The heatwave of last week could probably provide enough daily feature content to last a while! Today's featured chart presents a time series of 500 millibar heights from the sounding site near Omaha. Since pressure decreases with height and the ground surface is approximately 1000 mb, the 500 mb level represents an approximate "middle" of the mass weighted atmosphere and pressure surface analyses can provide significant insight into the current weather and forecast. Via a wonderfully simple relationship derived from the ideal gas law, the actual physical height above sea level that this pressure level resides provides a measure of the warmth of the air between the surface and that pressure level. So when the "heights are high", surface air temperatures are often quite warm. A number of sounding sites over the lower Midwestern US set records last week for recording the highest height of the 500 mb surface, including Omaha as shown in the featured image with 6,020 meters recorded last Monday evening. Forecast models are currently advertising the establishment of another very strong "ridge" of high pressure building this coming weekend and perhaps the September record height shown here of 5,970 meters could be challenged. This means we are not done with the hot weather just yet!

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