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’

Colorado weather lightning

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

Climate: Growing stream-flow variability threatens Chinook salmon spawning in Pacific Northwest

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Can Chinook salmon survive global warming?

Research documents more fall and winter flooding

Staff Report

FRISCO — Threatened Chinook salmon have been able to adapt to many changes over millennia, but climate change presents a big new threat, as many rivers around Puget Sound have seen bigger fluctuations in stream flows during the past 60 years.

“There’s more flooding in late fall and winter,” said Eric Ward, an ecologist at NOAA Fisheries’ Northwest Fisheries Science Center. “This is happening when the eggs are in the gravel or when the juveniles are most susceptible.”

More pronounced fluctuations in flow can scour away salmon eggs and exhaust young fish, especially when lower flows force adult fish to lay eggs in more exposed areas in the center of the channel. Continue reading

Climate: Study shows how smoke from distant wildfires can affect tornado formation

A tornado near Lakeview, Texas. Photo courtesy NOAA.

A tornado near Lakeview, Texas. Photo courtesy NOAA.

New study could help produce better tornado forecasting

Staff Report

FRISCO — Under certain conditions, wildfire smoke transported thousands of miles can intensify tornadoes in U.S., according to University of Iowa researchers, who studied how smoke from agricultural burning in Central America affected tornado conditions in the United States.

The research specifically looked at the smoke impacts on an April 27, 2011 tornado outbreak that spawned 122 twisters, killing 313 people, considered the most severe tornado event since 1950. Continue reading

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