Extratropical Highlights –September 2022

 

1. Northern Hemisphere

The 500-hPa circulation during September featured predominantly above-average heights with the largest above-average height anomalies centered over the North Atlantic and the North Pacific Oceans, with moderate above-average height anomalies over North America and moderate below-average heights anomalies over Siberia and the Bering Sea (Fig. E9). The main land-surface temperature signals include above-average temperatures for central Asia and western North America (Fig. E1). The main precipitation signals include above-average totals in Europe, south and east Asia, and below-average totals in east and north areas of North America (Fig. E3).

 

a. North America

The 500-hPa circulation over North America featured broadly above-average height anomalies for Canada and the west U.S., and near-normal height anomalies for the south and east U.S. (Fig. E9).  This pattern contributed to the moderate and strongly above-average temperature anomalies recorded for much of the western U.S. and western Canada.  Most regions recorded temperatures in the 70th and 90th percentile (Fig. E1).  The main precipitation signals include above-average rainfall totals for California and the Southwest U.S. (Figs. E5, E6) and below-average rainfall totals across Canada (Fig. E3) and the central U.S. (Fig. E6).  The Alaska Panhandle also recorded above-average rainfall (Fig. E3).

 

b. Europe and Asia

The 500-hPa height pattern featured moderately below-average heights across Europe (Fig. E9) that contributed to the above-average rainfall recorded for Northern and Southern Europe (Figs. E3, E4). Temperatures were near-normal for most of Eurasia and above-average in the United Kingdom, Scandinavia, and across central Asia where temperatures reached the 70th and 90th percentile of occurrences (Fig. E1). The precipitation totals were above-average for India, Southeast Asia, and eastern Russia, and below-average in China (Figs. E3, E4).

 

c. West African monsoon

The west African monsoon extends from June through September, with a peak during July-September. During September 2022, the west African monsoon system was enhanced (Fig. E3) with area-average rainfall totals reaching near the 100^th percentile of occurrences (see Sahel region, Fig. E4).

 

2. Southern Hemisphere

The 500-hPa height field during September featured a nearly concentric annular ring of above-average height anomalies with the strongest departures located in the South Pacific Ocean, and strongly below-average heights located over the Bellingshausen Sea (Fig. E15). For much of Australia and southern Africa, the temperature and precipitation signals for the month of September were largely near-normal, with drier than average conditions recorded across Uruguay and southern Chile and moderately above-average rainfall in Queensland (Fig. E3).

The Antarctic ozone hole typically develops during August and reaches peak size in September. The ozone hole then gradually decreases during October and November, and dissipates on average in early December. By the end of September 2022, the size of the ozone hole approached nearly 25 million square kilometers, which is above the 2012-2021 average size of the ozone hole (Fig. S8). Associated with the ozone hole during September was a strongly above-average polar vortex area and moderately above-average polar stratospheric cloud coverage (Fig. S8).