Extratropical Highlights – March 2024

 

1. Northern Hemisphere

The 500-hPa circulation during March featured a pattern of alternating anomalous ridging and troughing, with a maxima over Greenland and a minima over the North Atlantic Ocean and northern Russia (Fig. E9). The main land-surface temperature signals include above average temperatures across most of Eurasia and western North America (Fig. E1). The main land-surface precipitation signals include wetter than average conditions across Europe and the mid-eastern coast of North America (Fig. E3).

 

a. North America

The height pattern across North America featured weak, anomalous troughing along the U.S. West Coast and Manitoba, Canada, strong anomalous riding over the Canadian Maritime, and moderate to weak anomalous ridging from Quebec, Canada to the Mid-Atlantic U.S. Seaboard, and west toward the Ohio Valley (Fig. E9). This pattern contributed to warmer than average conditions for much of the eastern half of North America, with many areas reaching the highest 90th percentile of occurrences, such as Quebec, Canada where the monthly anomaly exceeded 5 degrees in some areas (Fig. E1). Wetter than average conditions were observed for northern Quebec, as well as along the U.S. East Coast from Maine to the Carolinas (Fig. E3). Above average rainfall totals were also observed in the Pacific Northwest, Southern California, and Inter-Mountain West, with rainfall exceeding at least the highest 70th percentile of occurrences (Figs. E5, E6). Drier than average conditions were observed for the Great Plains and the Alaska Panhandle (Figs. E3, E5, E6).

 

b. Eurasia

The 500-hPa height pattern for March featured anomalous troughing over the North Atlantic Ocean west of Europe, anomalous ridging over Scandinavia, and anomalous troughing over Dudinak, Russia, in the Russian Tundra (Fig. E9). Warmer than average conditions were observed in Europe and across central Asia (Fig. E1). Cooler than average conditions were observed in coastal areas adjacent to the Baltic Sea and the Gulf of Bothnia (Fig. E9). Wetter than average conditions were observed in Europe where some areas in Spain recorded rainfall in the highest 90th percentile of occurrences (Figs. E3, E4).

 

2. Southern Hemisphere

The 500-hPa height pattern featured an anomalous maxima in the South Pacific Ocean off the coast of Marie Byrd Land, Antarctica, and three local minima over the southern tip of Patagonia, South America, over the Indian Ocean off the coast of Enderby Land, Antarctica, and south of New Zealand (Fig. E15). Warmer than average conditions were recorded for most of South America outside of Brazil, adjacent to the coastal regions in Africa, and along the Great Dividing Range of Australia (Fig. E1). Drier than average conditions were recorded across much of South America with areas such as Venezuela, Columbia, Peru, and Bolivia recording rainfall in the lowest 10th percentile of occurrences and NE Brazil recording rainfall in the lowest 20th percentile of occurrences (Figs. E3, E4). Wetter than average conditions were recorded across Australia with the Tanami Desert in the Northern Territory recording rainfall in the highest 90th percentile of occurrences (Fig. E3). The South African monsoon season runs from October to April. Following a dry January and February, March rainfall totals approached the 50th percentile of occurrences, signaling near normal rainfall for the month (Fig. E4).