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December 2017 - Report and Summary

The month of December 2017 saw near normal temperatures and above normal precipitation. The year 2017 was the fourth warmest year since record-keeping began in 1896 with an average temperature of 68.7 deg. It was, though, 0.2 deg. Cooler than the year 2016. The year was 3.1 deg. Warmer than normal. 1921 was Tyler's warmest year, followed by 1998. Rainfall in 2017 was 7.39 inches greater than normal, and 14.45 inches wetter than 2016.

The thirty-day outlook for December 2017, issued on November 16, had called for near normal temperatures and below normal precipitation. This was not changed with the November 30 revision. Temperatures ran well above normal between the 2nd and 4th under upper air high pressure. Then, came a pattern change.

A strong cold front crossed on the night of the 4th/5th, with widespread showers and amounts averaging around one-half inch. At the same time, a strong upper air ridge set up over the Western United States, permitting cold fronts to reach the area at 48-72-hour intervals through the 15th. With only limited to no moisture return ahead of these fronts, there was no rain and temperatures ran below normal.

An upper air storm system crossed on the night of the 16th/17th. This brought widespread rain to the area, with amounts running between 1.5 and 3.5 inches. The headiest was 3.29 inches in Tyler. Another storm crossed on the 19th, with more widespread and heavy rainfall of between 1.0 and 6.0 inches. Avinger received 5.95 inches for the heaviest reported. Coverage with both of these systems was near 100 percent. An F-2 tornado snapped trees, utility lines, and damaged a roof southwest of Rusk on the evening of the 19th. In addition, the Rusk Elementary School was partially flooded.

Temperatures were above normal between the 17th and 21st because of weak and fluctuating upper air high pressure. Dense fog was present on the mornings of the 17th, 18th, and 19th because of wet soils combining with moist Tropical Maritime air. Another disturbance, accompanied by a strong cold front, crossed on the 22nd. Rains ranged from one-fourth inch over the southeast to more than two inches at a few locations over the central and northern counties. Mount Pleasant measured 2.74 inches, and Ben Wheeler 2.13 inches among the heavier reports.

The cold front of the 22nd introduced Arctic air to the region, which persisted through the end of the month. Fronts on the 24th, 26th, and 30th reinforced the cold air mass. A strong meridional upper air ridge over the Western states combined with low pressure over the Central and Eastern states to bring these fronts southward.

Light overrunning rain occurred on the 26th, with amounts under one-tenth inch. Coverage was about 60 percent, principally over the central and southern counties. Light rain preceded the front of the 30th, with coverage of about 80 percent and amounts under one-tenth inch. December 2017 was 4.2 deg. Cooler than December 2016, and 3.89 inches wetter. The year's coldest temperature of 15 occurred on January 7, while the highest of 100 came on July 28.

A much smaller than usual number of sub-freezing days occurred during the 2016-2017 Winter only 11 days. The growing season began on February 16 almost a month ahead of normal. The growing season was 255 days, ending with the first freeze on October 29 about three weeks earlier than normal. The normal growing season is 245 days. The warm season began with the first 90-degree high temperature on April 28, and ended on October 14. It was 169 days in length 24 days longer than normal.

The temperature reached 100 degrees only once, but reached 90 degrees on 82 days. Among records set were: February 2017 as the warmest February with an average temperature of 61.6 2.6 deg. Warmer than the previous record set in 2000; March the fifth warmest March with 64.5 deg.; August the wettest August with 11.65 inches 1.40 inches wetter than August 1915 which previously held the record; and September with 0.01 inch which was the second driest September with 1899 the driest with no rain.

The Winter of 2016-2017 was the warmest Winter on record with a mean temperature of 56.1 deg., easily besting the 54.7 deg. In Winter 1910-1911. Spring 2017 was the fourth warmest Spring with a mean temperature of 68.9 deg; Spring 2012 was the warmest on record with 70.5 deg. The Summer of 2017 was the second wettest Summer with 21.45 in.; Summer 2007 is the wettest with 23.35 in.

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 2017

MX MN OBS PCPN REMARKS

DECEMBER 2017, RECORDS AND SUMMARY:

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