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December 2004 - Report and Summary

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

The month of December 2004 saw near normal temperatures and below normal precipitation. The normal temperature values reflect wide swings during the month, as two persistent periods of tropical air were present, along with one strong Arctic outbreak. Compared with December 2003, the month was 0.3 deg. warmer and 0.77 inch drier. Yearly total precipitation in 2004 was 2.06 inches greater in 2004 than in 2003. The year 2004 was one of very few weather extremes in East Texas. Temperatures and precipitation were both near normal values for the entire year. The mercury did not reach 100 in Tyler in 2004; the last occurrence of 100 deg. or higher was 102 on Aug. 6, 2003.

The year's highest temperature of 98 was observed on July 24, and August 3, 4, and 5. The coldest temperature of 19 was observed on December 23. Rainfall totaled 45.61 inches, which was 0.34 inch greater than normal. Accumulating snow fell on February 14, with 3.0 inches measured. This was the first measurable snowfall since December 31, 2000. The 2004 growing season was 28 days longer than normal, beginning Feb. 26 and ending Nov. 25. Winter 2003-2004 was slightly cooler than normal, with near normal precipitation. Spring was near normal in both values, while Summer was cool and moist, and the Fall was warm and dry overall.

The seasonal averages mask the fact that June was extremely wet, while there were protracted dry periods from late-June into late-July, and from late-August into early-October. SEASON TEMP VNCE PCPN VNCE *Winter 2003-2004 48.1 -1.6 11.62 -0.24 Spring 2004 67.6 +0.9 11.51 -0.61 Summer 2004 79.8 -2.4 13.24 +4.82 Autumn 2004 69.7 +2.3 10.01 -2.86 2004 TOTAL 66.2 -0.4 45.61 +0.34 (Includes December 2003, since climatological Winter includes the months of December,January, and February. Climatological Spring is March, April, and May; Summer is June, July, and August; and Autumn is September, October, and November.) The thirty-day outlook for December 2004 had called for near normal temperatures and above normal precipitation.

The week November 28-December 4 saw temperatures about 5 deg. cooler than normal, and rainfall about 80 percent of normal. The week began with a modified Polar Maritime air mass in place. Tropical Maritime air returned rapidly on the 29th ahead of another cold front and storm system, which brought rain and colder temperatures for the 30th. A reinforcing front arrived on the 3rd, which kept temperatures at below normal levels through the remainder of the week. The week's average temperature was 48.4 deg., with precipitation 0.91 inch. This was 8.9 deg. cooler than the previous week. Compared with the same week in 2003, the week was 2.4 deg. cooler, and there was no rain during the week in 2003.

The week December 5-11 saw temperatures about 7 deg. warmer than normal, and near normal rainfall. A wet storm system crossed between the 5th and 7th, with a line of strong thunderstorms on the evening of the 6th. This was followed by a weak cold front, and then rapid warming on the 9th ahead of a blustery cold front which crossed the morning of the 10th. Moisture return was limited, and there was no rain with that one. The week's average temperature was 57.2 deg. and precipitation was 1.14 inches. The week was 8.8 deg. warmer than the previous week. Compared with the same week in 2003, the week was 8.6 deg. warmer, and 0.05 inch wetter.

The week December 12-18 saw temperatures about 3 deg. cooler than normal, and precipitation about one-third normal. A strong cold front crossed on the morning of the 13th, following very warm temperatures on the 12th. A polar Continental air mass dominated the area's weather for most of the week, with a northwest wind flow aloft continuing the transport of cold air into the region. The first front arrived on the early-morning of the 13th. A disturbance and reinforcing cold front on the 16th brought the week's only rainfall. Another reinforcing front arrived on the 18th. The 13th was windy; the 17th saw widespread dense fog. The week's average temperature was 46.4 deg., and precipitation was 0.38 inch. The week was 10.8 deg. colder than the previous week. Compared with the same week in 2003, the week was 0.1 deg. warmer, and 0.16 inch wetter.

The week December 19-25 saw temperatures 6 deg. colder than normal, and rainfall about 125 percent of normal. Temperatures warmed between the 19th and 21st ahead of a strong Arctic outbreak which reached the region the morning of the 22nd. This brought very cold air, which persisted until the 25th. Rain accompanied the front and its upper air storm system, with about two inches of snow north of IH-30. In Tyler, a light flurry occurred the afternoon of the 22nd. The counties north of IH-30 experienced about 72 hours of consecutive sub-freezing temperatures between the late-morning of the 22nd and the late-morning of the 25th. The storm which brought historic snowfall totals to South Texas on the 25th brought a few flurries as far north as Houston County on the evening of the 24th, and considerable cloudiness to the Tyler area overnight the 24th/25th. The week's average temperature was 41.8 deg., and rainfall was 1.26 inches. This was 4.6 deg. colder than the previous week. Compared with the same week in 2003, the week was 12.3 deg. colder, and 0.75 inch wetter. Polar Continental air continued to slowly modify between the 26th and 28th. On the 29th, it was rapidly replaced by Tropical Maritime air, which sent temperatures to well-above normal levels for the last three days of the month.

A few showers over the southern counties occurred on each of the last three days of the month, and dense fog was widespread on the morning of the 29th as the much warmer and more moist air mass moved over the still cold ground.

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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