Insights & News

MetSwift Publishes Their 2021 Hurricane Season Outlook

14th April 2021

In the wake of the most active on record in 2020, risk assessors are on high alert as we approach 2021’s Atlantic hurricane season (Jun-Nov). Will we see another ‘hyperactive’ season, or something quieter? Today, MetSwift provides skilful guidance on what we may expect.

Hurricane Season 2021:
Return of the Frantic Atlantic?

If we only considered a climatological baseline, such as 1981-2020, then the answer would be ‘probably not’. A hyperactive season is not something we see every other year.

That’s not really a prediction, though. To achieve that, MetSwift has established, through intensive scientific research, which historical years provide the best guidance for the 2021 season.

Graph showing how the MetSwift predicted hurricane season activity compares with the 1981-2020 average.

Climatology used is the 1981-2020 average.

As you can see, the resulting prediction is an above average 2021 hurricane season. It suggests a slow start (Apr-Jun), followed by a very busy peak season (Aug-Oct) and a little more post-peak activity than usual.

The predictions for the MetSwift Analogues issued each month since Dec 2020 are listed below.

An anomalously active season has been consistently predicted – we were already warning of the possibilities back in our 17th Dec 2020 newsletter to clients:

“The MetSwift analogues suggest a more active season than average, with a notable persistence of the active signal across all months for hurricanes and major hurricanes”.

The message was then reiterated during MetSwift’s attendance of Insider London Live on January 26th.

The only question has been just how much above average. At that level of detail, the prediction has been more variable, largely in relation to uncertainty regarding the persistence of an ongoing La Niña event (anomalously cool waters in the central and eastern tropical Pacific). When such an event continues right through summer, the hurricane season tends to be more active.

A steadier predictor has been the state of the North Atlantic Ocean. The waters there are widely warmer than usual, and this has been true for many months now. Importantly, this includes much of the tropical and subtropical region. Warmer waters provide more heat energy and moisture to ‘feed’ tropical cyclones.

This situation has been increasingly common in the past few decades. As a result, the climatological baseline is now higher than it was. On 9th April, the National Hurricane Center announced that they will now use a 1991-2020 baseline of 14 named storms, 7 hurricanes and 3 major hurricanes. The old baseline was 12, 6 and 3. Now, more than ever, it pays to prepare in advance for the hurricane season.


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