Hurricane Ian. PHOTO: NOAA

Following seven straight years of predicted “above-average” activity, top hurricane forecasters feel the 2023 Atlantic hurricane season will buck the trend.

Researchers at Colorado State University, now in its 40th year of forecasting the upcoming hurricane season, are predicting a slightly below-average Atlantic hurricane season, which starts June 1. CSU is forecasting there will be 13 named storms, six hurricanes, and two major hurricanes. Last year, CSU predicted 19 named storms, including nine hurricanes and four major.

CSUps Meteorology Project team anticipates the 2023 Atlantic hurricane season to be below average due to a number of factors, but uncertainty still remains.

Often used to paint a picture of the upcoming season is the El Nino Southern Oscillation (ENSO) — whether the waters in the central and eastern Pacific Ocean are warmer or cooler, typically referred to as El Nino (warmer) or La Nina (cooler).

“Current neutral ENSO conditions look fairly likely to transition to El Nino this summer/fall,: states CSU researches in the report. “However, there is considerable uncertainty as to how strong an El Nino would be, if it does develop. Sea surface temperatures in the eastern and central Atlantic are much warmer than normal, so if a robust El Nino does not develop, the potential still exists for a busy Atlantic hurricane season.”

CSU researches stated that when waters in the eastern and central tropical and subtropical Atlantic are warmer than normal, it tends to force a weaker subtropical high and associated weaker winds blowing across the tropical Atlantic.

“These conditions lead to warmer waters in the tropical Atlantic for the peak of the Atlantic hurricane season,” CSU officials stated. “The anomalously warm eastern and central tropical and subtropical Atlantic favor an above-normal season.”

The CSU team bases forecasts on a statistical model, as well as four models that use a combination of statistical information and model output from the European Centre for Medium-Range Weather Forecasts, the UK Met Office, the Japan Meteorological Agency, and the Euro-Mediterranean Center on Climate Change. These models use 25 to 40 years of historical hurricane seasons and evaluate conditions including: Atlantic sea surface temperatures, sea level pressures, vertical wind shear levels (the change in wind direction and speed with height in the atmosphere), El Nino (warming of waters in the central and eastern tropical Pacific), and other factors.

CSU said that thus far, the 2023 hurricane season is exhibiting characteristics similar to 1969, 2002, 2004, 2006, 2009, 2012, 2014 and 2015.

“Our analog seasons exhibited a wide range of outcomes, from below-normal seasons to hyperactive seasons,” said Phil Klotzbach, research scientist in the Department of Atmospheric Science and lead author of the report. “This highlights the large uncertainty that exists with this outlook.”

CSU predicts this year’s hurricane activity will be about 80% of the average season from 1991-2020. By comparison, 2022’s hurricane activity was about 75% of the average season. Last year’s season will be most remembered for its two major hurricanes: Fiona and Ian, which made landfall as a Category 4 hurricane in Southwest Florida, resulting in more than 150 fatalities and $113 billion in damage.

“It takes only one storm near you to make this an active season for you,” said Michael Bell, professor in the CSU Department of Atmospheric Science.

The CSU team will issue forecast updates on June 1, July 6 and August 3.

The Tropical Meteorology Project team also includes Alex DesRosiers, a PhD candidate in the same department. Bill Gray, who originated the seasonal forecasts, launched the report in 1984 and continued to author them until his death in 2016.