Extratropical Highlights – June 2023

 

1. Northern Hemisphere

The 500-hPa circulation during June featured a strong ridge over much of Canada and Scandinavia and moderate troughing over both U.S. coasts, western Alaska, and Siberia (Fig. E9). The main land-surface temperature signals during June were above-average temperatures across much of North America, Europe, Russia, and parts of Asia (Fig. E1). The main precipitation signals included drier than average conditions for most of Europe, Scandinavia, and parts of North America, and wetter than average conditions for parts of North America, and across southern Eurasia (Fig. E3).

 

a. North America

The 500-hPa circulation anomalies during June featured strongly above-average heights over much of Canada, and below-average heights over western Alaska, as well both the West and East Coasts of the U.S. (Fig. E9). The anomalous ridging pattern contributed to above-average temperatures for much of Canada with some regions recording temperatures in the 90th percentile of occurrences (Fig. E1).  In some regions of the western and mid-Atlantic Seaboard of the U.S., temperatures for the month of June were below-average (Fig. E1).  Above-average precipitation totals were recorded for parts of the central and southeast U.S., with the central region recording rainfall in the 90th percentile of occurrences (Fig. E3).  Of note during June were the wildfires across Canada which, in combination with the ridging pattern that set up over eastern Canada, brought smoke and hazy conditions to the mid-Atlantic Seaboard on several occasions and significantly degraded air quality.  June is the typical month for the yearly onset of the Southwestern Monsoon and this year the June precipitation totals associated with the monsoon were well below-average and recorded in the lowest 10th percentile of occurrences (Figs. E5, E6).

 

b. Eurasia

The 500-hPa height pattern featured above-average heights over Scandinavia, the North Sea, and northern Europe and below-average heights over central regions of Siberia (Fig. E9). The ridging pattern ushered in well-above average temperatures for Europe and below-average temperatures for northwestern Russia (Fig. E1).  Across Europe, temperatures were recorded in the highest 90th percentile of occurrences (Fig. E1).  Precipitation totals were below-average across northern Europe and Scandinavia and above-average along the north coast of the Mediterranean Sea and parts of Eurasia (Figs. E3, E4).

 

2. Southern Hemisphere

The 500-hPa circulation anomalies during June featured a wavetrain pattern with strongly above-average heights over the Indian Ocean and central South Pacific Ocean, as well as over Antarctica, and strongly below-average heights over the eastern portions of the South Pacific Ocean, south of South America and south of Australia (Fig. E15).  Above-average temperatures were recorded across many regions in South America with regions near Bolivia recording temperatures in the highest 90th percentile of occurrences (Fig. E1).  Temperatures in eastern Australia were also well above normal and in the 90th percentile of occurrences, while western Australia observed mildly below-average temperatures (Fig. E1). Precipitation totals were well below normal for much of the region north of central Brazil as well as in Patagonia (Fig. E3).  Precipitation totals were well above average in the Sahel of Africa as well as South Africa, where both regions recorded rainfall in the 90th percentile of occurrences (Fig. E3).