On Monday evening, forecasters at the National Hurricane Center determined that a low pressure system in the Atlantic Ocean had sustained winds of 40mph, and therefore should be named Subtropical Storm Andrea. This was the first named storm of the 2019 Atlantic season, and it could bring some moderate rainfall to Bermuda on Wednesday before dissipating.

Officially, the Atlantic hurricane season does not begin until June 1, and notionally ends on Nov. 30. However, the formation of Andrea marks the fifth year in a row—dating to Tropical Storm Ana in 2015—that a named storm has formed before June 1.

This is unprecedented. According to Phil Klotzbach, a hurricane scientist at the University of Colorado, the development of Andrea breaks the previous record of four consecutive years with a pre-June storm formation. The former record was set from 1951 through 1954, he told Ars. The total of seven pre-June storms this decade, the 2010s, has also tied the number recorded in the 1950s.

"I'm honestly not sure what exactly was going on in the 1950s to cause so many storms to be named during that decade," he said.

So what is going on? While some scientists have suggested that warmer oceans may cause a lengthening of hurricane seasons in the Atlantic and other basins, the interplay between hurricane activity and climate science is complex. There is no definitive answer as to whether the June 1 "beginning" of the Atlantic hurricane season should be brought forward.

In this case, Klotzbach said he thinks a lot of the reason for the heightened activity in the past decade is due to continued improvements in technology to detect storms and provide wind speed data. Given the overall rarity of such storms, it is difficult to discern any reliable decadal or multi-decadal variability—but that may be a factor as well, he said.

As for the rest of this hurricane season, Klotzbach will update his seasonal forecast in a couple of weeks. Earlier, he predicted slightly below normal activity in the Atlantic due to a number of factors, including the potential for an El Niño event to increase wind shear and disrupt storm formation. That would, of course, be most welcome during the heart of the Atlantic season in August, September, and October.