Friday, June 10, 2011

U.S. Climate Update May 2011


From NCDC: Climate Highlights - May 2011
•In May 2011 the United States had dramatic shifts in regional temperatures, but overall was slightly cooler and wetter than normal. Spring was marked by record wetness in the Northwest and Ohio Valley while drought conditions intensified across the South.
•The average U.S. temperature in May was 60 degrees F (15.6 degrees C), which is 1.0 degrees F (0.6 degrees C) below the long-term (1901-2000) average. Precipitation during the month was 0.34 inch (8.6 mm) above the long-term average.
•Average May temperatures across the western third of the country were below normal. Washington (tied) and Oregon experienced their sixth coolest May on record with average temperatures more than 3.6 degrees F (2 degrees C) below the 20th century normal. Wyoming and Utah had their seventh and eighth coolest May on record, respectively.
•Precipitation during May was above normal for much of the United States. Only the South and Southeast experienced average precipitation that was below normal. The average precipitation of 4.7 inches (119.4 mm) in the northern High Plains was a May record, 2.19 inches (56.6 mm) above the 20th century average.
•At the state level, average precipitation in every Gulf Coast state was below normal. Georgia had its fifth driest May, while it was sixth driest for Louisiana, eighth driest for both Mississippi and Texas, ninth driest in Florida, and the tenth driest for Alabama.
•A persistent storm track contributed to above normal precipitation for the majority of states across the northern half of the country. Many states were much above normal including: Utah and Wyoming (2nd wettest), Montana (3rd), Vermont (4th), New York (6th tied), and both Ohio and Nebraska (8th tied).
•The overall drought footprint across the contiguous U.S. remained above average, about the same as a month ago, at about 26 percent. The area of the country affected by the two most intense drought categories (Extreme and Exceptional) has increased for fifteen consecutive weeks, a streak dating to mid-February. Much of this very intense drought is focused in the Southern Plains and Southern Rockies.
•According to data from the Storm Prediction Center, tornado activity during May was above average with 368 preliminary tornado reports. This was significantly less than the April 2011 tornado count, despite the fact that May is typically the most active tornado month of the year.
•The EF-5 tornado which hit Joplin, Missouri on May 22nd resulted in 141 fatalities. This was the deadliest single tornado in the modern record (since 1950) and the seventh deadliest tornado of those known to ever affect the United States.

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