The United States was just hit by its 11th named storm of the season, which has never happened before.

Hurricane Zeta made a dramatic landfall over southeast Louisiana as a top-end category two system on Wednesday afternoon. It crossed the coast not far from New Orleans with sustained one-minute winds of 177km/h near its core, less than 100km away from where Hurricane Katrina landed back in 2005.

Image: Visible satellite image of Hurricane Zeta prior to landfall on Wedneday. Source: NOAA

While there was plenty of warning that Zeta was coming, the hurricane's strength caught many by surprise.

The system has been described as an 'overachieving storm' for its unexpected intensification prior to landfall.

Hurricanes (same as tropical cyclones) typically draw their energy from warm oceans that need to be at least 26.5ºC near the surface. As long as the water is warm enough, and the atmosphere is in a favourable state, hurricanes will maintain or gain strength.

So, when Hurricane Zeta moved over cooler waters on its approach to the U.S. Gulf Coast, forecasters were expecting it to weaken.

But it didn't.

A unique set of atmospheric conditions, which involved a strong jet steam to the north and west of Zeta, and relatively light winds above Zeta, allowed the hurricane to gain strength even as it moved over cooling waters.

A margin of miles making a world of difference when it comes to the interaction of this big trough with #hurricane #Zeta. Instead of shredding #Zeta, it's venting #Zeta aloft. Instead of shearing it if it were closer, the diffluence/divergence aloft is helping to strengthen it. https://t.co/DiEKdULQea

— Kathryn Prociv (@KathrynProciv) October 28, 2020

Unfortunately, the fact that Zeta strengthened more than forecasters were anticipating meant that communities in its destructive path may not have been as prepared for its arrival as they could have been.

But while the extent of the damage caused by Hurricane Zeta will take some time to realise, it's already broken a number of records.

Zeta is the 11th named storm to make landfall in the U.S. Prior to 2020, the record for any one season was nine, which occurred in 1916.

It's also the strongest hurricane to cross the U.S. coast this late in the season since 1899.

Hurricane Zeta is the 27th named storm in the Atlantic Basin this season, which is the earliest date on record to achieve this milestone.