Cyclonic Fury has released its July 2018 Atlantic hurricane season forecast update, and we now anticipate that the 2018 Atlantic hurricane season will see activity slightly below the long-term average. Our final forecast anticipates a total of 10-13 named storms to form in the Atlantic basin this year, along with 5-7 hurricanes, 1-3 major hurricanes and an Accumulated Cyclone Energy (ACE) index of 80 (+/- 20) units. This forecast includes the three systems that have already formed in the Atlantic basin this year: Subtropical Storm Alberto, Hurricane Beryl and Hurricane Chris. This forecast is primarily based on continued cooler than normal sea surface temperatures in the tropical Atlantic Ocean, a strong West African Monsoon, and that a weak El Niño event is likely to develop by late Autumn.

Atlantic Sea Surface Temperatures

While the Atlantic has usually seen an Atlantic Sea Surface temperature anomaly pattern resembling the positive (warm) phase of the Atlantic Multidecadal Oscillation (AMO) since 1995, 2018 continues to be an exception. Sea surface temperatures in the tropical Atlantic and far north Atlantic continue to be overall cooler than average – indicating a pattern typical of the negative phase of the AMO. Sea surface temperatures in the subtropical Atlantic are slightly warmer than average. This Atlantic sea surface temperature anomaly pattern is usually associated with inactive hurricane seasons. With a persistent positive phase of the North Atlantic Oscillation (NAO), strong trade winds have prevailed over the tropical Atlantic, limiting warming in the region. While the graphic above shows the tropical Atlantic as warmer than normal, it should be noted that it has a warm bias because the anomaly is based on an average sea surface temperature from a cold AMO era.

Most climate models predict that the tropical Atlantic will likely remain cooler than normal through the peak months of the season, though some slight warming is likely. Since the tropical Atlantic is generally cooler than normal, it is less likely that we will see strong hurricanes in this region this year. Last season, tropical Atlantic sea surface temperatures were well above normal, aiding in development of very intense Hurricanes Irma, Jose and Maria. In early July, we did see Category 1 Hurricane Beryl form over the deep Atlantic tropics, and development in this region before August is usually an indicator of an active season ahead. The formation and intensification of Beryl is likely an anomaly, since it was extremely small and formed with the help of a Convectively Coupled Kelvin Wave (CCKW). The cooler than normal tropical Atlantic will likely suppress convective activity, and climate models are in good agreement that this region will be drier than average during the peak of hurricane season. It remains too early to definitively conclude that the next cool AMO phase era has begun.

ENSO/PDO/PMM

The El Niño-Southern Oscillation (ENSO) remains neutral, though most of the east-central equatorial Pacific is slightly warmer than normal. The latest Niño 3.4 sea surface temperature anomaly is +0.3°C, 0.2°C below the El Niño threshold. Most climate models predict the warming of the Niño 3.4 region to weak El Niño levels by Autumn. El Niño events usually increase wind shear over the tropical Atlantic, making it more difficult for tropical cyclones to develop and strengthen. It is likely that this El Niño, if it develops, will be a more west-based event. However, it may be too late for El Niño to develop in time to have a major suppressing effect on the 2018 Atlantic hurricane season. The average 90-day Southern Oscillation Index (SOI) value, a measure of the pressure pattern over the South Pacific, is -0.56 – well within neutral range.

Most of the equatorial Pacific subsurface waters are warmer than normal, though the warmest anomalies have weakened in recent weeks while a small pool of cooler than normal waters has emerged over the eastern Pacific. The warmest anomalies remain about 3-4°C above average, though their extent has shrunk and weakened recently. Most of the equatorial Western and Central Pacific subsurface waters are warmer than normal, but not extremely so. Since El Niño has not yet developed and the extent of warm subsurface water has decreased, a moderate El Niño now appears unlikely, and a strong event is pretty much out of the question for fall 2018. With no significant Westerly Wind Bursts (WWBs) expected over the equatorial Pacific over the coming weeks, warming of the Niño regions should remain slow and gradual. An alternative possibility is that El Niño does not develop at all in 2018, but could develop and strengthen some time in 2019. However, it should be stressed that the evolution of ENSO is difficult to forecast, and remains uncertain beyond the fall.

The Pacific Meridonial Mode (PMM), which was strongly positive a couple months ago, has weakened significantly over the past two months. While this is typical in the summer months, a weaker PMM will likely make the eastern Pacific basin less active than originally predicted. Enhanced hurricane activity over the Eastern Pacific usually increases wind shear and subsidence over the Atlantic basin. The Pacific Decadal Oscillation (PDO) is currently near neutral, and this should have little effect on the 2018 Atlantic hurricane season.

West African Monsoon

The West African Monsoon (WAM) remains stronger than normal, with rainfall in the Sahel region of Africa above average. With a strong African monsoon, African tropical waves are usually stronger than normal and are more likely to survive and later develop into tropical cyclones. The NMME climate model mean predicts that above normal rainfall is likely to continue over western Africa into the August-October period. Although tropical waves are likely to be strong, so far this season (with the exception of Hurricane Beryl) they have generally lost nearly all of their deep convection upon entering the cool, dry tropical Atlantic. These waves will likely continue to struggle to develop for the next 2-3 weeks or so, with cool sea surface temperatures and continued Saharan Air Layer (SAL) dust outbreaks. After that time, the eastern tropical Atlantic should be warm enough for tropical cyclone development, and tropical cyclogenesis over this region will become more likely.

Where will the activity be?

I continue to expect that tropical activity will be greatest this season in the subtropical Atlantic and Gulf of Mexico, where I expect activity to be near or perhaps even slightly above average. The subtropical Atlantic has cooled somewhat in recent weeks, though it remains near average and generally warmer than the deep tropical Atlantic east of the Lesser Antilles. Due to cooler than normal sea surface temperatures, and an expected dry, stable environment, I continue to expect activity to be below normal in the tropical Atlantic Main Development Region (MDR). Wind shear is likely to be lower in the eastern half of the MDR than the western half near the Caribbean. Wind shear has been stronger than normal over the Caribbean Sea so far this summer, and this is likely to continue, especially if El Niño develops. As a result, I expect below average activity in the Caribbean Sea this season. Since tropical waves are strong, they may struggle to develop over the deep tropical Atlantic but may find more favorable conditions farther west or in the subtropics.

It remains nearly impossible to predict exactly which areas will get hit by tropical cyclones in a pre-season forecast, but it is possible to analyze which areas have a greater and lower risk looking at the expected basin activity. I would generally say that the Eastern Gulf Coast and East Coast of the United States, the Bahamas, and Bermuda may have a slightly enhanced risk for a tropical cyclone landfall this year due to warmer waters in the subtropical Atlantic than the deep tropical Atlantic. The Lesser Antilles, Greater Antilles (including Puerto Rico), and the Yucatan Peninsula will likely have a lower risk for a tropical cyclone landfall this season, due to the expected hostile deep tropics. I would say that the risk of a tropical cyclone affecting eastern mainland Mexico is near to slightly below average. It must be stressed that, even if conditions are generally unfavorable during a season, it only takes a short window of favorable conditions for a storm to intensify and affect a region!

Cyclonic Fury’s July 2018 Atlantic hurricane season forecast:

• 10-13 named tropical storms (average: 12)
• 5-7 hurricanes (average: 6)
• 1-3 major (Category 3+) hurricanes (average: 3)
• Accumulated Cyclone Energy (ACE) 80 +/- 20 (average: ~95)

Cyclonic Fury also gives the following probabilities of activity listed below. Since my May outlook, I have lowered the probability of a hyperactive or above normal season, and increased the probability of a near normal or below normal season – primarily due to the continued unfavorable Atlantic SST pattern and likely weak El Niño. I have also increased the predicted hurricane count slightly, primarily due to the fact we already saw two hurricanes form in the month of July which is somewhat unusual.

• Hyperactive season: Near 0% (Accumulated Cyclone Energy (ACE) of 153 or greater, given the parameters of an above-normal season are also met. Since tropical Atlantic sea surface temperatures are significantly cooler than average, and a weak El Niño is likely, hyperactive activity is not expected in the Atlantic basin this season.)
• Above normal season: 10% (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 will likely only occur if the tropical Atlantic unexpectedly warms significantly, and El Niño does not develop.)
• Near normal season: 40% (Does not fall into the Below Normal, Above Normal or Hyperactive criteria. This will likely occur if El Niño does not develop and the tropical Atlantic warms slightly)
• 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 will most likely occur if the tropical Atlantic remains very cool, and El Niño forms by the peak of the season.)

Cyclonic Fury also considers the following four years to be good analogs for the 2018 Atlantic hurricane season. It should be stressed, however, that every season is different and nobody should expect a “repeat” of any season.

• 1990 – 14 named storms, 8 hurricanes, 1 major hurricanes
• 1994 – 7 named storms, 3 hurricanes, 0 major hurricanes
• 2006 – 10 named storms, 5 hurricanes, 2 major hurricanes
• 2012 – 19 named storms, 10 hurricanes, 2 major hurricanes

Overall, Cyclonic Fury expects activity to be slightly below average, much less active than the hyperactive 2017 season. It should be stressed that, even in a quiet season, it only takes one storm to have a significant impact. If you live in a hurricane-prone area, be sure to have a hurricane plan this season, even though activity is likely to be near or below average this year!

This is the last Cyclonic Fury seasonal forecast for the 2018 Atlantic hurricane season. The next seasonal forecast will be an early look at the 2019 Atlantic hurricane season, and will be released some time in December 2018.