Wednesday, November 30, 2011

November 30: ORD

Today is November 30th. It's the 334th day of the year. 31 days remain. It's week 48 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.
Before this, the official site was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 40 and the normal low is 26. I've calculated the 33-year averages at 42 and 28.


On the warm side, in 1998 the high was 65 (our most recent 60s high and just a degree short of the record) with a low of 39. In 1982 the high was 56 with a low of 40. In 2003 the high was 54 (our most recent 50s high) with a low of 38. In 2001 the high was 48 with a low of 41 (our most recent 40s low), a seven degree spread. The other warm high was 61 in 1991. The record high of 66 was set in 1962 at Midway. The record warmest low of 51 occurred back in 1913, at a time
when the official readings were taken adjacent to Lake Michigan. 24 of the past 33 highs (73%) were in the: 30s (9) and 40s (15). There were consecutive streaks of 30s & 40s highs as follows: 1. seven years from 1984 through 1990 and 2. six years from 1992 through 1997. Five highs were in the warm: 50s (3) and 60s (2). Pre-1978, the 60s highs were 64 in 1962 and 62 in 1975. Four highs were in the cold 20s. Three of the four 20s highs occurred in a six year span from 1978 through 1983.

In looking back through the years to the first November at O'Hare in 1958, the following instances were notable: in 1976 the high was 21 with a low of 6, a cold day. In 1975 the high was a warm 62 with a low of 20, an incredible 42 degree spread . In 1974 the high was 39 with a low of 34, a five degree spread. In 1973 the high was a warm 54 degrees. In 1970 the high was 56 with a low of 38, a warm day. In 1964 the high was 20 with a low of 6, a cold day. In 1962 the high was a warm 64 with a low of 26, a 38 degree spread. In 1962, it was the first of three consecutive 60 degree highs. On December 1st the high was 64 and 64 again on December 2nd. In 1960 the high was a cold 27 degrees. In 1958 the high was 21 with a low of 1, a cold day.


More recently, there w
as a large spread of 36 degrees in 1991 (61/25). There were small spreads of four degrees in 2000 (36/32), five degrees in 1979 (29/24), six degrees three years ago, in 2008 (39/33), seven degrees in 1987 (40/33), seven degrees in 1992 (37/30) and seven degrees in 2005 (27/20).

On the cold side, in 1978 the high was 26 with a low of 11. In 1983 the high was 24 with a low of 18, a six degree spread. The other cold high was 27 in 2005, our most recent 20s high. The record low of -1 was set back in 1947 at Midway. The record coldest high of 14 occurred way back in 1896, at a time when the official readings were taken adjacent to Lake Michigan. 26 of the last 33 lows (79%) were in the: 20s (11) and 30s (15). There were consecutive streaks of 20s & 30s lows as follows: 1. 15 from 1984 through 1998 and 2. eight from 2003 through 2010 (ongoing). Five lows were in the cold 10s (a.k.a. teens). The most recent 10s low was 17 in 2002. Two lows were in the warm 40s.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1982 the high was 56 with a low of 40, overall 15 degrees ABOVE normal. Then in 1983 the high was 24 with a low of 18, overall 12 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:30 and sunrise is at 7:01. Sunset is at 16:23 and twilight ends at 16:54. There's a total of 9 hours, 22 minutes of daylight today and 10 hours, 24 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 6:31 and sunrise is at 7:02. The moon is waxing crescent. Illumination was 29% at midnight, will be 34% at noon and 39% at midnight tonight. Moonrise is at 11:15 this morning. Moonset is at 22:23 tonight. Moonrise is at 11:42 tomorrow morning. Moonlight time is 11 hours, 8 minutes which is 34 minutes longer than yesterday.

Cool Fall began November 2 and runs for 29 days through today, November 30. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 10s and 20s occur infrequently. Pearl Harbor Day is in seven days. Bill of Rights Day is in 15 days.