2000 Growing Season Weather Summary
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2000 Growing Season Weather Summary
With abnormally dry soils across large sections of the central U.S. and moderate to strong La Nina conditions in the equatorial Pacific, long lead outlooks at the time called for a warmer and drier than normal summer. Unexpectedly, an upper air troughing pattern set up across the Upper Midwest in May and persisted for several weeks. This pattern brought a series of low pressure centers and associated frontal boundaries through the region which led to several rounds of heavy rain. Rainfall totals across Michigan for the month of May alone ranged from less than 3 inches in northern sections of the state to more than 8 inches (more than 200 percent of normal rates) at some southern locations. The precipitation eased long term dryness but led to lengthy planting and fieldwork delays. Some locations exceeded all-time records for maximum monthly precipitation totals. A shift of the jet stream to a more northwest to southeast configuration across the Great Lakes and New England in June led to a cooler than normal temperature pattern which continued into August. Mean temperatures for July generally ranged from 1-5 degrees F below normal, leading to the coolest July and June-August period since the summer of 1992. Scattered frost and freezing temperatures were reported across the Upper and northern Lower Peninsulas on the July 19-20, breaking records at some locations for an event so late in the season. By mid-summer, growing degree day accumulations had fallen back (from above normal levels earlier in the season) to below normal levels, slowing crop growth and development, especially in eastern sections of the state. A return to an upper air ridging pattern across the Midwest during late September and much of October brought warmer, drier weather, which when combined with a later than normal first killing freeze of the fall allowed many crops slowed by earlier cool temperatures to reach maturity. Overall, for the 5-month May-September period, mean temperatures and growing degree day accumulations ranged from near to below normal statewide. Precipitation was highly variable, ranging from below normal totals in northern sections of the state to much above normal levels in the south. Jeff Andresen, Extension Agricultural Meteorologist Michigan State University |