Extratropical Highlights –March 2019

 

1. Northern Hemisphere

The 500-hPa circulation during March featured above-average heights over Alaska, the southern U.S., southern Europe, and north-central Russia, and below-average heights over the eastern North Pacific and from northeastern Canada to Scandinavia (Fig. E9).

The main land-surface temperature signals included above-average temperatures across Alaska and northwestern Canada, and throughout most of Eurasia, and below-average temperatures in the northwestern U.S. and southwestern Canada (Fig. E1). The main precipitation signals included above-average totals in the portions of the western U.S., and below-average totals in western Canada, the southeastern U.S. and southern Europe (Fig. E3).

 

a. North Pacific and North America

The 500-hPa circulation during March featured above-average heights over Alaska and the southern U.S., and below-average heights over the eastern North Pacific and northeastern Canada (Fig. E9). This anomalous circulation contributed to above-average surface temperatures (generally 5+°C above average) in Alaska and western Canada (Fig. E1). It also contributed to below-average temperatures in southwestern Canada and the northwestern U.S., with many areas recording temperatures in the lowest 10^th percentile of occurrences for the second consecutive month.

Precipitation was above average in portions of the western U.S. during March (Fig. E3), which led to a further restoration of soil moisture levels following long-term drought in many areas during the past year. Also, according to the U.S. Drought Monitor, the area of severe drought continued to diminish in the four-corner region of Utah, Colorado, Arizona, and New Mexico, and also in Oregon.

 

b. North Atlantic and Eurasia

The 500-hPa height pattern featured a north-south dipole characterized by above-average heights across the central North Atlantic and southern Europe and below-average heights across the high latitudes of the North Atlantic (Fig. E9). This pattern resulted in a continuation of above-average surface temperatures throughout Europe, with most areas recording departures in the upper 70^th percentile of occurrences (Fig. E1). It also contributed to exceptionally warm temperatures (generally 5+°C above average) in central Russia and Siberia.

 

2. Southern Hemisphere

The 500-hPa height field during March featured an anomalous zonal wave-3 pattern. Above-average heights were present over both the western and eastern South Pacific Ocean and also over the central Indian Ocean. Below-average heights were present south of Australia, and over the central South Pacific and South Atlantic Ocean (Fig. E15).

Much of Australia recorded above-average surface temperatures during March (Fig. E1), along with near-average rainfall (Fig. E3). In southern Africa, the monsoon season runs from October to April. During March, rainfall was again below average for the region as a whole (Fig. E3). The most significant deficits were observed in the northern portion of the monsoon region, where totals were in the lowest 10^th percentile of occurrences. Since October 2018, the monsoon region has recorded below-average precipitation in every month except January, when only slightly above-average totals were observed (Fig. E4).