Extratropical Highlights – March 2023

 

1. Northern Hemisphere

The 500-hPa circulation during March resembled the negative phase of the North Atlantic Oscillation with anomalous ridging over Greenland and anomalous troughing over the North Atlantic Ocean.  Enhanced above-average heights were observed across most of the North Pacific Ocean and Eurasia, and below-average heights along the U.S. West Coast and Russian Tundra (Figs. E7, E9).

The main land-surface temperature anomalies were enhanced above-average temperatures recorded for nearly all of Eurasia, and below-average temperatures for Scandinavia and central-eastern portions of North America (Fig. E1).  The main precipitation signals were above-average rainfall totals in parts of North America, Russia and the Middle East, and below-average rainfall along the Alaska Panhandle and U.S. Southeast (Fig. E3).

 

a. North America

The height pattern across North America featured anomalous troughing for much of the western and north-central parts of the U.S., as well as into Canada, and anomalous ridging over Alaska and the U.S. Southeast to Southern Plains (Fig. E9).  This pattern contributed to below-average temperatures and enhanced rainfall along the U.S. West Coast where many areas recorded rainfall in the highest 90th percentile of occurrences, and above-average temperatures and decreased rainfall for the U.S. Southeast where many areas recorded rainfall in the lowest 30th percentile of occurrences (Figs. E1, E3).  Localized totals of rainfall were recorded well above-average for the Pacific Northwest, Southern California, and the Intermountain West (Figs. E3, E5, E6).  During the December through March period, California recorded several atmospheric rivers and received record snow and rainfall totals.  The below-average temperature anomalies in the U.S. and Canada reached the lowest 10th percentile of occurrences (Fig. E1).  Observed temperatures across Alaska were predominantly near-normal with localized exceptions of below-average temperatures along the Aleutian Islands and above-average temperatures along the North Slope.  Drier than average conditions were observed along the Alaska Panhandle with areas recording rainfall in the lowest 10th percentile of occurrences (Figs. E1, E3). 

 

b. Eurasia

The 500-hPa height pattern for March featured moderate above-average heights across much of Eurasia which contributed to the enhanced above-average temperatures recorded for many parts of the area where temperatures were observed in the highest 90th percentile of occurrences (Figs. E9, E1).  Temperature anomalies were below-average in Scandinavia and the Kamchatka Peninsula (Fig. E1).  Precipitation totals were above normal for the United Kingdom and across Russia where some areas recorded totals in the highest 90th percentile of occurrences (Figs. E3, E4).  Below-average rainfall totals were recorded along the east Asia Coast and the Middle East where some areas observed rainfall in the lowest 10th percentile of occurrences (Figs. E3, E4).

 

2. Southern Hemisphere

The 500-hPa height pattern featured an anomalous annular wave-train pattern (Fig. E15).  Temperature anomalies across southern South America were well above-average with many areas recording temperatures in the highest 90th percentile of occurrences.  Notable precipitation anomalies include above-average rainfall recorded across central and southern Africa where some areas observed totals in the 70th percentile of occurrences, and below-average rainfall across north, central, and southern portions of South America (Figs. E1, E3).  The South African monsoon season runs from October to April. After a rather wet February, observed rainfall during March was moderately above-average (Fig. E4).