Midwest Overview - June, 2005

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Drought Intensfies Over Central Midwest
 

The third straight month of below normal rainfall in the central Midwest resulted in an intensification of drought in a narrow band from southeastern Missouri through Illnois into lower Michigan.  As of the June 28 edition of the U.S. Drought Monitor (Figure 1) southeastern Missouri much of the northern half of Illinois were depicted in Severe Drought conditions (D2 category).   Rainfall during June was generally abundant west of the Mississippi River, but spotty at best over much of the region east of the Mississippi River (Figure 2).  The exceptions were portions of central Indiana, which received one to three inches of rain from the remanants of Tropical Storm Arlene the second week of the month, and eastern lower Michigan which benefitted from increased thunderstorm activity near the end of the month.

The affects of the dry weather on agriculture on May were somewhat mitigated by the cooler weather that month.  However, that was not the case in June, where temperatures averaged 4^oF to 6^oF above normal in the north half of the core drought area (Figure 3).  Temperatures topped out at 90^oF or above on more than half the days during June especially over the southern half of the region.  When temperatures are high and soil moisture is deficient photosysnthesis decreases, and this can affect the success of pollination.  As the month ended and the pollination period approached, there were significant declines in the condition of the corn crop in Illlinois.   The corn crop in Illinois declined from only 11 percent in Poor or Very Poor condition for the week ending June 12, to 28 percent in Poor or Very Poor condition for the week ending June 26.  In contrast, there was little overall change in the condition of the corn crop in Indiana, Michigan, and Ohio during this same period.  In Illinois, the Governor activated the Drought Response Task Force on June 26.  By the end of the month 47 Illinois county Farm Service Agency (FSA) directors filed "flash reports", the first step to initiate a government disaster declaration. .
 

Upper Pattern Favors Severe Weather Across Upper Midwest

The mean 500 millibar level pattern (about 20,000 ft) for June reflected a trough in the west and a broad ridge in the central and eastern U.S. (Figure 4, Climate Diagnostics Center).  The weather systems that managed to make their way toward the Midwest were steered northeastward toward Minnesota, Iowa, and Wisconsin.  This pattern produced a very active month for severe weather across the upper Midwest, which typically does not occur until July.   Wisconsin averages about 21 tornadoes per season, but by the end of June the preliminary count for this season stood at 28.