What factors could lead to a tropical cyclone risk in the northern hemisphere this season?

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This content was recently posted to the Blogs section of the RMS website. It is republished here with permission.

With June 1 heralding the official start of the 2022 North Atlantic hurricane season, Tropical Storm Alex already on the scoreboard, and eight hurricanes having made landfall in the past two seasons, the question everyone is asking The question is: will the 2022 North Atlantic hurricane season have as much impact? and expensive like 2020 and 2021? And for the Western North Pacific: will this year again be close to the long-term average in terms of the number of storms?

We recently published an executive summary of the RMS® 2022 Northern Hemisphere Tropical Cyclone Outlook report, which includes a review of the North Atlantic and Northwest Pacific seasonal forecasts for this year and the key drivers behind those forecasts.

Seventh Consecutive Above-Normal Hurricane Season in the North Atlantic?

Even though 2021 was the third most active hurricane season on record in the North Atlantic, in terms of the number of named storms, insurers will remember it for just one event: Hurricane Ida. It seems likely that Ida will be one of the costliest hurricanes on record.

Insured losses seen for Ida to date are in line with RMS’ estimated range of between US$31 billion and US$44 billion. To put this into context, Ida’s total loss alone exceeds the total loss caused by the six hurricanes that made landfall in the United States in 2020.

Major weather forecasting agencies and groups have now released their initial forecasts for the hurricane season, and RMS has analyzed their predictions. Overall forecasts indicate that 2022 is likely to be another above-average hurricane season.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has predicted 14 to 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 higher). The outlook from other weather forecasting agencies and groups is broadly in line with the guidelines issued by NOAA calling for an above-average season.

If these current predictions prove accurate, 2022 would be a seventh straight above-par season, extending the current record of six seasons dating back to 2016.

What does an average hurricane season look like? Using NOAA’s 1991-2020 U.S. climate normals, an average season would produce 14 named storms, seven hurricanes, and three major hurricanes.

Not all hurricanes make landfall, but long-term statistics indicate that the likelihood of a hurricane making landfall in the United States increases during more active seasons. The Colorado State University (CSU) landfall forecast predicts a 76% chance of at least one major hurricane making landfall in the United States this season. Tropical Storm Risk (TSR) predicts that two hurricanes and four tropical storms will affect the contiguous United States in 2022.

It should also be remembered that climatologically, tropical cyclone activity in the North Atlantic Basin peaks between mid-August and late October. Some forecasting groups will release a revised forecast in early August to reflect the increased certainty of weather and ocean variables. So what are the main factors driving hurricane risk for this season?

Factors Determining the North Atlantic Basin Forecasts

The forecast for an above-average season reflects the influence of several key seasonal ocean and weather factors, including El Niño-Southern Oscillation (ENSO), sea surface temperatures (SST) in the tropical Atlantic and the Atlantic Multidecadal Oscillation (AMO), or Atlantic Multidecadal Variability (AMV) as it is more commonly referred to in recent literature.

Much of the uncertainty associated with seasonal forecasts of hurricane activity can be attributed to uncertainty about which ENSO phase will materialize during the peak months of the hurricane season. For a more detailed explanation of ENSO, how it was discovered, and how it works, check out this RMS blog.

For 2022, most forecasts favor cooler La Niña conditions, and absent the influence of any other atmospheric or oceanic conditions and all other factors remaining equal, this would generally result in tropical activity slightly above the average in the North Atlantic basin.

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

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

The number of storms that intensify into major hurricanes is significantly higher during warm phases than cold ones – at least twice as many.

There are other factors, such as the North Atlantic Oscillation (NAO), Madden-Julian Oscillation (MJO), and Saharan Air Layer (SAL), which can influence tropical cyclone activity over a weekly or monthly basis, but which are difficult to predict. on seasonal time scales.

Forecasts for the Pacific Northwest

In 2021, we’ve expanded our outlook report to cover seasonal forecasts in the Asia-Pacific region, and this year’s report also includes the latest predictions for typhoon activity in the Pacific Northwest for 2022.

Forecasts converge again around a near-average year in the Pacific Northwest basin, around 23-24 tropical storms compared to long-term averages of 25-27, reflecting the influence of major ocean factors and seasonal weather, including ENSO and SST in the Western North Pacific.

Cold Neutral or La Niña ENSO conditions and associated factors could result in slightly lower overall activity for the basin. SSTs in the western North Pacific Basin are expected to be near or above average between July and November, with warmer SSTs generally enhancing tropical activity by providing increased energy and humidity to the environment.

It only takes one major event to transform a season – as we saw with Hurricane Ida last year. As a trusted partner, RMS is once again ready to inform critical business processes with reliable insights and analytics during the most challenging events of the year, including data delivered to our cloud-native applications such as RMS ExposureIQ .

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