October 2011 Climate and Hydrology Summary

October 2011

Tulsa: October 2011 was the 42nd warmest (63.4°F, tied with 1982; since 1905) and the 42nd driest (1.87"; since 1888) October on record.

Tulsa fell below freezing for the first time this cold season on October 20, 2011.

Fort Smith: October 2011 was the 33rd warmest (64.9°F, tied with 1960, 1912) and the 52nd wettest (3.72") October since records began in 1883.

McAlester: Daily records set or tied this month include a record warm min temperature on 10/08/11; record warm mean temperatures on 10/07/11, 10/25/11; and a record rainfall on 10/27/11.

Fayetteville: Daily records set or tied this month include record min temperatures on 10/19/11, 10/20/11.

Rainfall totals for October 2011 ranged from less than 0.50” in Osage County in northeast OK to isolated areas near 5” near the I-40 corridor in east central OK and northwest AR. A large portion of eastern OK and northwest AR received between 1” and 3” of precipitation during the month, with the lowest totals occurring across far northeast OK and Choctaw County in southeast OK. All but a few locations along I-40 and across northwest AR received less than the normal October rainfall, with most of the area reporting only 25% to 75% of the normal amount of rain for the month. Northeast OK and far southeast OK had the largest deficits, receiving from near 0% to 25% of the normal October rainfall.

According to the Drought Monitor from November 1, 2011, exceptional drought (D4) conditions continued across portions of southeast Oklahoma, encompassing southern Pushmataha and Choctaw Counties. Extreme drought (D3) conditions were found across Osage, Pawnee, Washington, Nowata, northwest Rogers, Tulsa, Creek, Okfuskee, Okmulgee, southern Wagoner, western Muskogee, McIntosh, Pittsburg, southern Latimer, and northern Pushmataha Counties. Severe drought (D2) conditions stretched across the remainder of northeast Oklahoma. Moderate drought (D1) conditions were found across Benton, Carroll, Washington, Sebastian, Crawford, Madison, and Franklin Counties in northwest Arkansas.

According to the Oklahoma Climatological Survey (OCS) for October 2011, northeast Oklahoma ranked as the 21st driest, east central Oklahoma ranked as the 43rd driest, and southeast Oklahoma ranked as the 31st driest October since records began in 1921. For the last 120 days (July 4 5-October 31, 2011), northeast Oklahoma ranked as the 14th driest, east central Oklahoma ranked as the 23rd driest, and southeast Oklahoma ranked as the 3rd driest for this time period. For the year so far, northeast Oklahoma ranked as the 11th driest, east central Oklahoma ranked as the 21st driest, and southeast Oklahoma ranked as the 8th driest year-to-date on record.

No rivers exceeded flood stage this month. In fact, due to the ongoing drought, the soil absorbed most of the precipitation that fell this month, with little recharge in area lakes and rivers.

Outlook

The Climate Prediction Center (CPC) outlook outlook for November 2011 (issued October 31, 2011) indicates an enhanced chance for above normal temperatures across all of eastern Oklahoma and northwest Arkansas. This outlook also indicates a slightly enhanced chance for below median precipitation for locations south of I-40, with an equal chance for above, near, or below median precipitation elsewhere. This outlook was based primarily on short-term dynamical computer models with possible La Niña impacts considered.

For the 3-month period Nov-Dec-Jan 2011-12, CPC is forecasting an enhanced chance for above average temperatures and below median precipitation across all of eastern Oklahoma and northwest Arkansas (outlook issued October 20, 2011). This is consistent with a La Niña pattern, as well as long-range computer model output.

According to CPC, weak to moderate La Niña conditions were in place by the end of October. La Niña conditions are forecast to strengthen and continue through Winter 2011-12, with impacts lasting into early Spring 2012.

A La Niña Advisory is in effect, meaning that La Niña conditions are observed and expected to continue.