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September 2002 - Report and Summary

The month of September 2002 saw near normal temperatures and slightly below normal rainfall. The North American upper wind pattern began its transition from the warm season to the cool season, with the prevailing Westerlies dropping southward into the Central United States on a couple of occasions. This allowed cool air masses to enter the region, and also deflected Tropical Storm Isidore northeastward away from the Texas Coast late in the month. The month was 3.3 deg. warmer than September 2001, and 1.86 inches drier. Year-to-date precipitation was 14.19 inches less through September 30th in 2002 than it was through the same date in 2001. Twelve-month precipitation through September 30, 2002 is 98.8 percent of normal. The thirty-day outlook for September 2002 had called for near normal temperatures and near normal precipitation, and was accurate.

The week September 1-7 saw temperatures three degrees warmer than normal, and precipitation about five percent of normal. For most of the week, an upper air high pressure ridge was over Central North America. This brought warm temperatures. Early in the week, the air mass was dry, which, along with increasing darkness, allowed for lower nighttime temperatures. An easterly wave crossed early in the week, which brought widely scattered showers to the area. On the 5th, Tropical Storm Faye formed in the western Gulf of Mexico, and Tropical Storm Edouard crossed Florida and entered the eastern Gulf. Edouard dissipated, but its upper air windshift line brought rain on the afternoon of the 7th. Faye went onshore near Palacios on that morning, and contributed to the showers of the 7th. The week was 3.1 deg. warmer than the previous week. It was 5.7 deg. warmer than the same week in 2001, and 2.60 inches drier.

The week September 8-14 was one degree warmer, and about one-third wetter than normal. The week began with rains from Tropical Storm Faye over South Texas and the remnant of Tropical Storm Edouard on the 8th and 9th. Upper air high pressure built into the region on the 10th, and caused warmer temperatures. A haze layer moved in from the northeast on the 11th, and persisted through the remainder of the week. The week's average temperature was 80.0 deg., and precipitation was 1.06 inches. This was 2.7 deg. cooler than the previous week. Compared with 2001, the week was 4.3 deg. warmer and 0.91 inch wetter.

The week September 15-21 was two degrees cooler than normal, and rainfall was about twice normal. Heavy rains and scattered severe weather occurred on the 19th, when a cold front approached the region from the northwest. It interacted with an upper air disturbance, and with moisture from Eastern Pacific Tropical Storm Issell in the middle and upper atmosphere. The result was rainfall of between one and three inches in the area. There were reports of wind damage from parts of Tyler on that afternoon from gusty winds accompanying the thunderstorms. Lighter rains fell on the 16th in response to another cold front. Modified Polar Maritime air was over the region at the beginning of the week, with Tropical Maritime air present at mid-week. Late in the week, Polar Maritime air built in behind the front of the 20th. The week's average temperature was 75.2, which was 4.8 deg. cooler than the previous week. Compared with the same week in 2001, the week was 1.7 deg. cooler, and 45 percent wetter.

The week September 22-28 saw temperatures one degree cooler than normal, and there was no rainfall. Upper air high pressure was in control of the area's weather for much of the week, strengthening towards week's end. Tropical Storm Isidore, who moved ashore in South Louisiana on the 26th, caused a northeasterly wind on the 23rd, 24th, 25th, 26th, and 27th. Subsidence on the northwest quadrant of the storm also contributed to warming temperatures. Pollution levels were moderate towards week's end, with the Texas Commission on Environmental Quality issuing ozone action day statements on the 27th, 28th, and 29th. The week's average temperature was 72.7 deg., which was 2.5 deg. Cooler than the previous week. Compared with the same week in 2001, the week was 7.2 deg. Warmer, and 0.01 inch drier. Tropical air was over the region on the 29th and 30th with above normal temperatures and no rainfall

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.

September 2002


September 2002, RECORDS AND SUMMARY:

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