In just over two months, the 2019 Atlantic hurricane season will officially begin June 1. It should be noted, however, that the last four Atlantic hurricane seasons have all featured at least one named storm form before this date! Like any year at this time, there remains considerable uncertainty about how the El Niño Southern Oscillation (ENSO) as well as how the Atlantic sea surface temperature anomaly pattern will evolve between now and the peak of hurricane season. Currently weak El Niño conditions are present over the equatorial Pacific, and these conditions are expected to persist through at least the spring, possibly into the summer or even fall 2019. ENSO is notoriously hard to forecast through the next few months, a phenomenon known as the Spring Predictability Barrier (SPB), so it remains uncertain whether the El Niño will strengthen, dissipate, or just linger. Currently, the majority of the model guidance shows El Niño at least persisting to the point where it should have some effect on the upcoming hurricane season, so that will be factored in our forecast.

Atlantic Sea Surface Temperatures

Currently sea surface temperatures are close to average over the Atlantic Main Development Region (MDR). The majority of the model guidance, including the CFSv2, CanSIPS, and NMME, suggest the tropical Atlantic will warm relative to average over the next few months – possibly resulting in a positive Atlantic Multidecadal Oscillation (AMO) signature developing. Much of the subtropical Atlantic remains warmer than average, which has been the case for the vast majority of this decade. Last season, the subtropical Atlantic was very warm, which aided the formation of a record 7 subtropical storms as well as the re-intensification of Hurricane Florence. The far north Atlantic, however, is slightly cooler than normal, which is normally indicative of a negative AMO signature. However, this feature has been present on and off for much of the past several years and it has done little to hinder Atlantic hurricane activity. With the Atlantic featuring above-normal Atlantic hurricane activity for the last three seasons, it appears as if the multidecadal active phase, which began in 1995, is still ongoing. At this point, it does not appear likely that the Atlantic sea surface temperature profile will “make or break” the upcoming Atlantic hurricane season.

El Niño Southern Oscillation (ENSO)

Weak El Niño conditions are currently present over the equatorial Pacific. Although the Niño 3.4 sea surface temperature anomaly has been fairly consistently above +0.5°C since late last fall, the El Niño event was not officially declared until early last month. The majority of the model guidance predicts that El Niño will persist and perhaps strengthen through the end of 2019. This does indeed appear likely, with the CPC subsurface sea surface temperature anomaly map showing a massive area of warmer than normal water – as warm as 6°C above average in some areas! It should be noted, though, that the TAO/TRITON data is considerably cooler in the equatorial Pacific subsurface, showing maximum positive anomalies of only 3-4°C. Regardless, it does not appear likely that the current El Niño event will dissipate in the near future. Predicting the exact strength of the El Niño event is difficult considering we have not exited the Spring Predictability Barrier (SPB) yet, but I don’t think a super event is likely and I think it’s much more likely this event peaks in the moderate (but not very weak) range.

During El Niño events, wind shear is generally higher than normal over most of the tropical Atlantic, especially in the region between 40°W and 80°W south of 20°N. Based on the current model guidance, it appears likely that Altantic hurricane activity will be below normal in this region. However, if the West African Monsoon (WAM) remains strong this year as it has for much of the past decade, Atlantic tropical cyclone activity may actually be somewhat enhanced right off the coast of Africa (more on that below). It should also be noted that during El Niño years, wind shear may even be a little below average in the subtropical Atlantic, meaning this region could be quite conducive for tropical cyclone development. This was exemplified in 2015 when despite one of the strongest El Niño events on record, Hurricane Joaquin fell just short of Category 5 status near the Bahamas. Although model guidance is certainly pointing in the direction of El Niño conditions, this does NOT mean that there will not be a hurricane season in the Atlantic basin this year, and nobody should be complacent. Even if wind shear is above average during much of the season, that does not mean a tropical cyclone cannot find favorable conditions at any point during the season.

West African Monsoon (WAM)

One of the primary reasons why the 2018 Atlantic hurricane season was much more active than expected by most forecasts was the strong West African Monsoon (WAM), which resulted in many strong tropical waves developing over the cooler than average Atlantic MDR. The WAM has been fairly strong this decade, leading to the development of many MDR systems despite not having the most favorable sea surface temperature pattern for activity. Last year over a six-week stretch from late August to mid-October, six tropical cyclones – Hurricane Florence, Hurricane Helene, Hurricane Isaac, Tropical Depression Eleven, Tropical Storm Kirk and Tropical Storm Nadine formed over the region. The strong WAM likely played a significant role in the development of these systems.

The latest NMME model guidance predicts near-to-slightly above normal precipitation for the Sahel region of western Africa over July-August-September 2019. Last March, the NMME predicted a stronger WAM than what it is currently predicting now for peak season, which verified quite well. This could be a slight enhancing factor for the upcoming Atlantic hurricane season, but it remains to be seen how much. The exact strength of the WAM is hard to predict this far out, but it is a factor that will need to be watched closely over the coming months.

Cyclonic Fury’s March 2019 Atlantic hurricane season forecast

• 8-13 named storms (average: 12)
• 3-6 hurricanes (average: 6)
• 1-3 major hurricanes (average: 3)
• Accumulated Cyclone Energy (ACE) of 80 +/- 40 (average: 95)

Cyclonic Fury also gives the following probabilities of activity. Right now, we think a below-normal season is the most likely, though a season with activity close to normal remains a distinct possibility with such a large lead time.

• Hyperactive season: 5% (Accumulated Cyclone Energy (ACE) of 153 or greater, given the parameters of an above-normal season are also met. This is a highly unlikely scenario, unless the Atlantic MDR warms substantially with respect to normal, and the El Niño event dissipates by the peak of the season.)
• Above normal season: 15% (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 not a particularly likely scenario, but still could occur if the subtropical Atlantic is very active and the West African Monsoon (WAM) is strong.
• Near normal season: 30% (Does not fall into the Below Normal, Above Normal or Hyperactive criteria. This could occur if the warm subtropical Atlantic is enough to offset the expected hostile conditions in the tropical Atlantic, or if the El Niño does not strengthen further.)
• Below normal season: 50% (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 the most likely scenario and will most likely occur if El Niño strengthens into the summer and fall, and if the tropical Atlantic does not warm much with respect to normal.

Cyclonic Fury also considers the following four years to be the best possible analogs for the 2019 Atlantic hurricane season. It should be stressed, however, that every hurricane season is different and nobody should expect a “repeat” of any season.

• 1987 – 7 named storms, 3 hurricanes, 1 major hurricane
• 2002 – 12 named storms, 4 hurricanes, 2 major hurricanes
• 2009 – 9 named storms, 3 hurricanes, 2 major hurricanes
• 2015 – 11 named storms, 4 hurricanes, 2 major hurricanes
• Analog average – 9.75 named storms, 3.5 hurricanes, 1.75 major hurricanes

At this extended range, it is near impossible to predict which areas, if any, will have hurricane or tropical storm threats in 2019. The next Cyclonic Fury forecast for the 2019 Atlantic hurricane season will be released on May 21, 2019. 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.