January 2009: 7th warmest January on record

Earth recorded its 7th warmest January on record, according to statistics released by the National Climatic Data Center. The most notable extreme temperatures were recorded in southern Australia January 28-31, when the hottest weather since 1939 occurred. January 2009 Northern Hemisphere sea ice extent is unknown, according to the National Snow and Ice Data Center. A sensor error in January caused underestimation of the ice coverage during the month, and a correction needs to be applied to the data. At worst, January 2009 had the 6th lowest Arctic ice extent on record. The record January low was set in 2006. The sensor error does not affect months prior to January, and does not affect the records lows observed in September 2008 and 2007.

A dry January with average temperatures for the U.S.
For the contiguous U.S., January temperatures were near average. It was the 59th warmest January in the 114-year record, according to the National Climatic Data Center. The month was very dry, ranking as the 5th driest January on record. Only ten (preliminary) tornado reports were logged by NOAA's Storm Prediction Center in January, making it the quietest January for tornadoes since 2004, when only three tornadoes were recorded. U.S. records set in January 2009 (courtesy of http://extremeweatherguide.com/updates.asp):

Waterloo, IA: All-time coldest temperature record tied on 1/16, -34°F
Maine: All-time coldest temperature -50°F at Big Black River

At the end of January, 21% of the contiguous United States was in moderate-to-exceptional drought. This is an increase from the 19% figure at the end of December.


Figure 1. Forecast El Niño/La Niña conditions for a number of computer models. El Niño conditions are forecast when the SST anomaly in the Niño 3.4 region goes above 0.5°C (upper red line). La Niña conditions are forecast when the SST anomaly in the Niño 3.4 region goes below -0.5°C (lower red line). Nearly all of the computer models are forecasting neutral conditions during the 2009 hurricane season (August-September-October, ASO). Image credit: Columbia University's IRI.

La Niña conditions continue
La Niña conditions continued in the Eastern Pacific Ocean in January, and NOAA's Climate Prediction Center has issued a La Niña Advisory. They define La Niña conditions as occurring when the 1-month mean temperature anomaly in the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region") cools below -0.5°C and is expected to persist for three consecutive months. In addition, the atmospheric response typically associated with a La Niña must be observed over the equatorial Pacific Ocean. Sea surface temperatures were 1.0°C below average in the Niña 3.4 region during January, an increase from the -0.73°C anomaly observed in December. However, it appears that La Niña has peaked, as ocean temperatures in the Niña 3.4 region have warmed since late January. Many El Niño forecast models predict a continuation of La Niña conditions through May of 2009. Despite the unusually late start to this La Niña, expected impacts during Spring 2009 include above-average precipitation over Indonesia and below-average precipitation over the central and eastern equatorial Pacific. For the contiguous United States, potential impacts include above-average precipitation in the Ohio and Tennessee Valleys and below-average precipitation across the South, particularly in the southwestern and southeastern states. Other potential impacts include below-average temperatures in the Pacific Northwest and above-average temperatures across much of the southern United States.

Jeff Masters