CSU calls for 17 named storms, 8 hurricanes and 4 major hurricanes (Category 3 or higher). Each of these numbers is higher than the average seasonal average of 12 named storms, 6 hurricanes and 3 major hurricanes.
However, according to Ken Graham, director of the National Hurricane Center (NHC), seasonal averages are updating.
“We will have the new averages in the season. In the next few weeks we are going to release the information,” Graham said.
CSU is one of the many academic institutions, government agencies and private forecasting companies that bring out seasonal projections.
Although the official forecast from the National Oceanic and Atmospheric Administration (NOAA) will not come until the end of May, there is already a strong consensus that the Atlantic Ocean is still on an active season.
Factors that increase hurricane activity
Over most of the eastern Atlantic Ocean there is heat, where the surface temperature of the ocean in early April is 1-3 degrees above normal.
“The primary reasons we are above average are the low probability of a significant El Niño event and the relative heat in the tropical (Atlantic), but especially the subtropical eastern Atlantic,” said Phil Klotzbach, a researcher at CSU, said.
Sea surface temperatures are one of the ingredients needed to trigger hurricanes, so it is logical that there is a correlation between temperatures and an active season.
Another big factor is El Niño, or the lack thereof. When El Niño is present, it reduces Atlantic hurricane activity due to increased vertical wind shift – changes in wind speed and direction that prevent hurricanes from forming.
Average conditions or even La Niña conditions create a more favorable environment for tropical storm development. While we are coming off an active La Niña pattern, according to NOAA, it is not quite over yet.
At the moment, it seems that El Niño’s calming effect on the Atlantic hurricane season for 2021 is unlikely.
Changes to hurricane season coming
If the hurricane season before 2021 used all the names on the predetermined alphabetical list, the next plan was to use the Greek alphabet.
“The Greek alphabet will not be used in the future as it leads to the distraction of the communication of danger and storm warnings and is potentially confusing,” the WMO announced in March.
It was decided to use a separate list of names as backup.
The Greek alphabet will be replaced by a supplementary list of names that use the same rules as the Atlantic hurricane name list – a list with names AZ, but excluding the letters Q, U, X, Y and Z – if and when the initial list with names is exhausted.
It can more easily retire and replace the supplementary list of names if needed.
Hurricane preparation begins now
“It doesn’t matter if there are 30 storms or one … if it affects you, it’s a busy season,” Graham said.
Seven of the past ten years have seen tropical systems before the official start of the hurricane season, which is June 1st.
“We have some new storm surge models that we’m very excited about,” Graham says. “I think it’s really going to improve our ability to pull out the information for evacuations based on storm strength, even earlier than ever.”
This is very important because Graham points out that storm surge is historically the deadliest part of tropical systems. In addition, storm forecasts are the main driver for coastal evacuation plans.
“The best part, in some cases where we are confident, we are going to extract the information from 48 hours, which we are doing now, we are going to expand it to 60 hours,” Graham said. “It’s a big issue for decision makers to help them make the difficult decisions whether they want to evacuate now.”
The NHC’s official hurricane forecast will be released in May and ‘it looks like we’re tending to an average to above average again,’ says Graham.