September 2011 Climate and Hydrology Summary

Tulsa: September 2011 was the 17th coldest (70.7°F, since 1905) and the 47th driest (2.58"; since 1888) September on record.

Tulsa: Daily records set or tied this month include a record cool max temperature on 9/16/11; a record warm min temperature on 9/01/11; record min temperatures on 9/06/11, 9/07/11, and 9/09/11; a record warm mean temperature on 9/01/11; and a record cool mean temperature on 9/16/11.

Tulsa: The record warm minimum temperature of 82°F set on 9/01/2011 ties with 9/02/1936 and 9/03/1995 as the warmest minimum temperature recorded during the month of September.

Tulsa: Tulsa reached or exceeded 100°F twice in September 2011, making the yearly total number of days at or above 100°F 44 for 2011. 2011 ranks 6th for the most number of days with high temperatures at or above 100°F.

Fort Smith: September 2011 was the 45th coldest (72.8°F) and the 29th driest (1.47") September since records began in 1883.

Fort Smith: Daily records set or tied this month include a record cool max temperature on 9/16/11 and a record min temperature on 9/07/11.

Fort Smith: Fort Smith reached or exceeded 100°F once in September 2011, making the yearly total number of days at or above 100°F 49 for 2011. 2011 ranks 3rd for the most number of days with high temperatures at or above 100°F.

McAlester: Daily records set or tied this month include a record max temperature on 9/13/11; a record cool max temperature on 9/16/11; a record warm min temperature on 9/01/11; record min temperatures on 9/06/11, 9/07/11, 9/08/11, 9/09/11; and record warm mean temperatures on 9/01/11, 9/13/11; and record cool mean temperatures on 9/07/11, 9/08/11, 9/09/11, 9/16/11.

McAlester: McAlester reached or exceeded 100°F three times in September 2011, making the yearly total number of days at or above 100°F 56 for 2011. 2011 ranks 2nd for the most number of days with high temperatures at or above 100°F.

Fayetteville: Daily records set or tied this month include record cool max temperatures on 9/15/11, 9/16/11; a record warm min temperature on 9/01/11; and record min temperatures on 9/06/11, 9/07/11.

Fayetteville: Fayetteville did no reach or exceed 100°F in September 2011. However, the yearly total number of days at or above 100°F was 18 for 2011, ranking 2011 as the 9th the most number of days with high temperatures at or above 100°F (tied with 1930).

Bartlesville: Bartelsville reached or exceeded 100°F twice in September 2011, making the yearly total number of days at or above 100°F 39 for 2011. 2011 ranks 6th for the most number of days with high temperatures at or above 100°F.

Rainfall totals for September 2011 ranged from less than 0.50” in Choctaw County in southeast OK to isolated areas near 6” in Carroll County in northwest AR. A large portion of eastern OK and northwest AR received between 1” and 4” of precipitation during the month. All but far northwest AR along the MO state line received less than the normal September rainfall, with most of the area reporting only 25% to 75% of the normal amount of rain for the month (Fig. 1b). Far southeast Oklahoma had the largest deficits, receiving only 5% to 25% of the normal September rainfall. Locations north of Hwy 412 in northwest AR received near to above normal rainfall during September 2011. The greatest surplus occurred across northern Carroll County, where September totals were 150% to 200% of normal.

According to the Drought Monitor from September 27, 2011, exceptional drought (D4) conditions continued across portions of east central and southeast Oklahoma, encompassing far southwest Creek, southwest Okfuskee, far southern Pushmataha, and Choctaw Counties. Extreme drought (D3) conditions were found across far western Pawnee, southwest Creek, northwest Okfuskee, far southwest Okmulgee, far western McIntosh, Pittsburg, Latimer, Pushmataha, and Le Flore Counties. Severe drought (D2) conditions stretched across the remainder of northeast Oklahoma as well as western Sebastian, western Crawford, Washington, Benton, Carroll, and Madison Counties in northwest Arkansas. Moderate drought (D1) conditions were found across eastern Sebastian, eastern Crawford, far southern Madison, and Franklin Counties in northwest Arkansas

According to the Oklahoma Climatological Survey (OCS) for September 2011, northeast Oklahoma ranked as the 31st driest, east central Oklahoma ranked as the 30th driest, and southeast Oklahoma ranked as the 10th driest September since records began in 1921. For the last 120 days (June 5-October 2, 2011), northeast Oklahoma ranked as the 9th driest, east central Oklahoma ranked as the 6th driest, and southeast Oklahoma ranked as the driest for this time period. For the year so far, northeast Oklahoma ranked as the 17th driest, east central Oklahoma ranked as the 19th driest, and southeast Oklahoma ranked as the 6th driest year-to-date on record.

Water Year October 1, 2010-September 30, 2011

A large gradient in precipitation totals occurred across the region during Water Year 2011, going from very dry to not as dry as one moves west to east across eastern Oklahoma and into western Arkansas. Rainfall totals for Water Year 2011 ranged from 20" across Osage, Pawnee, Kay, Creek, Okfuskee, and Choctaw Counties in eastern Oklahoma to around 55" in northwest Arkansas (some areas of southwest OK and the OK panhandle received less than 10" during the entire water year!).

Portions of Pushmataha, Choctaw, and Okfuskee Counties in eastern Oklahoma only received 25%-50% of the normal precipitation during the water year. The remainder of eastern Oklahoma had between 50% and 100% of the normal rainfall, while northwest Arkansas was generally near normal for the water year.

According to the Oklahoma Climatological Survey (OCS) for Water Year 2011, northeast Oklahoma ranked as the 9th driest, east central Oklahoma ranked as the 10th driest, and southeast Oklahoma ranked as the 3rd driest Water Year since records began in 1921. The state as a whole ranked as the 2nd driest Water Year on record.

Tulsa received 27.04" of rain during Water Year 2011, ranking as the 10th driest Water Year on record (since 1894). Fort Smith received 38.52" of rain during Water Year 2011, ranking as the 52nd driest Water Year on record (since 1883).

Outlook

The Climate Prediction Center (CPC) outlook for October 2011 (issued September 30, 2011) indicates a slightly enhanced chance for above normal temperatures and above median precipitation across all of eastern Oklahoma and northwest Arkansas. This outlook was based primarily on long-range dynamical computer models with possible La Niña impacts considered.

For the 3-month period Oct-Nov-Dec 2011, CPC is forecasting an enhanced chance for above average temperatures and below median precipitation across all of eastern Oklahoma and northwest Arkansas (outlook issued September 15, 2011). This is consistent with a La Niña pattern, as well as long-range computer model output.

According to CPC, weak La Niña conditions were in place by the end of September. La Niña conditions are forecast to continue into Fall 2011, peak through the upcoming Winter, and begin to wane during Spring 2012.