Extratropical Highlights –July 2021

 

1. Northern Hemisphere

The 500-hPa circulation during July featured above-average heights over the North Pacific Ocean, central North America, eastern Russia, western Europe, and North Atlantic Ocean, and below-average heights over the Hudson Bay and north-central Russia (Fig. E9). The main land-surface temperature signals included above-average temperatures in western North America, Europe, and eastern Asia (Fig. E1). The main precipitation signals included above-average totals in southern and eastern Asia, central Africa and Southeast and Southwest U.S., and below-average totals across Canada, Japan, Latin America, and the Caribbean (Fig. E3).

 

a. North America

The 500-hPa circulation during July featured above-average heights over western and central Canada and northwest U.S. (Fig. E9). This pattern contributed to above-average surface temperatures in the western U.S. (Fig. E1). Much of the Pacific Northwest recorded temperatures in the upper 90^th percentile of occurrences. 

Also during July, below-average precipitation was recorded in the northwest U.S. leading to regional departures from normal (Fig. E6). Area-averaged totals in the region were in the lowest 20^th percentile of occurrences (Fig. E5).  Above-average precipitation anomalies in the Southwest and Southeast U.S. lead to departures from normal in the 90th and 70th percentiles for those regions, respectively (Fig. E3).  According to the U.S. Drought Monitor, areas in the Southeast indicate Class 1 and 2 improvements in drought conditions while the Southwest remains in Moderate drought conditions (or worse) despite the above-average rainfall for the area.

 

2. Southern Hemisphere

The 500-hPa height field during July featured a wave-like pattern of heights with above-average heights over the southern Pacific Ocean (nearest New Zealand), southern Indian Ocean, and over Antarctica.  It also featured below-average heights south of Australia, the southern Pacific Ocean (nearest South America), and the south Atlantic Ocean (Fig. E15).  Across Australia, above-average temperatures were observed (Fig. E1) along with near-normal precipitation conditions (Fig. E3).  Dry conditions were observed over the equatorial regions of Africa (Fig. E3).