The month of May 1998 equalled the record for the warmest May in National Weather Service records for Tyler, and was by far the driest. The month's temperature averaged 79.5 degrees. This was also the average for May 1896, though the average daily maximum was higher and the average nighttime minimum lower 102 years ago. Occupying second place until last month was May 1996, when the temperature averaged 78.7.
May 1988 was the previous driest May, with 0.56 inch. An upper air high pressure ridge established itself over the area in late-April. This kept away storm features, and brought quite warm temperatures through the entiremonth--especially after the 21st. May 1998 was 7.0 degrees warmer than May 1997, and 2.86 inches drier. Year-to-date rainfall through May 31 is 7.00 inches less in 1998 than in 1997. Rainfall over the past twelve months is 45.61 inches--101 percent of normal. The thirty-day outlook for the month had called for below normal temperatures and near normal precipitation.
During the first week in May, temperatures were four degrees above normal and there was but 0.01 inch of rainfall. A record high maximum was set on the afternoon of the 7th. Surface and upper air high pressure dominated the weather during the week. The second week in May saw temperatures four degrees above normal and no rainfall. Upper atmospheric high pressure was still in control of the weather through the week. Storm features passed well to the north of the region through the Central Plains.
Extensive jungle and agricultural fires over southern Mexico and northern Honduras brought smoke and haze to the area on four days. Temperatures during the third week in May were six degrees above normal and there was no rainfall. Upper air high pressure, extending from about 15N into the Central United States, kept a stagnant weather pattern of warm temperatures and no precipitation. Storm features were blocked from East Texas by this feature.
The week also saw considerable smoke and haze from the persistent jungle and agricultural fires in southern Mexico, Costa Rica, Guatemala, and Honduras. For much of the week, a public health advisory was in force, issued by the Texas Natural Resource Conservation Commission. The smoke was transported northward on a low-level southerly flow into Texas. Poorest visibilities were on the 16th, when Tyler's visibility was between two and four miles throughout the day. The smoke abted somewhat on the 18th and 19th, but returned on the 20th.
The final ten days of the month saw temperatures nine degrees above normal, and there was but 0.01 inch of rain. Upper atmospheric high pressure controlled the region's weather during the period. Smoke from the Mexican fires began abaiting after the 25th with the crossing to the north of an upper air low. This feature brought the period's only rainfall--a brief period of rain on the morning of the 27th. Torrential rains struck extreme Northeast Texas on the 28th, with Texarkana receiving 10.76 inches.
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
May 1998, RECORDS AND SUMMARY: