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'04 forecast: Hot, hot, hot
Shaun McKinnon
The Arizona Republic
Dec. 31, 2003 12:00 AM
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Sure it's cold this week, but 2003 will end tonight as one of the warmest years ever across Arizona and the outlook for 2004 calls for more of the same.
Dozens of heat records fell, including the hottest night ever recorded at Sky Harbor International Airport and the hottest January on the books.
The mean temperature for the year, an average of all the daytime highs and overnight lows, was 76.3 degrees at the airport, nearly 4 degrees above the 30-year average and just shy of the all-time record for the Valley. Statewide, the mean temperature was slightly more than 2 degrees above average.
In climate terms, 2 or 3 degrees over a year is significant. It can drive up the demand for water or reduce the amount of snow that falls in the mountains, leaving less runoff for reservoirs already choked by drought.
"A degree or two temperature difference can swing us one way or another," Arizona State Climatologist Andrew Ellis said. "It's critical. If it's so warm we get rain instead of snow, a lot of it soaks into the ground immediately or evaporates back into the atmosphere. We can hold onto it a lot better if that water is in snow."
The prospect for either rain or snow appears iffy at best over most of Arizona through at least March, according to the federal Climate Prediction Center. Most of the state is expected to be warmer and drier than normal.
The one bright spot is the snow accumulating in the mountains of Colorado and Utah. Some of that snow eventually feeds the Colorado River, one of Arizona's critical water sources.
Among the year's heat-related highlights:
• Records fell. And fell. At Sky Harbor, 57 daily high-temperature records were tied or broken, along with three records for hottest months, one for highest low and one for latest 100-degree reading.
• Nights grew warmer. July 15 was the hottest night ever at the airport, with an overnight low of 96 degrees. Of the 57 records broken, 38 were for high minimum temperatures. Climate experts blame the Valley's widening urban heat island, created when roads and buildings absorb daytime heat and hold it into the night.
• Heat wasn't just for summer anymore. January ended as the hottest January on record, with a mean temperature of nearly 62 degrees. A late-fall heat wave pushed the last 100-degree day to Oct. 23, a new record. The mercury hovered in the 70s for much of December and despite a Christmas week cold snap, the month will end at Sky Harbor with a mean temperature three degrees above the 30-year average.
The warming is "part of a trend we've been seeing over the last couple of decades around the West," said Kelly Redmond, deputy director of the Western Regional Climate Center in Reno. "The last several years in particular have been warmer than usual."
For neighboring New Mexico, 2003 was the warmest on record. Like Arizona, New Mexico is also suffering from a drought. Redmond and others say the heat and the dry conditions are linked.
"Temperature has consequences for water just as much as precipitation does," he said. "The demand for water is sort of proportional to temperature. With warmer temperatures, water is wanted by more things, whether it's people, plants or animals, and it doesn't go as far. Higher temperatures exaggerate the pain and speed up the loss of water."
This year, rainfall was as close to normal as climate watchers have seen in at least four or five years. At Sky Harbor, 6.82 inches of rain fell, 1.49 inches below the 30-year average, but a full 4 inches more than fell in 2002, the driest year ever in Arizona.
"Because we were so dry over the past four years, we actually improved droughtwise," Ellis said. "It was a bad year, but not as bad as the previous four."
Still, much of that moisture fell in early 2003. Arizona's high country has received little rain or snow this winter, leaving the state's snowpack - our water bank account - at two-thirds of normal or even less, which "isn't terribly good for us," Ellis said.
The Salt River Project, whose reservoirs depend on runoff from the Salt and Verde rivers, remains in drought mode, spokesman Jeff Lane said Tuesday.
The utility is using as little water as possible from the reservoirs, relying instead on groundwater. Thursday marks the start of a second year of water rationing by SRP, which will deliver one-third less water to cities and other customers.
Although the three-month outlook offers little hope for cool, wet conditions, Ellis said unsettled conditions in the Pacific Ocean are giving forecasters fits and producing wild shifts in the weather.
Utah was suffering through another dry year until last week, when a storm dumped more than two feet of snow at the Salt Lake City airport.
"It's very early in the season," Redmond said. "The storm track can keep dropping until about February or so and it only takes a storm or two to help things."
At the same time, forecasters are showing an unusually high level of confidence in their warm-and-dry outlook.
"Given the state of the bank account, it's not looking real great to get it back up above normal," Redmond said. "It's got to be disconcerting for water managers in Arizona."
Dennis
