Near to Slightly Below Average 2018 Atlantic Hurricane Season Expected, According to The Weather Company's Updated June Outlook
A near or slightly below average number of hurricanes and tropical storms are expected for the 2018 Atlantic hurricane season, according to an updated seasonal outlook released by The Weather Company, an IBM Business.
The Weather Company expects 11 named storms during the season, including four hurricanes and two major hurricanes of Category 3 or higher intensity.
This is slightly less activity compared to the May outlook, which called for 12 named storms and five hurricanes this hurricane season.
The updated forecast is near the Atlantic Basin's 30-year historical average (1981-2010) of 12 named storms, six hurricanes and three major hurricanes and slightly less than the Colorado State University outlook released earlier this month.
There are several reasons forecasters are calling for these near-average numbers in 2018:
1. Atlantic Ocean Temperature Patterns
A pattern of cooler-than-average water temperatures has persisted and expanded in the eastern Atlantic and in the central northern Atlantic.
The Weather Company compared sea-surface temperature anomalies in June for inactive vs. active hurricane seasons and found that the current pattern more closely represents inactive hurricane seasons.
Temperatures in between the Lesser Antilles and Africa are supportive for tropical growth nearly year-round, but the warmer the water in that region, the more likely a tropical cyclone is to develop, all other factors (wind shear, atmospheric moisture, forward speed, etc.) held constant.
Should this pattern of cooler-than-average ocean temperatures continue into the heart of hurricane season (August, September and October), we can expect less tropical activity east of the Caribbean.
The Gulf of Mexico, while supportive of tropical storms and hurricanes, has cooled relative to average since the last update in May. Subtropical Storm Alberto was able to develop over these waters in late May.
2. Transition Toward El Niño Becoming More Likely
Waters in the eastern equatorial Pacific Ocean have warmed to near-average, a sign of neutral conditions. A few spots are even warming to above average warmth in the central Pacific. Neither La Niña nor El Niño conditions are present as of mid-June, but we are watching for a transition to El Niño.
The latest outlook from the Climate Prediction Center, released June 14, forecasts neutral conditions to last through much of the summer if not into the autumn before El Niño conditions potentially take over later this fall. This is a few months earlier than forecast in earlier outlooks.
The atmospheric component of this global atmospheric and oceanic phenomena is, so far, also leaning toward a less active season than originally thought, according to The Weather Company's outlook.
How quickly waters warm in the equatorial Pacific Ocean is still a big question going into the upcoming hurricane season. A faster warming of the Pacific, or a quicker transition toward El Niño, could mean fewer storms and hurricanes, especially toward the end of hurricane season.
3. Increasing North Atlantic Oscillation
The North Atlantic Oscillation (NAO), defined as a pattern of pressure gradients over the northern Atlantic Ocean, is expected to remain positive through the next few months.
Both the Azores-Bermuda high-pressure system and the Greenland low-pressure system are strengthened in the positive phase of the NAO. This creates a stronger pressure gradient and increased wind between the two systems. This also creates more wind around the Azores-Bermuda high.
Typical setup for the positive phase of the North Atlantic Oscillation.
In the winter, this means a quicker storm track for winter storms crossing the northern Atlantic, but in hurricane season, it may bring a few less-than-favorable conditions:
Gustier winds across much of the subtropics and North Atlantic.
Cooler water temperatures.
A slightly faster tropical wave track across the Atlantic.
The positive phase of the NAO decreases the chances of an active year.
Other Hurricane Season Forecasts
Other seasonal forecasts for named storms (NS), hurricanes (HU) and major hurricanes (MH) include:
Colorado State University: 14 NS, 6 HU, 2 MH
North Carolina State University: 14-18 NS, 7-11 HU, 3-5 MH
Tropical Storm Risk/University College London: 9 TS, 4 HU, 1 MH
NOAA: 10-16 NS, 5-9 HU, 1-4 MH
What Does This Mean For the United States?
There is no strong correlation between the number of storms or hurricanes and U.S. landfalls in any given season. Residents near the coast should prepare each year, no matter what seasonal outlooks say.
A couple of classic examples that show the need to prepare each year occurred in 1992 and 1983.
The 1992 hurricane season produced only six named storms and one subtropical storm. However, one of those named storms was Hurricane Andrew, which devastated South Florida as a Category 5 hurricane.
In 1983, there were only four named storms, but one was Hurricane Alicia. The Category 3 hurricane hit the Houston-Galveston area and caused almost as many direct fatalities along the Texas coast as Andrew did in South Florida.
In contrast, the 2010 hurricane season was active. There were 19 named storms and 12 hurricanes that formed in the Atlantic Basin. Despite the high number of storms that year, no hurricanes and only one tropical storm made landfall in the U.S.
In other words, a season can deliver many storms but have little impact, or deliver few storms with one or more causing major impacts to the U.S. coast.
The U.S. averages one to two hurricane landfalls each season, according to NOAA's Hurricane Research Division.
It's impossible to know for certain if a U.S. hurricane strike, or multiple strikes, will occur this season. Keep in mind, however, that even a weak tropical storm hitting the U.S. can cause major impacts, particularly if it moves slowly and triggers flooding rainfall.
Hurricane season runs from June 1 through Nov. 30 in the Atlantic Basin.
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The Weather Company expects 11 named storms during the season, including four hurricanes and two major hurricanes of Category 3 or higher intensity.
This is slightly less activity compared to the May outlook, which called for 12 named storms and five hurricanes this hurricane season.
The updated forecast is near the Atlantic Basin's 30-year historical average (1981-2010) of 12 named storms, six hurricanes and three major hurricanes and slightly less than the Colorado State University outlook released earlier this month.
There are several reasons forecasters are calling for these near-average numbers in 2018:
1. Atlantic Ocean Temperature Patterns
A pattern of cooler-than-average water temperatures has persisted and expanded in the eastern Atlantic and in the central northern Atlantic.
The Weather Company compared sea-surface temperature anomalies in June for inactive vs. active hurricane seasons and found that the current pattern more closely represents inactive hurricane seasons.
Temperatures in between the Lesser Antilles and Africa are supportive for tropical growth nearly year-round, but the warmer the water in that region, the more likely a tropical cyclone is to develop, all other factors (wind shear, atmospheric moisture, forward speed, etc.) held constant.
Should this pattern of cooler-than-average ocean temperatures continue into the heart of hurricane season (August, September and October), we can expect less tropical activity east of the Caribbean.
The Gulf of Mexico, while supportive of tropical storms and hurricanes, has cooled relative to average since the last update in May. Subtropical Storm Alberto was able to develop over these waters in late May.
2. Transition Toward El Niño Becoming More Likely
Waters in the eastern equatorial Pacific Ocean have warmed to near-average, a sign of neutral conditions. A few spots are even warming to above average warmth in the central Pacific. Neither La Niña nor El Niño conditions are present as of mid-June, but we are watching for a transition to El Niño.
The latest outlook from the Climate Prediction Center, released June 14, forecasts neutral conditions to last through much of the summer if not into the autumn before El Niño conditions potentially take over later this fall. This is a few months earlier than forecast in earlier outlooks.
The atmospheric component of this global atmospheric and oceanic phenomena is, so far, also leaning toward a less active season than originally thought, according to The Weather Company's outlook.
How quickly waters warm in the equatorial Pacific Ocean is still a big question going into the upcoming hurricane season. A faster warming of the Pacific, or a quicker transition toward El Niño, could mean fewer storms and hurricanes, especially toward the end of hurricane season.
3. Increasing North Atlantic Oscillation
The North Atlantic Oscillation (NAO), defined as a pattern of pressure gradients over the northern Atlantic Ocean, is expected to remain positive through the next few months.
Both the Azores-Bermuda high-pressure system and the Greenland low-pressure system are strengthened in the positive phase of the NAO. This creates a stronger pressure gradient and increased wind between the two systems. This also creates more wind around the Azores-Bermuda high.
Typical setup for the positive phase of the North Atlantic Oscillation.
In the winter, this means a quicker storm track for winter storms crossing the northern Atlantic, but in hurricane season, it may bring a few less-than-favorable conditions:
Gustier winds across much of the subtropics and North Atlantic.
Cooler water temperatures.
A slightly faster tropical wave track across the Atlantic.
The positive phase of the NAO decreases the chances of an active year.
Other Hurricane Season Forecasts
Other seasonal forecasts for named storms (NS), hurricanes (HU) and major hurricanes (MH) include:
Colorado State University: 14 NS, 6 HU, 2 MH
North Carolina State University: 14-18 NS, 7-11 HU, 3-5 MH
Tropical Storm Risk/University College London: 9 TS, 4 HU, 1 MH
NOAA: 10-16 NS, 5-9 HU, 1-4 MH
What Does This Mean For the United States?
There is no strong correlation between the number of storms or hurricanes and U.S. landfalls in any given season. Residents near the coast should prepare each year, no matter what seasonal outlooks say.
A couple of classic examples that show the need to prepare each year occurred in 1992 and 1983.
The 1992 hurricane season produced only six named storms and one subtropical storm. However, one of those named storms was Hurricane Andrew, which devastated South Florida as a Category 5 hurricane.
In 1983, there were only four named storms, but one was Hurricane Alicia. The Category 3 hurricane hit the Houston-Galveston area and caused almost as many direct fatalities along the Texas coast as Andrew did in South Florida.
In contrast, the 2010 hurricane season was active. There were 19 named storms and 12 hurricanes that formed in the Atlantic Basin. Despite the high number of storms that year, no hurricanes and only one tropical storm made landfall in the U.S.
In other words, a season can deliver many storms but have little impact, or deliver few storms with one or more causing major impacts to the U.S. coast.
The U.S. averages one to two hurricane landfalls each season, according to NOAA's Hurricane Research Division.
It's impossible to know for certain if a U.S. hurricane strike, or multiple strikes, will occur this season. Keep in mind, however, that even a weak tropical storm hitting the U.S. can cause major impacts, particularly if it moves slowly and triggers flooding rainfall.
Hurricane season runs from June 1 through Nov. 30 in the Atlantic Basin.
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