Atlantic hurricane season to feature duel between likely El Niño and hotter Atlantic

Zoom in: The NOAA 2023 hurricane season outlook calls for a 40% chance of a near normal hurricane season, and a 30% chance of either a below or above average season.

• In terms of numbers, the agency calls for 12 to 17 named storms to form, of which 5 to 9 will become hurricanes and 1 to 4 will be "major" storms of Category 3 intensity or greater.
• This compares to the 30-year average of 14 named storms, 7 hurricanes and 3 major hurricanes.

Between the lines: A developing El Niño in the equatorial tropical Pacific Ocean would typically indicate a below average Atlantic hurricane season, and above average eastern Pacific season, is likely.

• El Niño events can reduce Atlantic tropical storm and hurricane activity by increasing winds in the upper atmosphere over the tropical Atlantic.
• Such wind shear can disrupt incipient storms before they can strengthen.
• However, heading into this summer, sea surface temperatures in the typical hurricane forming regions of the Atlantic along with most other areas are unusually warm for this time of year.
• That would suggest an unusually active season lies ahead.

What they're saying: For now, NOAA is threading the needle between the two influences, in addition to others.

• “It’s kind of like a clash between those big factors,” said NOAA hurricane seasonal forecaster Matt Rosencrans at a press conference.
• He added that the sea surface temperature anomalies are likely to stick around, particularly in the tropical Atlantic, through the summer.

The intrigue: The Atlantic is still in the midst of a largely natural multi-decade upswing in hurricane activity, though human-caused climate change is driving an increase in sea surface temperatures there and around the world.

• Globally-averaged ocean temperatures have been off the charts during April into May.

Threat level: Climate change is already having detectable changes to nature's largest and most powerful storms.

• A warmer atmosphere can carry more water vapor, which gets wrung out as heavy rains over land. On average, storms are now wetter than they used to be.
• In addition, increasing ocean and air temperatures are leading to more high-end, major hurricanes, but are not thought to be increasing the total number of storms overall.

• As was seen with Hurricanes Ida, Michael and Ian in recent years, hurricanes are exhibiting a greater tendency to rapidly intensify, leaping storm categories in short periods of time and potentially catching emergency managers off guard.
• Also, the magnitude of storms' rapid intensification is increasing in many parts of the world.

Of note: Some studies show that tropical storms and hurricanes are moving more slowly at landfall, related to slackening steering currents, though this is an area of active research. Slow-moving storms have a greater potential to cause inland flooding.

The big picture: Other forecast groups have also been seeking a balance between the potential El Niño and Atlantic sea surface temperatures.

• The University of Pennsylvania put out a new outlook calling for between 12 and 20 named storms, with a "best guess" of 16.
• A separate early outlook issued last month from forecasters at Colorado State University projects a slightly below-average Atlantic hurricane season

Yes, but: While the seasonal outlook helps spur storm preparation activities, it provides little to no guidance on where such storms may ultimately strike.

Editor's note: This story has been updated with additional reporting.