Experts Up Hurricane Season Forecast, Call Beryl a Harbinger of a Hyperactive Season

Forecasters at Colorado State University update their hurricane season outlook, predicting the most active hurricane season since 2005

Inside the eye of Hurricane Beryl from July 2, 2024, from NOAA Hurricane Hunters as it moved through the eastern Caribbean. Credit: Lt. Cmdr. Kevin Doremus, NOAA Corps

Beryl – the record-setting hurricane that struck Texas Monday – is likely a harbinger of a hyperactive season, according to updated hurricane season predictions issued Tuesday from experts at Colorado State University. The forecast team – first on the scene with seasonal hurricane predictions in the 1980s – raised their already bullish numbers from June, indicating a 2024 hurricane season that could rival the fiercest seasons ever observed.

In their July update, the CSU forecast team led by Dr. Phil Klotzbach called for up to 25 named storms, 12 hurricanes, and 6 Category 3 or stronger hurricanes. Their forecast nearly doubles the 30-year averages in every forecast category and is the most aggressive seasonal outlook to-date in the research group’s 41-year history.

As we’ve discussed in previous newsletters, though early season tropical activity isn’t usually a sign of things to come, when the early activity occurs in the deep tropical Atlantic (east of the Caribbean), it can point to a hyperactive hurricane season ahead. The research team credits Hurricane Beryl’s unusual early season formation as a Category 5 hurricane in this bellwether region in part for their adjustment upward yesterday.

Atlantic cooling some but not enough and in the wrong places

The tropical Atlantic has cooled down some since the beginning of June, but not enough to have much impact on the still-record to near-record water temperatures for the time of year.

Change in sea surface temperature (°C) from the first week of June to the first week of July. Waters have cooled some in the Atlantic but largely in the far eastern Atlantic north of the Main Development Region or MDR. The Atlantic MDR remains at record or near-record warmth for the time of year.

Over 80% of the Main Development Region or MDR – where most of our strongest hurricanes form each year – remains as warm or warmer than we’ve observed in any previous year to start July.

Additionally, the most significant cooling in the Atlantic has happened in the far eastern Atlantic near and to the west of the Canary Islands off Africa, which has a lower relationship with seasonal hurricane activity by July.

Relationship between sea surface temperatures and overall Atlantic tropical activity (as measured by Accumulated Cyclone Energy or ACE) for June and July. Warmer colors indicate areas that have a higher correlation with overall hurricane season activity. Note the lower correlation in July around the Canary Current in the far eastern Atlantic and a higher correlation across the deep tropics and Main Development Region. Credit: Phil Klotzbach/Colorado State University

Some of the cooling recently – most notably in the southern Gulf of Mexico and western Caribbean – has been due to cooler waters temporarily churned up from below by Hurricane Beryl. Mostly, though, the cooling has been the result of a stronger-than-average subtropical Atlantic high pressure, the same one that whisked Hurricane Beryl westward into the Caribbean.

Computer models forecast this Azores high to weaken again, which should relax the east-to-west flowing trade winds across the deep tropics. With less ocean mixing from weaker surface winds, we can expect the record warm Atlantic waters to reheat in the weeks ahead.

Record low wind shear to start the hurricane season

While sea surface temperatures are critical to fueling big, strong hurricanes like Beryl, the configuration of upper-level winds are arguably more important in the early months of the season when wind shear typically prohibits much development in the deep tropical Atlantic.

That hasn’t been the case so far in 2024. Wind shear across the Caribbean and Atlantic east of the islands has been among the lowest we’ve observed through the first week of July.

Wind shear departure from average from the start of the hurricane season through July 7^th. Notice the ribbon of cooler colors stretching from the Caribbean into the open Atlantic, indicating below average wind shear for the time of year.

Of course, this shouldn’t come as a surprise after Beryl’s unprecedented run as the strongest hurricane this early in the season.

The pattern of low wind shear in the deep tropics is consistent with a transition to La Niña conditions – cooler than average waters around the equator in the eastern Pacific. Though there’s been some slowdown of the transition to La Niña in recent weeks, the cooling is well underway and government forecasters anticipate full-fledged La Niña conditions over the next month or two as the Atlantic hurricane season peaks.

As the environment naturally becomes more conducive to storm development in August and September, La Niña will only hasten the reduction in wind shear that might otherwise help to stifle thunderstorms blossoming over the record warm Atlantic.

New area off the southeast U.S. not a concern

On Wednesday morning, the National Hurricane Center highlighted a broad area of low pressure off the southeast U.S. for low development odds.

None of our reliable forecast models suggest much in the way of development, and the system will move inland over the southeast this weekend. Other than perhaps a marginal bump up in rainfall chances tomorrow into Friday, we’re not expecting anything from this system in South Florida or elsewhere.

Overall the tropics are expected to settle down for the next week or two. By the end of the month and especially as we turn the calendar to August, look for activity to once again begin to pick up.