Cyclonic Fury’s early 2018 Atlantic hurricane season forecast: above-normal activity the most likely scenario, but questions remain

Cyclonic Fury’s early 2018 Atlantic hurricane season forecast: above-normal activity the most likely scenario, but questions remain

It may be December and the 2018 Atlantic hurricane season is over five months away, but it is not too early to begin to speculate on what the next hurricane season will be like. The Atlantic basin featured hyperactive activity in 2017, with 17 named storms, 10 hurricanes and 6 major hurricanes, along with a very high Accumulated Cyclone Energy (ACE) index of 226 units. The Atlantic’s 2017 season came after an also active but less intense 2016 season, which featured 15 named storms, 7 hurricanes and 4 major hurricanes, along with an ACE of 141. It is worth noting that the Atlantic basin often sees above-normal activity three years in a row (such as 1988-90, 2003-05 and 2010-12). Based on the last two Atlantic hurricane seasons, it appears as if we are almost certainly still in the active era of Atlantic hurricane activity which began in 1995. While this generally enhances storm activity, the state of the El Niño Southern Oscillation (ENSO) for next season is highly uncertain, and this makes forecasting the upcoming season a challenge at this extended range.

Current Atlantic Sea Surface Temperatures

Global sea surface temperature anomaly map for December 21, 2017. (Source: NOAA)

Above-normal sea surface temperatures currently dominate in much of the tropical, subtropical and far north Atlantic, which is generally an indicator of a positive Atlantic Multidecadal Oscillation (AMO). The “cold blob” that has typically been present over the far Northern Atlantic in recent winters is much weaker this winter and is barely even noticeable. This “cold blob” was believed by many tropical meteorologists to be a possible indicator of a negative phase of the AMO, however, the Atlantic’s back-to-back above-average seasons (including the hyperactive 2017 season) now casts doubt on this theory. If the current sea surface temperature configuration holds, we will likely see another above-average Atlantic hurricane season in 2018 if El Niño does not form. The Atlantic sea surface temperature anomaly pattern is very important for forecasting the upcoming Atlantic hurricane season, and will need to be watched over the coming winter for major changes. However, since it appears we are likely still in the active era of Atlantic hurricane activity, the ENSO may be a more important indicator for the 2018 season.

El Niño Southern Oscillation (ENSO)

CPC/IRI Official Probabilistic ENSO forecast. (Source: Columbia University)

It is well documented that El Niño conditions decrease Atlantic hurricane activity because of stronger westerly wind shear and faster trade winds over the tropical Atlantic, while the Atlantic basin typically is more active during ENSO-neutral or La Niña phases. At present, La Niña conditions are established over the Tropical Pacific, and are likely to strengthen a little during the next month or so before weakening is expected to begin by early 2018. While it is unlikely that this La Niña will become a strong event, it should last until around March or April, when ENSO is expected to become neutral. Considerable uncertainty exists after this point, however, on whether ENSO will stay neutral, we will see La Niña conditions return, or El Niño conditions will develop in summer 2018. Predicting ENSO is very difficult prior to May due to the “Spring Predictability Barrier” where models often struggle to determine the state of ENSO for the hurricane season. In early 2017, numerous models, including CFSv2, CanSIPS, NMME among others – predicted that a moderate to strong El Niño would develop, which would have suppressed storm activity. The expected El Niño did not develop, with ENSO remaining neutral until this fall when weak La Niña conditions developed. As a result, the 2017 Atlantic hurricane season saw very high activity, as noted above.

Since 1980, following second-year La Niña events like 2017-18, there have been neutral conditions twice (1985-1986 and 2012-13), La Niña conditions once (2000-01), and El Niño conditions once (2006-07). This is a rather small sample size; however, it is generally uncommon to see La Niña events rapidly transition into a moderate to strong El Niño the following summer and fall. While a late-developing Weak El Niño event is a definitely a distinct possibility, it appears unlikely a strong El Niño will develop for the 2018 Atlantic hurricane season. However, as stressed above, confidence in the ENSO forecast for next summer is very low. We should have a better idea on how ENSO will shape up for the 2018 Atlantic hurricane season by April or May.

December forecast

Cyclonic Fury’s 2018 probabilities of activity, released in December 2017.

Since it is only December, it is too soon to release a specific range of numbers. Cyclonic Fury is currently predicting the following probabilities of activity for the 2018 Atlantic hurricane season:

  • Hyperactive season: 20% (Accumulated Cyclone Energy (ACE) of 153 or greater, given the parameters of an above-normal season are also met. This is most likely if conditions similar to 2017 prevail.)
  • 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 is most likely if ENSO remains neutral but tropical Atlantic sea surface temperatures are cooler than in 2017.)
  • Near normal season: 25% (Does not fall into the Below Normal, Above Normal or Hyperactive criteria)
  • 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).

At this extended range, it is nearly impossible to predict the tracks the hurricanes will take or which areas they will hit. However, it is likely, but far from certain, that we will see at least 1-2 hurricanes make landfall in the United States in 2018. Residents who live in hurricane-prone areas should always be prepared, even in a quiet season, as it only takes one storm to make a season memorable. The next Cyclonic Fury forecast for the 2018 Atlantic hurricane season will be released in mid-March 2018.

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