What Might the Atlantic Hurricane Season of 2020 Have in Store?
The 2019 Atlantic hurricane season just ended on November 30, but a couple of agencies have already issued a first glimpse at what the 2020 Atlantic hurricane season might have up its sleeve. The 2020 hurricane season officially starts on June 1. The Tropical Meteorology Project (TMP) at Colorado State University will not release its first full forecast until April 2, but they released an initial discussion on December 12. This initial outlook examines the possibility of several hurricane season scenarios. The TMP is currently giving an approximately 45% chance of an above-normal hurricane season, a 45% chance of a near-normal hurricane season and a 10% chance of a below-normal hurricane season for the Atlantic basin in 2020. For reference the average Atlantic hurricane season has about 12 named storms (maximum winds >= 39 mph), 6 hurricanes (maximum winds >= 74 mph) and 3 major hurricanes (Saffir-Simpson Hurricane Wind Scale Category 3+, maximum winds >= 111 mph).
This forecast was based on the premise that North Atlantic sea surface temperatures are currently somewhat above-normal across the far North Atlantic and portions of the tropical Atlantic (Figure 1). In general, the North Atlantic has been slightly warmer than normal over the past several months. These sea surface temperature anomaly patterns can certainly change during the winter and spring, but if they were to persist, they would provide more fuel for developing storms during the 2020 Atlantic hurricane season.
The development of El Niño (warmer than normal water temperatures in the eastern and central tropical Pacific) is unlikely during this winter and spring according to the latest NOAA discussion. However, there is considerably uncertainty as to whether El Niño will develop next summer. El Niño typically produces stronger vertical wind shear (the change in wind direction with height in the atmosphere) in the Atlantic basin, tearing apart hurricanes as they are trying to develop.
The U.K.-based Tropical Storm Risk produced their first forecast for the 2020 season on December 19. Their initial forecast calls for a total of 15 named storms, 7 hurricanes and 4 major hurricanes. The number of hurricanes is slightly above the long-term average, but they are also predicting near average Accumulated Cyclone Energy (an integrated index that accounts for intensity and duration of storms). Their outlook was based on the premise that, next summer, tropical Atlantic low-level winds are predicted to be near their long-term average and tropical Atlantic sea surface temperatures are predicted to be slightly above normal.
Seasonal hurricane outlooks issued in December generally have low levels of skill, since the atmosphere and ocean can change considerably between the winter and the following summer. As such, these initial forecasts should be interpreted with caution. As the Atlantic hurricane season approaches, seasonal outlooks generally show improved skill. Regardless of any seasonal forecasts, readers are reminded that it only takes one hurricane making landfall near you to make it an active season. The hurricane off-season is an excellent time to review your disaster recovery plan.
Figure 1: Mid-December 2019 sea surface temperature anomalies across the North Atlantic.
About the Author:
Dr. Phil Klotzbach has received national and international attention for his work in researching weather patterns and forecasting hurricanes. For the past 10 years, Dr. Klotzbach has been lead author on Colorado State University’s Atlantic basin hurricane forecasts, which were founded by his late esteemed colleague Dr. William Gray.