The month of September 2004 saw near normal temperatures and much below normal rainfall. It has been over a decade since a month in Tyler was this dry- -July 1993 saw but 0.02 inch. Further, it has been over a century since a September this dry; no rain fell in September 1899. September 2004 becomes the second driest on record, replacing September 1931 in which 0.09 inch fell. Compared with September 2003, the month was 2.6 deg. warmer, and 3.50 inches drier. Year-to-date rainfall through September 30 2.83 inches less in 2004 than last year. The thirty-day outlook for September 2004 had called for below normal temperatures and above normal precipitation. This outlook was unchanged with the August 31 revision.
The week August 29-September 4 saw temperatures about 5 deg. cooler than normal, and rainfall about 10 percent of normal. The week's only reported rainfall fell on the 28th, and accompanied the front which moved through that evening. A reinforcing surge of cool air moved in on the evening of the 30th. This kept temperatures mild and humidities low until moist and warmer air returned ahead of another front on the 3rd. The average temperature was 76.3 deg., and precipitation was 0.07 inch. This was 5.6 deg. cooler than the previous week. Compared with the same week in 2003, the week was 0.8 deg. cooler and 1.38 inches drier.
The week September 5-11 saw temperatures about 3 deg. cooler than normal, and no precipitation. The week saw shower and thunderstorm activity on the 5th and 6th, in association with the cold front of the night of the 4th and a crossing upper air disturbance. No rain fell in Tyler. The high pressure ridge, which pushed the front through, interacted with the remnant of Hurricane Frances to pull in mild and dry air between the 6th and 9th. This held down temperatures and humidities. Upper air high pressure began ridging over the area from the southwest on the 9th, which caused a slow increase in temperatures. Humidities began increasing slowly on the morning of the 10th as moist air worked its way westward from the Lower Mississippi River Valley. No rain fell anywhere in the region from the 7th through the end of the week. The week's average temperature was 76.8 deg. This was 0.5 deg. warmer than the previous week. Compared with the same week in 2003, the week was 0.4 deg. warmer, and 1.60 inches drier.
The week September 12-18 saw temperatures about 3 deg. warmer than normal, and rainfall less than 10 percent of normal. For most of the week, Tropical Maritime air was in control, along with an upper air high pressure ridge. Active sea-breeze fronts ahead of Hurricane Ivan on the 13th, 14th, and 15th caused thunderstorms to the south of Tyler. One of these brought the only rain to the city on the 14th. The circulation around Ivan did bring in less humid air after he made landfall on the 16th in Alabama. However, the upper air high and subsiding air on the west side of Ivan caused very high temperatures on the 17th and 18th. The week's average temperature was 81.1 deg., and rainfall was 0.04 inch. This was 4.3 deg. warmer than the previous week. Compared with the same week in 2003, the week was 7.2 deg. warmer. There was no rainfall in 2003. A weak cold front moved into the area on the night of the 18th, which lowered temperatures by a few degrees. No rain accompanied the front.
The week September 19-25 saw near normal temperatures and no measurable rainfall in Tyler. The re-development of Ivan on the afternoon of the 22nd in the Gulf of Mexico brought rain late in the week, helped out by another front on the 24th. Tyler--City received only a trace, but parts of the area received as much as three inches. The week's average temperature was 75.8 deg., which was 5.3 deg. cooler than the previous week. Compared with the same week in 2003, the week was 1.7 deg. warmer, and 0.41 inch drier.
The final five days of the month saw a dry air mass in place, which allowed for mild nighttime but warm afternoon temperatures. There was no rain during this period. For much of September, upper air high pressure was in control, which kept the region warm and dry.
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.
MX MN OBS PCPN REMARKS
September 2004, RECORDS AND SUMMARY: