When NOAA forecasters predicted a below-average Atlantic hurricane season for 2026, they were careful to add a standard caveat: it only takes one storm. Tropical Storm Bertha, churning toward the US Gulf Coast on Tuesday with 65 km/h winds and potential storm surge, is illustrating that principle in real time.
The National Hurricane Center expects Bertha to make landfall near New Orleans, Louisiana, by Wednesday, carrying heavy rainfall, isolated tornadoes, and a storm surge of 1 to 4 feet (30 to 120 cm) along portions of the Louisiana and Mississippi coasts. The NHC has warned of a “life-threatening storm surge” in watch areas extending from the Ochlockonee River in Florida to the Jefferson-Plaquemines Parish border in Louisiana.
Bertha is only the second named storm of the 2026 season, after Tropical Storm Arthur brought flooding to the US last month. Its modest wind speed, barely tropical storm force, could lead some to underestimate it. But the storm’s slow crawl northwest at roughly 5 km/h means sustained rainfall over the same areas. Some locations could see up to 20 cm (8 inches) by Friday, and slow-moving storms are notoriously difficult to forecast for precise rainfall totals because small shifts in track double or halve the accumulation at any given point.
The El Niño paradox
The 2026 season was forecast to be quieter than average because of a developing El Niño event in the Pacific. El Niño typically suppresses Atlantic hurricane activity by increasing vertical wind shear, the change in wind speed and direction with altitude, which tears apart developing thunderstorms before they can organize into cyclones.
NOAA’s May outlook gave a 55% chance of below-average activity, citing El Niño as the primary driver. The Colorado State University team issued a similar prediction.
But El Niño is not a guarantee of quiet seas. It reduces the total number of storms but does not eliminate them, and the ones that do form can still be dangerous, especially if they are slow-moving, rain-heavy systems rather than the fast-moving wind machines that make headlines.
“Because El Niño exerts such a massive influence on global weather, scientists have poured immense effort into understanding how it behaves,” said Hosmay Lopez, an oceanographer at NOAA’s Atlantic Oceanographic and Meteorological Laboratory. “Today we can predict it months in advance. Yet, because nature always holds surprises, large uncertainties remain.”
What makes Bertha serious
The storm’s threat profile is dominated by water, not wind. The surge, ocean water pushed ashore by the storm’s circulation, could push deep inland through the low-lying Mississippi River delta. New Orleans officials have begun distributing sandbags and asking residents to clear storm drains. The city’s pumping system, rebuilt and upgraded after Hurricane Katrina in 2005, will face its first test of the season.
Flash flooding is the primary concern in urban areas across Florida’s Panhandle, Alabama, Mississippi, and Louisiana. The eastern semicircle of a Northern Hemisphere tropical cyclone typically carries the heaviest rain, and Bertha’s slow motion compounds the risk by parking convective bands over the same areas for hours.
The storm is forecast to weaken to a tropical depression by Thursday and may dissipate by the end of the week as it nears the Texas coast. But that outcome depends on the exact track and the interaction with an upper-level trough forecast to approach from the west, details that will only become clear hours before they happen.
The outlook beyond Bertha
El Niño events tend to intensify through the fall, meaning the peak months of the hurricane season (August through October) could see even stronger suppression of storm formation. But the 2026 season has already made its point: a below-average seasonal forecast is not a guarantee of safety, and the margin for preparedness error is exactly the same whether the season has 8 storms or 18.