For the fourth time in just over a year, the North Pole may near the melting point in winter, a previously rare event.

The textbook comma-shape storm is sprawling. The northern part of its core is near the southern tip of Greenland, while its trailing front extends southwestward almost to the tropics. On Sunday, the National Weather Service said it packed winds of over 90 mph (80 knots) near its center. Computer models suggest the storm has generated towering waves that exceed 46 feet southeast of its core.

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The storm was likely near peak intensity early Monday, with a minimum pressure of 932 millibars — a common reading in Category 4 hurricanes and ranking among the top tier of winter storms in this region.

The strongest North Atlantic winter storms on record, from December 1986 and January 1993, had even lower pressure of 900 and 916 millibars (the lower the pressure, the stronger the storm). A powerful storm in late December 2015, which also sent unusually mild air into the Arctic, had a pressure of 928 millibars.

This year’s storm is expected to weaken over the next few days but “is part of an overall pattern that is advecting warm, moist air poleward,” explained Ryan Maue, a meteorologist with WeatherBell Analytics.

Maue said the storm is teaming with a strong area of high pressure over northern Europe in forcing an onslaught of mild air toward the North Pole through the Barents and Kara Seas.

Temperatures in Svalbard, Norway — an island located approximately midway between continental Norway and the North Pole — are forecast to be 27 to 36 Fahrenheit (15 to 20 Celsius) warmer than normal for much of the upcoming week.

On Thursday, areas near the North Pole are predicted to be 50 to 60 degrees warmer than normal (which is around minus-30), which is near the melting point. This may mark the third occasion since November and the fourth time in just over a year that temperatures have warmed to this uncommon winter level near the Pole.

A recent study in the scientific journal Nature said that since the late 1950s, warmth of this intensity has only occurred about once or twice a decade. Due to a reduction in sea ice and warming winter temperatures, such warm events are expected to increase in frequency, the study said.

The remarkably mild 2016-2017 winter in the Arctic seems to suggest this increase in warm spikes has begun in earnest.