(University of Miami)

The 2016 hurricane season “officially” begins on Wednesday, June 1 — but this year it’s off to a running start.

The official season spans June through November, which simply encompasses the majority of storms during an average year. It doesn’t necessarily catch all of the hurricane activity.

Back in mid-January, we had the first hurricane of the season: Alex. And just this past weekend Tropical Storm Bonnie formed and made landfall on South Carolina, the first U.S. tropical cyclone landfall since June 16th, 2015 when Tropical Storm Bill hit Texas.

The last major hurricane, Category 3 or stronger, to hit the United States was Wilma in October 2005 — over 3,800 days ago. There have been nine U.S. Category 1-2 hurricane landfalls since then (if we include Sandy) with the strongest being Hurricane Ike in 2008.

But this gap is not for a lack of storms. Since the 2005 ultra-active season, 25 major hurricanes and about 12 major hurricanes have made landfall in areas south of the U.S.

Gaps between major hurricane landfalls on the United States. The current streak is the longest on record.

Florida, a state that is historically no stranger to hurricanes, has not had a hurricane of any intensity impact the state since 2005 (also Wilma), which smashes the previous “hurricane-free” period of about six years.

Gaps between hurricane landfalls on Florida. The current streak is the longest on record.

These post-2005 gaps are basically just luck. Major hurricanes have hit other countries, and lower-category hurricanes have hit other states — there’s no physical reason why both of these amazing records should be co-existing. One of these years, both streaks will end and be reset.

Seasonal outlook

NOAA just released its updated seasonal forecast last Friday, Colorado State University releases its on Wednesday, and several other agencies and companies have done the same over the past couple of months. The consensus is that we can expect a near-average to slightly above-average season in terms of overall activity.

There are no overwhelming patterns as of now that suggest an extremely suppressed or enhanced season, but as the recent strong El Niño decays, La Niña is forecast to take its place by the heart of hurricane season. Historically, hurricane activity is about 70 percent higher during La Niña compared to El Niño.

However, regardless of how active or inactive a season is, a single landfalling storm makes it a really bad season for that location. It really only takes one.

Historical relationship between Atlantic ACE and ENSO phase. The gray bars represent one standard deviation.

New Products

Storm surge watches and warnings will be issued when needed. Although this capability was introduced last year, it never had the opportunity to get put into action. The Saffir-Simpson hurricane wind scale only describes the peak sustained wind found somewhere in the hurricane, and storm surge is far more complex than that. Storm surge, the rise of water along coasts caused by onshore winds, is also sensitive to the storm’s size, coastal topography, and offshore bathymetry, among other factors. In the United States, a hurricane’s storm surge is about six times deadlier than its winds, so it makes sense to treat storm surge as the serious danger that it is.

A prototype of the storm surge watch and warning interactive maps. (NOAA)
A prototype of the storm surge watch and warning interactive maps. (NOAA)

The National Hurricane Center’s “cone of uncertainty” will be smaller again this year.

Each year, the cone is re-sized based on the previous five years of NHC forecast errors. Contrary to popular belief, the cone size is not designed to show where the impacts will be felt, it is only designed to show an average uncertainty of where the center of the storm is forecast to go with a 2/3 probability, so there is still a 1/3 historical probability that the storm center will track outside of the cone.

If the track forecasts were always near-perfect, the cone would be pencil-thin, but impacts such as flash flooding, storm surge, tornadoes, etc will certainly still be experienced far from the cone. The same reasoning holds for the current state of forecasting and cone size: a smaller cone does not mean storms are getting smaller!

Since the five-day forecast cone debuted in 2008 (prior to that it only covered three days), the cone is 22 percent smaller at the five-day position, and 27 percent smaller at the one-day position.

A comparison of the five-day “cone of uncertainty” from 2008 and 2016. (original image from NOAA, 2008 cone added by the author)

Realistically, not all storm tracks are equally predictable, but for now, the same cone size is used all season long for every storm and every forecast. There will (hopefully) come a time when the cone size dynamically adjusts depending on the actual atmospheric conditions — larger for trickier forecasts and smaller for more certain forecasts.

Since Alex and Bonnie are already on the books, the next name on the list is Colin. Two new names on the list are Ian, which replaces Igor (2010), and Tobias, which replaces Tomas (2010). This particular list was first used in 1980, and of the 21 original names, 13 remain. The record earliest known formation date for the third tropical storm is June 12 (1887), so if another storm should happen to form in the next 11 days, it will break that record!