The CSU is calling for 17 storms, 8 hurricanes and 4 major hurricanes (category 3 or higher). Each of these numbers is above the season average of 12 named storms, 6 hurricanes and 3 major hurricanes.
However, seasonal averages are being updated, according to Ken Graham, director of the National Hurricane Center (NHC).
“We’re going to have these new averages coming into the season. In fact, we’re going to publish that information in the next few weeks,” Graham said.
CSU is one of many academic institutions, government agencies and private forecasting companies that present seasonal forecasts.
Although the official forecast of the National Oceanic and Atmospheric Administration (NOAA) will come only at the end of May, there is already a strong consensus that the Atlantic Ocean is heading for another active season.
Factors that increase the activity of hurricanes
In much of the eastern Atlantic there is significant heat, where the ocean surface temperature is 1-3 degrees Celsius above normal for early April.
“The main reasons we’re going above average are the low probability of a significant event in El Niño and the relative heat in the tropics (Atlantic), but especially in the subtropical eastern Atlantic,” said Phil Klotzbach, a CSU scientist.
Sea surface temperatures are one of the ingredients needed to feed hurricanes, so it makes sense to have a link between these temperatures and the active season.
Another big factor is El Niño or lack thereof. When El Niño is present, it reduces the activity of hurricanes in the Atlantic Ocean due to increased vertical wind shear – changes in wind speed and direction that prevent the formation of hurricanes.
The average conditions or even the conditions of La Niña create a more favorable environment for the development of tropical storms. As we emerge from an active La Niña model, according to NOAA, it is not over yet.
So for now, the calming effect of El Niño on the hurricane season in the Atlantic does not seem likely in 2021.
Changes in the hurricane season are coming
Before 2021, if hurricane season used all the names on the predefined alphabetical list, the next plan of action was to use the Greek alphabet.
“The Greek alphabet will not be used in the future because it creates a distraction from the communication of danger and storm warnings and is potentially confusing,” the WMO announced in March.
It was decided that a separate list of names would be used as a backup.
The Greek alphabet will be replaced by an additional list of names using the same rules as the main list for naming the Atlantic hurricane season – a list of names AZ, but without the letters Q, U, X, Y and Z – if and when the original list with names is exhausted.
This will allow the additional list of names to be more easily withdrawn and replaced when the need arises.
Hurricane preparedness 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 last 10 years have seen the formation of tropical systems before the official start of the June 1 hurricane season.
“We have some new models of storms that we’re really excited about,” Graham said. “I think it will really improve our ability to bring out this storm-based evacuation information, even earlier than ever.”
This is very important because Graham points out that storms have historically been the deadliest part of the tropics. In addition, storm forecasts are usually the main driver of coastal evacuation plans.
“The best part, in some cases, when we’re really confident, it’s going to be 48 hours to get that information out, which we’re doing now, we’re going to extend that to 60 hours,” Graham said. “It’s a big job for decision makers, helping them make these really difficult decisions whether to evacuate or not.”
The official forecast for the NHC hurricane will be released in May, and “We seem to be aiming for average to above average again,” Graham said.