The 2020 Atlantic hurricane season officially begins June 1, just over two months from today. The Atlantic has not been following these seasonal boundaries lately, though, with the past five years all having at least one named storm form prior to June 1 (most of these storms have been weak, however). Forecasting Atlantic hurricane activity in March is challenging because of uncertainties with the Atlantic sea surface temperature anomaly pattern as well as El Niño Southern Oscillation (ENSO).

Currently, the early indicators suggest a higher chance of a busier season than usual. ENSO is currently in the warm neutral range, with nearly all models showing cooling into the cool neutral or perhaps La Niña range by the peak of the season. Climate models also suggest the tropical Atlantic will likely be warmer than average during the peak of the hurricane season, which would enhance the risk of Atlantic hurricane activity in the deep tropics. It should be worth noting, however, that if the 2020 Atlantic hurricane season ends up above average, it would be the fifth above average season in a row – something that has never happened on record.

Atlantic Sea Surface Temperatures

Currently, the North Atlantic has an odd sea surface temperature anomaly profile. Warmer than normal sea surface temperatures prevail in the Caribbean Sea, Gulf of Mexico, Subtropical Atlantic, and the far eastern Tropical Atlantic. Cooler than normal sea surface temperature anomalies have been present over the far north Atlantic and central tropical Atlantic. At the moment, there appears to be a weak negative AMO (Atlantic Multidecadal Oscillation) signal with a cool horseshoe of. This pattern is not typically one associated with active Atlantic hurricane seasons. However, an upcoming negative phase of the North Atlantic Oscillation (NAO) over the coming weeks could cause the AMO pattern to become more positive, as well as warming the tropical Atlantic. It should also be stressed that March sea surface temperature anomalies have proven to be a poor indicator for predicting Atlantic hurricane activity, as a similar negative AMO signal has been present during March for most of the last four seasons – all of which finished with above average Atlantic hurricane activity. Since 1995, the Atlantic has been in a high-activity era for hurricane activity, usually accompanied by a positive AMO signature. After three consecutive below average seasons from 2013-15, there was some doubt over whether this active era was still ongoing, but four consecutive above average seasons from 2016-19 seems to have confirmed the active era continues.

El Niño Southern Oscillation (ENSO)

For much of the year, the Niño 3.4 region has been fluctuating between warm-neutral and weak El Niño levels, though an El Niño event has not been declared by the Climate Prediction Center. The latest weekly Niño 3.4 sea surface temperature anomaly was +0.5°C, right on the El Niño threshold. The Oceanic Niño Index (ONI) has been at exactly +0.5°C for the last three trimonthly periods, so it remains a distinct possibility 2019-20 could be retroactively classified as a weak El Niño year. For much of the Northern Hemisphere winter, the atmosphere somewhat resembled a weak El Niño, with persistent rising motion near the Date Line. This signature has begun to broke down in the past month, suggesting further warming in the equatorial Pacific is unlikely over the next few months. The 90-day average Southern Oscillation Index (SOI) was -2.67, which is in the warm neutral range.

Despite the Spring Predictability Barrier typically resulting in low-confidence ENSO forecasts this time of year, there remains strong model agreement that the Niño 3.4 region will likely cool in Northern Hemisphere summer and fall 2020, with a La Niña event possible by the peak of the Atlantic hurricane season. The CFS model is the most aggressive with ENSO cooling, predicting a moderate La Niña event by the peak of the season. Other models, such as the ECMWF and UKMET, are close to ENSO-neutral for the peak of the season. No major model is currently predicting the development of El Niño conditions for summer 2020.The recent cooling of the subsurface in the equatorial Pacific gives some support to the idea of a cooling ENSO over the next several months. During the last several weeks, an upwelling Kelvin Wave has caused cooler than normal sea surface temperatures to strengthen and expand eastward over the equatorial Pacific subsurface. In addition, the warm subsurface anomalies have propagated eastward and weakened. This is not a trend typically seen prior to developing El Niño events, but rather a transition to cool ENSO events. I still have some doubts we will see a major La Niña event this fall, since most of the strongest La Niña events follow the discharge phase of major El Niño events (which did not occur in 2019-20). I think the most likely outcome is a slowly cooling ENSO over the next several months, with a weak La Niña event possible by early fall 2020. Although La Niña events are typically associated with high Atlantic hurricane activity, some of the most active seasons (such as 1995, 2005 and 2017) occurred in a cool-neutral/weak La Niña pattern rather than a moderate/strong La Niña pattern. La Niña events typically reduce the vertical wind shear over the central and western tropical Atlantic, leading to enhanced hurricane activity in this region. An interesting difference in 2020 compared to recent years is the Pacific Decadal Oscillation (PDO) appears to be slightly negative, whereas in recent years it has been generally positive. It appears likely at this time that ENSO will be an enhancing factor for the 2020 Atlantic hurricane season, but it should be stressed that ENSO forecasts in March are of lower confidence than other times in the year. The ENSO outlook should be much clearer for our May forecast (though it appears to be more confident than average at this lead time).

West African Monsoon (WAM)

In recent years, the Sahel region of western Africa, which is the source of most tropical waves that develop into tropical cyclones over the Atlantic Ocean, has been generally wetter than normal. This has lead to an increase in development over the eastern tropical Atlantic in recent years, even when the overall large-scale pattern is very hostile in this region. During the past month, precipitable water has been above normal over most of the Sahel, suggesting an increased chance of a strong African monsoon for the 2020 Atlantic hurricane season.

The multi-model NMME suite is suggesting an enhanced chance of precipitation over western Africa, as well as the Atlantic Main Development Region (MDR), for August-September-October 2020, likely as a result of an enhanced West African Monsoon. If the recent trend of a strong WAM continues, it appears likely the Atlantic MDR will have more tropical cyclone activity than usual, especially with a favorable ENSO and possibly warmer than normal sea surface temperatures.

Cyclonic Fury’s 2020 Atlantic hurricane season forecast:

• 13-18 named storms (average: 12)
• 6-10 hurricanes (average: 6)
• 2-5 major (category 3+) hurricanes (average: 3)
• Accumulated Cyclone Energy 140 +/- 50 (average: 100)

Cyclonic Fury also gives the following probabilities of activity. Right now, our forecast leans on the above normal side due to an expected lack of El Niño and a continuation of the active era of Atlantic hurricane activity. However, it should be stressed that forecasts in March are of low confidence due to the Spring Predictability Barrier.

• 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 ENSO is cool-neutral or La Niña, and the tropical Atlantic is much warmer than normal at the peak of the season.)
• Above normal season: 40% (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 is the most likely scenario, and will likely occur if ENSO cools to neutral, but the Atlantic sea surface temperature pattern is not conducive enough for a hyperactive season.)
• Near normal season: 20% (Does not fall into the Below Normal, Above Normal or Hyperactive criteria. This is possible if a negative AMO setup is present at the peak of the season, but ENSO is favorable enough to prevent a below-average season.)
• 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 it cannot be ruled out yet at this lead time. Also, there always is a slight chance of non-ENSO factors leading to much less activity than expected, as in 2013.)

At this extended range, it is near impossible to predict which areas, if any, will have hurricane or tropical storm threats in 2020. The next Cyclonic Fury forecast for the 2020 Atlantic hurricane season will be released on May 26, 2020. By this 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 Forecasts 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.