2.4
Dec 30.........41.9 / 64.2.......43.9 / 60.6...........+0.8
Dec 31.........53.8 / 70.5.......43.7 / 60.4..........+10.1

The totals for highs and lows are official readings at KSSI, not temperatures I record at home.


Highs for 2011

40s...........4
50s.........26
60s.........58
70s.........94
80s.........109
90s.........73
100s.........1

Lows for 2011

20s..........4
30s.........17
40s.........47
50s.........92
60s.........65
70s.......131
80s...........9

Freezes.....6


8 day model forecast graphic: