2023 Atlantic hurricane consensus rises: TSR ups forecasts

Warm Atlantic sea temperatures will trump hoped-for El Niño conditions to bring more Atlantic tropical storm activity in 2023 than previously expected, the UK government-supported research venture Tropical Storm Risk (TSR) has said in an update to its seasonal forecast.

TSR’s slate of seasonal forecasts shifts from below the historical average as predicted at end-May to figures close to or slightly above the 10-year and 30-year averages.

“We anticipate the warm sea surface temperatures in the Atlantic will partially override the increased vertical wind shear and trade wind strength normally present during El Niño,” analysts said in what is becoming a growing consensus.

The June runs of tropical storms Bret and Cindy further shows the likelihood of a heavier early season, analysts added.

That “exceptional” run of early storms “implies the tropical Atlantic has become favourable for development much earlier than normal.”

On the bottom line, TSR upped its forecast for accumulated storm energy for the North Atlantic by 35 points or 39% to 125, including a 60% increase for the tropical North Atlantic and a 216% increase in forecast ACE for storms at US landfall or over the US mainland.

By storm count, the TSR forecast for the full North Atlantic is up by 31% or another four storms to 17. Eight of those 17 will hit hurricane status (up 2), of which three will become intense hurricanes (up 1). All of the increase in storms and hurricanes focus on the tropical Atlantic, including one at US landfall.

Forecast probabilities for the full North Atlantic and the tropical North Atlantic are tipped to the upside. TSR sees a roughly one third chance of a season in the upper third of the historical range and a roughly one fifth chance of hitting the bottom third. US landfall probabilities tip the other way.

Forecasters at TSR and other leading institutions have struggled to grapple in 2023 with the array of opposing forces at hand. Warm surface temperatures in the Atlantic can be storm supportive, but the shift underway into El Niño is expected to create the type of wind shear that can tear up developing systems.

Forecasters at Colorado State University’s Tropical Weather & Climate Research department have likewise recently upgraded their forecasts for the 2023 season as they grapple with the impact of the opposing forces.

“Uncertainties remain,” TSR authors claim. But TSR claims forecast skill at this point in time for the full North Atlantic is considerably higher than it was at this point last year when key drivers had lined up for a stronger than usual storm season. Forecasts for the tropical North Atlantic are nearly in line with the prior year. Only forecasts for development into intense hurricanes is lower this year than in 2022.

TSR’s July forecast is its fourth for the 2023 season. The end-May report offered a slight upward tweak to forecasts issued late April. TSR had taken the early crack at it in early December.

The next TSR forecast update for the 2023 North Atlantic hurricane season is slated to be issued on Tuesday, August 8.

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