Apr 15, 2024 - Energy & Environment

La Niña on track to amplify Atlantic hurricane season, slightly cool globe

Probability of El Niño or La Niña
Data: NOAA; Chart: Axios Visuals

The tropical Pacific Ocean continues to trend toward a La Niña phase, coming out of one of the strongest El Niño events on record since 1950.

Why it matters: This has potentially huge implications, since depending on the timing, a switch could bring ideal conditions for Atlantic hurricanes.

Zoom in: The latest federal outlook for the larger climate cycle known as the El Niño-Southern Oscillation, or ENSO, calls for the currently fading El Niño to give way to neutral (sometimes called, "La Nada") conditions this summer.

  • This is likely to be followed by a 60% chance of the onset of a La Niña during the June through August timeframe, and the odds increase from there going into the fall and early winter.
  • Different types of computer models, along with studies of past La Niña events, all support a coming event, but they differ on the exact timing and intensity.

Context: While El Niño features unusually warm water temperatures in the equatorial tropical Pacific Ocean, La Niña is characterized by the opposite, with cool anomalies present in the same general region.

  • The ways these two cycles affect global weather patterns differ, however.

Between the lines: The Climate Prediction Center, which is part of NOAA, assigns 80% odds for a La Niña to be in place by the August through October period.

  • This is virtually unchanged ("noise level" changes from last month's outlook, according to NOAA meteorologist Michelle L'Heureux) from NOAA's March ENSO outlook.
  • This transition matters because during a typical La Niña, winds over the tropical Atlantic slacken, which reduces the amount of wind shear present across the region.
  • Wind shear, which occurs when winds blow in different directions and/or at varying speeds with height, inhibits tropical storms and hurricanes.
  • The more shear there is during a hurricane season, the fewer storms there tend to be.

Threat level: For more than a year now, ocean surface temperatures in the North Atlantic have been at record highs, and current water temperatures are nearing their typical July levels.

  • This indicates that one key ingredient — sufficiently warm waters, will be present in spades this hurricane season.
  • At the same time, models are consistently projecting below-average shear, likely tied to La Niña, which is another indication of an active season.
  • These factors and more have prompted early seasonal outlooks to call for an extremely active season, with potentially more storms threatening the U.S. East and Gulf coasts than usual.

What's next: Every step in La Niña's evolution will be closely monitored and factored into forthcoming hurricane outlooks from other forecast groups, including NOAA's, which will be released in May.

Our thought bubble: And this La Niña would be a climate wild card, given that it comes after a near-record string of 10-straight record-warm months worldwide.

  • Typically, La Niña years feature lower global average temperature rankings than El Niño years, but with human-caused climate change accelerating (the pace and causes of this acceleration are under debate), each La Niña's cooling influence tends to get more muted.
  • The latest NOAA outlook, released last week, calls for a 55% chance of 2024 ranking as the warmest year on record, with a 95% confidence level of the year coming in as the first or second-warmest to date.

The bottom line: There's a lot to watch, and coastal residents have many reasons to prepare for this upcoming hurricane season.

  • But La Niña will have consequences beyond just the Atlantic and is of keen interest to climate scientists.
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