El Niño predicted to flood both coasts: Here’s where risk is highest

(NEXSTAR) – El Niño is expected to reach its peak this winter, bringing heavy snow to some states, unseasonably warm temperatures to others and flooding to the coast. NASA scientists say the risk of flooding is actually increasing along the West and East coasts this winter, but for different reasons.

On the West Coast, a strong El Niño will cause even more storm surge flooding. The probability of a “strong” El Niño occurring this year is over 55%. With about a 35% chance, it could even be one of the strongest ever, like what we saw in 2015-2016 and 1997-1998.

According to , extreme storm surges called “king tides” typically don't hit the West Coast except in El Niño years. NASA's Sea Level Change Science Team. But this winter, cities like Seattle and San Diego could experience up to five once-in-a-decade floods in a single season.

“A 10-year flood is a flood that has a 1 in 10 chance of occurring in a given year,” NASA explains. More severe flooding of this type is expected to become more common in coming decades due to climate change.

Rudy Sales (center) stands in the midst of a tidal wave that washes over San Francisco's Embarcadero on Wednesday, January 11, 2017. (AP Photo/Jeff Chiu)

In addition to increasing the chance of spring tides, California is expected to have a wetter-than-usual winter, which could cause problems for low-lying roads and buildings.

On the East Coast, an analysis by the National Oceanic and Atmospheric Administration found: El Niño causes storm surge flooding Mid-Atlantic states are unaffected, while areas further north and along the Gulf Coast are less affected.

But NASA sea surface researcher Ben Hamlington says these areas won't be fully revealed this winter.

The additional storm surge flood days above the storm surge flood days due to sea level rise (shown in the left panel) are based on the nine-month averaged 2023-24 El Niño forecast. Ocean Niño Index (ONI) Value is 1.2 degrees Celsius (Credit: NOAA graphic, adapted from original by Billy Sweet)

“El Niño could cause further flooding along the Gulf and Southeast coasts this winter, Hamlington explains. “But the reasons for that are different than along the West Coast, where sea levels themselves are rising.”

In the Gulf Coast and Southeast, El Niño storms that bring large amounts of rain over short periods of time increase the risk of flooding.

A wide range of states from Louisiana to the Carolinas are expected to experience above-average precipitation this winter.

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