El Nino weather pattern likely to provide break from drought
Forecasters predict a wetter-than-normal winter in Arizona, but not as much runoff from the north into Lake Powell.
By CYNDY COLE
Sun Staff Reporter
Friday, December 04, 2009
A slightly warmer Pacific Ocean is expected to shift the jet stream south in Arizona this winter, loosening somewhat the iron grip of drought in the Flagstaff region this year.
But projections hold for below-average inflows into Lake Powell and the Colorado River system. That's because some of the seven states feeding the Colorado River farther north aren't expected to have as heavy a winter, weather officials said Thursday.
The Colorado River Basin provides water for about 30 million people, but many of its regions typically receive less than 15 inches of rainfall annually.
An El Nino weather pattern is likely to bring moisture from California to Florida beginning in January for northern Arizona.
"There's definitely a wet and cool signal," said Jon Gottschalck, of the National Oceanic and Atmospheric Administration.
What he and others at NOAA can't predict is exactly how much rain that will translate into for various regions.
EVEN MORE PRECIPITATION SOUTH
January through March showed the greatest chances for above-average precipitation in northern Arizona, said the agency's Phoenix office, with southern Arizona likely to get more precipitation than the northern parts of the state.
These storms are still unpredictable, though.
"As I've said, that can change dramatically as we get into the winter season and see some big winter storms, or not storms," Kevin Werner, a hydrologist at the Colorado Basin River Forecast Center, said of precipitation levels.
If the rain or snow comes, it will be at least a short break in a drought that began in 1994 and that this year cut off summer monsoon rains.
"We're in uncharted territory as far as short-term drought and not getting summer precipitation," Mike Crimmins, of the University of Arizona and Arizona Cooperative Extension, told a group of researchers at U.S. Geological Survey on Thursday.
Most of northern Arizona was considered in extreme drought as of a report released Tuesday.
Earlier this fall, its grazing land for livestock was rated as being in the worst shape of any state in the country.
Northeast Arizona is heading for record dryness, with sand dunes becoming more mobile on the Navajo Nation and some roads there becoming more undrivable than they have ever been, said USGS research scientist Margaret Hiza Redsteer.
The Southwest has had "mega" droughts in previous centuries that are documented in tree rings and far exceed today's in intensity.
But researchers with the USGS and Northern Arizona University note that changes such as tree mortality or grazing land lost with this drought could become irreversible when combined with rising global temperatures and more precipitation lost to evaporation more quickly under warming.
Flagstaff was on track for the driest calendar year in more than a century of record-keeping as of Thursday morning, with 8.8 inches of precipitation for the year.
The driest year on record until now was 1942, which had 9.9 inches.
Cyndy Cole can be reached at 913-8607 or at email@example.com