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December 2007 - Report and Summary

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

The year 2007 was one of very dramatic contrasts: an extremely wet first half and a proportionally even drier second half. Through July 14, the city picked up 48.15 inches of rainfall 201.4 percent of normal. From July 15 through year's end, only 9.53 inches of rain fell 45.1 percent of normal.

The heavy rains of the first half of the year ended the drought, which began in the Spring of 2005. Rainfall in 2005 was only 51.2 percent of normal, while that in 2006 improved to 84.8 percent of normal, helped along by near to above normal rainfall during the last five months of the year. Flooding occurred in Tyler four times during the year: April 25, June 25, July 6, and the most serious on July 8. July 2007 was the wettest July on record, with 13.75 inches of rain falling in the city. Lake Tyler, which was more than 100 inches down in December 2006, rose to 33 inches above full pool by early July, with a 2-foot rise in one twenty-four hour period.

The year's coldest day was February 16, when the temperature fell to 17 degrees. The temperature did not reach 100 in Tyler, with August 13, 14, and 15 topping out at 99. July 2007 was the third coolest July on record. Tyler observed its third latest snowfall on record, when a trace fell on April 7. Three days earlier, a microburst (strong downdraft from a thunderstorm) produced a peak wind gust of 67 mph. The wet first half of the year delayed the onset of the warm season the first day with a maximum at or above 90 degrees. The median date for that is May 8; in 2007, it happened on June 7. The end of the warm season was on October 8 one week later than normal. The temperature reached or exceeded 90 in Tyler on 74 days well under the average of 110. The warm season was 124 days. The growing season was longer than average in 2007. The first freeze came about three weeks late on December 4, after the last freeze coming 10 days early on March 5. This yielded a 273-day growing season, compared to the normal 245 days. The month of December 2007 was slightly warmer and drier than normal.

The average temperatures in December 2006 and December 2007 were identical; December 2007 was 1.96 inches drier than the previous December. Annual rainfall was 19.41 inches greater in 2007 than in 2006. Reflecting the increased rainfall, the year's average temperature was 66.2 deg. This was 1.9 deg. Cooler than 2006, and 0.3 deg. Cooler than normal. 2007 is the coolest year since 2003, and the wettest since 2001. The thirty-day outlook for December 2007 had called for above normal temperatures and below normal precipitation.

The week November 25-December 1 saw slightly below normal temperatures and rainfall about 75 percent of normal. The week began cold and wet as an upper air storm slowly departed. Cold fronts on the 25th and 28th held down temperatures until the end of the week when a moist flow set up off the Gulf of Mexico. The week's average temperature was 51.8 deg., and rainfall was 0.85 inch. This was 3.3 deg. Cooler than the previous week. Compared with the same week in 2006, the week was 2.5 deg. Cooler, and 0.20 inch drier.

The week December 2-8 was about 6 degrees warmer than normal, with rainfall about 5 percent of normal. The week began and ended warm. A cold front, crossing on the afternoon of the 2nd, brought the week's only rainfall, and also the season's first freeze on the morning of the 4th. Temperatures warmed afternoons at mid-week because of a dry atmosphere, with rapid moistening beginning the night of the 6th ahead of a storm system and cold front which affected the area early in the following week. The week's average temperature was 56.8 deg., and rainfall was 0.08 inch. The week was 5.0 deg. Warmer than the previous week. Compared with the same week in 2006, the week was 15.6 deg. Warmer, and 0.8 inch wetter.

The week December 9-15 saw temperatures about 3 degrees warmer than normal, and rainfall about 150 percent of normal. The week began warm, with a strong and short-lived cold front on the 9th, followed by rapid morning on the night of the 10th. On the 12th, another front crossed, introducing Polar Continental air which lowered temperatures to below normal levels. Crossing storms on the 12th and 15th brought the week's rainfall. Another Polar front crossed on the morning of the 15th, bringing windy and chilly conditions for the end of the week. The week's average temperature was 62.8 deg., and rainfall was 1.76 inches. The week was 4.0 deg. Colder than the previous week. Compared with the same week in 2006, the week was 5.1 deg. Cooler, and 1.01 inches wetter.

The week December 16-22 saw temperatures about 3 degrees warmer than normal, and rainfall about 5 percent of normal. The week began cold, but temperatures moderated at mid-week ahead of cold fronts on the 20th and 22nd. These brought the week's rains, with the front of the 22nd introducing another Arctic air mass. Very windy conditions accompanied the latter front, with gusts in excess of 41 mph. The week's average temperature was 50.5 deg., and rainfall was 0.08 inch. The week was 2.3 deg. Colder than the previous week. Compared with the same week in 2006, the week was 7.4 deg. Colder, and 0.36 inch drier.

Christmas Week (December 23-29) was chilly and wet. Polar air was present for the entire week. A storm system, crossing on the 26th, brought significant rainfall to the entire area. The week's average temperature of 42.1 was about 5 degrees below normal. The rainfall of 1.56 inches was about 150 percent of normal. Compared with the previous week, the week was 8.4 deg. Colder. Compared with the same week in 2006, the week was 0.8 deg. Warmer, and 2.69 inches drier. The final two days of the year were sunny and seasonably cool, with a strong cold front crossing mid-day on the 31st.

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.

DECEMBER 2007

MX MN OBS PCPN REMARKS

DECEMBER 2007, RECORDS AND SUMMARY:

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