Tell me if this DOESN'T BITE
Shaun McKinnon
The Arizona Republic
Oct. 17, 2003 12:00 AM
It may seem premature to talk about winter, what with the air-conditioner still clattering at full speed and the ice cream melting in the back seat. But it is mid-October, and federal climate experts issued their seasonal outlook Thursday.
The forecast, in a word: warm.
Winter warm, to be sure, which is much more bearable than summer warm but warmer than normal. And that bodes poorly for the drought-ravaged region, experts said.
"We're seeing pretty severe drought conditions in the West and Southwest," said Ed O'Lenic, senior meteorologist and lead forecaster at the Climate Prediction Center. "Even if we were to have normal precipitation, it would not be enough to alleviate these conditions. And in many areas, it's likely to continue into the winter."
The prospect of a warmer-than-average winter doesn't have much to do with the current heat wave, which threatens to break the record for the latest 100-degree day at Sky Harbor International Airport (Oct. 20).
"There's not much of a correlation temperature-wise between summer and winter," state climatologist Andrew Ellis said. "We're talking about two entirely different atmospheric processes, particularly where we are."
In the summer, Valley temperatures are more influenced by tropical and subtropical air flows, while winter weather comes from more northern latitudes, Ellis said.
Right now, you can blame a pesky high-pressure system for the streak of hot days that will probably continue well into next week, according to the National Weather Service. Conditions are curiously summerlike, forecasters say, right down to the higher dew points, which are typically a monsoon indicator.
Temperatures Saturday and Sunday could easily top 100 degrees, breaking records, and the heat is expected to linger into the middle of next week.
"It's extremely unusual," Ellis said. "The magnitude we're looking at is something almost unprecedented. It's not a good sign for a greater storm frequency this winter. We would hope the atmosphere would be shifting to something more fall-like, but this weekend is looking more like monsoon season. It doesn't look anything like fall or winter."
Precipitation uncertain
Whether winter looks much like winter is still unclear, according to the seasonal outlook.
Although forecasters say they're reasonably confident we're looking at a warmer-than-average winter, they say they don't have enough information to predict the winter's rain or snow.
In part, that's because there is no active El Niño or La Niña, oceanic weathermakers that can influence precipitation.
"Without a strong El Niño or La Niña signal as a guide, there is more uncertainty in our forecast. But we do expect winter to bring its typical weather variability," said John Jones Jr., deputy director of the National Weather Service.
Ellis said so-called neutral years have actually delivered above-average precipitation to parts of Arizona in the past, so there's still hope.
If precipitation is just normal, however, a warm winter could worsen drought conditions, climate experts said. Storms would drop more rain than snow in many locations, and the snow that did fall could melt earlier than usual.
That would leave less runoff to fill the reservoirs in the spring.
Snow is a more efficient way to store water through the winter because it evaporates much more slowly than water in a reservoir.
No quick fix for drought
In terms of precipitation, even a normal or slightly above-average winter won't pull Arizona and the West out of the drought, now in its sixth year.
"It's going to take multiple years to recover," said Rick Clayton, a hydrologist for the U.S. Bureau of Reclamation, which oversees the reservoirs along the Colorado River.
The soil in the high country is so dry that it will suck up some of whatever falls as precipitation, Clayton said.
A winter that delivered 120 to 150 percent of normal rain and snow could produce just 80 to 90 percent of normal runoff.
"For the drought to continue is a pretty safe bet," Ellis said. "It's taken four or five to six years to get into it, and one good winter isn't going to change that dramatically. It would help and prevent it from worsening, but it's not going to be a quick fix."
Dennis
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