The CSU outlook calls for 19 named storms, nine of which are expected to become hurricanes, and four of those hurricanes becoming major hurricanes – Category 3 or higher (115-plus-mph winds) on the Saffir-Simpson Hurricane Wind Scale.
This forecast is well above the 30-year (1981-2010) average of 13 named storms, seven hurricanes and three major hurricanes and is one hurricane and one major hurricane more than its first outlook issued in early April.
CSU's outlook is in agreement with outlooks released last month by NOAA and The Weather Company, an IBM Business.
Though the official Atlantic hurricane season runs from June through November, storms can occasionally develop outside those months. This was the case in May when Tropical Storm Arthur and Tropical Storm Bertha formed. It was the sixth straight year at least one named storm formed before the June 1 official start of the season.
This week, Cristobal became the record-earliest-in-season third named Atlantic storm – previously held by Tropical Storm Colin on June 5, 2016.
CSU's outlook for named storms includes the three named storms that have already formed, so they expect another 16 named storms to form through the end of the hurricane season.
CSU's outlook is based on a number of climate factors.
Trending Toward La Niña?
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.
ENSO conditions are expected to remain either neutral - neither El Niño nor La Niña - or trend toward La Niña through the summer and fall.
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.
Warm Ocean
One of the other ingredients that meteorologists consider in hurricane season outlooks is current sea-surface temperatures across the Atlantic Ocean.
CSU tropical scientist Phil Klotzbach noted ocean temperatures in early June were particularly warm in a ribbon from the Gulf of Mexico across the subtropical Atlantic Ocean. Klotzbach says warm ocean temperatures this time of year tend to occur during active hurricane seasons.
Furthermore, climate models suggest that most of, if not the entire, Atlantic Basin will be warmer than average during the peak of the hurricane season, August through October.
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.
Assuming other atmospheric factors are favorable, warmer waters in this MDR allow tropical waves – the formative engines that can eventually become tropical storms – to get closer to the Caribbean and the U.S.
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 13 to 19 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.
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.
While you should prepare for hurricane season every year, it is critically important to do so this year.
"As Americans focus their attention on a safe and healthy reopening of our country, it remains critically important that we also remember to make the necessary preparations for the upcoming hurricane season," said Secretary of Commerce Wilbur Ross during NOAA's outlook announcement in May.