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March 2003 - Report and Summary

The month of March 2003 was slightly colder and considerably drier than normal. An unusually late freeze occurred on the 30th--about two weeks after the normal date for the latest freeze of the season. High pressure aloft over Western North America and low pressure over Central North America allowed for frequent intrusions of cold air. Also, the southern branch of the jet stream was well to the south of East Texas during much of the month. This kept the area dry. March 2003 was, however, warmer than March 2002, by 1.9 deg. March 2002 was 2.76 inches wetter than March 2003. Year-to-date precipitation was nearly identical through March 31 in 2002 and 2003. The figure in 2002 was 9.85 inches, while that for 2003 was 9.79 inches. Precipitation over the twelve months ending March 31, 2003 is 101.2 percent of normal. The 30-day outlook for March 2003 had called for below normal temperatures and above normal precipitation.

The week February 23-March 1 saw temperatures 15 degrees colder than normal, and near-normal precipitation. The week began warm and windy, with peak wind gusts of 46 mph clocked twice around mid-day on the 23rd. An Arctic air mass moved into the region on the night of the 23rd. The air mass was shallow, and was overrun by moist and warm air just above the surface. This introduced a period of cloudiness, which persisted from 11 p.m. on the 23rd through 6 p.m. on the 1st, with 139 consecutive hours of overcast recorded. A couple of crossing upper air disturbances combined with the Arctic air mass to bring freezing rain and sleet to the northwestern half of the area from the evening of the 24th through mid-day of the 26th. Though ice accumulated only on vegetation in Tyler on the morning of the 26th, numerous schools and main highways were closed to the northwest of Tyler on the 25th and 26th.

The Arctic air mass slowly eroded beginning on the 26th, though temperatures remained well below normal through the end of the week.Frozen precipitation occurred in Tyler on two days during the week, and a record low maximum temperature was observed on the 26th. It was not the coldest week of the cool season, but it did have the greatest divergence from normal. The week's average temperature was 39.8 deg., which was 8.6 deg. colder than the previous week. Precipitation was 0.99 inch. Compared with the same week in 2002, the temperature was 6.1 deg. colder and 0.97 inch wetter.

The week March 2-8 saw temperatures seven degrees colder than normal, and rainfall about one-fourth of normal. Shallow Arctic air masses were over the region on the 3rd and again on the 5th. Both were followed by warming as the surface high pressure ridges bringing the cold outbreaks went to the east. Precipitation occurred on the 3rd and 5th as moist air overran the cold air masses. The week's average temperature was 51.2 deg., which was 11.4 deg. warmer than the previous week. Precipitation totaled 0.25 inch. Compared with the same week in 2002, the week was 0.2 deg. colder, and 0.14 in. wetter.

The week March 9-15 saw temperatures five degrees warmer than normal, and precipitation about three-fourths of normal. A significant change in the upper air flow pattern over North America began on the 7th. Upper air high pressure re-located eastward to Central North America from its position off the Pacific Coast. This did two things:

A cold front moved in on the 9th, but the cold air stayed just to the north and west of the area. A second front on the 13th had little effect on temperatures. A weak upper air storm crossed on the 13th with the second cold front. This brought the week's precipitation, as thunderstorms developed across the region during the morning hours. Dense fog was over the southern counties on the mornings of the 13th and 14th, as warmer air off the Gulf of Mexico crossed the still cool ground. The week's average temperature was 64.0 deg, which was 12.8 deg. warmer than the previous week. Precipitation totaled 0.61 inch. Compared with the same week in 2002, the week was 6.5 deg. warmer and 0.28 inch drier. The week marked a sharp transition from the cool into the warm season.

The week march 16-22 saw temperatures three degrees cooler than normal, and near normal rainfall. Two storms affected the area during the week. The first was between the 18th and 20th. A slow-moving upper air low brought rain to the area on the 18th, and gusty winds on the 19th and 20th with significant cooling on the 20th. A fast-moving storm crossed on the 22nd, with light rain. The week began warm, but a weak cold front on the night of the 16th began the downward trend in temperatures. The week's average temperature was 58.0 deg, which was 6.-0 deg. cooler than the previous week. Rainfall totaled 0.70 inch. Compared with the same week in 2002, the week was 1.0 deg. warmer, and 2.52 inches drier.

The week March 23-29 saw temperatures four degrees cooler than normal, and rainfall about 125 percent of normal. A line of strong to severe thunderstorms crossed on the evening of the 25th. It resulted in golf ball-sized hail in Tyler, and most of the week's rainfall. Rains were confined largely to the western one-half of the region, with light amounts over the eastern half. At the beginning of the week, a Polar Maritime air mass brought cool temperatures. Tropical Maritime air returned on the 25th, replaced by Polar Maritime air on the 26th. Tropical air returned briefly on the 27th, until a Polar Continental air mass moved in on the 28th. This lowered temperatures sharply during the late-week. Some light rain fell on the 28th.

Conditions were windy on the 25th, 27th, 28th, and 29th. The week's average temperature was 59.3 deg. which was 1.3 deg. warmer than the previous week. Precipitation was 1.05 inches. Compared with the same week in 2002, the week was 0.9 deg. cooler. There was no rainfall during the same week in 2002. /The final two days of the month were cool, with a warming trend beginning 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.

March 2003



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