Climate and Hydrology Highlights for December 2009

December 2009

Tulsa: December 2009 was 11th coldest (34.6°F, since 1905), the 49th wettest (1.88", since 1888), and the 6th snowiest (7.4", since 1900) December on record.

Tulsa: A record snowfall of 5.4" was set on Christmas Eve. The previous record was 1.0" in 2002. This marked only the 4th time snow has fallen on Christmas Eve since records began in 1900.

Tulsa: This past decade (2000-2009) had 3 of the top 10 (and 3 out of the top 6) highest December snowfalls on record, which is the most of any decade. This decade also had 4 out of the top 12 snowiest Decembers (since 1900).

Fort Smith: December 2009 was the 12th coldest (37.7F), 10th snowiest (3.0", tied with 1896), and 59th wettest (2.87") December since records began in 1882.

Fort Smith: A record snowfall of 3.0" was set on Christmas Eve. The previous record was 0.5" in 1975. This marked only the 3rd time snow has fallen on Christmas Eve since records began in 1882.

A White Christmas is defined as 1 inch of snowfall on the ground Christmas morning, and Tulsa and Fort Smith both recorded an official White Christmas for 2009. Tulsa previously had a White Christmas in 2002, 2000, 1983, and 1966. Fort Smith had a White Christmas in 1990, 1975, and 1963.

McAlester tied record low temperatures on 12/04 and 12/05 and tied a record low mean temperature on 12/04.

Fayetteville set a record low temperature on 12/10 and set record low maximum temperatures on 12/25 and 12/27.

The first Blizzard Warning ever issued for Tulsa County was for the Christmas Eve Winter Storm (this was also only the second time a Blizzard Warning has been issued for northeast OK). However, only near-blizzard conditions were actually recorded in northeast OK during this storm.

Most eastern Oklahoma and northwest/west central Arkansas received below normal rainfall for December.

The Poteau River near Panama had minor flooding on Christmas Day due to rain on 12/23.

Our area typically sees a greater number of days with warmer minimum temperatures during El Nino episodes. However, this December, Tulsa recorded the 14th coldest average minimum temperature and the 11th coldest average maximum temperature; and Fort Smith had the 22nd coldest average minimum temperature and the 12th coldest average maximum temperature.

According to CPC, a moderate El Nino continues though is likely near its peak intensity. Therefore, a moderate event (and not a strong event) is expected through the remainder of the winter. An El Nino Advisory remains in affect.

For December 2009, the North Atlantic Oscillation (NAO) was the lowest December value on record (records began 1950). Similarly, the Arctic Oscillation (AO) was negative during December, with a value of -3.4. This AO value is the lowest ever for December and the lowest since January 1977. Much of the eastern half of the U.S., including eastern Oklahoma and northwest Arkansas, tend to see below normal temperatures during the negative phase of the AO. These strong negative anomalies have likely overwhelmed the El Nino signal and may have played a role in the cold December of 2009 (and first part of January 2010).

According to the Drought Monitor, no drought conditions exist across eastern OK or northwest AR.