Record Heat, Dangerous Heat Continues

Today we target a high temperature of 107 degrees.  This right at the standing record high for this date set just last August 1st.  And this after tying yesterday's record high of 106 degrees.  Our Heat Advisory continues through tomorrow evening, however it has been expanded to cover all of North Texas as you can see in the graphic below.  If we get to 108 degrees, that would make today the hottest day of the year and the hottest since last August 4th when we hit 108.

While 106-108 degree highs will occur for most of North Texas, the hottest readings will again be from Gainesville toward Wichita Falls.  Gainesville hit 109 yesterday for the second time in July, was at 95 by 10 AM and will likely hit 110 today!  Today's Heat Index won't be much above the air temperature.  For western areas there will not be a Heat Index because of drier air.  So, the air temp will feel the same or a degree lower there.  But, that doesn't matter because this flat out dangerous heat for all of North Texas.

Here's what we are watching for today and tomorrow:  a slow, southerly shift of the high pressure ridge that sponsors our heat wave.  Two subtle changes have taken place over the past 24 hours.  First, the ridge is not weakening as was forecast.  Second, the position is little more southward than forecast with the center circulation over West Texas.  This is key because it puts more of North Texas into the northeast quadrant of the ridge's core circulation.  Why is this important?  Because subsidence or sinking air occurs under the ridge with the strongest subsidence in the northeast quadrant.  As air sinks in the atmosphere, it is compressed by the increasing barometric pressure as air sinks to the surface.  The laws of physics state that compressing a gas heats it up and expanding gas cools it down.  Anyone who has ever let cool air out of a hot tire can attest to this fact.

The heat should be just as intense Thursday, however by Friday and into the weekend that strong subsiding zone should weaken and yield high temps close to 102-103 versus 105+ readings.  However, for two days now our computer model guidance is pointing to the ridge intensifying again by Monday and Tuesday.  I'll reflect this thinking in our 7 day forecast by upping forecast highs from near 100 back toward 105 next week...maybe going hotter.  Yes, I know:  UGH.  And the heat goes on.