October 2019 Climate and Hydrology Summary

Tulsa: October 2019 was the 6th coldest (57.9°F; since 1905) and the 24th wettest (5.89"; since 1888) October on record. A trace of snow fell, which ties as the 2nd snowiest (ties 1957, 1967, 1996, 2000; since 1900) October on record.

Tulsa: Daily records set or tied this month include a record cold maximum temperature, a record warm minimum temperature, record warm mean temperatures, a record daily snowfall, and a record daily rainfall.

Fort Smith: October 2019 was the 45th coldest (61.8°F; since 1882) and the 5th wettest (9.41"; since 1882) October on record.

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

Fayetteville: October 2019 was the 10th coldest (55.8°F, tied 1957; since 1949) and the Record wettest (12.07", previous record 10.69" in 2009; since 1949), and the 2nd snowiest (Trace, tied 1957, 1989, 1991, 1994, 1996; since 1949) October on record.

Fayetteville: Daily records set or tied this month include a record cold minimum temperature, a record warm mean temperature, record daily rainfall, and record daily snowfall.

McAlester: Daily records set or tied this month include record cold maximum temperatures, record warm and record cold minimum temperatures, record cold mean temperatures, and a record daily rainfall.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for October 2019 ranged from 2” to around 20” across eastern OK and northwest AR. Areas northwest of a line from Pawnee to Nowata received 2”-4”, with 5”-15” for much of the area southeast of that line. The greatest rainfall totals of 10”-20” affected areas from east central OK into northwest AR. These rainfall totals correspond to 50%-100% of the normal October rainfall northwest of a Pawnee to Nowata line, and 150% to near 500% for much of the remainder of eastern OK and northwest Arkansas.

Heavy rain resulted in both flash flooding and river flooding this month. Portions of eastern OK and northwest AR received more than 8” above their normal October rainfall this month.

Major flooding occurred along the entire Illinois River this month, with additional flooding during the month. Moderate flooding occurred along Flint Creek near Kansas.

According to the Drought Monitor from October 29, 2019, Abnormally Dry, but not in drought, conditions (D0) were present in southern Choctaw County in eastern OK. The remainder of eastern OK and northwest AR was drought free.

According to the Oklahoma Climatological Survey, October 2019 was the 7th wettest for northeast Oklahoma, the 4th wettest for east central Oklahoma, and the 6th wettest for southeast Oklahoma. Records go back to 1921. For the Cool Growing Season September 1 - October 31, 2019, northeast Oklahoma ranked as the 14th wettest, east central Oklahoma was the 10th wettest, and southeast Oklahoma was the 7th wettest period. For Year-to-Date 2019 (January 1-October 31, 2019), northeast Oklahoma ranked as the Record wettest, east central Oklahoma was the 4th wettest, and southeast Oklahoma was the 9th wettest Year-to-Date.

According to the National Centers for Environmental Information (NCEI), the northeast Oklahoma climate division had an average of 57.95” of rain (20.78” above the 1981-2010 normal) for the 10-month period January through October, ranking as the wettest first 10 months of the year for that corner of the state (previous record was 52.64” in 2008). This 10-month total also broke the record annual rainfall, 57.82” from 1973, for northeast OK.

Five tornadoes (EF0-EF2) developed on the leading edge of a line of thunderstorms that moved through eastern OK and northwest AR during the late evening hours of the 20th and the early hours of the 21st (https://arcg.is/1X8eW1 for more information on the tornadoes). These tornadoes brought the Oklahoma tornado total to 146 for 2019, setting a new record for most tornadoes in one year for the state.

A leading band of pre-frontal showers and isolated thunderstorms moved across northeast OK during the morning and early afternoon hours of the 5th, and across northwest AR during the early evening. The cold front then moved into northeast OK, with new convection developing along it by mid-afternoon. These storms remained fairly isolated through mid-evening as the front slowed and stretched from southwest MO to southwest OK. As the low-level jet increased after sunset, scattered showers and thunderstorms increased over northeast OK and northwest AR, north of the front. The front eventually stalled over southeast OK and west central AR, with convection continuing north of it through the night. A band of heavy rain set up from near Claremore, OK to Jay, OK to Springdale, AR during the pre-dawn hours and continued through the late-morning hours of the 6th. Additional thunderstorms developed across east central and southeast OK and into northwest AR during the afternoon. This activity continued until it moved east of the area by late evening. A brief line of elevated showers and thunderstorms affected southeast OK and west central AR for a few hours after midnight on the 7th. A large area of far northeast OK and northwest AR received 5”-8” of rain during this event, with portions of Delaware, Benton, Washington AR, and Carroll Counties receiving 8”-13” of rain. Widespread flash flooding occurred in Benton and Washington Counties in northwest AR, primarily due to the heavy rain on the morning of the 6th. Numerous roads were closed due to high water and several swift water rescues were needed. The NWS COOP observer in Gravette reported Spavinaw Creek was the highest it’s been in many years. The river gage on Osage Creek near Elm Springs stopped reporting after rising over 14’ in about 10 hours, and according to the USGS, the gage house went under water. The Elm Springs rain gage a few miles upstream from this location measured 9.16” in 18 hours, with a storm total of 9.28”. This heavy rain fell over the headwaters of the Illinois River, and resulted in Major flooding along the entire Illinois River upstream of Lake Tenkiller. This rain also fell in the Flint Creek basin, with Moderate flooding occurring along Flint Creek near Kansas.

A strong cold front moved into the region on the 10th. During the morning, scattered showers and thunderstorms affected eastern OK and northwest AR within an area of strong warm air advection ahead of the frontal system. The front then moved into northeast OK by noon, with showers and thunderstorms developing along and ahead of it. Post-frontal storms continued during the evening and overnight hours due to isentropic lift, though the front itself had moved through all of the area by mid-evening. Most of this activity had shifted east of the area by sunrise on the 11th, though some showers lingered until mid-morning in southeast OK and west central AR. A large portion of eastern OK southeast of I-44 and western AR received 1.5”-3” of rain, with pockets of 4”-6”. This rain fell over the Illinois River basin, which had just had a major flood a few days prior, resulting in another flood of Minor to Moderate severity.

Thunderstorms rapidly developed near a cold front on the evening of the 20th as a potent upper-level trough moved out of the central Rockies and into the Plains. A very moist atmosphere was in place ahead of the front, with precipitable water (PWAT) values of 1.5”-2.0”, along with strong low-level wind shear. Discrete cells were initially able to develop ahead of the front as well, within an area of large-scale ascent from warm advection, before transitioning into a line of thunderstorms by late evening. These thunderstorms were severe, with reports of 70-80 mph winds across northeast OK and northwest AR, and reports of hail of 1.75” (golf ball-sized) to 2.5”(tennis ball-sized) in Creek and Tulsa Counties. Five tornadoes (EF0-EF2) developed on the leading edge of a line of thunderstorms that moved through eastern OK and northwest AR during the late evening hours of the 20th and the early hours of the 21st (https://arcg.is/1X8eW1 for more information on the tornadoes). These tornadoes brought the Oklahoma tornado total to 146 for 2019, setting a new record for most tornadoes in one year for the state. The storms moved quickly east overnight, exiting the area in the pre-dawn hours of the 21st. Rainfall totals were 0.50” - 1.5” for much of eastern OK and northwest AR, though pockets of 1.5” to around 2.5” fell in eastern OK). Some areas received less than 0.50”.

Showers and thunderstorms developed along the I-44 corridor during the evening of the 23rd, increasing in coverage through the overnight hours, as a cold front moved through the region. Most of the rain was post-frontal, in an area of enhanced isentropic lift. By 7 am on the 24th, the cold front stretched from southeast OK into west central AR, and most of northeast OK south of I-44, east central OK, and northwest AR had received 0.75” to 3” of rain. The front brought much colder temperatures, with a 24-hour temperature change of 20°-25°F at mid-morning on the 24th. Widespread showers with embedded thunderstorms then continued for much of the day on the 24th as the zone of isentropic lift and high PWAT persisted across the region. Though some locations received breaks in the rain, overall, the rain continued across eastern OK and western AR through the night and into the morning of the 25th. By 7 am on the 25th, 0.75”-4” of rain had fallen, with the highest totals of 2.5”-4” occurring along a band from McAlester to Ozark . The calendar day total rainfall for McAlester, OK was 6.25” on the 24th, setting a new daily record (and this is the 3rd highest daily rainfall on record in October). A closed low then tracked along the Red River on the 25th, with wrap-around precipitation falling over eastern OK and northwest AR through the day. While much of the rain decreased from morning through the afternoon, coverage began to increase again during the evening hours as the upper-level storm system approached. Periods of heavy rain occurred during the overnight and early morning hours, primarily over east central OK. This rain brought another widespread 0.50”-2.5” of rain to eastern OK south of I-44 and far west central AR by 7 am on the 26th. The rain finally moved east of the area by early afternoon on the 26th as the upper-level system departed the area. East central OK and northwest AR received another 0.50” to around 1.5” before the rain ended. The heavy rain from the 23rd through 26th resulted in Minor flooding along the Illinois River, with several crests along the lower portion of the river near Tahlequah. Rises also occurred along the lower Arkansas River and the lower Poteau River, but the rivers did not reach flood stage.

A front lifted slightly north into southeast OK and northwest AR on the 29th. Moisture overriding the boundary combined with a strong upper-level trough, resulting in increasing coverage of showers and isolated thunderstorms across eastern OK and western AR from late morning through afternoon. Widespread precipitation then continued for much of the overnight hours. Most of the rain had ended by mid-morning on the 30th, though scattered showers and thunderstorms remained over southeast OK and west central AR through noon. Rainfall totals were 0.50” to around 1.5” for nearly all of eastern OK and western AR. This rain once again caused a rise along the Illinois River, but the river remained in its banks. Drizzle lingered behind the departing storm system, and as colder air moved in from the north, there were snow flurries across northeast OK and northwest AR. Little to no accumulation occurred, but even so, snow is rare in October. Measurable snow has only been recorded once in October in Tulsa and in Fayetteville, and a trace of snow has been recorded only four other times in Tulsa and five other times in Fayetteville.