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January 2003 - Report and Summary

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

The month of January 2003 was colder and much drier than normal. For much of the month, Polar Continental air masses dropped into the region on a northwest flow aloft. Upper air high pressure over Western North America and the Polar Vortex over Hudson's Bay during the middle of the month made this possible. The southern branch of the jet stream was relatively inactive, which limited precipitation.

The month was 6.8 deg. cooler than January 2002, and 0.96 in. drier. Last month was the coldest January since 1985, when the average temperature was 39.2 deg. January 2003 is the fourth driest January on record. In 1996, 0.14 inch fell for the driest; 0.18 in. of precipitation occurred in 1971, and 0.29 in. in 1986. January 1959 slips to fifth place in the driest January category, with 0.65 in. Precipitation for the twelve months preceding January 31, 2003 was 101.3 percent of normal. The thirty-day outlook had called for below normal temperatures and above normal precipitation.

The week December 29, 2002-January 4, 2003 saw temperatures about three degrees warmer than normal and rainfall about 200 percent of normal.A strong storm system crossed on the 30th, and a weaker storm and cold front on the 1st. The storm of the 30th brought widespread severe weather on the evening of the 30th, and the week's only rainfall. Small hail occurred in Tyler at late-afternoon on the 30th. Strong winds blew on the 31st, and again on the 2nd. This brought cold conditions on those two days. Winds became southwesterly on the 4th, allowing for rapid warming. The week's average temperature was 49.5 deg., which was 7.1 deg. warmer than the previous week. Precipitation totalled 1.96 inches. Compared with the same week in 2001-2002, the week was 14.8 deg. warmer. Precipitation during the week was 1.83 in. greater than that for the same week in 2001-2002.

The week January 5-11 saw temperatures one degree warmer than normal, and no precipitation. Polar Maritime air was over the area early in the week. At mid-week, a rapid warm-up occurred prior to a transition in the upper air flow pattern. On the night of the 9th, the first in a series of Arctic air masses arrived, introducing a period of much below normal temperatures. The absence of available moisture prevented any rain with the front on the 9th. The week's average temperature was 48.0 deg., which was 1.5 deg. cooler than the previous week. Compared with the same week in 2002, the week was 2.4 deg. cooler, and 0.50 inch drier.

The week January 12-18 saw temperatures nine degrees colder than normal, and precipitation about one-fourth of normal. The week's precipitation fell on the 12th, first as rain, and then as a rain/snow mix. A light dusting of snow covered the ground over northern parts of the county, though not in the city. Cold fronts crossed on the 12th, 16th, and 18th. Windy conditions accompanied the front of the 16th, which continued into the 17th. This brought low wind chill equivalent values. The week's average temperature was 38.5 deg., which 9.5 deg. colder than the previous week. Precipitation totaled 0.22 inch. Compared with the same week in 2002, the week was 9.9 deg. cooler, and precipitation for the two weeks was identical.

The week January 19-25 saw temperatures four degrees cooler than normal, and there was no measurable precipitation. The Arctic air mass, present early in the week, was replaced with a strong warming trend on the 20th and 21st. On the night of the 21st, another Arctic front arrived, with a reinforcing cold surge on the morning of the 23rd. This caused above normal temperatures on the 20th and 21st, and below normal temperatures during the remainder of the week. With moisture sources largely shut off, the only precipitation was some light sleet on the morning of the 25th-- which did not result in measurable precipitation.

Gusty winds on the 22nd and 23rd lowered the wind chill equivalent values well below the actual air temperatures. The week's average temperature was 43.9 deg., which was 5.4 deg. warmer than the previous week. Compared with the same week in 2002, the week was 5.8 deg. cooler, and 0.72 in. drier.

The final six days of the month saw cold fronts on the 26th and 29th, with a warming trend in between, and again on the 31st prior to yet another cold front. Rain occurred with the fronts of the 26th and 29th. The front of the 29th was followed by a temperature inversion, which kept conditions overcast and chilly between the late-afternoon of the 29th and mid-day of 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.

January 2003



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