Very warm November assures 2012 will be warmest year in U.S. history

The heat is on again in the U.S. After recording its first cooler-than-average month in sixteen months during October, the U.S. heated up considerably in November, notching its 20th warmest November since 1895, said NOAA's National Climatic Data Center (NCDC) in their latest State of the Climate report. The warm November virtually assures that 2012 will be the warmest year on record in the U.S. The year-to-date period of January - November has been by far the warmest such period on record for the contiguous U.S.--a remarkable 1.0°F above the previous record. During the 11-month period, 18 states were record warm and an additional 24 states were top ten warm. The December 2011 - November 2012 period was the warmest such 12-month period on record for the contiguous U.S., and the eight warmest 12-month periods since record keeping began in 1895 have all ended during 2012. December 2012 would have to be 1°F colder than our coldest December on record (set in 1983) to prevent the year 2012 from being the warmest in U.S. history. This is meteorologically impossible, given the recent December heat in the U.S. As wunderground's weather historian Christopher C. Burt reported, an early-December heat wave this week set records for warmest December temperature on record in seven states. December 2012 is on pace to be a top-20% warmest December on record in the U.S.

November 2012 was the 8th driest November on record for the U.S., and twenty-two states had top-ten driest Novembers. The area of the contiguous U.S. experiencing moderate-to-exceptional drought grew from 59% on November 6 to 62% on December 6. This is the largest area of the U.S. in drought since 1954.


Figure 1. Historical temperature ranking for the U.S. for November 2012. Arizona, Colorado, New Mexico, Utah, and Wyoming had top-ten warmest Novembers, while only North Carolina had a top-ten coldest November. Image credit: National Climatic Data Center (NCDC).


Figure 2. Historical temperature ranking for the U.S. for the January - November period. Eighteen states were record warm, and an additional 24 states were top ten warm. Image credit: National Climatic Data Center (NCDC).

Most extreme January - November period on record
The year-to-date January - November period was the most extreme on record in the contiguous U.S., according to NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought. The CEI was 46% in January - November, more than double the average of 20%. A record 86% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically during the first eleven months of 2012, and 71% of the U.S. of the U.S. had warm minimum temperatures in the top 10%--2nd highest on record. The percentage area of the U.S. experiencing top-10% drought conditions was 32%, which was the 4th greatest since 1910. Only droughts in the Dust Bowl year of 1934, and during 1954 and 1956, were more extreme for the January - November period. Heavy 1-day downpours have been below average so far in 2012, though, with 9% of nation experiencing a top-10% extreme, compared to the average of 10%.


Figure 3. NOAA's U.S. Climate Extremes Index (CEI) for January - November shows that 2012 had the most extreme first eleven months of the year on record, with 46% of the contiguous U.S. experiencing top-10% extreme weather-more than double the average of 20%.

Jeff Masters