Monday, December 21, 2009

December 19: ORD

Today is December 19th. It's the 353rd day of the year. 12 days remain. It's week 51 of the year.

Unless noted, the following data is based upon observations collected by the National Weather Service, Chicago, at O'Hare International Airport (ORD) between November 1978 and last year. ORD has been the official site of record for Chicago since Thursday, January 17, 1980.


According to the National Climatic Data Center (NCDC), the normal high is 33 and the normal low is 19. I've calculated the 31-year averages at 32 and 18.


On the warm side, in 2002 the high was 55 with a low of 34. In 1997 the high was 50 with a low of 31. In 1988 the high was 56 with a low of 23, a 33 degree spread. Other warm lows were 33 in 1993, 31 in 1978 and 31 in 1987. The record high of 64 and record warmest low of 57 were set on the same day way back in 1877.
Over the last 31 years, 13 highs were in the 30s. Nine highs were in the warmer: 40s (6) and 50s (3). Nine highs were in the cooler: 0s (aka single digits)(1), 10s (aka teens)(7) and 20s (1).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1977 the high was 39 with a warm low of 35, a four degree spread. In 1976 the high was 49 with a low of 35, a warm day. In 1973 the high was 30 with a low of 24, a six degree spread. In 1972 the high was 37 with a low of 35, a mere two degree spread. In 1970 the high was a warm 46 degrees. In 1968 the high was 47 with a low of 31, a warm day. In 1966 the high was 37 with a warm low of 31, a six degree spread. In 1963 the high was 2 with a low of -14, a cold day. That high of 2 was colder than the record coolest high and the low of -14 equals the record low. In
1962 the high was 45 with a low of 35, a warm day. In 1961 the high was 36 with a low of 30, a six degree spread. In 1960 the high was 24 with a cold low of 5, a cold day.

More recently, there w
ere no other large spreads of 30 degrees or more. There were small spreads of three degrees in 1993 (36/33), six degrees in 1978 (37/31), six degrees in 1982 (35/29) and six degrees in 1987 (37/31).

On the cold side, in 1983 the high was 6 with the record low of -14. In 2005 the high was 11 with a low of -1. In 1985 the high was 15 with a low of -5. In 1996 the high was 13 with a low of 3. In 1989 the high was 15 with a low of 1. In 1980 the high was 16 with a low of 2. A year later, in 1981, the high was 19 with a low of 1. In 2004 the high was 18 with a low of 4. In 2000 the high was 20 with a low of 7. Another cold low was 6 in 1991. The record coolest high of 5 was set in 1963. 14 of the last 31 lows were 20s. 11 lows were in the cooler: negative 10s (1), negative 0s (2), single digits (7) and 10s (aka teens) (1). Six lows were in the warmer 30s.

In 1973, O'Hare had 3.5 inches of snow today. This was the seventh day of a string of eight days through tomorrow which produced 17.6 inches, or 94% of the month's total of 18.8 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:46 and sunrise is at 7:18. Sunset is at 16:23 and twilight ends at 16:55. Tomorrow twilight begins at 6:46 and sunrise is at 7:18. There's a total of 9 hours, 5 minutes of daylight today and 10 hours, 9 minutes between twilights. The moon is waxing crescent. Illumination was 7% at midnight, will be 9% at noon and 12% at midnight tonight. Moonrise is at 9:29 this morning. Moonset is at 19:30. Moonrise is at 9:56 tomorrow morning. Moonlight time is 10 hours, 1 minute which is 30 minutes longer than yesterday.

Christmas Eve is in five days and Christmas Day is in six days. New Year's Eve is in 12 days and New Year's Day is in 13 days. -Bernie-

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