Hurricane Season Forecasters Up Numbers Again, Predict Above Average Activity in 2023

Record warmth across the North Atlantic expected to counteract the usual El Niño-driven wind shear

For the second time since their initial forecasts were released in April, experts at Colorado State University (CSU) – the group to pioneer seasonal hurricane forecasting during the 1980s – increased their predictions for 2023, calling for an above average hurricane season despite a formidable El Niño that would typically discourage Atlantic hurricane activity. Forecasters credit the continuation of record abnormal warmth across the North Atlantic for the boost in their numbers this season. July outlooks historically demonstrate a strong correlation with seasonal hurricane activity.

The most significant seasonal hurricane forecast predictor in early July is water temperatures across the eastern North Atlantic observed during June.

June 2023 sea surface temperature departures from average. Warmer colors indicate above average water temperatures. The outlined region typically shows a strong relationship with overall hurricane season activity and is the top July predictor cited by Colorado State University seasonal hurricane forecasters.

Sea surface temperatures in this region during June were not only the warmest on record, but the departure from average was over double that of the previous June record from 2008, according to government data.

June 2008 sea surface temperature departures from average. June 2008 was the previous record holder for abnormal warmth in the eastern North Atlantic according to U.S. government data.

CSU’s latest outlook notes that of the top five warmest North Atlantic Junes (1995, 2008, 2010, 2020, and 2005), all ended with above average hurricane seasons and all but one was classified as hyperactive. Although none of these previous hurricane seasons coincided with a Pacific El Niño – a phenomenon that usually reduces Atlantic hurricane activity through increased wind shear – experts believe the extreme Atlantic warmth will lessen El Niño’s influence this year across the basin.

As we’ve highlighted in previous newsletters, El Niño is revving up for a late summer charge. The consensus of the most recent climate model forecasts calls for a moderate to strong El Niño by the peak of the Atlantic hurricane season this fall.

Model predictions for El Niño for overlapping 3-month periods. The dynamical models (bold maroon line) show a much stronger El Niño by the peak of hurricane season (ASO in the plot above) than statistical models (green line). Credit: Columbia Climate School International Research Institute (IRI) for Climate and Society.

CSU experts point to the unusually cooler than average waters in the Pacific west of Mexico and California – the negative phase of a phenomenon known as the Pacific Decadal Oscillation or PDO – for a potential softening effect on El Niño that would make the most aggressive forecasts for the 2023 El Niño less likely.

Sea surface temperatures for June 2023. The Niño 3.4 monitoring region along the central and eastern equatorial Pacific is outlined in black. Cooler than average waters west of Mexico and California are associated with the negative phase of the Pacific Decadal Oscillation or PDO.

With competing factors this hurricane season, forecasters caution there’s a higher level of uncertainty in potential outcomes for 2023. While more overall hurricane activity can lead to more U.S. impacts, it’s not always the case. The 2010 hurricane season, one of the more active this century, produced 12 hurricanes but no U.S. landfalls. By contrast, 1985 produced an average seven hurricanes but six of those struck the U.S., tying for the most U.S. hurricane landfalls in a single season.

It only takes one bad hurricane to make for a bad season, so prepare this year as you would any other.

CSU will issue their final hurricane season forecast of 2023 in August. NOAA will also update their May seasonal forecast at the beginning of next month.