2017-18 Arctic cyclone season

The 2017-18 Arctic cyclone season is an ongoing event in polar cyclone formation over the Arctic basin. The season officially began on October 15, 2017 and will end on January 7, 2018, with the start date being moved up to October 15 due to the recent uptick in early-season activity. The season officially began with the formation of Subpolar Depression One early on October 4, 11 days before the official start of the season. This season will reuse the same naming list as the 2015-16 season two years earlier, with the exception of the retired name Noel.

The Bob Nekaro Weather Center (BNWC) monitors the basin including the Hudson Bay, the Baffin Bay, the Labrador Sea, the Atlantic north of 50 degrees North, and the North Sea.

Seasonal Forecasts
On July 21, the BNWC issued their initial seasonal forecast for the 2017-18 season, predicting below average activity with 5-8 named storms, 2-4 polar cyclones and 1-2 major polar cyclones. The prediction was based on higher-than-normal wind shear over the Arctic. On August 10, the Garfield International Hurricane Center released its forecast, predicting below-average activity with 5-6 named storms, 2-4 polar cyclones and 0-2 major polar cyclones. That same day, the Collin D Meteorological Center released its forecast, predicting 7-9 named storms, 2-4 polar cyclones, and 0-3 major polar cyclones. The BNWC issued an updated forecast on September 11, raising their numbers slightly as wind shear was not expected to be as strong in the Arctic basin as expected two months ago. That same day, HTMC released its prediction, predicting below average activity with 7-11 named storms, 3-5 polar cyclones, and 1-3 major polar cyclones. The NKWC released their prediction that day as well, predicting 11 named storms, 6 polar cyclones and 2 major polar cyclones. Floyd Meteorological Center also released their prediction on September 11, predicting slightly below average activity with 9-12 named storms, 3-7 polar cyclones and 0-3 major polar cyclones. On September 13, GIHC updated their forecast, raising their numbers to 9-12 named storms, 4-7 polar cyclones, and 1-4 major polar cyclones. On September 15, Money Hurricane Massachusetts Weather Service released their forecast, predicting 4-7 named storms, 2-3 polar cyclones and 1-2 major polar cyclones. On October 2, BNWC released their October forecast, raising their numbers to 9-13 named storms, 4-8 polar cyclones and 2-4 major polar cyclones. Conditions were not expected to be as hostile as expected in earlier forecasts. On October 2, HOWC released its forecast, predicting 12 named storms, 7 polar cyclones and 3 major polar cyclones. On October 17, CSHC released their first forecast for the season, predicting 11 named storms, 6 polar cyclones and 3 major polar cyclones.

Mid-season outlooks
On November 1, BNWC updated their numbers, raising their prediction to 11-16 named storms, 5-10 polar cyclones and 3-5 major polar cyclones, as more conducive conditions had emerged than originally predicted by forecast models, as well as a fast start to the season. On November 3, both FMC/PLS and PMC released outlooks, predicting near average activity. PMC issued an updated forecast on November 17, predicting above average to even hyperactive activity based on the fast start to the season. On November 20, BNWC issued their final forecast for the season, predicting above average activity.

Seasonal Summary
The 2017-18 Arctic cyclone season officially began on October 15, 2017, and will end on January 7, 2018. This is the third Arctic cyclone season to be monitored by the Bob Nekaro Weather Center.

October
Activity began before the season officially began for the third consecutive year. The first cyclone of the season, Subpolar Depression One, formed early on October 4 over the Labrador Sea. One became fully polar the next day, although it did not strengthen initially. The depression opened up into a polar wave and later regenerated into a polar cyclone on October 9, and was named Polar Storm Angel that day. Angel made landfall on Baffin Island on October 10, dissipating the next day. Three days after Angel dissipated, Polar Storm Bell formed over the southwestern Hudson Bay the day before the season officially began. Bell made landfall in Nunavut, Canada on October 16 and dissipated early on October 17. At 15:00 UTC on October 31, Polar Depression Three formed over the Baffin Bay.

November
At 03:00 UTC on November 1, Three strengthened into Polar Storm Candle, the third named storm of the season. Candle eventually strengthened into the first polar cyclone of the season 24 hours later. Candle made landfall in Northwestern Greenland late on November 2, dissipating early on November 4. Polar Depression Four formed over the Labrador Sea late on November 9, strengthening into Polar Storm Donner the next day. Donner then intensified into a Weak Polar Cyclone early on November 11, the second of the season. Donner transitioned into a Post-Polar Cyclone two days later.

Early on November 15, Polar Storm Eggnog formed over the Southern Hudson Bay. The next day, Fir formed over the Open Atlantic. Fir dissipated on November 17, while Eggnog intensified into a Weak Polar Cyclone and made landfall in Southampton Island, Canada. Eggnog then fluctuated in intensity for the next few days.

The current Accumulated Cyclone Energy (ACE) for the 2017-18 Arctic cyclone season, as of 21:00 UTC November 19, is 17.7 units.

Polar Storm Angel
The BNWC began monitoring the southeastern Labrador Sea for possible polar or subpolar development on September 29. At 00:00 UTC on October 4, the disturbance developed into a subpolar depression, the first of the season, 11 days before the season officially began. The depression moved slowly northwestward, transitioning into a fully polar cyclone by 18:00 UTC that same day. The polar depression failed to strengthen as its forward speed increased the next day, and at 12:00 UTC on October 6, the depression degenerated into a polar wave. The polar wave became better organized on October 7 as winds increased to polar storm force, although the remnants did not have a well-defined circulation at that time. The polar wave's circulation became better defined the next day, and it is estimated that the wave developed into Polar Storm Angel at 00:00 UTC on October 9. However, operationally, BNWC restarted advisories on Polar Depression One at 03:00 UTC on October 9, while it was located over the Davis Strait. It was operationally named six hours later. Angel strengthened slightly, peaking with maximum sustained winds of 50 mph and a minimum pressure of 1003 mbar by 18:00 UTC on October 9. Angel then began to weaken shortly thereafter, and made landfall in Baffin Island as a polar storm with maximum sustained winds of 40 mph and a minimum pressure of 1006 mbar. After landfall, Angel began to weaken, becoming a polar depression by 00:00 UTC on October 11. Angel dissipated over Baffin Island at 12:00 UTC that same day.

Polar Storm Bell
A broad area of low pressure over the southwestern Hudson Bay acquired sufficient organization to be classified as Polar Storm Bell at 15:00 UTC on October 14. Bell began to strengthen shortly after formation, eventually strengthening to peak intensity just under polar cyclone strength with maximum sustained winds of 70 mph and a minimum pressure of 989 mb at 03:00 UTC on October 16. Bell weakened slightly before making landfall in the Nunavut Province of Canada around 11:30 UTC on October 16, with maximum sustained winds of 65 mph and a minimum pressure of 994 mb. Bell then began to rapidly weaken later that day as it moved north-northwestward inland. Bell degenerated into a remnant low at 03:00 UTC on October 17.

Weak Polar Cyclone Candle
A polar wave developed into Polar Depression Three at 15:00 UTC on October 31, located over the Southern Baffin Bay. Twelve hours later, the depression strengthened into Polar Storm Candle. Candle gradually became better organized the next day, nearing polar cyclone strength by 21:00 UTC on November 1. At 03:00 UTC on November 2, Candle strengthened into a weak polar cyclone, becoming the first polar cyclone of the season. Candle made landfall at 23:55 UTC that day, east of Savissivik, Greenland, as a weak polar cyclone with maximum sustained winds of 80 mph. Candle then weakened to a polar storm by 03:00 UTC on November 3. Candle further weakened to a polar depression by 21:00 UTC that day, degenerating into a remnant low by 03:00 UTC on November 4.

Moderate Polar Cyclone Donner
On November 7, the BNWC began to monitor a slow-moving polar wave over the Eastern Labrador Sea for possible development. The system quickly organized, becoming a polar depression by 22:30 UTC on November 9. At 03:00 UTC on November 10, the depression strengthened into a Polar Storm and was assigned the name Donner. Donner began quickly intensifying that same day, becoming a Weak Polar Cyclone by 03:00 UTC on November 11 and a Moderate Polar Cyclone 12 hours later. Donner then began to slowly weaken early the next day as it moved into a less favorable environment, transitioning into a post-polar cyclone by 09:00 UTC on November 13.

Weak Polar Cyclone Eggnog
A broad area of low pressure developed over the Southern Hudson Bay in mid-November eventually organized into Polar Storm Eggnog by 03:00 UTC on November 15. Eggnog struggled to strengthen after formation due to marginally favorable conditions and the broad nature of the system, unexpectedly weakening to a polar depression by 21:00 UTC that same day. Eggnog regained polar storm intensity by 03:00 UTC on November 17, and began to strengthen. Eggnog rapidly intensified into a Weak Polar Cyclone by 03:00 UTC on November 18, with maximum sustained winds of 75 mph and a minimum pressure of 983 mb. Eggnog subsequently made landfall in Southampton Island at this intensity, and weakened to a polar storm later that same day.

Polar Storm Fir
A small area of low pressure developed into Polar Storm Fir at 15:00 UTC on November 16, while located over the open Northern Atlantic. Struggling with very dry air and moderate wind shear, Fir was not able to strengthen at all, eventually weakening to a polar depression by 15:00 UTC the next day and becoming a remnant low six hours later.

Names Used
This season will use the same Christmas-themed naming list as the 2015-16 Arctic Cyclone Season, with the exception of North, which replaced the retired name Noel.

Season effects
This is a table of all the cyclones that have formed in the 2017-18 Arctic cyclone season. Damage figures are denoted in millions of United States Dollars (USD). Death and damage totals also include totals when the cyclone was post-polar, a low, or a polar wave.