A look at weather extremes and the big-picture climate connections.

Texas Drought Eases, But It’s Too Late for Some

Defying seasonal climate forecasts, this winter has been very good to Texas, which has been locked in the grips of one of the worst droughts in state history. But the unexpectedly generous winter storms have come too late for some, since water supplies are still running low.

As I reported in late January, managers of the Lower Colorado River are likely to take the unprecedented step of denying water for rice growers in Southeast Texas, putting several thousand jobs at risk. Although the decision won't be made until March 1, it is unlikely that Texas will receive enough rainfall to put reservoirs above the mark set by water managers, who must balance the needs of agricultural producers with the water demands of the city of Austin, power companies, and myriad other users.

Precipitation during the past three months in Texas. The outlined areas show the region where water flows into the Highland Lakes reservoirs. Credit: Victor Murphy/NOAA.

The Houston Chronicle reported this week that the Lower Colorado River Authority "may have no choice but to cut off the farmers. The Highland Lakes, two large reservoirs near Austin, must hold a combined 850,000 acre-feet of water by next week before the growers' share can be released, under a drought emergency plan now in effect. As of Wednesday, the lakes had 830,000 acre-feet, 41 percent of capacity."

The fact that the reservoirs are still so low indicates the severity of the long-term precipitation deficit that Texas is still dealing with, despite a three-month period with above average rainfall. 

The rains have certainly eased the drought in the short-term, however, as seen in the U.S. Drought Monitor. On Dec. 6, 2011, 90 percent of Texas was experiencing between "severe" to "exceptional" drought conditions. In the latest update to the map, however, 67 percent of the state falls into that range, and a sliver of the state is shown to be free of drought conditions entirely, at least for now.

U.S. Drought Monitor for Texas as of Feb. 21.

U.S. Drought Monitor for Texas as of early January.

The above-average rainfall this winter stands in stark contrast to the bone dry weather pattern of a year ago. For example, during the past five months, several Texas cities have received at least 120 percent of the rainfall they saw in the preceding 12 months. Brownsville, a costal city that sits at the southernmost edge of the state, has seen more than 4 inches of rain this month, which is 500 percent of their normal rainfall in February.

The beneficial rainfall (and in some cases, snowfall) so far this winter has surprised weather forecasters, who had called for drier-than-normal conditions across the entire southern tier of the U.S. However, drought conditions seem to have shifted eastward, with an expanding drought in the Southeast, particularly in Florida.

So why has Texas been so lucky lately, when luck had not been on its side for so long?

According to Victor Murphy, the climate service program manager for the National Weather Service's southern region, Texans should thank a combination of factors. First, there is natural climate variability, the effects of which are difficult to predict. Second, he said, the weak La Niña event in the tropical Pacific Ocean is playing a role.

Last winter also featured La Niña conditions, which tend to result in drier-than-average winters in Texas, but last year's La Niña was much stronger than this year's event. La Niña conditions are characterized by cooler-than-average water temperatures along the equator in the Pacific Ocean, which can influence weather patterns worldwide.

The other key factor, Murphy said, is the jet stream -- the high altitude river of air that helps steer storms and air masses across the country. This winter, the jet stream has run across the northern U.S., allowing slow-moving storms to meander across Texas, dropping beneficial rains as they went along.

"The same anomaly in the jet stream that is causing the contiguous U.S. to have its fourth warmest winter on record through the end of January is mainly responsible for the wetness across Texas," Murphy said via email. 

The big question now is whether this wet weather pattern will last long enough to make a lasting dent in the drought. Unfortunately, the spring outlook still calls for below average rainfall. If this happens, look for a swift end to the recent improving trend, and drought conditions could worsen once again during spring and summer.

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