An extraordinarily rare July front is on the way
Late July is generally one of the quietest times for our local weather. Barring tropical systems, typically at this point the summer pattern has become entrenched with high temperatures and very few atmospheric triggers for rain aside from the occasional afternoon thunderstorm sparked by the sea-breeze. This is what makes the weather situation this week exceptionally unique. If you have not heard by now, we are expecting a fairly robust front (by July standards) to push through here today which will make the next couple of days a treat. I suppose technically it is a cold front but there really isn't much real cold behind it, but none the less it is a refreshing front which will bring noticeably lower humidity and make mornings and evenings absurdly comfortable (again, by July standards).
As the front makes its way through today rain and a few storms will be possible, but nothing that will be too serious. Most of us could use the rain as the area by and large, has been dry since the beginning of the month. Today you may not really notice a whole lot of change from this front, but come Wednesday morning you certainly will. Wednesday and Thursday morning dew point temperatures will drop into the 50s for many spots except for maybe the immediate coast. Correspondingly the actual temperatures will fall into the upper 60s in many spots especially the further from the coast you get since drier air is easier to cool down at night. During the day on Wednesday and Thursday, temperatures will still rise to about 90 degrees but it definitely won't feel as hot as the heat index will for once closely resemble the actual temperature.
A word about Dew Points.
The dew point temperature is one of the most important figures in meteorology and it gets totally shafted in weather forecasts directed to the public. Basically, the dew point is a measure of moisture in the atmosphere – and a critically important factor in forecasting things like thunderstorms, the heat index or whether we can squeeze out some snowflakes down here in the winter. Relative humidity gets all the publicity, but I find that the dew point is really a far better measure for judging how humid it feels. When the dew point is above 65 degrees it feels muggy out, and the higher it goes the stickier and more oppressive the air feels. During the summer the dew point in our area typically stays somewhere between the upper 60s and the upper 70s. Once the dew point drops into the lower 60s and into the upper 50s you can distinctly notice the air feels dryer.
Ok, so what is all this fuss about the dew point about? Well the dew point is also a fantastic measure of a cold front and especially so in July. To express how rare a front like the one we are getting this week is in July I went back and looked through the hourly dew point readings at Bush Airport (the official climate recording site for Houston) for the last 10 years. Over the 7,440 hours that make up the last 10 Julys, the dew point has been below 60 degrees for a grand total of 35 hours! And 32 of those hours happened during a two day span in 2013. This means in the past 10 Julys the dew point has been below 60, in the comfortable feeling range, just 0.47% of the time.So with that in mind get out and enjoy the next couple of days because it may be a very long time before we see another "comfortable" day in July.