Extratropical Highlights –August 2022

 

1. Northern Hemisphere

The 500-hPa circulation during August featured above-average heights for most of the hemisphere with the largest above-average height anomalies centered over Eurasia and the Bering Sea, and moderate below-average heights anomalies over central Russia (Fig. E9). The main land-surface temperature signals included above-average temperatures in Europe, China, and across much of North America (Fig. E1). The main precipitation signals included above-average totals across eastern Asia and the southern states across the United States, and below-average totals in north-central Europe (Fig. E3).

 

a. North America

Other than a slight tilt toward below-average height anomalies for the western half of Alaska, much of North America had near-normal to moderately above-average height anomalies for the month of August (Fig. E9). The above-average height anomalies were centered over the Pacific Northwest and surrounding regions in the U.S., as well as New England and the Newfoundland area (Fig. E9).  This pattern contributed to the moderate and strong above-average temperature anomalies recorded for much of the U.S. and Canada.  Most regions recorded temperatures in the 70th and 90th percentile (Fig. E1).

The main precipitation signals were a slight tilt toward below-average rainfall for the Pacific Northwest and the Central Plains, and moderate to strongly above-average rainfall for the southern U.S. states where some areas recorded rainfall in the 90th percentile or greater (Figs. E3, E5).  The Alaska Panhandle also recorded above-average rainfall (Fig. E3).

 

b. Europe and Asia

The 500-hPa height pattern featured strongly above-average heights across northern Eurasia and strongly below-average heights across most of Russia (Fig. E9). This pattern contributed to large above-average surface temperature anomalies across Europe, western Russia, and Asia, with the largest departures ( > 5.0C) observed north of the Black and Caspian Seas (Fig. E1).  A tilt toward slightly below-average temperatures were recorded for central Russia (Fig. E1).  The main precipitation signals included above-average rainfall for central Russia and eastern Asia with vast areas exceeding the 70th and 90th percentile (Fig. E3).  Drier than average conditions were recorded for eastern Europe and western Russia (Fig. E3).

 

c. West African monsoon

The west African monsoon extends from June through September, with a peak during July-September. During August 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 August broadly featured 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 August were largely near-normal, with drier than average conditions recorded across Patagonia (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 (Fig. S8). By the end of August 2022, the size of the ozone hole approached approximately 17 million square kilometers, which is near the 2012-2021 average size of the ozone hole. Associated with the ozone hole during August was a strongly above-average polar vortex area and slightly above-average polar stratospheric cloud coverage (Fig. S8).