Major water woes looming in the West

Record low streamflows expected in many areas this summer

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Precipitation for the 2015 water year- to-date is now below normal over most of the West except for some northwestern areas. The dry March has significantly affected this picture since a month ago, when far more of the West was near normal.

Staff Report

FRISCO —Federal water watchers say their April 1 readings show that precipitation thus far in the 2015 water year (beginning October 1, 2014) is now below normal over most of the West except for some northwestern areas and coastal Alaska.

Snowpack has declined significantly since last month throughout the West due to the warm and dry March. Only high- elevation areas in the Rocky Mountains and Interior Alaska retain somewhat near normal snowpack.

Streamflow forecasts have dropped since last month due to a lack of snow accumulation during March and an early snowmelt, with most regions now expecting below normal streamflow. Reservoir storage is currently below normal in the Southwest and Nevada, with near to above normal storage elsewhere. Continue reading

Study: Global warming not to blame for fierce winter

Findings from Swiss-American team present nuanced view of how climate change affects weather extremes

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One of this past winter’s northeastern snowstorms swirls off the coast of New England in the satellite image via NASA Earth Observatory.

Staff Report

FRISCO — Adding more fuel to the debate over climate change and extreme weather, Swiss and American scientists this week said their new study shows that global warming tends to reduce temperature variability.

The cold and snowy weather that gripped much of the eastern U.S. this winter was probably not linked to Arctic amplification and increased waviness of the jet stream, according to the scientists with ETH Zurich and the California Institute of Technology.

Changes in the north-south difference in temperatures play a greater role in modifying temperature variability than changes in the jet stream, the researchers said. Continue reading

Climate: Does La Niña increase the odds of tornadoes?

Finding a signal amidst the climate noise isn’t easy

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Does La Niña increase the odds of tornadoes?

A new NOAA study tracks the occurrence of seasonal tornadoes across the U.S.

Study finds links between ENSO and tornado frequency in the Southern U.S. Photo courtesy NOAA.

Staff Report

FRISCO — Teasing out a link between large-scale atmospheric patterns and specific weather events isn’t easy against the backdrop of natural variability.

But a new study of the El Niño-La Niña cycle in the Pacific Ocean suggests that La Niña — the cool phase of the cycle — increases the frequency of tornadoes and hail storms in some of the most susceptible regions of the United States.

During La Niña, both vertical wind shear and surface warmth and moisture increase significantly in the southern states, making conditions favorable to severe storm occurrence.

The study, published in the current issue of the journal Nature Geoscience, may help provide more information for medium- and long-range extreme weather forecasts. Continue reading

Climate: Arctic sea ice meltdown weakens summer storms, leading to longer, hotter heatwaves

‘The risk of high-impact heat waves is likely to increase’

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Monsoonal summer thunderstorms help regulate heatwaves. bberwyn photo.

Staff Report

FRISCO — Summer heatwaves, already getting longer and hotter because of human-caused global warming, are set to get even worse, as the overall climate-warming trend disrupts atmospheric circulations that bring relief from long spells of hot weather.

A recent study by scientists with the Potsdam Institute for Climate Impact Research one measurement of accumulated summer storm energy has already declined by 10 percent since 1979. The researchers linked the findings to changes in the Arctic caused by man-made global warming. Continue reading

Climate: Studying thunderstorms in Africa may lead to better hurricane forecasts for the U.S.

A NASA visualization of Hurricane Floyd approaching the Florida coast.

A NASA visualization of Hurricane Floyd approaching the Florida coast in 1999. Hurricane Floyd formed from a tropical wave moving off the coast of Africa to become one of the largest and strongest Atlantic Hurricanes on record.

Spatial cloud coverage offers clues to tropical storm formation

Staff Report

FRISCO — Closely monitoring thunderstorms over Africa may help meteorologists develop better forecasts for Atlantic hurricane development.

“Eighty-five percent of the most intense hurricanes affecting the U.S. and Canada start off as disturbances in the atmosphere over Western Africa,” said Tel Aviv University Prof. Colin Price, who recently published a new study on hurricane formation in Geophysical Research Letters. “We found that the larger the area covered by the disturbances, the higher the chance they would develop into hurricanes only one to two weeks later.”

Working with graduate student Naama Reicher of the Department of Geosciences at TAU’s Faculty of Exact Science, Price analyzed satellite images of cloud cover to track the variability in cloud cover blocking the earth’s surface in West Africa during hurricane season.Using infrared cloud-top temperature data gathered from satellites, Prof. Price assessed the temperatures of the cloud tops, which grow colder the higher they rise. He then compared his cloud data with hurricane statistics — intensity, date of generation, location, and maximum winds — from the same period using the National Hurricane Center data base. Continue reading

Climate: Warming oceans may increase New England hurricane risk

Hurricanes and global warming

A NOAA satellite image of Hurricane Bob, which raked the New England coast in 1991.

Historic record shows series of intense storms during eras of warmer sea surface temps

Staff Report

FRISCO — Climate researchers say New England’s coastal communities may need to prepare for major hurricane strikes sooner rather than later as the Atlantic Ocean continues to warm.

“We may need to begin planning for a category 3 hurricane landfall every decade or so rather than every 100 or 200 years,” said Jeff Donnelly, a scientist at Woods Hole Oceanographic Institution in Massachusetts, explaining that new research findings show that a string of giant storms pummeled the region during the first millennium, from the peak of the Roman Empire into the height of the Middle Ages. Continue reading

Climate research shows clear trend of more Midwest flooding during past 50 years

Warmer atmosphere means more moisture, more rain

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Missouri River flooding in July, 2011, via NASA’s Earth Observatory program.

Staff Report

FRISCO — After carefully reviewing data from hundreds of stream gauges, University of Iowa scientists say they’ve identified a clear trend of increasing floods during the past 50 years.

“It’s not that big floods are getting bigger, but that we have been experiencing a larger number of big floods,” said Gabriele Villarini, a civil and environmental engineer and corresponding author on the paper, published Feb. 9 in the advance online edition of the journal Nature Climate Change. Continue reading

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