Over the past few weeks of hot and dry conditions, I have wondered whether or not this year had any connections, meteorologically and climatologically speaking, with 1988. The drought of 1988 is seen by much of the scientific and agricultural communities as the worst drought of the 20th century.
The main reason for any summer drought in the Central United States is a weather pattern called Omega Block. The Omega Block is characterized by a large ridge of high pressure flanked by two troughs of low-pressure on either side giving a shape of the Greek letter Omega (Ω) on a weather map of the country. The ridge of high pressure leaves the central U.S. hot and dry. The weather map in 1988 showed this typical Omega block. The drought was enhanced by a winter and spring with unusually low precipitation and thus soil was already dry throughout the central U.S. These factors caused over 40 billion dollars in damages (using 2012 dollars) across the Mid-West and Great Plains.
So far this summer, the omega pattern has once again blocked itself into the central U.S. and the Mid-West is hot and dry. The omega block pattern seemed to set in the middle of May and has continued now through the end of June and has no signs of breaking any time soon.
There are, however, differences in the two years weather patterns. Winter and early spring had above normal liquid equivalent (when snow is melted down to liquid form) so we did not start out as dry as we did in 1988 when there was such a low precipitation total that barges could not travel down the Mississippi past Cairo, IL. There is also a difference in the omega pattern itself. Looking back at previous maps, the peak of the ridge of high pressure was all the way up into Canada. The peak of the current ridge is in the upper Mid-West and a so-called “ring-of fire” scenario has set up where thunderstorm complexes travel along the ridge dumping rain into Iowa, Minnesota, Wisconsin, and Northern Illinois and hopefully that continues for at least a couple of days.
The best way to break-up the current dry spell in the Mid-West (other than busting through this omega block) may be getting the remnants of a tropical storm to hit (not that I want that to happen to the Gulf states). The tropics brought no relief to the Mid-West and Great Plains in 1988 as there was only one tropical depression in the Atlantic from May to July and only 19 total storms for the whole year. The tropics have been relatively active this year with four named storms in the Atlantic.
A special thank you to Pops for letting me post on his blog and a thank you to the American Meteorological Society for posting past journal articles that were used in the blog and can be seen at the links below.
Bloomburg carried a recent article on the potential agricultural costs of the 2012 drought.
Bloomburg carried a recent article on the potential agricultural costs of the 2012 drought.
Zach Rahe
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