Terwijl wij een "gematigde "zomer meemaken beleeft men in de VS een topzomer. Ook de komende dagen wordt volop hitte verwacht. Hieronder een citaat van het blog van Jeff Masters
A massive upper-level high will envelop most of the contiguous U.S. in the last half of July, setting up what could be a prolonged bout of extreme heat for millions of Americans. If the scorching weather persists into August, the odds of a “flash drought” in the nation’s heartland will rise sharply (along with the odds that the U.S. will notch its hottest summer on record, in line with what’s very likely to be Earth’s warmest year on record). Even though it appears that heat and humidity will combine to put residents, pets, and livestock through the wringer, it’s quite possible that the croplands of the Midwest and Plains will fare better than one might expect, thanks to a fortunate confluence of factors.
There’s certainly no mercy in the pattern projected for the next few days at upper levels. As shown in Figure 1, the upper high at 500 millibars (about four miles up) encompasses nearly all of the contiguous U.S. by Thursday night, July 21. Because air expands as it warms, a higher 500-millibar surface is associated with a warmer air mass at lower levels. Although the most extreme 500-mb heights projected in earlier model runs have dropped just a bit, both the GFS and ECMWF models have been consistent with their portrayal of a mammoth upper ridge centered near the nation’s midsection for at least the next week to ten days, perhaps longer. The atmospheric variables predicted to take shape later this week are similar to those observed during some of the nation’s most notorious heat waves of recent decades, according to the CIPS Analog website from the Cooperative Institute for Precipitation Systems/Saint Louis University. At the time period shown below in Figure 1 (8 PM Thursday, July 21), the closest analog for conditions predicted for the Midwest (taking into account temperatures, moisture, and other factors at various layers) is July 13, 1995--the second day of a catastrophic five-day heat wave that took more than 700 lives in the Chicago area. The top analogs also include July 4, 2012, and August 7, 1980, two peak days from the devastating central U.S. drought years of 2012 and 1980. Excessive heat watches for later this week have already been issued by the National Weather Service for parts of Illinois, Iowa, Kansas, Minnesota, Nebraska, North Dakota, and South Dakota