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December 2011 - Report and Summary

by Robert K. Peters, Ph.D. - National Weather Service Cooperating Observer

The year 2011 was warm and dry. In fact, the year tied for the fourth warmest year on record, and becomes the sixth driest. 2011 equals the 68.1 F. Average temperature from 1939 and 2006. The year was 2.5 deg. Warmer than 2010, and 5.65 inches drier.

The warmest year on record was 1921 with 69.6 F., and the driest was 1956 with 24.01 inches. Rainfall was 30.25 inches, about 65 percent of normal. The drought, which commenced in the Summer of 2010, persisted for much of 2011, with some relief beginning in mid-November. Rainfall since July 1, 2010 is 41.56 inches about 60 percent of normal.

The year's coldest temperature of 14 came on February 2, while its warmest at 108 came on August 9 tying for the third warmest temperature recorded and the warmest reading since August 1956. January and the first week in February were cold, with a warm-up commencing then. March and April were quite warm and dry, with cooling for part of May until Summer's heat commenced near May's end. Hot temperatures persisted into late-September, before more seasonal readings came in early- October.

Monthly record set in 2011 were: March, driest with 0.48 inch, April fifth warmest with 70.6 F., June fifth warmest with 85.2 F., July second warmest at 88.4 F., and August warmest August and warmest month ever at 91.0 F. In addition, the Summer of 2011 was the warmest Summer with a mean temperature of 88.2 F.

Likewise, there were more days at or above 100 F. Than in any other Summer 57; and August 2011 with 28 days at or above 100 F. Now has the record for the month with the greatest number of days where the mercury reached the century mark. The number of cooling degree days was 137 percent of normal, with a total of 3249. The growing season was 264 days 19 days longer than normal. The last freeze of the 2010- 2011 cool season came on the morning of March 6, while the first freeze of the 2011-2012 cool season came on the evening of November 27.

The warm season was eight days longer than normal, finishing the year at 153 days and extending from May 7 through October 7. Weather records in Tyler extend back to 1896.

The thirty-day outlook for December 2011 had called for above normal temperatures and below normal precipitation. In fact, the month saw near normal temperatures and above normal rainfall.

For much of the month, a west to southwest flow aloft permitted storm systems to cross. These fed on Gulf and Pacific moisture to produce a number of rain events. These systems crossed on the 3rd-5th, 15th and 16th, 20th, 22nd, and 24th-26th. During most of these events, temperatures were at or below normal. The only sustained period of above normal temperatures came in the 48 hours prior to the system of the 15th-16th.

The year ended dry following the exit of the final wet system on the 26th. December 2011 was 0.3 deg. Warmer than December 2010, and 5.59 inches wetter.

The reporting period for temperatures and phenomenon on each day is for the twenty-four hours ending at midnight hours GMT--6 p.m. CST and 7 p.m. CDT. The reporting period for precipitation is for the twenty-four hours ending at noon GMT--6 a.m. CST and 7 a.m. CDT. All times are given using the twenty-four hour clock, and are expressed in Greenwich Mean Time.

Observations are from NWS Station 41/9207/4 in Tyler, Texas. The term "normal" refers to averages from the standard climatic period 1971-2000.




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