The 2020 Atlantic hurricane season was the most active Atlantic hurricane season on record in terms of named storms, featuring a record-breaking 30 named storms, 13 hurricanes, and 6 major hurricanes pending remaining reanalysis. The season exhausted the conventional naming list, requiring usage of the Greek Alphabet for the second time. Since two Greek Alphabet names were retired, Eta and Iota, they could not be replaced in the current system. The names Dorian from 2019 and Laura from 2020 were also retired, replaced by Dexter and Leah respectively. This prompted the World Meteorological Organization to replace the Greek Alphabet auxiliary list with an auxiliary list of 26 new names. In addition, after six consecutive seasons with an Atlantic named storm prior to June 1, the National Hurricane Center has decided to begin issuing routine Tropical Weather Outlooks on May 15 rather than June 1, even though the season does not officially begin until June 1. The 2021 Atlantic hurricane season will officially begin in just over two months, and there are now indications of how the season may shape up to be, though it is still very early.

Early indicators suggest an above-average season is more likely than a below-average one – but it is extremely unlikely 2021 comes anywhere close to 2020’s astonishing 30 named storms. This is because El Nino development appears unlikely in the short term, though it should be noted that the tropical Atlantic is cooler than it was at this time in 2020.

Atlantic Sea Surface Temperatures

Currently, the Atlantic sea surface temperature anomaly profile is actually not one typically associated with active seasons. The tropical Atlantic is cooler than normal. However, I am hesitant to suggest at this point that a quiet season is likely. The first reason is because the tropical Atlantic has frequently been cooler than normal at this time of year in recent years, only to warm up significantly by the peak of the season. The western subtropical Atlantic is warmer than normal, and the far northern Atlantic is cooler than normal, resembling a “negative AMO” look. Once again, I would caution against saying that this may be a sign that the Atlantic multidecadal active era is ending, since this has been a common sea surface temperature anomaly pattern for the Atlantic in recent years during Northern Hemisphere spring. We will have to see how sea surface temperature anomalies evolve over the coming months; if the tropical Atlantic remains this anomalously cool or cools further over the coming weeks, I may have to lower my numbers for my May forecast. The correlation between tropical Atlantic sea surface temperature anomalies and overall Atlantic hurricane activity becomes much stronger between March and May. The second reason I am not calling for a quiet season is because El Niño development appears unlikely before ASO 2021 (more on this below).

El Niño-Southern Oscillation (ENSO)

La Niña conditions continue to prevail over the equatorial Pacific, though the event has weakened in the last few months. The event peaked as a moderate La Niña during October-November-December (OND) trimonthly period with a minimum Oceanic Niño Index (ONI) value of -1.3°C, which was the strongest La Niña event since 2010-11. This event has been quite long in duration, as it developed late in summer 2020 and had a significant effect on the 2020 Atlantic hurricane season. As is typical for ENSO events, the event has weakened lately, and the latest weekly Niño 3.4 sea surface temperature anomaly is -0.7°C. The equatorial Pacific has also warmed substantially, and have recently warmed above average. In addition, the averaged Southern Oscillation Index (SOI) for the last month has been very slightly negative, consistent with the transition away from La Niña. If current trends continue, La Niña will likely dissipate within the next month or so. The uncertain part of the forecast is what happens during summer and fall 2021. The Spring Predictability Barrier (SPB) makes ENSO forecasting this time of year very difficult. I am not bullish on El Niño forming because of climatology and historical records. History suggests an El Niño event following a moderate or stronger La Niña event is unlikely, as only one year (1976-77) has ever followed a moderate or stronger La Niña event since 1950. It will also take time for the La Niña atmospheric state to decay and have a noticeable effect on the Atlantic hurricane season. There is also a significant chance La Niña could make a comeback in late summer or autumn as the easterly trades increase in strength The CPC/IRI forecast for ENSO estimates a 44% chance of La Niña, a 46% chance of ENSO-neutral, and only a 10% chance of El Niño for August-September-October 2021 (the peak of Atlantic hurricane season). Double dip La Niña events are fairly common, as 8 of the last 11 first-year La Niña years were followed by another year of La Niña conditions. Although La Niña years typically have reduced wind shear over the tropical Atlantic and Caribbean, ENSO-neutral years can be quite active as well, and with El Niño appearing unlikely at this time, that is one factor favoring an active tropical Atlantic in 2021.

West African Monsoon

In recent years, a strong West African Monsoon (WAM) has been a major enhancer of Atlantic tropical cyclone activity. The NMME forecast from March predicts above average precipitation over Africa for August-September-October 2021, which suggests the WAM is fairly likely to be strong once again. In addition, the model calls for above-average precipitation over the tropical Atlantic east of the Lesser Antilles, but below-average precipitation in the Caribbean Sea. It should be noted that precipitation anomaly forecasts are not a good indicator of tropical cyclone activity in a certain region, however.

Cyclonic Fury’s 2021 Atlantic hurricane season forecast:

• 14-19 named storms (1981-2010 average: 12.1)
• 6-9 hurricanes (1981-2010 average: 6.4)
• 2-4 major (category 3+) hurricanes (1981-2010 average: 2.7)
• Accumulated Cyclone Energy 135 +/- 50 (1981-2010 average: 93)

Cyclonic Fury also gives the following probabilities of activity. Right now, our forecast leans above average, because El Niño appears unlikely and the Atlantic remains in an ongoing active era that began in 1995. However, we are slightly less bullish than we were at this time last year on an intense hurricane season. I have decided to continue to use 1981-2010 climate normals for now, as the tropical cyclone reports have not all been finalized for 2020, and NOAA has not confirmed the new averages.

• Hyperactive season: 20% (Accumulated Cyclone Energy (ACE) of 153 or greater, given the parameters of an above-normal season are also met. This will likely occur if La Niña redevelops and the tropical Atlantic anomalously warms significantly over the next two months.
• Above normal season: 35% (Accumulated Cyclone Energy (ACE) of 112-152, with at least two of the following three parameters met or exceeded: 13 named storms, 7 hurricanes and 3 major hurricanes. This scenario is likely if ENSO remains cooler than normal, but the tropical Atlantic is not as anomalously warm as hyperactive seasons.
• Near normal season: 25% (Does not fall into the Below Normal, Above Normal or Hyperactive criteria. This is possible if the current tropical Atlantic cooling trend continues, and ENSO is not favorable enough to overcome the unfavorable tropical Atlantic sea surface temperature profile.
• Below normal season: 20% (Accumulated Cyclone Energy of 65 or below, or none of the following three parameters met or exceeded: 10 named storms, 5 hurricanes and 2 major hurricanes. This is not a particularly likely scenario since El Niño appears unlikely, but the chance for an unexpected late developing El Niño cannot yet be ruled out, along with additional tropical Atlantic anomalous cooling.

At this extended range, it is near impossible to predict which areas, if any, will have hurricane or tropical storm threats in 2021. The next Cyclonic Fury forecast for the 2021 Atlantic hurricane season will be released on May 25, 2021. By that time, we should have a much clearer idea on the ENSO forecast for the season as well as the Atlantic sea surface temperature profile and the West African Monsoon.

Cyclonic Fury March forecast verification

Cyclonic Fury has issued March pre-season Atlantic hurricane season forecasts since 2018. In 2018, in our March forecast, Cyclonic Fury predicted 11-16 named storms, 5-9 hurricanes, 2-4 major hurricanes, and an Accumulated Cyclone Energy (ACE) of 125 units. This forecast verified quite well, as 15 named storms, 8 hurricanes, and 2 major hurricanes formed, with an ACE index of 133. In 2019, our March forecast was much less accurate, as Cyclonic Fury predicted 8-13 named storms, 3-6 hurricanes, 1-3 major hurricanes and an ACE index of 80. Actual activity was significantly higher, as El Niño dissipated sooner than expected, with 18 named storms, 6 hurricanes, 3 major hurricanes, and an ACE index of 132. In 2020, our March forecast correctly anticipated potential for an active season, as we predicted 13-18 named storms, 6-10 hurricanes, 2-5 major hurricanes with an ACE index of 140 units. However, our forecast was too low in every category since record-breaking activity occurred.