Extratropical Highlights –July 2022

 

1. Northern Hemisphere

The 500-hPa circulation during July featured above-average heights over the North Pacific Ocean, central North America, eastern regions of the North Atlantic Ocean, Europe, central Eurasia, and the Sea of Okhotsk, and below-average heights over the Bering Strait and Hudson Bay (Fig. E9). The main land-surface temperature signals included above-average temperatures in North America, Europe, Scandinavia, eastern Russia, and Japan (Fig. E1). The main precipitation signals included above-average totals in central Asia, the Middle East, parts of the U.S., and central Africa, and below-average totals across parts of Canada, the Gulf Coast and surrounding regions, Europe, and parts of Russia (Fig. E3).

 

a. North America

The 500-hPa anomaly pattern over North America resembled a positive Pacific/North America teleconnection (PNA, Fig. E9) pattern, which aligns with the moderate-to-strong positive PNA index as reported on the Monthly Teleconnection Indices (Fig. E7).  This pattern contributed to modest above-average heights for central North America, and modest below-average heights for Eastern Canada (Fig. E9).  This pattern also contributed to above-average surface temperatures across much of the U.S. and Western Canada, where temperatures reached the 70th percentile of occurrences for much of the continent, and the 90th percentile of occurrences for a broad area stretching southeastward from the Alaskan Panhandle to the Gulf Coast (Fig. E1). Large urban cities in the Northwest had record-setting conditions including seven consecutive days above 95F for Portland, Oregon and six consecutive days above 90F in Seattle, Washington.

The main precipitation signals included below-average precipitation anomalies for the Great Plains and New England, and above-average precipitation anomalies for the Ohio Valley and the Southwest (Fig. E6).  Rainfall in the Ohio Valley reached the 90th percentile of occurrences while the Great Plains, New England, and Gulf Coast areas recorded rainfall amounts in the lowest 20th percentile of occurrences, or lower (Fig. E5).  According to the U.S. Drought Monitor, areas in the Great Plains reported a 3-class degradation in drought conditions over the month of July while parts of the Southeast and Ohio Valley reported a 2- to 3-class improvement in drought conditions.

 

b. Eurasia

The strongly positive 500-hPa anomaly field over Europe and parts further east brought a significant number of heatwaves to the region during the month of July.  Record temperatures were recorded in parts of Spain and death tolls reached over 10,000 people.  Temperatures exceeded the 90th percentile for all of Europe, eastern Russia, and Scandinavia (Fig. E1).  The main precipitation signals included below-average precipitation across Europe, and parts of Russia, and above-average precipitation in central Asia as well as Scandinavia (Fig. E3).

 

 

2. Southern Hemisphere

The 500-hPa height field during July featured a mixed pattern of above- and below-average height anomalies.  The main features were strongly above-average heights across the Tropic of Capricorn over the South Pacific Ocean, and moderately below-average height anomalies stretching from Cape Horn to the Ross Sea (Fig. E15).  The main temperature signals included above-average anomalies for south-central South America and below-average temperatures in Northeast Australia (Fig. E1).  The main precipitation signals included above-average rainfall for the Sahel and Northeast Australia, where rainfall amounts reached the 80th percentile and greater for those regions, and below-average rainfall for Southern Africa where rainfall was recorded in the lowest 20th percentile of occurrences (Figs. E3, E4).