A tame year for extreme weather in U.S., but California really needs rain

California had its driest year on record, and Michigan and North Dakota their wettest years. The interior of the Lower 48 had 7 combined tornado, flooding, and drought disasters. But, overall, 2013 was unremarkable for weather extremes, NOAA’s end-of-year report finds.

NOAA’s Climate Extreme Index, an integrated measure of the severity of temperature, precipitation and tropical storms, was below average in 2013 for the first time since 2009 – bucking an apparent trend towards more extreme weather since around 1970.

Climate Extremes Index, 1895 to 2013 (NOAA)

Climate Extremes Index, 1910 to 2013 (NOAA)

Related: The 5 top U.S. weather stories of 2013

Temperatures weren’t anything out of the ordinary. 2013 tied 1980 as the 37th warmest year on record since 1895 and 17th straight warmer than normal year, but it was 2.9 degrees cooler than the warmest year on average, 2012, and the coolest year since 2009.

In a departure from recent norms, record daily cold temperature records outnumbered record high temperatures, according to a preliminary analysis by Climate Central in December.  NOAA’s report confirmed this: “On a local level during 2013, approximately 26,100 daily warm temperature records were tied or broken (10,100 warm daily maximum records and 16,000 warm daily minimum records); while approximately 28,800 daily cool temperature records were tied or broken (16,900 cool daily maximum records and 11,900 cool daily minimum records).”

Ratio of record highs to record lows (Climate Central)

Ratio of record highs to record lows from 1993 to 2013 (Climate Central)

On balance, it was wetter than average across the nation, ranking 21st wettest on record, and the wettest since 2009. Drought coverage in the Lower 48 shrunk from 61 percent at the end of 2012 to 31 percent by the end of 2013 thanks to prosperous rains in the Plains and Midwest. Parts of the Southeast were especially wet – Asheville, Macon, and Knoxville had their wettest years on record.

Preliminary map showing locations which had record warmest, coldest, dry and wet years in 2013 (NOAA)

Preliminary map showing locations which had record warmest, coldest, dry and wet years in 2013 (NOAA)

But the lack of rain in parts of the West was remarkable. California’s statewide average was just 7.38 inches, some 15.13 inches below average, and 2.42 inches below its previous driest year, 1898. San Francisco had its driest year in 67 years of records, picking up just 3.39 inches of rain, less than half that of Phoenix. Sacramento, Eureka and Fresno also had their driest years. Los Angeles had its second driest year in 68 years of records, logging only 3.65 inches of rain.

Oregon was also extraordinarily dry: Eugene, Medford and Salem all had their driest years. State-wide, it was the 4th driest year on record.

Most of 2013′s high impact weather concentrated between the East and West Coasts. Of the year’s 7 billion dollar weather disasters, none affected coastal areas.

2013's billion dollar weather disasters (NOAA)

2013′s billion dollar weather disasters (NOAA)

Several tornado and severe weather outbreaks affected the Southeast, Ohio Valley and Plains (notably Oklahoma), even though the preliminary number of tornadoes, 891, – overall – was below average (1,253).

“Depending on the final confirmation rate, this could be the slowest tornado year since 1989 when 856 tornados were confirmed,” NOAA writes.

Tornado counts (NOAA)

Tornado counts, 1950-2013 (NOAA)

Like tornado activity, hurricane activity was also depressed well below average levels.

“The Accumulated Cyclone Energy (ACE) index of tropical cyclone activity also indicated a below-average season in the North Atlantic,” NOAA writes. “[The 2013 season had] the lowest ACE for a hurricane season since 1983 and the 14th lowest in the 1851-present period of record.”

Related: 2013 Atlantic hurricane season wrap-up: least active in 30 years

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