Sunday, November 25, 2012

November 18: ORD

Today is November 18th. It's the 323rd day of the year. 43 days remain. It's week 47 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. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. 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 47 and the normal low is 32. I've calculated the 34-year averages at 48 and 33.


On the warm side, in 1979 the high was 71 with a low of 44. Two decades later, in 1999, history repeated as the high was again 71 with a low of 44. 1979 and 1999 are O'Hare's co-warmest November 18th days and the highs of 71 degrees are O'Hare's co-warmest highs of the date. In 1991 the high was 67 (O'Hare's third warmest high of the date) with a low of 44. A decade after that, in 2001, the high was 63 with a low of 48. In 1985 the high was 60 with a low of 50 (O'Hare's warmest low of the date). In 2004 the high was 61 with a low of 49 (O'Hare's second warmest low of the date). The year prior, in 2003, the high was 61 with a low of 48. The other warm high was 60 degrees in 1998.
The record high of 72 degrees was set in 1953 at Midway. The record warmest low of 55 degrees occurred back in 1941 at the University of Chicago. 25 of the past 34 highs (74%) were in the: 30s (7), 40s (10) and 50s (8). Eight highs (23%) were in the warm: 60s (6) and 70s (2). Our most recent 60s highs were 61 degrees in both 2003 and 2004. One high (3%) was in the cold 20s. O'Hare's second warmest November 18th was in 1975 as the high was 68 (O'Hare's second warmest high of the date) and low of 44. The other warm days were in: 1971 (high of 61, low of 43) and 1973 (high of 60, low of 43).

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 58 with a low of 26, a 32 degree spread. In 1975 the high was 68 with a low of 44, a warm day. In 1973 the high was a warm 60 with a low of 43, a warm day. In 1972 the high was a cold 35 with a low of 32, a three degree spread. In 1971 the high was 61 with a low of 43, a warm day. In 1969 the high was 55, then the temperature began falling to a low of 15 degrees on the 20th, a 40 degree plunge. In 1968 the high was 39 with a low of 34, a five degree spread. In 1965 the low was a cold 20 degrees. In 1959 the high was 32 with a low of 13, a cold day. 


More recently, there were no large spreads. There were small spreads of four degrees two years ago in 2009 (47/43), five degrees in 1995 (39/34), six degrees in 1992 (41/35), six degrees in 1996 (34/28) and six degrees in 2007 (43/37).

On the cool side, in 1989 (O'Hare's coolest November 18th) the high was 26 (O'Hare's coolest high and only 20s high of the date) with a low of 15 (O'Hare's second coldest low of the date). In 2000 the high was 32 (with 1959, O'Hare's second coolest high of the date) with a low of 21. In 2008 the high was 34 with a low of 21. The other cold low of 20 degrees occurred in 1965. The other cool highs were 34 degrees in 1996 and 35 degrees in 1972. The record low of 8 degrees was set way back in 1880. The record coolest high of 22 degrees occurred way back in 1903. Both records occurred at a time when the official readings were taken adjacent to Lake Michigan. 25 of the last 34 lows (74%) were in the: 20s (13) and 30s (12). One low (3%) was in the cold 10s (a.k.a. teens). Eight lows (23%) were in the warm: 40s (7) and 50s (1).  O'Hare's second coolest November 18th was in 1959 as the high was 32 (with 2000, O'Hare's second coolest high of the date) and low of 13 (O'Hare's coldest low of the date).

There was an instance of a warm year followed by a cold year and then back to a warm year. In 1999 the high was 71 with a low of 44, overall 18.5 degrees ABOVE normal. Then in 2000 the high was 32 with a low of 21, overall 12.5 degrees BELOW normal. Then in 2001 the high was 63 with a low of 48, overall 16.5 degrees ABOVE normal. We had back to back very warm years. In 2003 it was 15.5 degrees above normal (61/48) and in 2004 it was 16 degrees above normal (61/49).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:18 and sunrise is at 6:48. Sunset is at 16:29 and twilight ends at 16:59. There's a total of 9 hours, 41 minutes of daylight today and 10 hours, 41 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:19 and sunrise is at 6:49. The moon is waxing crescent. Illumination was 25% at midnight, will be 30% at noon and 36% at midnight tonight. Moonrise was at 11:13 this morning. Moonset is at 21:50 tonight. Moonrise is at 11:49 tomorrow morning. Moonlight time is 10 hours, 37 minutes which is 28 minutes longer than yesterday.

Cool Fall began on November 2nd and runs for 29 days through November 30th. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 20s, 60s and 70s occur infrequently. Thanksgiving is in four days. Pearl Harbor Day is in 19 days.     

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