New report reveals key drivers behind northern hemisphere tropical cyclone risk


A new report by RMS looks at the key drivers behind northern hemisphere tropical cyclone risk. Forecasts indicate overall that 2022 is likely to be another above-average hurricane season.

The US National Oceanic and Atmospheric Administration (NOAA) has forecast between 14 and 21 named storms, of which six to 10 are expected to become hurricanes and three to six are expected to become major hurricanes (Category 3 or stronger).

Outlooks from other meteorological forecast agencies and groups are broadly in line with the guidance issued by NOAA in calling for an above-average season.

If these current forecasts prove right, 2022 would be a record seventh consecutive above-normal season, extending the current ongoing record of six seasons dating back to 2016.

The forecasts of an above-average season reflect the influence of several key seasonal oceanic and meteorological factors, including the El Niño-Southern Oscillation (ENSO), sea surface temperatures (SST) in the tropical Atlantic, and the Atlantic Multidecadal Variability (AMV).

A large proportion of the uncertainty associated with seasonal hurricane activity forecasts can be attributed to the uncertainty about which ENSO phase will materialize during the peak months of the hurricane season.

For 2022, most forecasts favour cooler La Niña conditions, and this would generally result in slightly above-average tropical activity in the North Atlantic Basin.

Another key factor is the AMV, which is a mode of natural climate variability that results in 25-to-40-year periods of increased or suppressed hurricane activity in the North Atlantic. In its positive (warm) phase, with SST anomalously warm, this is conducive to increased hurricane activity in the basin. The opposite impacts are associated with its negative (cool) phase.

According to NOAA, the AMV has been in a positive (warm) phase since 1995, which is representative of a high-activity era. Current model predictions indicate that SST anomalies in the tropical Atlantic are warmer, which typically enhances tropical activity by providing increased energy and moisture to the environment.

The number of storms that intensify into major hurricanes is noticeably greater during warm rather than cool phases – at least twice as many.

It takes just one major event to turn a season – as we saw with Hurricane Ida last year. Observed insured losses for Ida to date are in line with the RMS estimated range of between US$31 billion and US$44 billion. To put this into context, the total loss from Ida alone exceeds the total loss caused by the six hurricanes that made landfall in the US in 2020.

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