Snowicanes Cometh

The year 2013 was the hurricane season that wasn't, despite dire predictions of expert climatologists.

What if you had a hurricane season and no hurricanes came? That's pretty close to what's happening this year, according to a report on climatecentral.org. The report points out that the 2013 Atlantic hurricane season has not produced a single land-falling hurricane in the United States. 

NOLA.com | The Times-Picayune reporter Mark Schleifstein pointed out in September that the 2013 Atlantic hurricane season was kicked off with dire warnings from the National Hurricane Center and Colorado State University climatologists Philip Klotzbach and William Gray that there would be an above average number of hurricanes and severe hurricanes. Those storms have failed to materialize. 

Instead, there have been just 11 named storms, two of which have been hurricanes, and none that have been major hurricanes.

After the Times-Picayune article, there was one more minor tropical storm, as the season ended as quietly as it had started, according to the Washington Post.

The 2013 Atlantic hurricane season was the least active in thirty years.  The season officially ends on Saturday, but in this lackluster year, it looks like we can wrap it up a little early. 

On average (1981-2010), 12 tropical storms form during an entire season, 6-7 of those go on to become hurricanes, and 2 of those reach major hurricane intensity (category 3+). In 2013, there were 13 tropical storms, 2 hurricanes, and no major hurricanes. Even the two hurricanes that formed were just briefly minimal category 1 storms. 

Tracks of all Atlantic tropical cyclones during the 2013 season.  Along the right side, the wind speed and central pressure are listed at the storm’s peak intensity.

The last time a season ended up with only two hurricanes was 1982, and the last season to have zero major hurricanes was 1994. The most intense storms this year had maximum sustained winds only reach 75 knots (Humberto and Ingrid). Dr. Phil Klotzbach, a researcher at Colorado State University, noted that is the weakest maximum intensity for a hurricane during a season since 1968. And you may recall that the first hurricane (Humberto) formed just hours before the record latest first hurricane formation date on September 11.

In terms of Accumulated Cyclone Energy, or ACE, the seasonal total stands at 31.1 (the units are 10,000 knots squared if anyone is curious), the lowest seasonal total since 1983… and that’s just 30% of average.  Looking back to 1950, only four other years come in with lower ACE totals: 1983, 1982, 1977, and 1972.

Accumulated daily ACE for all seasons going back to 1950. The average is the black line, 2013 is the red line, the four less active seasons are the green lines, and the rest of the years are the blue lines.

To put that in perspective, Hurricane Igor (2010) alone racked up about 140% of this season’s entire total.  Dr. Ryan Maue at WeatherBell keeps thorough statistics on ACE around the world, and this chart displays values of accumulated daily ACE for each season going back to 1950.Accumulated daily ACE for all seasons going back to 1950. The average is the black line, 2013 is the red line, the four less active seasons are the green lines, and the rest of the years are the blue lines. 

High expectations 

Heading into the season, all of the typical signals and precursors pointed forecasters to a fairly uniform conclusion: the season will be very active.  Forecast teams from CSU, NOAA, FSU, UK Met Office, Tropical Storm Risk, etc released their seasonal outlooks in late May to early June and every one of them was predicting about 7-9 hurricanes, and about 130-165% of an average season’s ACE.   Only ECMWF {European Center for Medium-range Weather Forecasting) predicted a slightly below-active season at about 80% of average ACE, although they also predicted 6-7 hurricanes.  Recall that the season has ended with just 2 hurricanes and 30% of the average ACE.Even among the groups that issue periodic mid-season updates and forecasts, the success rate was not any higher. 

Here in the northern Rockies we have arctic high pressure air masses; it's not tropical systems that are blowing things about. Sunday, just up the road at Bridger Bowl, the ridge experienced hurricane force wind gusts (topping out at 83 mph) to go along with subfreezing temperatures.

Hourly wind readings Bridger crest.

And along Michigan's upper peninsula, Lake Superior spawned a Snowicane.

Well defined eye created by a spinning mesolow over Lake Superior, Sunday December 15, 2013.

Meanwhile, we look forward to falling back into the deep freeze later this week back in Bozeman.

Good luck to all.