September 2018 Climate and Hydrology Summary

Tulsa: September 2018 was the 30th warmest (75.9°F, tied 2012, 1920; since 1905) and the 63rd driest (3.06", tied 1997; since 1888) September on record.

Fort Smith: September 2018 was the 23rd warmest (77.1°F, tied 1977, 1947; since 1882) and the 23rd wettest (5.75", tied 2007; since 1882) September on record.

Fort Smith: Daily records set or tied this month include a record daily rainfall.

Fayetteville: September 2018 was the 13th warmest (71.8°F; since 1949) and the 15th driest (2.05"; since 1949) September on record.

Fayetteville: Daily records set or tied this month include a record cold maximum temperature.

McAlester, OK set a new daily rainfall record for the entire month of September with 5.79" of rain on 9/21/2018. The previous record was 4.21" on 9/20/1974.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for September 2018 ranged from 0.5” to isolated amounts around 12” across eastern OK and northwest AR. The highest rainfall totals of over 6” were primarily across eastern OK and west central AR southwest of a Tulsa to Fort Smith line. This corresponds to 10% to around 200% of the normal September rainfall across the area, with only 10%-25% of the September rainfall normal in the northeast corner of OK.

There was a large rainfall gradient from north to south across eastern OK and northwest AR in September 2018. Rainfall in southeast KS resulted in river flooding along the Neosho River this month.

Showers and thunderstorms trained over the western portion of Osage and Pawnee Counties during the morning of the 4th under the influence of a mid-level wave, with widely scattered convection across the remainder of eastern Oklahoma throughout the day. While most locations that saw rain received around 0.25” or less, western Osage and Pawnee Counties received 0.50” to around 2” of rain. Scattered showers and thunderstorms continued for much of the 5th as a weak frontal boundary interacted with a moisture rich southerly flow across eastern OK and far northwest AR. Most of the affected areas received 0.25” to 1” of rain, with localized totals of 1”-3”. Rainfall lingered across Tulsa through Nowata Counties during the morning of the 6th, with isolated showers and thunderstorms in eastern OK in the afternoon and evening hours. This brought an additional 0.50” to near 2.5” in a few spots.

The remnants of Tropical Storm Gordon brought tropical moisture into the Southern Plains, which interacted with a front. Heavy rainfall of 1”-4” across southeast KS and northern Ottawa County on the 7th fell in the Neosho River basin, resulting in minor flooding at Commerce.

A cold front moved into eastern OK and northwest AR on the 21st, with plenty of tropical moisture ahead of it from the western Gulf of Mexico and remnants of Pacific Tropical Depression 19. The front stalled, and combined with the tropical moisture and a strong upper-level trough, resulted in heavy rainfall across the area. Widespread 1.5”-4” of rain fell south of Highway 412 by 7am CDT on the 22nd, with several areas receiving higher amounts of 4”-10” of rain in just 24 hours. An additional 0.50”-3” of rain fell on the 22nd south of I-40, with the highest totals along the Red River. This resulted in widespread 4”-7” of storm total rainfall south of I-40, with localized totals of 7”-11” in McIntosh, Pittsburg, Latimer, Pushmataha, and Le Flore Counties. Between Highway 412 and I-40, rainfall totals were 2”-4”, with localized amounts of 4”-7” in Creek, Tulsa, and Wagoner Counties. Several roads in the Tulsa metro area were closed due to high water. Large rises occurred along the Poteau, Kiamichi, and Red Rivers in southeast OK, but the rivers all remained in their banks. The Poteau River near Panama, however, was bank full.

According to the Drought Monitor from September 25, 2018, Severe (D2) Drought conditions were impacting Osage, far northwest Tulsa, and southern Washington Counties in eastern OK. Moderate (D1) drought conditions were present across portions of Osage, Washington, Tulsa, Nowata, and Rogers Counties in eastern OK, and far northeast Benton County in northwest Arkansas. Abnormally Dry (D0) but not in drought conditions encompassed portions of Pawnee, Osage, eastern Kay, Washington, Tulsa, Rogers, Mayes, Nowata, Craig, Ottawa, Delaware, Cherokee, and Adair Counties in eastern Oklahoma and Benton, Carroll, and Madison Counties in northwest Arkansas.

According to the Oklahoma Climatological Survey, September 2018 was the 37th driest for northeast Oklahoma, the 36th wettest for east central Oklahoma, and the 13th wettest for southeast Oklahoma. Records go back to 1921. For the 60-day period August 2-September 30, 2018, northeast Oklahoma ranked as the 49th wettest, east central Oklahoma was the 23rd wettest, and southeast Oklahoma was the 7th wettest period. For Water Year 2018 (October 1, 2017-September 30, 2018), northeast Oklahoma ranked as the 30th driest, east central Oklahoma was the 38th wettest, and southeast Oklahoma was the 31st wettest Water Year.

Water Year 2017 (Oct. 1, 2017-Sep. 30, 2018)

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for Water Year 2018 ranged from 25” to 70” across eastern OK and northwest AR. The highest rainfall totals of 50”-70” occurred across southeast OK and west central AR, while the lowest values of 25”-35” occurred across northeast OK. This corresponds to 50-150% of the normal water year rainfall across the area. A large portion of eastern OK and northwest AR ended the water year with 90%-110% of normal.

In Tulsa, OK, Water Year 2017-18 ranked as the 21st warmest Water Year (62.2°F, tied Water Year 2011; since records began in 1905-06) and the 44th driest Water Year (34.97”; since records began in 1893-94).

Fort Smith, AR had the 15th warmest Water Year (63.4°F, tied Water Year 1943; since records began in 1882-83) and the 37th wettest Water Year (46.14”; since records began in 1882-83).

Fayetteville, AR had the 16th warmest (58.4°F, tied Water Year 1987, 1955) and the 26th driest (43.88”) Water Year since records began in 1949-50.