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December & Year 2015
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- Fort Smith: December 2015 was the 2nd warmest (49.3°F; since 1882) and the Record wettest (10.81"; since 1882) December on record. The previous record wettest December was 10.09" in 1971. No snow fell in December.
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- Fayetteville: December 2015 was the 3rd warmest (44.2°F; since 1949) and the Record wettest (10.95"; since 1949) December on record. The previous record wettest December was 8.54" in 1982. Only a trace of snow fell in December.
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- Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for December 2015 ranged from around 3” to 16”. Most of eastern OK and northwest AR received 6”-12” of rain this month (similar totals also occurred in Nov. 2015). This corresponds to 150% to around 500% of the normal December rain across eastern OK and northwest AR.
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- Record rainfall, record flooding, and widespread major flooding devastated a large portion of eastern OK and northwest AR this month. Much of the area received 3 to 5 times the normal December rainfall. All of eastern OK and northwest AR received above normal rainfall during December 2015 due to heavy rain during the middle and end of the month.
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- Minor to record river flooding occurred during the month.
- 9 forecast points went into flood mid-month, including the Neosho River near Commerce, the Illinois River near Watts and Tahlequah, the Arkansas River at Van Buren and at Ozark Lock and Dam, Lee Creek near Van Buren, the Poteau River near Poteau and Panama, and the Kiamichi River near Antlers.
- 22 forecast points went into flood at the end of the month, including Polecat Creek near Sapulpa, the Caney River near Ramona and near Collinsville, Bird Creek near Sperry and near Owasso, the Neosho River near Commerce, the Spring River near Quapaw, the Illinois River near Watts and Tahlequah, the Baron Fork near Eldon, Flint Creek near Kansas, the Arkansas River near Muskogee, at Van Buren, and at Ozark Lock and Dam, the Poteau River near Poteau and near Panama, Lee Creek near Van Buren, the Kings River near Berryville, the Deep Fork River near Beggs, the Kiamichi River near Antlers, and the Red River near Arthur City. Record flooding occurred on the Illinois River and Lee Creek.
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- An unseasonably warm and moist airmass covered most of the HSA by early morning of the 12th. Widespread showers lifted north northeast across eastern OK and northwest AR during the evening hours in response to a wave moving through New Mexico and a cold front located over western OK. Widespread showers and isolated thunderstorms continued through the night due to the strong forcing from an upper-level low near the TX panhandle. Moderate to heavy rain continued into the morning of the 13th before the bulk of the rain pushed east with the cold front. Some light wrap-around rain fell later on the 13th as the upper-low passed. Due to the abnormally moist atmosphere, the 2-day rainfall total was high, ranging from around 1” to around 4” for much of eastern OK and northwest AR. Higher totals of 4” to around 6” occurred over southern Le Flore County in southeast OK. The majority of the rain fell prior to 6am CST on the 13th, with 1.5”-6” reported over far eastern OK and far western AR. This rainfall, on top of the heavy rain over the same area at the end of November, resulted in both flash flooding and minor to moderate river flooding. In addition to the flooding, some wind damage was reported and an EF-1 tornado occurred in Raymond Gary State Park near Fort Towson in Choctaw Co. on the evening of the 12th.
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- A devastating flash flood and river flood event occurred over the Christmas 2015 weekend as a strong upper-level low lifted northeast across western TX and approached eastern OK and western AR from the southwest. Tremendous lift in the diffluent region of the approaching low, along with precipitable water values near 1.5” (near record values for the end of December), resulted in an extended period of heavy rain. Bands of rain with embedded thunderstorms developed across northeast OK and northwest AR during the early morning hours of the 26th as a warm front lifted north. This activity increased across southeast OK and west central AR through the morning hours. By midday on the 26th, widespread showers and thunderstorms were affecting much of eastern OK northwest of a McAlester to Grove line. Moderate to heavy rain continued over this area through the afternoon and evening, while also spreading southeast. By midnight on the 27th, the entire HSA was enveloped in rain. Primarily moderate rain then continued for the next 14 hours over all of eastern OK and northwest AR as the frontal boundary remained in the area. Colder air began to filter into the back side of the system, bringing some reports of freezing rain and a quarter inch of ice accumulation to trees in northwest Osage County at noon on the 27th. Moderate to heavy rain continued generally across locations southeast of I-44, with the precipitation coming to an end during the evening hours northwest of I-44. The rain pushed east, finally coming to an end in eastern OK by midnight on the 28th, but continued across northwest and west central AR. However, additional bands of rain began to move north across eastern OK and northwest AR from midnight on the 28th through 1:30pm CST as the closed low moved east across central TX and then northeast along the OK/AR state line. Snow and sleet occurred across northeast OK and northwest AR during the morning hours of the 28th within this wrap around precipitation as the bands interacted with the colder airmass. Reports of 0.20”-1” of sleet accumulation were reported, along with a dusting to 1.5” of snow accumulation. All of the precipitation finally exited the HSA by 1pm on the 28th.
Widespread 5”-12” of rain fell over most of eastern OK and northwest AR from the 26th through the 29th, with the majority of the rain occurring over the 2-day period from the 26th-27th. This amount of rain is 2-4 times the normal amount received during the entire month of December. According to NOAA Atlas 14 Point Precipitation Frequency Estimates, 11.9” of rain in a 2-day period for Tahlequah, OK is approximately a 0.5% annual chance of occurrence event (also referred to as a 200-year event). This means that every year there is a 0.5% chance of receiving 11.9” of rain in 48 hours in Tahlequah. 6.82” of rain fell in a 24-hr period 12/26-12/27 at Fayetteville, AR, which is between a 4% and 2% annual chance of occurrence (or between a 25- and 50-year event). All of this rain resulted in Record and Major river flooding for several river basins in the NWS Tulsa HSA, flash flooding. Two fatalities occurred during this event.
Widespread flooding affected most of the eastern third of OK and northwest AR, causing numerous road closures, including state highways, throughout the area. Roadways were damaged from the high, fast-moving water. Swift water rescues were necessary throughout the affected area. High river levels and very fast flows along the Arkansas River halted barge traffic on the McCellan-Kerr Arkansas River Navigation System, causing significant financial impact to related commerce activities. This 445-mile navigation channel allows for commerce from the Mississippi River to eastern Oklahoma. Several reservoirs neared or exceeded the top of their flood control pools. Record reservoir releases occurred out of Grand Lake, Hudson Lake, Ft. Gibson Lake, and Tenkiller Lake.
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- According to the Drought Monitor from December 29, 2015, there were not drought or abnormally dry conditions present in eastern OK and northwest AR.
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- According to the Oklahoma Climatological Survey, December 2015 was the Record wettest for northeast Oklahoma, east central Oklahoma, and southeast Oklahoma. Records go back to 1921. For the Year 2015, northeast Oklahoma ranked as the 4th wettest, east central Oklahoma was the 1st (record) wettest, and southeast Oklahoma was also the 1st (record) wettest Year.
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| Year 2015 |
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- Fort Smith: 2015 was the 17th warmest (63.1°F, tied 1936; since 1883), the Record wettest (73.93"; since 1882), and the 41st snowiest (6.6"; since 1884) Year on record. The previous record wettest year was 71.81" in 1945. 2015 was 28.47” above the normal (163% of the normal) annual Fort Smith rainfall of 45.46".
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- McAlester: 2015 was the record wettest Year with 78.65" (records began in 1954; data missing in 1996-98, 1953, 1955). The previous record was 66.40” in 1973 and the normal annual rainfall is 42.04”. The 2015 rainfall was 36.61” above normal or 187% of normal annual rainfall in McAlester.
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- Muskogee: 2015 was the 2nd wettest Year on record with 68.75". The current record is 70.18" in 1973.
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- The 2015 statewide average rainfall total for Oklahoma is 52.96” (from the National Centers for Environmental Information (NCEI) formerly NCDC). This sets a new annual rainfall record for the state of Oklahoma, besting the previous record of 47.88” in 1957. The majority of this rain fell in 6 of the 12 months in 2015, resulting is widespread flooding, especially in May and December. According to the OK Climatological Survey, this equates to 64.3 trillion gallons of water. Oklahoma Mesonet rainfall animation from 2015 as a series of 8,760 year-to-date rainfall maps: https://www.youtube.com/watch?v=NtsfyNF2MwI&feature=youtu.be
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- Rainfall totals for the year 2015 ranged from 33” in northern Osage Co. to 88” in southeast and east central OK. Most locations along and south of I-44 in eastern OK and western AR had 20”-40” above the normal (1981-2010) annual rainfall amount. In fact, a large area received 1.5 to 2 times the normal annual rainfall in 2015. Only northern Osage County ended the year with below normal rainfall, receiving 75%-90% of the normal annual rainfall, or 4”-8” below normal.
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| Outlook |
- The Climate Prediction Center (CPC) outlook for January 2016 (issued December 31, 2015) indicates equal chances for above, near, and below normal temperatures and precipitation across eastern OK and northwest AR. This outlook is based on both short- and extended-range weather forecasts as well as strong El Niño influences. The Madden-Julian Oscillation (MJO) effect on the tropical convection implies a transition to a colder pattern over the CONUS. Shorter term outlooks also indicate an active southern stream, which is consistent with El Niño and MJO conditions.
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- For the 3-month period January-February-March 2016, CPC is forecasting an equal chance for above, near, and below normal temperatures across all of eastern OK and northwest. This outlook also indicates an enhanced chance for above median precipitation across central into southeast OK, with equal chances for above, near, and below median rainfall elsewhere (outlook issued December 17, 2015). This outlook is based primarily on both statistical and dynamical forecast tools, as well as typical impacts resulting from El Niño conditions.
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- According to CPC, strong El Niño conditions persist, and El Niño is likely at its peak. The ongoing El Niño is among the strongest on record and has tied the 1997-98 event as the strongest El Niño on record (using the Oceanic-Niño Index, ONI). This event is likely to transition to neutral conditions during the late spring or early summer 2016. An El Niño Advisory is in effect.
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