The 2018 hurricane season was full of extremes. Here’s what we expect in 2019.

Both the Atlantic and Pacific areas saw a record number and intensity of storms.

Hurricane season is over at long last—a lengthy one for both the Atlantic and Pacific regions. The Atlantic saw two historic hurricanes make landfall in the United States, while the eastern Pacificsaw the greatest number of scale-topping storms on record. The stories of the two ocean basins are divergent lessons in how a hurricane season can land in the record books.

The Atlantic Ocean saw fifteen named storms this year, which is a few ticks above the average twelve. Eight of those storms went on to become hurricanes, and two of them—Florence and Michael—reached major hurricane status. Hurricane Florence made landfall in North Carolina and crawled its way inland with historic rains before the storm lifted away a few days later. Hurricane Michael reached the Florida Panhandle as one of the strongest storms ever recorded at landfall in the United States, packing winds just a hair below category five status.

The Pacific Ocean’s hurricane season was a much different story. This basin saw the most intense hurricane season ever recorded. The basin saw 22 named storms between the eastern and central parts of the Pacific, stretching from the west coast of Mexico to the Hawaiian Islands. The season saw a record-breaking ten hurricanes reach category four or five on the Saffir-Simpson Hurricane Wind Scale. Despite the high number of intense storms, fortunately, relatively few of them managed to make landfall. Hurricane Lane came extremely close to making landfall in Hawaii as a strong hurricane, and Hurricane Willa did make landfall near Mazatlan, Mexico, as a major hurricane.

The best way to measure the strength of a hurricane season isn’t to count the number of storms that form, but to take into account their strength and how long they last. That’s where Accumulated Cyclone Energy comes in. This value considers a storm’s maximum sustained winds and how many hours the event lasts. Stronger storms that last longer have higher ACE values than weak storms that quickly peter out.

The Pacific hurricane season saw a total ACE of 316.3, which blows away the basin’s previous record set in 1992. For perspective, the Atlantic Ocean has never seen a season’s total ACE exceed 259, which is a testament to the absolute strength and longevity of the storms that formed in the Pacific this year.

All the right ingredients came together to allow the Pacific to churn out one storm after another. The hyperactivity was likely influenced at least in part by a developing El Niño, the warm waters of which generate thunderstorms that seed the development of tropical cyclones and also provide those storms the fuel they need to strengthen.

The Atlantic hurricane season also finished with an above-average ACE thanks in large part to just three storms. It’s much harder for storms to find the perfect conditions to grow into monsters in the Atlantic Ocean because there are more opportunities for things to go wrong. Tropical cyclones require persistent thunderstorms, warm waters, tropical air, and low wind shear. There’s usually too much—or too little—of at least one of those factors in the Atlantic, which makes it difficult for storms to develop and then sustain themselves at full strength for very long.