Seasonal Amount Forecast for North Atlantic Tropics Reduced Slightly; Mostly “Fish” Storms. Still…Expect 2 Major Hurricanes to Strike U.S.

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Executive summary: Due to unexpected cooler than normal waters in the North Atlantic basin subtropics and only near normal SSTA in the deep tropics the 2022 seasonal tropical cyclone forecast is reduced slightly in the latest Climate Impact Company update. A La Nina climate persists and the attendant low-shear upper tropospheric wind to allow tropical cyclones to flourish is still expected. However, slightly reduced upper ocean heat will make this season slightly less robust than previously indicated. The analog years suggest that most of this season’s storms will stay out to sea. However, the analog years also suggest renegade unusually strong storms making landfall on the U.S. Coast is likely and they could occur as late as October. Operational forecasts indicate limited or no risk of tropical cyclone activity the next 15 days (through August 7th). This season is shaping up as a delayed start to the core of the seasonal activity and once the pattern becomes active lingering later than normal (through October) is (now) expected.

 Tropical StormsHurricanesMajor HurricanesACE Index
7/24/22 FCST1883130
After 8/11583127
2022 So Far3003
5/3/22 FCST20105149
4/7/22 FCST1994135
15-YR NML16.47.33.2110.6
30-YR NML14.87.33.2120.5
50-YR NML12.66.42.699.2
Last Year2174146

Table 1: The Climate Impact Company 2022 North Atlantic basin seasonal tropical cyclone activity forecast for May 3rd compared to the April outlook and various climatology and the past 2 seasons.

Updated climate discussion: The central and southern North Atlantic basin is unusually cool for late July (Fig. 1). The daily tropical North Atlantic (TNA) index representing SSTA in-between the Caribbean Sea and coastal Northwest Africa region is +0.10C and has cooled slightly the past couple weeks. This oceanic zone is the main development region (MDR) for hurricanes in the North Atlantic basin. Additionally, waters to the north near and east of Bermuda are also unusually cool for this time of year and the 30-day trend indicates cooling has continue. The Gulf of Mexico has recently warmed to +0.49C. Waters off the Mid-Atlantic and Northeast U.S. are warming rapidly.

Fig. 1: The daily North Atlantic basin SSTA analysis.

The early tropical cyclone season upper-level pattern is established. The North Atlantic semi-permanent upper-level high-pressure ridge known as the “Bermuda High” extends from just east of Bermuda northeastward to Spain (Fig. 2). This feature has been stronger than normal and helped to inspire a Western Europe heatwave. In the subtropics weak low-pressure aloft is dominant helping to explain the cool SSTA pattern in that region. Of course, most dominant is the gigantic high-pressure ridge anchored over the U.S. drought area (Fig. 3). The influence of the U.S. drought on the prevailing upper air pattern and the cooler than 20-year climatology SSTA across the North Atlantic tropics and subtropics weigh heavily on the updated season tropical cyclone activity forecast for 2022.

Fig. 2-3: The prevailing upper air pattern for North America and across the North Atlantic for meteorological summer so far plus the daily U.S. soil moisture anomalies identifying widespread dryness.

Updated seasonal activity forecast: The NEW analog years selected to produce the updated seasonal tropical cyclone activity outlook for the North Atlantic basin are 2000, 2011, 2012 and 2018. The activity from each analog year is taken beginning August 1st. The results for each year (Table 2) are remarkably similar and average 15 tropical storms, 8 hurricanes and 3 intense hurricanes. So far in 2022 three tropical cyclones have formed (Alex, Bonnie and Colin). Adding observed and forecast data yields a new seasonal forecast of 18 tropical storms, 8 hurricanes and 3 intense hurricanes. The seasonal activity forecast remains above normal but eases back slightly due to the cooler waters in the outer North Atlantic tropics and subtropics.

YearTropical StormsHurricanesMajor HurricanesACE Index
7/24 FCST14.4 (15)7.5 (8)2.75 (3)126.75 (127)
2022 So Far3002.8
5/3/22 FCST20105149
4/7/22 FCST1994135
Last Year2174146

Table 2: The Climate Impact Company updated seasonal activity forecast for the 2022 North Atlantic basin tropical cyclone season compared to the previous outlooks and various climatology.

Other forecasts: Other leading forecasters of seasonal tropical cyclone activity for the North Atlantic basin remain reasonably close in their projections for 2022. Currently, Colorado State University is most active with Tropical Storm Risk U.K. indicating slightly less activity similar to the Climate Impact Company update. Each forecast was updated in July. The NOAA outlook issues a range of possibilities and the CIC, CSU and TSR forecast all fall within that range. The CSU forecast is also the most dangerous indicating an accumulated cyclone energy forecast of a robust 180 while TSR (150) and CIC (130) are closer to normal.

Tropical StormsHurricanesIntense HurricanesACE Index
CIC 7/141883130
CSU 7/520105180
TSR 7/51894150
NOAA 5/2414-216-103-6N/A
30-Year NML14.87.33.3126.3

Table 3: Lead providers of seasonal tropical cyclone activity for the North Atlantic 2022 season.

Projected tracks: Due to the similarities in the general upper-level pattern and attendant steering currents the analog years (2000, 2011, 2012 and 2018) each offer remarkably similar prevailing tropical cyclone tracks (Fig. 4-7). Each analog year produced tropical cyclone tracks turning north more quickly than normal keeping Gulf of Mexico risk relatively suppressed while most storms missed the Est Coast and moved out-to-sea sometimes referred to as “fish storms”. However, there are some notable exceptions including Major Hurricane “Sandy” in 2012 and Major Hurricane “Michael” striking the Florida Panhandle in 2018. Both landfalls occurred in October. Consequently, there is historical precedent for significant late season tropical cyclones striking the U.S. in either the Gulf of Mexico or on the East Coast.

Fig. 4-7: Analog years selected to generate the North Atlantic basin tropical cyclone season activity amount which identifies most storms staying out-to-sea.