Near record warm oceans, developing El Niño escalates hurricane risks

Threats from the still-emerging Atlantic hurricane season are converging as oceanic and atmospheric trends underscore how climate change is creating unprecedented storm conditions.

The big picture: The tropical Atlantic is especially toasty, particularly temperatures in a crucial swath of the sea known as the "Main Development Region," where many tropical storms and hurricanes form and intensify.

• Ocean temperatures in this area are closely watched at the start of the season and used as a determining factor in predicting storm activity.
• In many seasons, freshening trade winds tend to cool those waters down. This year, that’s not expected to happen.
• Climate change is a major factor driving ocean temperatures higher.

Why it matters: Warmer waters are a concern for officials and meteorologists responsible for tracking landfalling storms along the East and Gulf Coasts, since it would suggest a more active season ahead.

• As a reminder to expect the unexpected this season, the first tropical cyclone of the season — known simply as Tropical Depression Two — formed Thursday in the northeastern Gulf of Mexico.
• It may briefly become Tropical Storm Arlene on Friday, but is no threat to land.

Meanwhile... A likely El Niño event in the tropical Pacific Ocean continues to form, with unusually warm sea surface temperatures at play there, too.

• There are signs the atmosphere is beginning to respond to the ocean conditions in a key region that helps climate scientists diagnose El Niño events, known as "Niño 3.4."
• The atmosphere's feedback is a prerequisite for the climate cycle's formation and staying power.
• Some reliable computer models project a moderate-to-strong El Niño may soon be underway, possibly by the height of the hurricane season in the late summer and early fall.
• Typically, these events make for less active Atlantic hurricane seasons based on how they affect weather patterns.

Yes, but: With climate change elevating ocean temperatures throughout the Atlantic, beyond the tropics, and large stretches of the expansive Pacific, there is nothing typical about this setup.

• In fact, ocean temperatures have been at or close to record levels globally this spring.

This season is in nearly uncharted territory, with no consistent past lessons for forecasters to draw from in order to get a sense of where things are headed.

• Will it be another record-breaker, with storms extending into the Greek alphabet, as in 2020? Most likely no, federal and private sector forecasts indicate — but Atlantic Ocean conditions look eerily similar.

• Still, it's also unlikely to be below average, like previous El Niño years.

Threat level: An additional risk that warm water brings is the increased likelihood of rapidly intensifying tropical storms and hurricanes. That has been happening with greater frequency and magnitude as the climate warms.

Context: Emphasizing this point, a hurricane forecast group at Colorado State upped its Atlantic outlook on Thursday to a total of 15 named storms this season, citing ocean temperatures as a key reason.

• This is an increase from 13 named storms in its previous forecast.
• Of that number, it predicts 7 will become hurricanes with 3 major hurricanes of Category 3 or greater, which are also increases.
• Forecasters cited sea surface temperatures as the main reason for the change.

What they're saying: Michael Lowry, a hurricane specialist at WPLG Local 10 in Miami, said current historically high sea surface temperatures, along with the moderate-to-strong El Niño and warmth in the tropical Atlantic, have no real precedent.

• "We don't have many great analogs in part because global sea surface temperatures have never been so warm," he said.