Texas, second only to Alaska in size, lies in the south-central U.S. To its west are the dry landscapes of Mexico and the Desert Southwest while, to its east, is the Gulf of Mexico. Stagnant weather patterns, common across the Continental U.S., can trigger prolonged periods of drought or, as we have seen this month, episodes of abundant rainfall and severe flooding.
Persistent domes of high pressure often develop over the Southern Plains and play an important role in the annual Southwest Monsoon. Under such conditions, Pacific storm systems are deflected across the Northern Plains and onshore flow from the Gulf of Mexico is shunted across Mexico and into the Four Corners region. Deprived of Gulf moisture, Texas enters a period of drought which may last for months or years.
By contrast, persistent atmospheric troughs across the Western U.S., as has occurred this spring, direct Pacific storms across the Southern Plains. Ahead of these systems, copious moisture is pulled northwestward from the Gulf of Mexico; thunderstorms, igniting ahead of the cold fronts, may "train" over the same regions, dropping prodigious amounts of rain and leading to destructive floods. This May, such bands of thunderstorms have dumped more than two feet of rain over parts of Oklahoma, Texas and Arkansas. Of course, flooding in eastern Texas may also arise from hurricanes and tropical storms that lash the Gulf Coast from June to November.
