October 2018 Climate and Hydrology Summary

Tulsa: October 2018 was the 39th coldest (61.5°F, tied 1980; since 1905) and the 55th wettest (3.09"; since 1888) October on record.

Fort Smith: October 2018 was the 54th warmest (63.7°F, tied 1991, 1985, 1916, 1902; since 1882) and the 14th wettest (6.70"; since 1882) October on record.

Fort Smith: Daily records set or tied this month include record cold maximum temperatures.

Fayetteville: October 2018 was the 28th warmest (59.1°F, tied 2005, 1961; since 1949) and the 35th driest (3.25"; since 1949) October on record.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for October 2018 ranged from 2” to isolated amounts around 10” across eastern OK and northwest AR. The lowest rainfall totals of 2”-4” were primarily from just north of the I-44 corridor to I-40 in northeast OK and northwest AR. This corresponds to 50% to 300% of the normal October rainfall across the area.

Heavy rain occurred across southeast OK and west central AR, as well as across north central into northeast OK this month, resulting in some minor to moderate river flooding.

Moderate flooding occurred along the Neosho River near Commerce, and minor flooding along the Arkansas River at Ralston and Poteau River near Panama.

According to the Drought Monitor from October 30, 2018, Moderate (D1) drought conditions were present across portions of Osage, Washington, Nowata, Tulsa, Rogers, Mayes, Delaware, and Cherokee Counties in eastern OK. Abnormally Dry (D0) but not in drought conditions encompassed portions of Pawnee, Osage, Creek, Washington, Tulsa, Rogers, Mayes, Nowata, Craig, Delaware, Cherokee, and Adair Counties in eastern Oklahoma and Benton, Carroll, and Washington Counties in northwest Arkansas.

According to the Oklahoma Climatological Survey, October 2018 was the 25th wettest for northeast Oklahoma, the 24th wettest for east central Oklahoma, and the 7th wettest for southeast Oklahoma. Records go back to 1921. For the Cool Growing Season September 1 - October 31, 2018, northeast Oklahoma ranked as the 43rd wettest, east central Oklahoma was the 28th wettest, and southeast Oklahoma was the 5th wettest period. For Year-to-Date 2018 (January 1-October 31, 2018), northeast Oklahoma ranked as the 39th driest, east central Oklahoma was the 14th wettest, and southeast Oklahoma was the 9th wettest Year-to-Date.

Shortly after midnight on the 4th, a line of showers and thunderstorms moved south out of KS and into northeast OK. Most of this activity remained north of I-44 and dissipated by noon. Rainfall totals ranged from around 0.25” to around 2.5”, with the highest totals across eastern Kay, Osage, Washington, and Nowata Counties.

A frontal boundary waffled back and forth over the Plains on the 6th-7th. The front moved south into northeast OK on the 6th and eventually stalled from far northwest AR to between Tulsa and McAlester. Shower and thunderstorms developed primarily along and north of the boundary during the afternoon and continuing through the overnight hours, with isolated storms south of the boundary. By 7am on the 7th, a portion of northeast OK from Wagoner through Ottawa Counties received 1.5”-3” of rain. Scattered showers and thunderstorms then continued for much of the 7th. During the evening hours, convection increased across eastern Kay, Pawnee, Osage, and Washington Counties, before lifting back north into KS after midnight as the quasi-stationary boundary slowly retreated north. While rainfall totals were generally 0.25”-1.5”, eastern Kay, northwest Pawnee and northwest Osage Counties received 2”-4” of rain. An EF-0 tornado also occurred near Fairfax in Osage County (see https://arcg.is/1f5Ob4 for details).

Thunderstorms then moved back south into eastern Kay, western Pawnee, and western Osage Counties during the evening of the 8th. Additional showers and thunderstorms spread over eastern OK through the overnight hours. This activity brought an additional 1”-3” to eastern Kay, far western Pawnee, and northwest Osage Counties, and brought the 2-day total in the area to 3”-6”.

A quasi-linear convective system then moved into eastern OK during the late morning of the 9th, stretching from the KS/OK state line to the TX/OK state line. Numerous transient low-level circulations occurred along the line, resulting in areas of wind damage, as the line moved across eastern OK and northwest AR. However, no tornadoes occurred, as determined by the damage survey team. Showers and thunderstorms continued behind the line through the mid-evening, before finally exiting the region. Rainfall totals from this activity ranged from 0.25” to 1.5” across all of eastern OK and northwest AR. This additional rainfall brought the 7-day totals to 5”-8” across eastern Kay, western Pawnee, and northwest Osage Counties. This rainfall, plus the heavy rain further upstream across the Upper Arkansas River Basin, resulted in minor flooding along the Arkansas River at Ralston. Heavy rain fell across eastern KS during this time frame as well, affecting the Neosho River. Moderate flooding occurred along the Neosho River near Commerce for several days.

Widespread showers and isolated thunderstorms affected eastern OK and northwest AR mid-morning through late afternoon on the 13th as the remnants of Pacific Hurricane Sergio interacted with a frontal zone. The heaviest rain axis was along and south of I-40, where 1”-2.5” of rain fell.

Isolated to widely scattered showers and thunderstorms occurred across eastern OK and northwest AR during the afternoon and evening hours of the 14th as a strong cold front moved through the area, with additional widespread activity across southeast OK and west central AR during the overnight hours and continuing through the morning of the 15th. This activity finally came to an end during the afternoon. An additional 0.50”-1.5” of rain fell across southeast OK into west central AR.

Showers and thunderstorms increased across eastern OK and western AR mid-morning on the 31st as an upper-level trough approached the region. The system was slow to clear the area, resulting in lingering rainfall and soggy trick-or-treating across southeast OK and west central AR during the evening hours. Rainfall totals ranged from 1”-3” southeast of a McAlester to Springdale line. This rain also resulted in minor flooding along the Poteau River near Panama.