Wildfires soar as La Niña effects keep rain at bay
By ERIC BERGER
Copyright 2010 Houston Chronicle
Dec. 8, 2010
The great drought of 2011 may have started two months ago.
Since Tropical Storm Hermine drenched central Texas in September, the state has been very dry, with large swaths receiving less than 10 percent of normal rainfall levels. Locally, nearly all but the southeastern corner of Harris County has received less than 50 percent of normal rain.
According to the National Climatic Data Center, the two-month period of October and November was the state’s eighth driest on record, and second driest in 44 years. If Texas doesn’t receive at least 0.78 inches in December, it would be the driest October-December period since the 1950s.
The beginnings of drought conditions now — an updated U.S. Drought Monitor released this morning will show much of Harris County now in a moderate and worsening drought — trouble
meteorologists because there’s little reason to expect relief during the next few months.
“Continuing dry weather is likely to persist at least into the spring,” said John Nielsen-Gammon, the state climatologist and a professor of atmospheric sciences at Texas A&M University. “It’s probably going to get worse before it gets better.”
The big concern is that, absent a wet spring, a large part of the state could experience a severe drought in 2011.
“For now it’s impossible to predict summer rainfall,” Nielsen-Gammon said. “But as things look right now, there will be very little subsurface moisture heading into late spring. These are hair-trigger conditions for a drought.”
More immediately there’s the threat of wildfires as the state dries out.
An active fire season
Partly in response to the looming drought, the Texas Forest Service convened a workshop this week in College Station to alert state and federal fire agencies about the threat, and to prepare.
“There are important indicators however that at least an active fire season is at hand,” said Todd Lindley, a senior forecaster at the National Weather Service office in Lubbock.
Rainfall late in the state’s growing season fed the growth of grasslands that are now drying out, which will provide fuel for any fires sparked.
Wildfires are common in Texas, especially in Lindley’s forecasting area, during these months as strong winter systems bring gusty wind conditions that can easily spread fires.
Forecasters expect a dry fall to continue this winter because of strong La Niña conditions in the equatorial Pacific — where sea surface temperatures are cooler than normal — which typically leads to drier and warmer winters.
The warmth matters too, when it comes to drought, as warmer daytime highs increase the rate of evaporation, further drying the soil.
For Houston a strong La Niña phase almost always yields a very dry winter. According to data compiled by forecaster Chuck Roeseler with the Houston/Galveston office of the National Weather Service, La Niña conditions this winter will be most similar to the winters of 1916-1917, 1917-1918, 1955-1956, 1975-1976 and 1999-2000.
During a typical October-to-March period in Houston, the city receives 22.4 inches of rain. On average, during those five La Niña winters, the city recorded just 10.5 inches of rain, or less than half of normal levels.
“Numbers very similar to this hold true for nearly all of central and south Texas,” said Victory Murphy, a climate expert with the National Weather Service’s Southern Region Headquarters in Fort Worth. “As one moves northward into northern Texas, the signal for dryness is somewhat muted.”
In response to the drying conditions 80 Texas counties have already enacted burn bans, including Waller, Fort Bend and Chambers counties nearby.
Murphy said the agricultural impacts could also be acute if the drought persists. During the last major state drought in 2008 to 2009, farming losses were estimated to be $3.6 billion by Carl Anderson, of A&M’s Agriculture Extension Department.
“This impact will need to be monitored very closely by dry land farmers as well as pasture and rangeland producers starting in the springtime when planting begins,” Murphy said.
There’s no immediate threat to stream or river flows, however. Widespread, heavy rains helped Texas emerge from a drought late in the summer of 2009 and, through this past June have raised water reservoir levels into good shape.
However, absent spring rains or — be careful what you wish for — a few good, soaking tropical systems next summer, there could be impacts on water usage and pumping next April and May when homeowners seek to green their lawns, and farmers their fields.
courtesy: Brown & Caldwell Water News, Dec. 15, 2010