Brian Donegan and Jonathan Belles
Published: April 16, 2020
The 2020 Atlantic hurricane season is predicted to be more active than usual, according to an outlook released Thursday by The Weather Company, an IBM Business.
The outlook created by Dr. Todd Crawford, chief meteorologist at The Weather Company, calls for 18 named storms, nine hurricanes and four major hurricanes – one that is Category 3 or higher (115-plus-mph winds) on the Saffir-Simpson Hurricane Wind Scale.
This forecast is significantly above the 30-year (1981-2010) normalized average of 13 named storms, seven hurricanes and three major hurricanes.
Numbers of Atlantic Basin named storms (those that attain at least tropical or subtropical storm strength), hurricanes and hurricanes of Category 3 or higher intensity forecast by The Weather Company, an IBM Business, and Colorado State University compared to the 30-year average (1981 to 2010) and totals from the 2019 season.
Though the official Atlantic hurricane season runs from June through November, storms can occasionally develop outside those months, as was the case in the previous three seasons with Subtropical Storm Andrea in May 2019, Tropical Storm Alberto in May 2018 and Tropical Storm Arlene in April 2017.
The Weather Company outlook is based on a number of factors, including Atlantic Ocean sea-surface temperatures, La Niña and other teleconnections, computer model forecast guidance and past hurricane seasons exhibiting similar atmospheric conditions.
"Weighing all of the factors, we have started the bidding at 18 named storms, nine hurricanes and four major hurricanes for the 2020 North Atlantic tropical season," Crawford said. "However, we think there is still some upside to these numbers, and that a 'hyperactive season' like we had in 2010 and 2017 is still in play."
2010 tied for the third-most-active Atlantic hurricane season on record for named storms, with 19, 12 of which became hurricanes. 2017 was the fifth-most-active season, with 17 named storms and 10 hurricanes, including major hurricanes Harvey, Irma and Maria.
Here are some questions and answers about what this outlook means.
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. One or more of the 18 named storms predicted to develop this season could hit the U.S. or none at all. That's why residents of the coastal U.S. should prepare each year no matter the forecast.
A couple of examples of why you need to be prepared each year occurred in 1992 and 1983.
The 1992 season produced only six named storms and one subtropical storm. However, one of those was Hurricane Andrew, which devastated South Florida as a Category 5 hurricane.
In 1983, there were only four named storms, but one was Alicia. The Category 3 hurricane hit the Houston-Galveston area and caused almost as many direct fatalities there as Andrew did in South Florida.
In contrast, the 2010 Atlantic season was quite active, with 19 named storms and 12 hurricanes. 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 and have one or more hitting the U.S. coast with major impact.
Named storm tracks in the 2019 Atlantic hurricane season. The colors correspond to intensities of each named storm during that section of the track, except for the black sections, which correspond to either a remnant or the time during which a system was a tropical wave before forming into a depression or storm.
The U.S. averages one to two hurricane landfalls each season, according to NOAA's Hurricane Research Division statistics.
In 2019, there were two U.S. hurricane landfalls – Barry in Louisiana and Dorian in North Carolina.
In 2018, four named storms impacted the U.S. coastline, most notably hurricanes Florence and Michael within a month of each other.
In 2017, seven named storms impacted the U.S. coast, including Puerto Rico, most notably hurricanes Harvey, Irma and Maria, which battered Texas, Florida and Puerto Rico, respectively.
Before that, the U.S. was on a bit of a lucky streak.
The 10-year running total of U.S. hurricane landfalls from 2006 through 2015 was seven, according to Alex Lamers, a meteorologist at the National Weather Service. This was a record low for any 10-year period dating to 1850, and considerably lower than the average of 17 per 10-year period in that same span.
None of the U.S. landfalls from 2006 through 2015 were from major hurricanes.
So it's impossible to know for certain if a U.S. hurricane strike will occur this season. Keep in mind that even a weak tropical storm hitting the U.S. can cause major impacts, particularly if it moves slowly and triggers flooding rainfall.
How Much of a Role Will El Niño or La Niña Play?
El Niño/La Niña, the periodic warming/cooling of the equatorial eastern and central Pacific Ocean, can shift weather patterns over a period of months. Its status is always one factor that's considered in hurricane season forecasting.
As of early spring, a weak Modoki El Niño was in place, but waters in March slowly cooled. Crawford noted that this cooling trend will likely continue, and he expects a transition toward La Niña conditions as the spring and summer progress.
Long-range forecasters at both NOAA and Colorado State University were generally in agreement with Crawford, suggesting that neutral conditions (neither El Niño nor La Niña) are anticipated through the first half of the hurricane season (June through August, or JJA), with either neutral or La Niña conditions possible in the second half (September through November, or SON).
Model-Based El Niño/La Niña Outlook Through the End of 2020
We should note here, before talking about the impacts of a possible La Niña, that the status of the El Niño-Southern Oscillation (ENSO) is notoriously difficult to predict. This is especially true from February to May, when the "spring predictability barrier" is in play, a period when forecast skill is lower than the rest of the year.
La Niña generally acts as a speed boost to the Atlantic hurricane season, but it is just one factor that can lead to an active year. Hurricane seasons can be active even if La Niña is not in play.
La Niña typically corresponds with a more active hurricane season because the cooler waters of the Eastern Pacific Ocean end up causing less wind shear along with weaker low-level winds in the Caribbean Sea. La Niña can also enhance rising motion over the Atlantic Basin, making it easier for storms to develop.
The La Niña years of 2010 and 2011 are among several tied for the third-most-active Atlantic seasons on record (both years had 19 named storms). The next La Niña year, 2016, was also active, with 15 named storms that included Category 5 Matthew and three other major hurricanes. La Niña conditions recurred midway through the hyperactive and catastrophic 2017 season that produced Harvey, Irma and Maria.
Other Factors in Play
One of the other ingredients that meteorologists, including Crawford, are considering for hurricane season is current sea-surface temperatures across the Atlantic Ocean.
Much of the Atlantic's waters are already warmer than average as of mid-April. The Gulf of Mexico is also several degrees above average, given recent heat and the lack of rain over the Southeast. Taken as a whole, Atlantic Basin sea-surface temperatures are currently at record-warm levels, "supporting a big season," Crawford said.
The tropical and subtropical Atlantic generally is warmer than normal. The region with above-normal SSTs in Atlantic correlates fairly well with typical March SST pattern associated with above-normal #hurricane seasons. Exception is current cold anomaly in far North Atlantic.
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But it isn't ocean temperatures in April that will help boost or curtail tropical systems; Rather, it is water temperatures during the hurricane season.
Climate models suggest that most of, if not the entire, Atlantic Basin will be warmer than average during the peak of the hurricane season.
Forecast Sea-Surface Temperature Anomalies for August through October 2020
An above-average number of tropical storms and hurricanes is more likely if temperatures in the main development region (MDR) between Africa and the Caribbean Sea are warmer than average. Conversely, below-average ocean temperatures can lead to fewer tropical systems than if waters were warmer.
Assuming atmospheric factors are favorable, warmer waters in the MDR allow tropical waves – the formative engines that can eventually become tropical storms – to get closer to the Caribbean and the U.S.
The prevalence of wind shear and dry air across the Atlantic will also need to be watched over the next six to eight months.
If La Niña does kick in, as many forecasters expect, and the atmosphere responds to it, there could be less wind shear and more favorable conditions for hurricane growth toward the end of the season.
How much dry air rolls off the coast of Africa will also need to be monitored. Even if water temperatures are very warm and there is little wind shear, dry air can still disrupt developing tropical cyclones and even prohibit their birth.
Hurricanes need a precise set of ingredients to come together in order for them to fester, and those ingredients will need to be monitored this year.
Crawford also noted that computer model forecasts for tropical forcing during the heart of the hurricane season are "strongly suggestive of an active season," and his forecast is similar to the model consensus.
The Atlantic hurricane season officially begins June 1 and runs through Nov. 30. This article provides a list of potentially life-saving tips to help you prepare for a hurricane.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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