December 2019 Climate and Hydrology Summary

Tulsa: December 2019 was the 9th warmest (44.9°F, tied 1959; since 1905), the 36th driest (0.96"; since 1888), and the 28th least snowy (Trace, tied 27 other years; since 1900) December on record.

Fort Smith: December 2019 was the 21st warmest (45.8°F, tied 1900; since 1882) and the 18th driest (0.87"; since 1882) December on record.

Fort Smith: Daily records set or tied this month include a record warm minimum temperature.

Fayetteville: December 2019 was the 10th warmest (43.0°F; since 1949), the 15th driest (1.33", tied 1996; since 1949), and the 15th least snowy (Trace, tied 21 other years; since 1949) December on record.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for December 2019 ranged around 0.50” to 2.5” across eastern OK and northwest AR. These rainfall totals correspond to 10%-75% of the normal December rainfall across the area, with most of eastern OK and northwest Arkansas receiving 25-50% of normal.

December 2019 was warm and dry across eastern OK and northwest AR, with well below normal precipitation. However, there was a weak tornado this month and rainfall at the end of November resulted in minor flooding on the Illinois River at the start of the month.

According to the Drought Monitor from December 31, 2019, eastern OK and northwest AR were drought free.

According to the Oklahoma Climatological Survey, December 2019 was the 36th driest for northeast Oklahoma, the 29th driest for east central Oklahoma, and the 8th driest for southeast Oklahoma. Records go back to 1921. For the Year 2019, northeast Oklahoma ranked as the Record wettest, east central Oklahoma was the 5th wettest, and southeast Oklahoma was the 12th wettest Year.

Scattered rain showers began to develop on the morning of November 29th in a zone of stronger isentropic lift and warm air advection ahead of a cold front and continued through the afternoon hours. Deeper low-level moisture surged north into the area by evening as a strong upper-level jet streak lifted into the Central Plains in association with larger scale upper low moving over the Intermountain West. Scattered thunderstorms affected locations along and north of I-40 through the evening hours. A few of these storms became severe, producing hail of 1.25” (half dollar size) - 2” (hen egg size) in northeast OK. These thunderstorms shifted east of the region by midnight. A line of showers and thunderstorms then developed across eastern OK during the overnight hours with the aid of a 60 knot southwesterly low-level jet and a potent mid-level low spinning over western Nebraska. At the surface, a warm front had surged northward to near I-40, and a Pacific cold front stretched across northeast OK into south-central OK. This line of rain continued to move east across eastern OK and northwest AR, exiting the area by mid-morning on the 30th as the cold front moved east through the region. Rainfall totals from both rounds of precipitation ranged from 0.10” to near 2.5”. The heaviest rain of 1.5”-2.5” fell over the Illinois River basin, resulting in minor flooding along the Illinois River on December 1st.

Nearly all forms of precipitation – freezing drizzle, freezing rain, snow, sleet, thundersleet, thunderstorms, rain, drizzle, and hail – fell across eastern OK and northwest AR on the 16th. Light freezing drizzle, with pockets of sleet and snow flurries, impacted portions of northeast OK and northwest AR during the early morning hours within an area of sub-freezing temperatures. Ice accumulations were light, with a glaze on elevated surfaces and slick spots primarily on bridges and overpasses. Precipitation, including thunderstorms and thundersleet, developed during the morning within an area of warm advection in advance of an approaching upper-level trough. The convective activity ended by noon, and the freezing line stretched from southeast OK into northwest AR. Bands of light snow, freezing drizzle, and drizzle continued through the afternoon and evening before exiting the area as the upper-level wave lifted northeast. Despite all of the precipitation types, rainfall/liquid equivalent totals were light. Portions of far eastern OK and northwest AR received around 0.50”-1.5” of rain, with much of the region seeing around 0.10” or less. Snow/sleet/ice accumulations were generally a trace, though a few locations reported 0.1”-0.2” of snow/sleet.

On the 28th, a line of showers and isolated thunderstorms spread east into eastern OK by mid-morning and into northwest AR by noon. A second, more intense, line of storms moved east into the region during the mid-afternoon as a strong 150 kt upper-level jet streak lifted into the region ahead of the main upper-level trough axis. Broken lines of thunderstorms developed ahead of an approaching cold front and moved through eastern OK during the afternoon and early evening hours. Although instability was weak, low LCL heights, dewpoints in the 60s, and the very strong low-level wind shear was more than enough to support the development of low-level rotation in a couple of the stronger convective lines. One such line produced a weak (EF0) tornado in Broken Arrow, OK (see https://arcg.is/1X8eW1 for more information). These storms pushed east of the area by midnight on the 29th. Rainfall totals across all of eastern OK and northwest AR ranged from around 0.50” to around 2.5”, with the majority of the area receiving 0.75”-1.5”. This rainfall resulted in a rise to Action Stage along Flint Creek near Kansas.

Year 2019

Tulsa: 2019 was the 48th warmest (60.9°F; since 1905), the 4th wettest (59.55"; since 1888), and the 12th least snowy (1.4"; since 1900) Year on record.

Fort Smith: 2019 was the 27th warmest (62.7°F, tied 1990; since 1883), the 3rd wettest (67.50"; since 1882), and the 24th least snowy (1.0"; since 1884) Year on record.

Fayetteville: 2019 was the 22nd warmest (57.9°F, tied 1963; since 1950), the 5th wettest (65.26"; since 1950), and the 11th least snowy (1.9", tied 1962; since 1950) Year on record.

Rainfall totals for the year 2019 ranged from 40” to 85” across eastern OK and northwest AR. These rainfall totals correspond to 110%-200% of the normal annual rainfall across eastern OK and northwest Arkansas, except southeast OK were totals were 75%-125% of normal. A large portion of northeast OK and northwest AR along and northeast of a Stillwater, OK to Fort Smith line received 20”-40” more than normal. The northeast OK climate division recorded its wettest year on record with 63.20” of rain in 2019, greatly exceeding the previous record of 57.82” in 1973.

This heavy rain, which also fell across north central OK and central and eastern KS, resulted in mainstem river flooding each month this year, with major and record-breaking flooding occurring in May-June 2019. The numerous storm systems also brought 69 tornadoes to eastern OK and northwest AR in 2019, the 2nd highest total for the NWS Tulsa county warning area (see all tornado information and tracks at https://arcg.is/1X8eW1).