Extratropical Highlights –February 2022

 

1. Northern Hemisphere

The 500-hPa circulation during February featured an amplified anomalous wave pattern (Fig. E9), and was strongly influenced by La Niña, the Tropical/Northern Hemisphere pattern (TNH), and the North Atlantic Oscillation (NAO).  Above-average heights were observed over the North Pacific and North Atlantic Oceans as well as across Europe and northern Russia and below-average heights over the Hudson Bay, Greenland, and Scandinavia (Fig. E9).

The main land-surface temperature signals during February included above-average temperatures for Alaska and much of Eurasia and below-average temperatures across both central Canada and the central U.S. (Fig. E1). The main above-average precipitation signals were recorded in the Eastern U.S, Alaska Panhandle, and around the North Sea and below-average precipitation was recorded in the Western U.S., Southeastern U.S., and Southern Europe (Figs. E3, E6). 

 

a. North America

The anomalous height pattern for February projected onto a few teleconnection patterns that each constructively influence temperature and precipitation over North America (Fig. E7).  In addition to a typical wintertime La Niña pattern, the height pattern also projected onto the positive phases of the NAO (+1.4) and the TNH (+1.9).  The main features of the height anomaly pattern were a ridge over the North Pacific and North Atlantic Oceans and a trough over Eastern Canada.  Both ridges contributed to above-average temperatures for Alaska and along the U.S. East Coast (Fig. E1).  The North Pacific ridge and trough over the Hudson Bay contributed to below-average temperatures for central Canada and the U.S. Plains (Fig. E1). The anomalous ridge over the North Pacific likely also contributed to the well below-average rainfall recorded along the West Coast of the U.S. (Fig. E3).  Typically, La Niña wintertime patterns bring wetter than average conditions to the West Coast however, with the influence of the positive TNH pattern, the North Pacific ridge was further east and south, displacing the Pacific Jet Stream equatorward and thus reducing storm tracks along the West Coast (Figs. E7, T21).  Departures from normal in this region were on the order of 150mm and greater and in lowest 10th percentile (Figs. E6, E3).  According to the U.S. Drought Monitor, conditions along the West Coast degraded by 1 class in some areas.  The Southeast U.S. also experienced below-average rainfall totals (Fig. E3) and are also identified by the Drought Monitor as degrading by 1 or 2 classes in some areas.

 

b. Eurasia

The 500-hPa height pattern featured an extension of the canonical NAO pattern with above-average heights over southern Europe and below-average heights over the United Kingdom and Scandinavia (Fig. E9).  The rest of Eurasia also favored above-average heights with maxima centered over Northern Siberia and the Bay of Biscay (Fig. E9).  While most of Eurasia observed near-to-normal precipitation totals for the month of February, the temperature anomalies were well-above average for the region (Fig. E1).  Temperature anomalies were widely in the 70th percentile with many areas reaching the 90th percentile of occurrences (Fig. E1). 

 

2. Southern Hemisphere

Compared to the Northern Hemisphere, the 500-hPa circulation anomalies during February were overall weaker.  The highest amplitudes were located between Australia and Antarctica, over central Antarctica, and over the Drake Passage (Fig. E15).  Below-average heights were observed over the southern Indian Ocean and the South Pacific Ocean (Fig. E15).  The main temperature signals were primarily off the coasts of southern Africa, Paraguay and western Brazil, and Western Australia (Fig. E1).  The main precipitation signals were below-average rainfall totals in northern regions of Australia, southeastern regions of Africa, Brazil, and Paraguay and above-average rainfall for east-central Africa (Fig. E3).  The Southern Africa region, Northeast Brazil, and Southeast South America were all in the 20th percentile of rainfall for their regions, respectively (Fig. E4). 

The South African monsoon season runs from October to April. During February, rainfall was well below-average for the region as a whole (Fig. E4). The most significant departures were observed in the southeastern portion of the monsoon region, with totals in the lowest 10^th-30^th percentile of occurrences (Fig. E3). In addition to November 2021, February marks the second month of the monsoon season to record below-average precipitation.