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September 2019
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- Fort Smith: No daily records were set or tied this month.
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- Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for September 2019 ranged fromfrom 1.50” to around 10” across eastern OK and northwest AR. These rainfall totals correspond to 25%-90% of the normal September rainfall for a large portion of eastern OK and northwest Arkansas (Fig. 1b). However, some areas did receive 125%-250% of the normal September rainfall.
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- Most of eastern OK and northwest AR received below normal rainfall this month, though some places did experience flash flooding late in the month. September 2019 was a very warm month, with most locations 7-8 degrees above normal. Fayetteville, AR recorded its warmest September, while Fort Smith, AR and Tulsa, OK ranked as 2nd warmest this year.
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- Around midnight on the 1st, showers and thunderstorms developed across east central OK and northwest AR in response to a mesoscale convective vortex (MCV), slowly drifted eastward, and then dissipated shortly after sunrise. Rainfall totals ranged from 0.10” to around 2”.
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- A line of weak showers and thunderstorms initially moved into eastern Kay and Osage Counties during the early afternoon of the 12th ahead of a cold front. Convection then increased in coverage and intensity by late afternoon along and just ahead of the cold front from west central OK into eastern KS. The line of storms then moved southeast across northeast OK through the evening hours, with only isolated storms affecting northwest AR. As the front stalled, the convection continued primarily across northeast OK through the overnight hours. Most of the activity dissipated by sunrise on the 13th. Rainfall totals were 0.25” to around 2” for much of the affected area, though higher totals of 2”-5” fell over portions of Creek, Pawnee, and Osage Counties.
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- The remnants of Imelda moved north out of northeast TX and into southeast OK and west central AR during the morning of the 20th and persisted for much of the day. Precipitable water (PWAT) values were in excess of 2.2” within a zone of enhanced moisture transport, and this, combined with lift from a shortwave trough, resulted in back-building storms and heavy rain across southeast OK. The rain finally dissipated during the evening, after bringing 3”-8” to portions of Choctaw, Pushmataha, and Le Flore Counties in southeast OK. The remainder of southeast OK and west central AR received 0.50”-2” of rain. 24-hour rainfall totals from Oklahoma Mesonet stations on the 20th: Antlers 4.92”; Cloudy 4.09”; Hugo 3.47”.
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- Scattered showers and thunderstorms occurred across southeast OK, along and south of a weak frontal boundary, during the late morning through early evening hours on the 23rd. These storms brought 0.25” to around 3” of rain to southeast OK (higher totals occurred in McCurtain Co., which is not part of the NWS Tulsa area of responsibility). As the low-level jet increased during the night, new convection developed near the boundary along and north of I-40 in east central OK and west central AR. A warm advection regime at the tail end of a retreating frontal zone led to widespread showers and thunderstorms across northeast OK and northwest AR through the morning and early afternoon of the 24th. Precipitable water (PWAT) values were very high, on the order of 2” to 2.25”, which is nearly 220% of normal for this time of year. The high PWAT combined with training storms resulted in heavy rain and flash flooding. Reports of water rescues and numerous flooded roads were received from Benton, Washington AR, Muskogee, Tulsa, Craig, and Rogers Counties. This rain also resulted in higher levels along the Illinois River, though flood stage was not exceeded (see preliminary hydrographs at the end of this report). Rainfall totals were widespread 1” to 5” across eastern OK and northwest AR, along and north of I-40, with very heavy rainfall rates. Showers and thunderstorms then developed during the afternoon hours of the 24th across southeast OK, primarily south of I-40, and shifted east across southeast OK and west central AR through the evening hours before pushing east of the region. These storms also produced heavy rain, with many locations in southeast OK receiving 1”-2” of rain. Southern Latimer and northern Pushmataha had higher totals of 3” to around 6” of rain.
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- A few isolated showers and thunderstorms, the remnants of a KS mesoscale convective system (MCS), affected northeast OK and northwest AR during the morning of the 25th. A cold front then sagged south into northeast OK and northwest AR during the evening and stalled over the area. The upper-level flow was parallel to the front and PWAT values were in the 1.75”-2” range, setting the stage for training of storms capable of producing heavy rainfall. A line of thunderstorms began to develop during the late evening hours near the OK/KS state line near the front, with isolated thunderstorms ahead of the front in northeast OK and northwest AR. The line moved south during the overnight and early morning hours. While most of the rain had moved southeast of the region shortly after sunrise on the 26th, scattered showers and thunderstorms lingered across eastern OK through early afternoon. By 7 am 9/26, most of eastern OK and northwest AR north of I-40 had received 1”-2.5” of rain, with localized amounts of 2.5”-5”. Some of the higher 24-hour rainfall totals (by 7 am CDT 9/26/2019) included: Ralston, OK 4.25”; Miami 2NE, OK 3.43”; Big Cabin 5NE, OK 3.15”; Vinita 10NNW, OK 3.05”. Street flooding was reported in Broken Arrow, OK; Bella Vista, AR; Pawnee, OK; and Scipio, OK. An additional 1”-3” fell through the remainder of the morning and afternoon hours. This rain once again caused the Illinois River to rise to unsafe levels for recreation, but it remained below flood stage. The 4-day rainfall totals, ending at 8:45 am CDT 9/26/2019, were widespread 1”-4”, though several locations received 4”-9”. The entire 7-day active weather period, ending at 3:50 pm CDT 9/26/2019, resulted in widespread 3”-5” of rain, and several areas of 5”-11” of rain.
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- According to the Drought Monitor from October 1, 2019, Moderate (D1) Drought conditions were occurring near the Red River in southern Choctaw County. Abnormally dry, but not in drought, conditions (D0) were present in portions of Le Flore, Pushmataha, and Choctaw Counties in eastern OK and Sebastian County in west central AR. The remainder of eastern OK and northwest AR was drought free.
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- 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.
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| Water Year 2019 (Oct. 1, 2018-Sep. 30, 2019) |
- Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for Water Year 2019 ranged from 40” to 80” across eastern OK and northwest AR. These rainfall totals correspond to 125% to near 200% of the normal Water Year rainfall for much of northeast OK, and 100% to around 150% for the remainder of eastern OK and northwest Arkansas.
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- Water Year 2019 was above normal for the entire area, with Fort Smith, AR having its 2nd wettest Water Year on record.
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- In Tulsa, OK, Water Year 2018-19 ranked as the 53rd warmest Water Year (60.7°F, tied 1995, 1985, 1982, 1966, 1965, 1957, 1943; since records began in 1905-06) and the 7th wettest Water Year (56.33”; since records began in 1893-94).
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- Fort Smith, AR had the 30th warmest Water Year (62.5°F, tied 1955, 1933, 1923, 1914, 1898; since records began in 1882-83) and the 2nd wettest Water Year (66.21”; since records began in 1882-83).
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- Fayetteville, AR had the 30th warmest (57.6°F, tied 1983, 1964) and the 10th wettest (56.97”) Water Year since records began in 1949-50.
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