Highlights –February 2023
1. Northern Hemisphere
The 500-hPa circulation during
February resembled a positive Arctic Oscillation pattern with below-average
heights over northern latitudes and above-average heights over the middle
latitudes (Fig. E9). During the month of February, the North
Atlantic Oscillation was also positive (Fig.
E7) and in combination, these two teleconnections
contributed to the above-average temperatures and below-average precipitation
across much of Eurasia (Figs. E1, E3). In North America,
colder than average conditions were observed for much of Canada and the western
U.S. while both Alaska and the eastern U.S. recorded warmer than average
conditions. The main precipitation signals for North America were primarily in
the U.S. and included above-average rainfall in the Great Lakes region and
below-average rainfall for the Southeast, much of West Coast, and Alaska
Panhandle (Fig. E3).
a. North America
height pattern over North America was distinguished by anomalous ridging over
the North Pacific Ocean and the eastern half of the U.S., while Canada and much
of Alaska observed moderate anomalous troughing, and
the western U.S. observed mild anomalous troughing (Fig. E9). The
anomalous ridge over the eastern U.S. contributed to warmer than average and
drier than average conditions, to include some areas reaching the 90th
percentile of above-average temperature conditions (Fig. E1). Conversely, the anomalous
trough in the western U.S. contributed to colder than average conditions, to
include some areas reaching the 30th percentile of occurrences (Fig. E1).
Precipitation patterns across the U.S. included above-average rainfall in the
Great Lakes region, where some areas reached the 80th percentile of occurrences,
and moderately below-average (30th percentile) rainfall conditions were
observed along the U.S. Pacific Northwest, Southeast and Alaska Panhandle (Figs. E3, E5, E6).
height pattern across much of Eurasia featured anomalous ridging (Fig. E9). This pattern likely contributed to the
widespread above-average temperatures, which reached the 70th percentile of
occurrences for much of the region (Fig.
E1). The main precipitation signals included
drier than average conditions for western Europe and
slightly wetter than average conditions for eastern Europe (Fig. E3).
2. Southern Hemisphere
The 500-hPa pattern in the Southern
Hemisphere resembled an anomalous wave-train pattern across the South Pacific
Ocean (Fig. E15). Warmer than average and drier than average
conditions were observed across much of South America while the north-central
territories of Australia observed cooler than average conditions and drier than
average conditions were observed across the southern half of the country (Figs. E1, E3, E4).
The South African monsoon season runs from
October to April. During February, rainfall was well above-average, reaching
the 90th percentile of occurrences (Fig.
E4). As a comparison, in the previous months of
December and January, observed rainfall in the monsoon region of South Africa
was relatively near-normal (~50th percentile, Fig. E4).