It's Hurricane Season. (Again.) Here's What To Expect Heading Into The Summer Months.

Well...here we are. Even though the de facto beginning of the Atlantic hurricane season came on May 15, and we’ve seen our first named storm already, this week is still the official start of the season on paper. Forecasters expect above-average activity in the Atlantic Ocean this year. While we probably won’t come close to matching last year’s all-time record of 30 named storms, even one storm is bad news if it hits land.

The Forecasts

An average Atlantic hurricane season produces 14 named storms, about half of which become hurricanes and a few of those strengthen into major hurricanes. This 30-year average includes both hyperactive years (2005 and 2020) and relatively quiet years (2014 and 2015) alike.

Forecasters (see CSU and NOAA for examples) generally expect an above-average hurricane season this year. These forecasts are based on a variety of trends in long-range models, including water temperatures in the eastern Pacific, water temperatures in the Atlantic, and other factors like overall wind and pressure patterns.

One annoying feature of these long-range forecasts is that they predict a specific number of storms. Ignore the numbers. There’s not much anyone can do to alter their hurricane preparedness based on whether we’re expecting 14 named storms or 17 named storms. Even one storm poses a grave threat to safety and property if it approaches land.

The Niño

El Niño and La Niña get huge billing at the beginning of a hurricane season. There’s lots of talk about it, but little talk about why it’s important.

It seems counterintuitive, but water temperatures in the eastern Pacific matter for storms over in the Atlantic because of the El Niño-Southern Oscillation (ENSO), which produces El Niño and La Niña events. El Niño describes warmer-than-normal waters in the eastern Pacific, while those same waters are colder-than-normal during a La Niña.

These temperature anomalies can affect weather patterns over the region, which in turn influences the potential for tropical development over the Atlantic Ocean. El Niño events often lead to destructive wind shear flowing over the Atlantic that nips developing tropical cyclones in the bud, while La Niña events can suppress wind shear and remove a major obstacle to tropical development in the Atlantic.

The latest projection from the Climate Prediction Center calls for ENSO-neutral conditions to persist through the summer months, with water temperatures right around normal for this time of year and neither El Niño nor La Niña present. The Atlantic tends to see healthy tropical development during ENSO-neutral conditions, so that factors into the forecasts.

The NHC

The National Hurricane Center’s website should be one of your first visits in the morning if you live anywhere near the coast. (Let’s be honest...if you’re reading this, it probably already is. Good on you.)

Hurricanes.gov is responsible for providing information about tropical cyclones in the Atlantic, the eastern Pacific, and the central Pacific basins, which covers everyone from Hawaii to Portugal.

The agency issues daily tropical weather outlooks at 2:00 AM/PM and 8:00 AM/PM Eastern every day between May 15 and November 30. Tropical weather outlooks cover potential tropical development over the next five days, with the option for more additional updates as needed. These should be required reading during the summer and fall months.

Once the NHC initiates advisories (forecasts) on a storm, forecasters will release new advisories at 5:00 AM/PM and 11:00 AM/PM Eastern for the duration of the system. If there are any watches or warnings in effect for land, they’ll issue intermediate advisories in between full advisories, giving us updates on the storm every three hours. (All times are an hour earlier once we set the clocks back in the fall.)

Each full advisory offers plenty of written and graphical information about storms, including:

• A three-day and five-day forecast map for the storm’s path and intensity
• Watches and warnings for land near the storm’s path
• The current extent of tropical storm force/hurricane force winds
• The estimated and likely arrival times of tropical storm/hurricane force winds
• Wind speed probabilities for locations along the storm’s predicted path
• Storm surge forecasts for coastal areas in the United States

The Cone

The single most important product to understand is the cone of uncertainty.

The cone of uncertainty is the historical margin of error in the National Hurricane Center’s forecast track. The center of the storm stays within the cone of uncertainty about 66 percent of the time, which means it tracks outside of the cone the remaining one-third of the time.

It’s so important to understand the cone of uncertainty because it gives us a clue of where the storm could travel based on errors made in past hurricane forecasts. Forecasters calculate the extent of the cone using forecast errors from the previous five years, so 2021’s forecast errors include the 2016-2020 hurricane seasons.

The cone is actually a radius drawn around each of the eight timesteps in the forecast period—12 hours, 24 hours, 36 hours, 48 hours, 60 hours, 72 hours, 96 hours, and 120 hours.

The error is smaller at 12 hours than it is at 48 hours, and the error smaller at 48 hours than it is at 120 hours. This year, the error at 12 hours is 31 miles while the error at 120 hours is 230 miles. All of these circles get smoothed out and joined together so they create one cone that’s narrow at the beginning of the forecast and large at the end of the forecast, visualizing the potential for error in the track forecast.

Even though the cone looks pudgy on some forecasts and super narrow in others, the margin of error always remains the same throughout the season. The shape of the cone depends on the speed and shape of the forecast track. A slower forward speed or a curvy track will result in a shorter and thicker cone because the error circles around each timestep overlap with one another.

Some forecasts are easier to nail than others. Last year’s Hurricane Laura is a great example of a storm that falls on both ends of the spectrum. The storm’s forecast track was tough to pin down early in its existence when it was weak and there were lots of factors pushing and pulling on the storm, but the NHC's forecast came within a few miles of its landfall point in southwestern Louisiana within more than three days before the category four hurricane moved ashore.

The Names

Names are the most important non-issue when it comes to a tropical storm or hurricane. The system of naming hurricanes is occasionally cumbersome or controversial, especially when an unnamed tropical disturbance causes major flooding but it’s still too disorganized to earn a name. 

This year’s list of names was last used in 2015. The World Meteorological Organization retired the names Erika and Joaquin after that season due to the damage caused by those storms, replacing them with Elsa and Julian on this year's list.

Names became a big deal last year because the Atlantic hurricane season produced so many storms that we exhausted the official list of 21 names, requiring the use of the Greek alphabet to name the final nine storms. The resulting confusion and need to retire two of the names (Eta and Iota) forced the WMO to ditch using the Greek alphabet as a fallback.

Beginning this year, in the unlikely event that this or any future season exhausts its list of names, we have supplementary name lists for both the Atlantic and eastern Pacific basins ready to serve as a fallback. These names should cause less confusion going forward and they’re easier to replace if needed.

The Prep

Hurricanes don’t really sneak up on us anymore. If there’s a bad storm heading for land, we usually get a couple of days to prepare before it arrives. That gives folks in harm’s way plenty of time to hit all the checkmarks on the to-do list, like filling up the gas tank and getting ready to leave if told to do so.

You have to wait until the storm is on its way to do the disruptive last-minute prep. There’s plenty you can do now to make things easier if and when the time comes to take action.

Keep a reserve of non-perishable food on hand in case the power goes out. This isn’t just helpful for hurricanes, but it's useful for any summertime storm that could knock out the power. It’s easy to forget how much we rely on electricity for food until the electricity turns off. Stuff like canned foods, Pop Tarts, and fruit cups are easy to store, fine to eat cold, and they have a long shelf life.

Make sure you have batteries and flashlights. The flashlight feature on cell phones is fine in a pinch, but it’s not there to get you through a power outage. That bright light kills your cell phone battery in a hurry. Have a couple of real flashlights (and battery refills) on hand so you don’t have to worry about draining your phone’s juice or burning unsafe candles during a lengthy outage.

Speaking of cell phones, invest in one (or more) cell phone battery charging packs. They’re relatively cheap nowadays and they’re good for a couple of recharges before the charging pack itself has to be recharged.

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