Extratropical Highlights – January 2024

 

1. Northern Hemisphere

The 500-hPa circulation during January resembled a weak negative Arctic Oscillation (AO) teleconnection pattern with above-average heights over the Polar region and below-average heights in the middle latitudes (Fig. E9). The main land-surface temperature signals include above-average temperatures across most of Europe, Asia, eastern Canada, and the western U.S. (Fig. E1). The main precipitation signals include above-average rainfall in the eastern U.S. and eastern Europe (Fig. E3).

 

a. North America

The 500-hPa circulation over North America in January was characterized by above-average heights over the eastern half of Canada and Alaska, and slightly below-average heights over the central U.S. (Fig. E9). For much of the U.S., temperature anomalies were largely near normal with the exception of the Pacific Northwest where temperatures were above normal with some areas recording anomalies in the highest 90th percentile of occurrences.  In eastern Canada, temperature anomalies were above normal with a large area recording values in the highest 70th percentile of occurrences (Fig. E1). The eastern half of the U.S. recorded above-average rainfall with a large area reaching the highest 90th percentile of occurrences and many areas seeing a Class 1 Improvement in drought conditions, according to the U.S. Drought Monitor. The Great Lakes and Midwest recorded rainfall in the 90th percentile or greater during January, after a previous 4 months of below-average rainfall (Figs. E3, E5 E6). The Pacific Northwest also recorded wetter than average conditions with some areas reaching 175% of normal (Figs. E3, E5, E6). 

 

b. Europe and Asia

The 500-hPa height anomalies featured below-average heights over central Russia and above-average heights over eastern Russia and southern Europe (Fig. E9). Temperatures were above normal across southern Eurasia and central Russia with many areas recording values in the upper 70th and 90th percentile of occurrences (Fig. E1). The strongest anomalies were in a widespread area located in central Russia (Fig. E1). Central and southern parts of Scandinavia recorded below-average temperatures (Fig. E1). The majority of Eurasia recorded near normal precipitation anomalies. Eastern Europe recorded precipitation in the upper 70th and 90th percentile of occurrences (Fig. E3).

 

2. Southern Hemisphere

The 500-hPa height pattern during January featured below-average heights over the Polar region and above-average heights in the middle latitudes.  Temperatures across South America were above-average with many areas recording values in the highest 90th percentile of occurrences.  Near the coasts in Africa, temperatures were above-average, and along the eastern region of Australia, temperatures were also recorded at above-average values (Fig. E3). Most of South America experienced drier than average conditions during January (Figs. E3, E4). Drier than average conditions were recorded for western portions of central Africa with the Democratic Republic of Congo and Gabon recording values in the lowest 10th percentile of occurrences (Fig. E3). The eastern portion of Africa recorded above-average rainfall in areas such as Tanzania, Kenya, and Uganda where values reached the highest 90th percentile of occurrences (Fig. E3). Precipitation anomalies were also elevated in the eastern half of Australia where areas recorded precipitation in the highest 70th percentile of occurrences (Fig. E3). The South African monsoon season runs from October to April. This area received below-average rainfall for January with values recorded in the lowest 20th percentile of occurrences (Fig. E4).