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).