Weeks into a global health emergency that has virtually brought the world to a halt, the Republic of Vanuatu is dealing with another calamity: a monster tropical cyclone that struck at an intensity equivalent to a Category 5 hurricane. The cyclone, named Harold, rammed into the archipelago Monday, packing sustained winds up to 165 mph.

Vanuatu is a series of 83 islands nestled about 1,200 miles east of Brisbane, Australia, and 750 miles west of Fiji. The nation is sometimes struck by earthquakes and tropical cyclones, but Harold was on the high-end of tempests that occasionally batter the islands. While referred to as a cyclone in the western Pacific Ocean, the storm is no different from a hurricane

Harold is the strongest storm to strike Vanuatu since 2015′s tropical cyclone Pam, which also had 165-mph sustained winds and caused $380 million in damage.

According to the BBC, at least 27 people were killed in the nearby Solomon Islands during Harold’s weekend passage after a ferryboat on which they were traveling succumbed to the ferocious seas.

Thereafter, Harold rapidly intensified before striking Espiritu Santo and Malo islands in Vanuatu at Category 4 status on Monday. Harold continued to spike to Category 5 strength as it barreled into Pentecost Island on Monday night local time.

Hardest hit were likely parts of Pentecost Island near the community of Bunlap. The island has a population of nearly 17,000 and suffered a direct hit of the cyclone’s eyewall — which likely featured winds topping 160 mph, a potentially devastating storm surge, torrential rainfall and a barrage of lightning. No word on casualties was immediately available.

Officials on Vanuatu were already preparing the island nation for the ongoing global health crisis associated with covid-19. While there were no confirmed cases of the novel coronavirus across the country, the widespread pandemic in Australia and other regional nations was expected to make the mobilization and relief of foreign aid that much more challenging for small island nations.

After exiting Vanuatu, Harold is forecast to remain over mainly open waters of the South Pacific though Tuesday, after which the storm could skirt Fiji.

The storm has been around for only a week, but Harold stunned forecasters on multiple fronts. The cyclone earned its name on Thursday, spending most of Friday as a Category 1 equivalent before lurching to Category 4 strength on Saturday.

Following its bout of rapid intensification, Harold briefly faltered to Category 3 status before attaining high-end Category 4 status once again as it charged toward Vanuatu on Monday (Sunday night Eastern time). Later on Monday, it underwent one final burst of strengthening, catapulting to Category 5 intensity.

Assisting in its rapid intensification were unusually warm sea surface temperatures and a reduction in the amount of wind shear in the atmosphere. Wind shear is a change of wind speed or direction with height. An abundance of shear can tear apart or disrupt a storm’s circulation, while the absence of shear can encourage episodes of speedy strengthening.

Water temperatures in that part of the world are also up to 2.5 degrees Fahrenheit (1.5 degrees Celsius) above average, adding fuel to the storm. Studies have shown an increase in rapid intensification events in recent decades as ocean temperatures have warmed due to climate change.

The evolution of Harold’s landfall in Vanuatu

Harold and its eyewall, the zone of most destructive winds surrounding its calm center, first directly struck southern areas of Espiritu Santo as well as Malo. The interaction with land briefly weakened the storm and disrupted its structure.

But when it reemerged over water, Harold’s disheveled eye rapidly cleared out as intense thunderstorms blossomed in the eyewall. Over the next six hours, Harold would again strengthen from a 135-mph storm to at least a 165-mph Category 5 monstrosity as it aimed directly toward Pentecost Island.

As the storm rapidly intensified, its eyewall began churning out prolific lightning strikes, unusual for most tropical cyclones and a sign of rapid intensification. In fact, developing such a ring of dense lightning activity — know as the enveloped eyewall lightning (EEL) signature — is common in only the most extreme storms.

Vaisala, a company that operates a global lightning network, detected 23,000 lightning strikes from Harold in the last 24 hours.

Pentecost Island was impacted on Monday night local time with extreme Category 5 winds, a likely devastating storm surge, an anticipated 8 to 10 inches of rain and possible tornadoes.

Jason Samenow contributed to this report.