December 2010 Revisited

Compared to historical averages, December in Hood River was warmer, wetter, and less windy.

At my weather station, the average temperature of 36.2° was warmer than long term averages (35.7°), and also warmer than the more recent (2000-2009) average of 35.6°.

The high heat index for the month was 51°, and the low wind chill was 20°. Barometric pressure peaked at 30.40", with a low of 29.22".

December's precipitation (6.91") was above average (5.83"). The month started out dry, but turned quite wet from 12/8 to 12/14, as a moisture-laden atmospheric river took direct aim at the Pacific Northwest. 75% of the monthly precipitation fell in that time frame. That was followed by 3 days of snow, during which a total of 10 inches of snow fell. All in all, we had 11" of snow for the month, higher that the long term snow average of 8.7".

Given that this was a strong, well established La Nina winter, with the jet stream fire hose pointed firmly at us, things took an odd turn halfway though the month. The jet stream moved south big time, drenching California with record rains and snowfall. Our precipitation fell off dramatically for the rest of the month. It turns out this may have been due to a shorter term climate cycle called the Arctic Oscillation, which turned strongly negative, and pushed the jet stream further south.

I happened to be on vacation in southern California around Christmas, and had great fun watching the flash floods move through Palm Springs.

Meanwhile, back in Hood River, the 24 hour avg wind speed for December was 0.9 mph, compared to a historical average of 1.5 mph. The high wind gust at my station was 34 mph on Dec 29th.

There was 1 local weather record set in December. On 12/12, at the peak of the Pineapple Express, we received 1.61" of rain, which broke the old record of 1.55" (1946).

The tabular data below is from my home weather station. To view its December 2010 monthly summary and graphs at Weather Underground, click here.

The "historical average" numbers for temperature and rainfall are from the Hood River MCAREC data. Historical wind average is from my station's 2000 to 2009 data. Note that average wind speeds include all 24 hours of the day and night, which is why they are way lower than daytime peak winds. In addition, the wind speed at this station is considerably lower than on the Columbia River.

	High	Low	Average	Historical Average
Temperature (F)	51	22	36.2	35.7
Wind (mph)	34		0.9	1.5
Rainfall (in)	1.45		6.91 (total)	5.83

California... a nice place to have grown up, and to visit, but luckily, I didn't get stuck there again.