Dec. 1, 2011 - When state climatologist John Nielsen-Gammon said in September that the current drought could last until 2020, some people took that to mean he was predicting the current drought would last another nine or 10 years. He was called alarmist, and worse in some quarters, though he noted at the same time that the drought could also end next week. While he's not ready to give odds on the drought lasting to 2020, Nielsen-Gammon believes the odds are good that drought will be with us at least another year.
"La Nina is back," he told a water symposium in Belton recently. "The drought is likely to continue through the winter. It will take a lot of rain in the summer to break it, so I think we're in for another drought-susceptible period over the next year."
As for how long the drought could last, a lot depends on when you think it actually began. Richard Cortese, a Bell County farmer, suggested that the drought has been with us nearly every year -- with the exception of occasional floods -since 1996, which would put the state 15 years into the current drought.
Weather data shows drought conditions in Texas in 1996 and 1998-2005, 2008-09 and 2010-11, which suggests that Cortese has a point: this has been going on for a while.
The core of this drought and extreme droughts of the past is the La Nina weather system, which shifts the jet stream north and takes the storms tracking east to west with it. The result is less rainfall and warmer temperatures in Texas and the Southwest. A strong to moderate La Nina influence was present most of this year. It has weakened a bit, but Nielsen-Gammon said it is expected to strengthen again in the next two to three months, making the prospect of atypically heavy summer rains to break the drought less likely.
"La Nina is difficult to forecast beyond April and May," he said. "It comes down to weather forecasting at that point, and you can't do that six months in advance."
As for how long the current drought might last, a 2006 study by Malcolm Cleavland with the University of Arkansas Tree Ring Laboratory and researchers from the Blanco River Authority examined droughts through the ages by using tree rings to study droughts dating back to 1648, half a century more than previous studies. The report concluded: "It would appear unwise for civil authorities to assume that the 1950s drought represents the worst-case scenario to be used for planning purposes in water resource management."
The worst droughts on record since 1895 show droughts in 1909-12, 1917-18 and 1925, which was the driest year ever in much of East Texas. The 1950s drought was the fourth worst that researchers found in the tree ring study. That drought was followed by an often overlooked drought in the early to mid 60s that had a significant impact, but paled in comparison to the 50s drought.
In South Central Texas, according to the report, the worst drought -- not necessarily the longest -- occurred from 1708 to 1717. The second worst was from 1696-1705 and third worst was from 1884-94. A new study of bald cypress tree rings (the first study used post oak rings) is expected to extend the data back even farther.
The current drought is showing signs that, in terms of severity and heat, it can hold its own with any of the documented droughts. Sixty-five percent of the state is an "exceptional" drought, the most severe of all the ratings with just a two percent chance of it occurring at any given time.
"We broke records everywhere in the state except for a part of North Central Texas and they came pretty close," Nielsen-Gammon said. "East Texas got the amount of rain that West Texas usually gets. West Texas got the amount of rain that Death Valley usually gets."
The last major rain event over most of the state occurred on Sept. 27, 2010. East Texas was already dry by that time. Since then, every month has been among the top 10 driest of all time. "The last four years, no place in the state has had above normal rainfall," he said.
Most of the state has been at least 50 percent below normal rainfall and some areas of West Texas around Midland have received one-tenth of the normal rainfall. "The entire state is below normal rainfall, which is unheard of in Texas because of its size," Nielsen-Gammon said.
Aside from being one of the driest years on record, 2011 will also go on record as being the hottest summer ever in Texas. The climatologist said the heat actually makes the drought worst by evaporating all the soil moisture; when it's gone it's not there to help create clouds which help form the storms that could put an end to the drought.
"The expectation is that the droughts will become hotter," he said. "Evaporation will be a bigger factor in future droughts."
The state climatologist is involved mostly with the big picture -- long term temperature and moisture projections. It's different from weather forecasting, which is typically pretty accurate up to about four or five days.
"It's November now, so I'm pretty confident about the 2011 forecast," he deadpanned. "It's going to be hot and dry."
