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9 hours ago
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A disturbing weather pattern could wreak havoc across the US at the end of this year's hurricane season, experts have warned.
November tropical storms may be affected by La Niña, according to Matthew Rosencrans, the lead hurricane seasonal forecaster with the National Oceanic and Atmospheric Administration (NOAA).
La Niña is part of a natural climate cycle known as El Niño-Southern Oscillation Neutral (ENSO), which alternates between warmer and cooler seawater along the equator in the Pacific Ocean.
During a La Niña event, trade winds are stronger than usual, pushing warmer water westward while colder water then rises to the surface off the west coast of North America. These cold waters on the west cause a northward jet stream.
The pattern can lead to drought in the southern US but also heavy rains and flooding in the Pacific Northwest of the country, according to the NOAA's Ocean Service.
'La Niña conditions are associated with [roughly double the amount of] activity in November when compared to ENSO and especially when compared to Novembers with El Niño conditions,' Rosencrans told USA TODAY.
An El Niño brings the opposite effect, with warmer Pacific waters that typically suppress Atlantic storm activity.
A La Niña is predicted to be heading to the US in November and could cause heavy rain and flooding
While La Niña is potentially treacherous, the pattern is natural and is an interconnected part of the climate cycle known as El Niño-Southern Oscillation
The latest La Niña is predicted to be weaker than previous patterns and fairly short-lived. However, it should not be underestimated.
Jon Gottschalck, the chief of the Climate Prediction Center's operational prediction branch, said: 'Even though it is considered a weak event, likely shorter than normal in duration, its impact is likely to be strongest during the winter season and so plays a large role in the outlooks.'
Even a mild La Niña can potentially lead to extreme weather.
A typical La Niña winter can bring cold and snow to the Northwest and unusually dry conditions to most of the southern states, according to the Climate Prediction Center.
In areas such as Southern California, dry conditions caused by a La Niña can cause a horrific fire season if precipitation fails to arrive.
Scientists from the National Oceanic and Atmospheric Administration (NOAA) use various tools to monitor and forecast temperature changes in the Pacific Ocean, including satellites, sea level analysis, and moored, drifting and expendable buoys.
A La Niña appears when cool water on the ocean's surface is present; the opposite conditions would then cause an El Niño system
This can lead to drought in the southern US but also to heavy rains and flooding in the Pacific Northwest
The latest La Niña is expected to be weaker than previous patterns and fairly short-lived. However, it could still cause extreme weather
'Predicting the onset of a warm or cold phase is critical in helping water, energy and transportation managers, and farmers plan for, avoid or mitigate potential losses,' the NOAA said.
'Advances in improved climate predictions will also result in significantly enhanced economic opportunities, particularly for the national agriculture, fishing, forestry and energy sectors, as well as social benefits.'
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