APRIL ON RECORD IN U.S.
May 16, 2006 — The contiguous United States experienced its warmest April ever based on records dating back to 1895, according to scientists at the NOAA National Climatic Data Center in Asheville, N.C. Drier-than-average conditions and severe drought persisted across large portions of the southern and southwestern United States. April also was marked by a series of tornado outbreaks during the first half of the month impacting large parts of the Midwest and central Plains, into the Deep South. The global surface temperature was the seventh warmest April on record. (Click NOAA illustration for larger view of warmest April on record. Please credit “NOAA.”)
A beneficial, late-season heavy snowfall blanketed the Black Hills of South Dakota and surrounding areas April 18-20. Most of the affected area received 12 to 24 inches of snow. More than 60 inches fell in Lead, S.D. High elevations in California continued to have well above normal spring snowpack with some places more than 200 percent of the 1951-2000 average at the end of April. Unusually warm temperatures and rapid snow melt in Wyoming reduced early May snowpack levels there to well below average.
Ten states were drier than normal, primarily in the southwestern and southeastern United States. Only Colorado experienced well below normal precipitation, recording its 11th driest April. Precipitation deficits in the Southeast followed a record dry March for the region and led to a continuation or worsening of conditions in the region.
At the end of April, moderate-to-extreme drought (as defined by a widely used measure of drought—the Palmer Drought Index) affected 31 percent of the contiguous U.S., an increase of 5 percent from March. Drought persisted across much of the south central and southwestern United States, stretching into the western High Plains and Missouri Valley. Drought and abnormally dry conditions also extended from parts of the Northeast to Florida and Gulf coastal areas, according to the U.S. Drought Monitor. Parts of the Upper Peninsula of Michigan and northern Wisconsin also were in moderate drought. Exceptional drought developed during April in southeastern Arizona and southwestern New Mexico, and persisted in southern Texas.
Four tornado outbreaks occurred in the eastern Plains and Midwest in April. On April 2, 86 tornadoes were reported in the region bordered by Arkansas, Iowa, Indiana and Tennessee in association with a strong cold front. Tennessee was particularly hard hit, with 23 confirmed fatalities. An April 7 outbreak of 91 reported tornadoes occurred in the Tennessee valley, killing nine in the suburbs of Nashville. Twenty tornadoes were reported on April 13, mostly in eastern Iowa. One person was killed, and there was significant damage in Iowa City. A final large outbreak of 24 reported tornadoes hit east central Illinois on April 16 with no deaths reported.
Heavy rain events and associated flooding occurred throughout April in Yemen, Colombia, Eastern Europe, northeastern Australia, Indonesia and northern Argentina. Flooding and landslides caused significant loss of life and property damage in many of these locations. Precipitation estimates for northwestern Colombia from March 1 to April 16 exceeded 27 inches (700 mm). In Eastern Europe in mid-April, the Danube River reached its highest level in 111 years. Cyclone Monica became the strongest tropical cyclone of 2006. It reached Category 5 on the Australian scale, with 135 knots (155 mph) sustained winds before weakening as it crossed over northeastern Australia. The tropical cyclone season in the Australian region has been near average with the development of 12 storms, two more than average. Although final assessments of tropical cyclone strength are continuing, it is thought that 25 percent of these storms reached Category 5 strength on the Australian scale.
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