20 cyclones attaining tropical depression status,
18 cyclones attaining tropical storm status,
9 cyclones attaining hurricane status, and
5 cyclones attaining major hurricane status.
I predict that the 2020 Atlantic hurricane season will continue the active trend of the last few years and likely feature a well above-average number of cyclones, although uncertainty in my forecast is higher than average. Note that the average Atlantic hurricane season (1981-2010 average) has 12.1 tropical storms, 6.4 hurricanes, and 2.7 major hurricanes. The main factor in support of this claim is the potential for a neutral to negative El Niño Southern Oscillation (ENSO) index this summer and autumn. This index, a measure of equatorial sea temperature anomalies in the Pacific ocean, has an inverse correlation with Atlantic hurricane activity: negative indices (corresponding to a La Niña) tend to favor more active seasons.
Unlike the last two years, there is a great deal of spread in the model forecasts for this year's ENSO. Some models have the index remain positive, while others show a strong La Niña event developing by season's end. The dynamical models (whose average is represented by the thick red line) lean toward La Niña more than the statistical models (green), which favor using historical data for prediction over simply modeling future changes in weather. Due to a rapid plunge of Pacific equatorial sea surface temperature anomalies in the last few weeks, I'm putting more weight on the dynamical solution. This would suggest a very active season, especially since 2018 and 2019 were active despite neutral to slightly positive ENSO index conditions.
Meanwhile, Atlantic water temperatures are running uniformly warmer than average for this time of year, and this is expected to continue through the summer. No particular regions stand out though: the Gulf of Mexico, Caribbean, and subtropical Atlantic will all have moderately high anomalies, and the tropical Atlantic just a little bit less so. Expect tropical cyclone formation in many areas this year, and not quite as much emphasis on the subtropical Atlantic.
The above image shows the strength of the Saharan Air Layer (SAL) of the atmosphere as it appeared on May 12, 2020. Tropical trade winds carry dust particles and dry air from the Sahara desert over water throughout the year, but this has particular relevance to the development of tropical waves emerging off of the west African coastline: the more dry air and dust, the more thunderstorm activity in the region is suppressed. The SAL is quite strong as of now (though there is a typical decline throughout spring), so expect a late start for long-track hurricanes this year. Come September, however, other factors indicate high risk for Cape Verde hurricanes.
I'll discuss a few more smaller-scale factors in association with assigning risks to different parts of the Atlantic basin. My estimates are on a scale from 1 (least risk) to 5 (most risk):
U.S. East Coast: 4
The position of the Bermuda/Azores high pressure system correlates with the ENSO index and has a great influence on tropical cyclone tracks. I predict that this high will remain further east than typical La Niña events, increasing the risk to the east coast but lowering it for the Gulf of Mexico. The threat to the east coast will start early to the season, in July and August.
Yucatan Peninsula and Central America: 4
The western Caribbean is at higher risk for tropical cyclones than in any of the last 3 seasons, particularly when early fall rolls around. Some of the Atlantic's highest ocean temperatures will be in this region, and wind shear will be below normal. Expect some low-latitude cyclones, possibly affecting Nicaragua and Honduras.
Caribbean Islands: 4
The Caribbean, too, looks to be at greater-than-average risk this year. Once the tropical wave train gets going in earnest, look for long-track storms approaching from the east (primarily in September). The east Caribbean should be less of a hurricane graveyard than the last few seasons, so cyclones following tracks similar to Hurricane Matthew and approaching Hispaniola and Puerto Rico from the south are likelier than average.
Gulf of Mexico: 3
Waters in the Gulf are once again very warm, and some "home-grown" cyclone development is likely. Nevertheless, I forecast that the strongest cyclones will track elsewhere for most of the season. Come October, however, there is still a moderate chance for storms moving south to north from near the Yucatan Peninsula toward the United States gulf coast, similar to Hurricane Michael.
Overall, I expect the 2020 Atlantic hurricane season to feature well above-average activity. Nevertheless, this is just an amateur forecast. Individuals in hurricane-prone areas should always have emergency measures in place. For more on hurricane safety sources, see here. Remember, devastating storms can occur even in otherwise quiet seasons.
Sources: https://www.tropicaltidbits.com/analysis/models/, https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf, http://trackthetropics.com/saharan-air-layer-sal-tracking/
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