Forecast model presentations on July 7, for the 10-day timeframe ending July 17, are very dramatic to finish out the week. The big feature is a strong hint at hotter and drier conditions spreading into the central and eastern Midwest during this period. The hint is suggested by the European forecast model, which has a 5,940-meter height for the 500-millibar constant pressure value parked over the southern Midwest.
Heights of the 500-millibar constant pressure level can be used to estimate surface temperatures, since the height of a pressure surface is related to the temperatures of the air beneath it. When the air is warmer, the height of the constant 500-millibar pressure value rises. And, during midsummer, the surface temperature underneath a 5,940-meter (594 decameters) high location of the 500-millibar pressure value is in the 95-100 degree Fahrenheit range.
The location of this feature, as suggested by the Euro forecast model, puts conditions for corn pollination into a stressful category. That is obvious underneath the ridge top itself -- but farther away, the heat also would be evident. If the Euro-suggested pattern indeed sets up, the central and eastern Midwest temperatures would likely be in the range of 88-95 F. Such values have already stressed crops in the Northern Plains and in the western Midwest, so this development would put corn pollination-hindering temperatures into the entire Corn Belt -- right in the midst of this phase of the crop season.
The evolution of the upper air pattern will get worldwide focus going into and through the weekend. Primary attention will be to see which model "wins" so to speak, because there's not much room for compromise in this difference of depictions.
Bryce Anderson can be reached at firstname.lastname@example.org
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