Hurricane-vergence: Katrina's 10th Birthday, New Tropical Storm, UCI-NASA Link Fires

As if on cue, the 10th anniversary of Hurricane Katrina is coming as weather forecasters reveal a tropical storm may become the first hurricane of the 2015 North Atlantic season while UC Irvine and NASA unveil research showing a strong link between high wildfire risk in the Amazon basin and the devastating hurricanes that ravage North Atlantic shorelines.


“Hurricane Katrina is indeed part of this story,” says James Randerson, Chancellor's Professor of Earth system science at UCI and senior author on the paper that appears in the journal Geophysical Research Letters near the 10th anniversary of Katrina's calamitous August 23-31, 2005, devastation of New Orleans and surrounding areas.

“The ocean conditions that led to a severe hurricane season in 2005 also reduced atmospheric moisture flow to South America, contributing to a once-in-a-century dry spell in the Amazon,” Randerson continued. “The timing of these events is perfectly consistent with our research findings.”

Lead author Yang Chen discovered that in addition to the well-understood east-west influence of El NiƱo on the Amazon, there's also a north-south control on fire activity that's set by the state of the tropical North Atlantic. Warm ocean waters help hurricanes develop and gather strength and speed on their way to North American shores. They also tend to pull a large belt of tropical rainfall–known as the Intertropical Convergence Zone–to the north, drawing moisture away from the southern Amazon and leading to heightened fire risk over time, according to Chen.

“North Atlantic hurricanes and Amazon fires are related to one another through shared linkages to ocean-atmosphere interactions in the tropical Atlantic Ocean,” he said.

Douglas Morton of NASA's Goddard Space Flight Center in Greenbelt, Md., and a study co-author says, “The synchronization of forest damages from fires in South America and tropical storms in North America highlights how important it is to consider the Earth as a system.”

Randerson believes the study may help meteorologists develop better seasonal outlooks for drought and fire risk in the Amazon, while also giving policymakers throughout the hemisphere a basis for decisions about coastal protections in hurricane-prone areas and fire management in drought-affected areas.

“The fires we see in the U.S. West are generally lightning-ignited, whereas they're mostly human-ignited in the Amazon, but climate change can have really large effects on the fire situation in both regions,” Randerson said. “Keeping fire out of the Amazon basin is critical from a carbon-cycle perspective. There's a huge amount of carbon stored in tropical forests; we really want to keep the forests intact.”

Tropical Storm Danny became a tropical depression on Tuesday morning and could become a hurricane on or before Thursday as the system continues to move through favorable atmospheric conditions in the short term, according to Accuweather's Expert Meteorologist Alex Sosnowski.

The system moved westward across Africa during the first part of August and continues to move westward this week at 10-15 mph.

“Showers and thunderstorms continue to spiral around an area of circulation and organization seems to be increasing as this feature moves through favorable conditions during the middle days of this week,” says AccuWeather Meteorologist Jordan Root.

Much of the islands in the Caribbean Sea are in drought and would trade the inconvenience and hazards that a tropical storm would bring for rainfall, according to the experts, who note even a poorly organized tropical depression or storm could bring an uptick in drenching showers.

Meanwhile, another significant area of disturbed weather is forecast to soon emerge off Africa later this week, forecasters say.

AccuWeather is predicting eight tropical storms, four hurricanes and one major hurricane for the 2015 season with two to three landfalls in the United States, Sosnowski says.

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