Sunday, February 8, 2015

Utah's Mega-Storms

It's been estimated that since 1847, Utah has experienced over five dozen Mega-Storms. The climatological definition for such storms is as follows: 1) Size: Mega-Storms usually cover a huge area or region (usually at least one-quarter of the Beehive State); 2)Duration: Mega-Storms usually last more than 24 hours, and continue until the synoptic conditions that initially produced them changes significantly; 3) Precipitation: Mega-Storms usually produce precipitation amounts (of either rainfall or snowfall) whose "return period" is at least a "1-in-25 year" event or longer.
     During October 17-22, 2004, much of Utah experienced a Mega-Storm. This storm resulted when a cold-upper trough dropped southward and collided with warm moist air off the southern California coast, setting up a southwesterly flow that pumped extensive moisture and weather disturbances into Utah for several days. During this time period, Zion National Park (at Lava Point in southern Utah) received at least 10.28" of rain--which is a 1-in-100 year event, while Alta Ski Resort (in northern Utah) received 8.11" of water and 60" of snowfall--which is more than a 1-in-25 year event. Numerous other locations in the Beehive State also received extensive and/or record breaking precipitation during this Mega-Storm.
     During January 5-12, 2005, extensive moisture fell over the Beehive State, causing weather-related deaths and millions of dollars in property damage. A series of storms deposited heavy amounts of rain and snow across the state, on top of already soggy ground. Heavy rain combined with melting snow in the mountains of southern Utah that produced unprecedented floods along many streams and rivers which destroyed dozens of homes in Washington County. Several inches of rain in northeastern Utah County caused groundwater seepage and surface water to flow into dozens of homes in Pleasant Grove. Massive avalanches occurred in the northern mountains of Utah--one of which killed some winter sports
enthusiasts near Park City.   
Climatological analysis indicates that the Mega-Storms of October 17-22, 2004 and January 5-12, 2005 put a significant "dent" inUtah's current multi-year drought.
Famous Utah Mega-Storms:
December 20-26, 1916
February 5-12, 1949
September 4-6, 1970
September 26-30, 1982
May 4-9, 1986
September 5-10, 1991
October 26-28, 1991
January 6-11, 1993
May 3-7, 1993
October 5-9, 1993
October 17-22, 2004
January 5-12, 2005
For information on Mega-Snowstorms in the Salt Lake Valley, click here.

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