Severe Drought in Texas

Diana from between San Antonio and Austin, Texas, writes:

To answer her questions, geography generally doesn't turn storms away, but it certainly can have an effect. We have a geographical effect here in Central Pennsylvania, with the Appalachians to our west -- when air descends down a mountain, it cools and dries, killing storms and reducing rainfall. So any precipitation coming from Diana's west could be affected by the descent down the hills.

In general though, droughts are caused by shifts in the general storm tracks for a hemisphere, or by lack of hurricane rainfall. The latter has severely affected Texas this year; hurricanes actually exist solely to transfer heat from the equator to the poles. Take a look at the tracks of all tropical storms this year and you won't see a single one going into Texas.

Looking at historical data from AccuWeather.com Premium, I pulled up historical data for NEW BRAUNFELS, TX (709') and it definitely looks like her area is in a dry spell, only about 25% of normal rainfall for the last 3 months. There has been no rain to speak of this month, and only two days with significant rain in September or October.

Below, you can see that I combined a precipitation departure map from AccuWeather.com Professional with an elevation map from JHU-APL (you can see the hills Diana mentions).

As you can see, not only is the area around Diana suffering this year, so is much of the state, with some areas coming up short by amounts as much as 30 inches of rain, which is really big news considering that most of Texas only receives between 20 and 40 inches per year on average!

The map above, produced by the government, shows the Palmer Drought Index for Texas. This index combines rainfall information with temperatures and is standardized to local climates. On this map, northeastern Texas is labeled "Severe" while all of Eastern Texas qualifies as being in a dry spell or general drought.

Temperatures have also been very high at New Braunfels -- 6.5 degrees above normal for November and September, 2 degrees in October.

Unfortunately, there's not a lot of good news for Texas. Both our 30-day and 90-day outlooks (shown below) indicate drier than usual weather for the Lone Star State.