Hurricane season officially starts today, June 1, in the Atlantic Ocean. (NASA)

Today, June 1, marks the official start of the six-month Atlantic hurricane season. The season, which forecasters suspect will be a quiet one, will last through the end of November.

There are no active storms, and no hints of anything developing in the foreseeable future, but that is fairly typical for early June. On average, the bulk of the season ramps up in August, reaches a peak in September, then begins to slow down in October. Of course, individual seasons may not follow this timeline.


Climatological seasonal cycle of tropical cyclone activity in the Atlantic, broken down into three intensity categories.

There is a consensus among agencies that make seasonal hurricane forecasts that the 2015 season will be quieter than average, largely due to a strengthening El Niño which tends to enhance activity in the East Pacific and suppress activity in the Atlantic. But if you’re in Wilmington, Miami, New Orleans, or any hurricane-vulnerable city along the coast, the overall number of storms should not concern you, because it only takes one. Now is the time to prepare basic materials and plans, not when a storm threatens.

[NOAA calls for below-average hurricane season, but emphasizes preparedness]

names

The 2015 list of storm names for the Atlantic is shown here, and of the 21 names, 14 are still from the original 1979 list.  There are no new names this year, since none were retired after the 2009 season. We already had Tropical Storm Ana form in early May, so the next names on deck are Bill, Claudette and Danny.

The “drought” of major hurricane landfalls in the U.S. continues deeper into record-setting territory. The last major hurricane (category 3 or stronger on the Saffir-Simpson scale) to strike the U.S. was Wilma, which hit the southwestern Florida peninsula on Oct. 24, 2005.  However, that is not to be interpreted to mean that there has not been much “action” in the Atlantic since then.


Chart showing the number of days between U.S. major hurricane landfalls, from 1900-2015. (modified from http://rogerpielkejr.blogspot.com/)

The U.S. has been struck by seven category 1 or 2 hurricanes (eight if you include Sandy, which was not technically a hurricane at landfall) since then, some of them quite destructive and deadly. Furthermore, there have been 25 major hurricanes in the Atlantic since Wilma, and nearly half of them made landfall (or a very close encounter), just not on the United States. Countries to our south such as Cuba, Mexico and the Bahamas certainly have not had the same good fortune as we have these past ten years.

[Study says major hurricane drought is just “dumb luck"]

How long will the streak last? Hurricanes do not have any memory of where they’ve hit, or any built-up pressure by not hitting a particular location, so the concept of being “overdue” does not apply. The U.S. is not overdue, it has just been lucky, and the luck could end this year, or continue for yet another year.

Even during relatively quiet seasons, very notable hurricane landfalls can happen. Suppose there are only three hurricanes in the entire season but all three of them make landfall near Houston — it will still be an inactive season, but one that will be very memorable there!

There are a few new products available from the National Hurricane Center this season. For storms approaching the U.S. coast, storm surge watches and warnings will now be issued. This can be different from the areas under a hurricane watch or warning, and should prove to be a very valuable separate product. Storm surge is the number one killer in hurricanes, ahead of rain, surf and wind.

Sample storm surge watch and warning map, based on last year's Hurricane Arthur. (NOAA)
Sample storm surge watch and warning map, based on last year’s Hurricane Arthur. (NOAA)

In the past, the National Hurricane Center’s 5-day tropical weather outlook has been available by text, and the graphical outlook historically covered out to two days. This year, 2-day and 5-day graphical outlooks are available. This map shows the locations of any existing disturbances and the areas in where they could develop, as well as areas to monitor for possible formation. The areas are shaded by probability of formation within the next two or five days.


Example 5-day graphical tropical weather outlook. (NOAA)

Also, each season, the “cone of uncertainty” changes size. The cone’s size is based on actual track forecast errors averaged over the previous five seasons (2010-2014, in this case) and will be the same size for all storms this season. Most importantly, note that the cone does not include any information on impacts or storm size. The cone is designed to show a two-thirds probability of where the center of the storm will track, based on errors from the past five years. There is still historically a one-third probability that the center could track outside of the cone. Damaging impacts such as wind, rain, and storm surge will likely extend hundreds of miles away from the center, well outside the cone, even with a perfect track forecast.


Comparison of the “cone of uncertainty” for this year (red) and from 2009 (green).

Although not new this season, I want to highlight two other extremely useful products that are relatively new: the storm surge flooding map and the wind speed probability map. Examples of each are shown here.


Examples of the storm surge flooding map (left) and the wind speed probability map (right). (NOAA)

Throughout hurricane season, check in with the Capital Weather Gang for updates and outlooks on developing and active storms!