Extratropical Highlights - May 2026

 

1. Northern Hemisphere

The 500-hPa circulation during May featured above average height anomalies over the North Pacific Ocean, the Canadian Maritime, and intermittently across Eurasia, and below average height anomalies over the Bering Sea, and eastern Canada (Fig. E9). The main land-surface temperature signals were above average temperatures across Europe and eastern Russia (Fig. E1). The main precipitation signals were above average rainfall in the southern United States (Fig. E3).

 

a. North America

The 500-hPa circulation during May featured near normal to weakly amplified height anomalies across North America. Moderately strong ridging was recorded off the U.S. Northwest coast and Alaska Panhandle, along with weak ridging over the Florida peninsula, and moderate troughing over the Bering Sea, and between the Hudson Bay and the U.S. Great Lakes (Fig. E9). Warmer than average temperatures were recorded across most of the western U.S. and Canada and cooler than average conditions were recorded for the Great Lakes and regions to the north (Fig. E1). Above average precipitation was recorded across the U.S. Gulf Coast and Southeast, with many areas exceeding the highest 90th percentile of occurrences (Figs. E3, E5).

 

b. Eurasia

The 500-hPa circulation during May featured near normal heights and weak ridging across Eurasia. Moderately strong ridging was recorded over central Eurasia and over eastern Russia, centered over the West Siberian Plain and the Chersky Range, respectively (Fig. E9). Warmer than average conditions were recorded across Europe and eastern Russia with many regions reaching the highest 90th percentile of occurrences (Fig. E1). Drier than average conditions were recorded for the United Kingdom and France and wetter than average conditions were recorded for eastern and central Russia with some areas reaching the highest 90th percentile of occurrences (Fig. E3).

 

2. Southern Hemisphere

The 500-hPa height anomalies featured a wavetrain pattern of amplified ridging and troughing along the middle latitudes around Antarctica (Fig. E15). Temperature anomalies were generally near normal across Africa, and moderately below normal for southern South America and northern Australia, where large areas reached the lowest 30th percentile of occurrences (Fig. E1). Drier than average conditions were recorded across central South America with many areas reaching the lowest 10th percentile of occurrences (Figs. E3, E4). Drier than average conditions were also recorded across Western Australia and the coastal region of Queensland (Fig. E3).