Hurricane Safety and Preparedness

August 2023 Hurricane Season Outlook Update: NOAA Bumps Expectations Upward

At a Glance

NOAA released their latest hurricane season outlook in mid-August.
Conflicting signals continue to bring a somewhat uncertain forecast.
Atlantic Ocean water is extremely warm in many areas, which could enhance storms.
But a strong El Niño is increasingly likely, which tends to limit the number of storms.
There's an increasing chance the warm Atlantic Ocean could exert more influence.

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Forecasters at NOAA's Climate Prediction Center now believe that the 2023 Atlantic hurricane season will be more active than average, according to their final update for the year.

Their update calls for 14 to 21 total storms, six to 11 of which are expected to become hurricanes and two to five of which will reach at least Category 3 status.

This is an increase of two to three storms, one to two hurricanes and one major hurricane since their previous outlook, which was released in July. The increase in storms and the overall outlook from NOAA take into account five storms that have already occurred this year.

Other forecasts from The Weather Company/Atmospheric G2 and from Colorado State issued earlier in the season fall in the higher end of the ranges of NOAA's update, and are well above the latest 30-year average tallies.

Don formed in July; Arlene, Bret and Cindy formed in June; and an unnamed subtropical storm developed in January that was retroactively upgraded by the National Hurricane Center in May.

The fifth storm of the season doesn't typically arrive until late August, according to the NHC.

These are the 2023 Atlantic Basin hurricane season tracks as of Aug. 10, 2023.

“The main climate factors expected to influence the 2023 Atlantic hurricane activity are the ongoing El Niño and the warm phase of the Atlantic Multi-Decadal Oscillation, including record-warm Atlantic sea surface temperatures,” said Matthew Rosencrans, lead hurricane season forecaster with NOAA’s Climate Prediction Center in a press release.

Atlantic Ocean Warmth Is Still Off The Charts

One of those factors is dominating right now.

A major contributor to the planet's hottest July on record was record warmth in the Atlantic Basin where hurricanes and tropical storms form.

According to AG2 meteorologists Todd Crawford, Ed Vallee and James Caron, an index that tracks the warmth of the North Atlantic Ocean known as the Atlantic Multidecadal Oscillation (AMO) was at its highest level since at least 1950.

"This anomalous warmth is why CSU's seasonal hurricane forecast has increased, despite (a) likely robust El Niño," wrote Phil Klotzbach, tropical scientist and lead of the CSU forecast team, in a tweet prior to the CSU outlook release earlier in July.

The scope and magnitude of this anomalous warmth as of late July was well beyond what was seen in other warm ocean hyperactive hurricane seasons such as 2020, 2017 and 2005.

Sea surface temperatures as of Aug. 10. Orange and red colors indicate where water temperatures are above average. The warmer the color, the more above average the water temperatures are.

This is important because assuming other factors are equal, the deeper and warmer the ocean water, the stronger a storm or hurricane can become.

Typically, there is a cooler pocket of water early in hurricane season from the Cabo Verde Islands to Bermuda to the northern Leeward Islands. Tropical waves reaching this pocket of colder waters often succumb to otherwise hostile conditions.

This warmth we're seeing right now is more typical of the peak of hurricane season, with plenty of time for additional warming.

This unusually warm water was one factor behind the development of tropical storms Bret and Cindy, the first time two storms developed over the strip of the Atlantic Ocean between Africa and the Lesser Antilles in June.

But What About El Niño?

Another factor could have the opposite effect of the warm Atlantic waters.

As of Aug. 10, there is a 95% chance that El Niño will stick around through hurricane season and into the winter.

An El Niño that was declared in early June is now of moderate strength and is likely to gain a bit more intensity by the peak of hurricane season, which lasts through October, according to the latest outlook from NOAA issued in mid-August.

The reason this strip of water far from the Atlantic Basin matters is that it's one of the strongest influences on hurricane season activity.

In El Niño hurricane seasons, stronger shearing winds often occur over at least the Caribbean Sea and some adjacent parts of the Atlantic Basin. This tends to limit the number and intensity of storms and hurricanes, especially if the El Niño is stronger, as we investigated in a March article.

That said, NOAA says "those limiting conditions have been slow to develop and climate scientists are forecasting that the associated impacts that tend to limit tropical cyclone activity may not be in place for much of the remaining hurricane season."

"(A) high chance of a robust El Niño is why CSU's hurricane forecast is not for even more activity given (a) record warm Atlantic," wrote Klotzbach in another Tweet.

The AG2 forecast team also noted a tendency in El Niño hurricane seasons for fewer Gulf of Mexico storms and more storms to either curl north, then northeast out into the open Atlantic Ocean or to impact parts of the East Coast.

That's because the Bermuda high tends to be weaker, and it's also due to a more persistent dip in the upper-level winds in the southeastern U.S. during El Niños, according to the AG2 forecast team.

A typical "recurve" pattern that can be in place in hurricane season.

Which Competing Factor Will Win?

"The combination of an incipient El Niño and historically warm North Atlantic SSTs (sea-surface temperatures) is unprecedented in the recent record," wrote the AG2 forecast team in their outlook.

That's not providing decent matches from past years to use as analogs, making this year's outlook particularly challenging.

At least some of El Niño's typical influence in the atmosphere could be drowned out by the widespread Atlantic Ocean warmth. As mentioned earlier, that's why seasonal outlooks are trending up as far as the number of storms and hurricanes are concerned.

One plausible scenario to the rest of the hurricane season is more storm tracks in the eastern and central Atlantic Ocean, feeding off the unusually warm water, but perhaps fewer in the Caribbean Sea and Gulf of Mexico, assuming more hostile wind shear from El Niño kicks into gear.

Prepare The Same Every Hurricane Season

What these outlooks cannot tell you is whether or not your area will get struck this season and when that might happen.

A season with fewer storms or hurricanes can still deliver the one storm that makes a season destructive or devastating.

In 2015, one of the strongest El Niños on record reduced the hurricane tally to four that season. However, one of those was Joaquin, which devastated the central Bahamas.

In this aerial photo, homes are seen under the floodwaters caused by Hurricane Joaquin in the Southern area of Long Island, Bahamas, Monday, Oct. 5, 2015. Joaquin unleashed heavy flooding as it roared through sparsely populated islands in the eastern Bahamas last week, as the Coast Guard searched for crew members of the U.S. container ship El Faro which they concluded sank near the Bahamas during the storm. (AP Photo/Tim Aylen) — In this aerial photo, homes are seen under the floodwaters caused by Hurricane Joaquin in the Southern area of Long Island, Bahamas, Monday, Oct. 5, 2015.
(AP Photo/Tim Aylen)

And it doesn't take a hurricane to be impactful, especially regarding rainfall flooding.

Also in the 2015 season, Tropical Storm Erika was ripped apart by wind shear and dry air near the Dominican Republic. But before that happened, it triggered deadly and destructive flooding in Dominica.

These outlooks serve as a reminder that the time to be ready for hurricanes is now. Information about hurricane preparedness can be found here.

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Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. Follow him on Twitter and Facebook.

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