DISCUSSION: Over the past five to seven days and them some across the Great Plains in particular, there has been a persistent period of excessive heat which has unfolded. There is no doubt that Summer-time heat waves are not completely unprecedented. However, something which is not all that common is the total coverage of the 600 decameter height contour which was analyzed on the 500 millibar height map for the evening of July 4th. The reason for why this observation is so significant is due to the fact that higher pressure contour values in the mid-levels of the atmosphere indicate the presence of a stronger high-pressure system being in place.
Therefore, as shown above, the vast coverage of the 600 decameter height contour at 500 millibars is a classic indication of a robust high-pressure system being in control at that point in time. It is also important to understand that underneath a strong high-pressure system, there is a corresponding propensity for strong sinking motion which allows for the compressional warming of associated air parcels. Thus, the effective sinking of air underneath this multi-regional high-pressure system allowed for notably warm (and in many cases, sizzling) day-time high temperatures. This multi-regional heat wave impacting the lives of millions of people across many parts of the Central and Eastern United State as they often do.
Thus, many millions of people who were unfortunate underneath to be positioned under this massive high-pressure system felt the full-force of its widespread heat-producing capacity. It is also worth noting that even in the days since the Fourth of July, there is still expected to be notably high temperatures during the daytime with highs in excess of 90 degrees Fahrenheit across many parts of the Central United States. Therefore, be sure to stay cool and hydrated if you are living and/or travelling to these areas in the coming days.
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© 2018 Meteorologist Jordan Rabinowitz