Another Broken Record?

By: LPerezIII , 3:04 AM GMT on July 13, 2012

No, I'm not talking about the heat. Thankfully. However, in true "careful what you wish for" fashion, Mother Nature responds to the pleas for cooler temperatures and rain with way more rainfall than we really need at the moment.

Today alone, part of NW Harris county received between 8-10 inches of rainfall. That amount of rainfall in such a relatively short time frame, on already saturated ground, caused some serious flooding in parts of Tomball and Cypress that caused some families to evacuate. Hopefully everyone is safe this evening.

Map of Today's Rainfall

Unfortunately, the situation is not going to change for tonight going into tomorrow. Over the last few days the story has been the same. There is a stationary front that is separating warm moist air to its south, and somewhat cooler and drier air to its north. It runs from the Carolinas all the way into Texas, as depicted by this map by the HPC:

As the warm moist air collides with the dry air, the moist air is lifted and that leads to convection, or thunderstorms. It might sound contradictory, but dry air is heavier than moist air, and that's why the moist air is forced upward forming storms. Don't believe me? It's proven by this simple example. What weighs more? Two diatomic oxygen molecules (representing air) or water vapor plus a diatomic oxygen molecule (representing moist air): (O2 + O2) or (H2O + O2)?

Well, numerically, the equations look like this 2(15) + 2(15) or [2(1)+15] + 2(15) which leads us to the answers of 60 or 47 with 47 representing the atomic weight of water vapor plus one diatomic oxygen molecule. Clearly 47 is less than 60 so moist air is, in fact, lighter than dry air!! Now, that was super simplified, but the concept is the same in the real atmosphere.

Back to local weather...

The Broken Record is as follows: Rain develops overnight as the atmosphere destabilizes. Thunderstorms propagate slowly southward and as the atmosphere re-stabilizes the rainfall ends from the point of origin southward. Then it repeats. Therefore, tonight, around 2am-4am, more rain and thunderstorms will develop, seemingly, where it developed last night, hopefully with less coverage, and then the models project it to propagate south-southeastward off the coastline by mid-day Friday. I hope that the initial storms spare the areas that were hard hit today though. The last thing they need is more rain, but the whole area has really been inundated with rainfall. However, there are a few pockets where not much has fallen as seen in the map below.

Map of Rainfall over the last 7 Days

Over the next few days, rain chances will remain somewhat elevated, but coverages will shrink as the stationary front become more diffuse and stretches out towards west Texas. That means that this constant overnight to mid-day rain events should subside by the weekend, but the Sea Breeze will become active in its place which will lead to spotty afternoon showers and thunderstorms through the latter part of the weekend and into next week.

There's a chance that some much drier air could filter into the region by the end of next week which would help dry the area out and bring some substantial sunshine back for next weekend!

In the mean time, stay dry and be safe out there! Watch out for flash flooding again tomorrow and look for an update right here going into next week!
Thanks for reading!!

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About LPerezIII

I have a passion for Mother Nature's fury, serenity, and beauty. I express my soul through my music and photography. B.S. in Meteorology from TX A&M.

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