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meteorologists expect another hyperactive season

(CNN) — After last year’s record hurricane season, meteorologists are expecting another hyperactive season in 2021.

Colorado State University (CSU) released its forecast for the 2021 Atlantic hurricane season on Thursday and predicts an above-average season again this year.

CSA predicts there will be 17 named storms, eight hurricanes, and four major hurricanes (Category 3 or greater). All of those numbers are above the average for a typical season of 12 named storms, six hurricanes, and three powerful hurricanes.

However, the averages are in the process of updating, according to Ken Graham, director of the National Hurricane Center (NHC).

“We will have these new averages for the season. In fact, we’re going to release that information in the coming weeks, ”says Graham.

CSU is one of many academic institutions, government agencies, and private companies that screen the seasons.

Although the official forecast from the National Oceanic and Atmospheric Administration (NOAA) will not arrive until the end of May, there is already a strong consensus that the Atlantic is heading for another active season.

Factors that increase hurricane activity

There is considerable heat over much of the eastern Atlantic, where the ocean surface temperature is 1-3 degrees Celsius above normal for early April.

“The main reasons we are above average are the low probability of a significant El Niño event and the relative warmth in the tropical (Atlantic), but especially the eastern subtropical Atlantic,” said Phil Klotzbach, research scientist at CSU.

Sea surface temperatures are one of the necessary ingredients to fuel hurricanes, so it makes sense that there is a correlation between temperatures and an active season.

Another big factor is El Niño, or its absence.

When El Niño is present, it reduces hurricane activity in the Atlantic due to increased vertical wind shear. These are the changes in wind speed and direction that prevent hurricanes from forming.

Most dynamic modeling and statistical models at this time indicate that there is little chance that El Niño will develop between August and October.

“Current El Niño probabilities for NOAA are quite low for August-October (10%),” according to Klotzbach.

Average or even La Niña conditions create a more favorable environment for the development of tropical storms. While we are emerging from an active La Niña pattern, according to NOAA it is not quite over yet.

So, for the moment, it does not seem likely that this 2021 will influence the calming effect of El Niño on the Atlantic hurricane seasons.

Source: Climate Prediction Center of the National Meteorological Service.
Graphic: Curt Merrill, CNN.

Hurricane Season Changes Ahead

The 2020 Atlantic hurricane season ended with a total of 30 named storms, the highest annual number on record. People living along the coast from Texas to Maine were affected by at least one named storm during the season. But the postseason brought some significant changes, including the removal of three individual named storm names, as well as the full roster of backup names.

The Hurricane Committee of the World Meteorological Organization (WMO) held its annual meeting last month to discuss past hurricane seasons and update its operational plans.

Before 2021, if all the names from the default alphabetical list were used in the hurricane season, the next plan was to use the Greek alphabet.

“The Greek alphabet will not be used in the future because it creates a distraction in the communication of hazard and storm warnings and is potentially confusing,” the WMO announced in March.

The decision was to have a separate list of names as backup.

The Greek alphabet is to be replaced with a supplemental list of names that follows the same rules as the main list of hurricane names for the Atlantic season. This will be used in case the initial listing runs out. Names range from A to Z, but exclude the letters Q, U, X, Y, and Z.

This will allow the supplemental list of names to be more easily removed and replaced when needed.

Source: NHC.

Preparation for hurricane season begins now

About 30% of all Atlantic hurricanes make landfall in the United States. However, the 17 predicted storms do not need to make landfall for this to be an impact season.

“It doesn’t matter if there are 30 storms or one (…). If it hits you, it’s a busy season, ”says Graham.

That is why it is important that you start preparing now by reviewing your evacuation plans and making sure your evacuation kit is in order and up to date.

The NHC is already beginning its preparations for the 2021 season. This year, the center will release its forecasts for the Atlantic starting May 15, rather than June 1. The goal is to better serve communities affected by tropical systems that arrive early in the season.

In seven of the last 10 years there were tropical systems before the official start of the hurricane season, which is June 1.

Storm surge patterns

The NHC also improved its storm surge models.

“We have some new storm surge models that we are very excited about,” says Graham. “I think it’s really going to improve our ability to get that information for storm surge-based evacuations, even earlier than ever (so far),” he explains.

This is very important because, according to Graham, storm surges are historically the deadliest parts of tropical systems. Additionally, storm surge forecasts tend to be the main driver of evacuation plans on shore.

“The best part is that in some cases where we are very confident, we are going to go from posting that information 48 hours in advance, as we do now, to 60 hours,” said Graham. “That is important for decision makers to help them make those difficult decisions to evacuate or not.”

The NHC’s official hurricane forecast will be released in May. “We seem to be trending toward an above-average average once again,” Graham said.

Source: NHC.

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