Extratropical Highlights �June 2024

 

1. Northern Hemisphere

The 500-hPa circulation during June featured a strong ridge over the northernmost latitudes, over the North Atlantic Ocean, and south of the Black Sea (Fig. E9). Below average heights were observed over northern Canada, Greenland, and the Norwegian Sea (Fig. E9). The main land surface temperature signal during June included much above average temperatures across the U.S. and Eurasia (Fig. E1). The main precipitation signals include below average rainfall in the eastern half of the U.S. and above average rainfall across the Ural Mountains (Fig. E3).

 

a. North America

The 500-hPa circulation anomalies during June featured weakly above average heights across most of the U.S. and moderately below average heights in central Canada (Fig. E9). Temperatures were widely above average during June across the continental U.S. and Alaska with many areas reaching the highest 90th percentile of occurrences (Fig. E1). Across the western U.S., temperature anomalies were more than 5-degrees (C) above normal (Fig. E1). Above average rainfall was observed near the Great Lakes region and parts of the Gulf Coast, and below average rainfall was widely observed across the Midwest, Ohio Valley, Southeast, and Mid-Atlantic regions of the U.S., with some regions reaching the lowest 10th percentile of occurrences (Figs. E3, E5, E6). June is the typical month for an early onset of the Southwestern Monsoon and this year the June precipitation totals are slightly above average in the region and perhaps indicating an enhanced monsoon season will prevail this year (Fig. E6).

 

b. Eurasia

The 500-hPa height pattern across Eurasia featured predominantly above average, and near normal, heights (Fig. E9). Small areas featured below average heights, for example, over the Sea of Okhotsk, the Kara Sea, and the Norwegian to North Seas (Fig. E9). The predominant ridging pattern across Eurasia contributed to widespread above average temperatures (Fig. E1). Many areas reached the highest 90th percentile of occurrences and recorded anomalies in excess of 5-degrees (C) above normal (Fig. E1). Observed rainfall was largely near normal for most of Eurasia with a few exceptions, specifically across the Ural Mountains, along the eastern banks of the Caspian Sea, Austria, and eastern Asia, where above average rainfall was recorded (Fig. E3). Many areas along the Ural Mountains, in particular, reached the highest 90th percentile of rainfall occurrences (Fig. E3).

 

2. Southern Hemisphere

The 500-hPa circulation anomalies during June featured a near annular pattern of above average heights with centers of maxima south of Africa and New Zealand, and a minima in heights north of the Weddell Sea (Fig. E15). Above average temperatures were recorded widely across South America, Africa, and the southwestern flank of Australia (Fig. E1). Many areas in Africa and South America reached the highest 90th percentile of temperature occurrences, with regions in the east of equatorial Peru and Paraguay recording anomalies in excess of 5-degrees (C), on average, for the month of June (Fig. E1). Observed rainfall across South America was below average, with many areas reaching the lowest 10th percentile of occurrences (Figs. E3, E4). Rainfall totals across some regions of Africa were above normal for the month of June, including the Sahel and South Africa, where rainfall totals reached the highest 90th percentile of occurrences (Figs. E3, E4).