Extratropical Highlights –July 2016

 

1. Northern Hemisphere

The 500-hPa circulation during July featured above-average heights over the high latitudes of the North Pacific, Greenland, southern Europe, and northwestern Russia (Fig. E9). The main land-surface temperature signals during July included above-average temperatures in Alaska, western Canada, much of the continental U.S., Europe, and western Russia (Fig. E1). The main precipitation signals included above-average totals in the central U.S. and eastern Europe (Fig. E3).

 

a. North Pacific/ North America

The 500-hPa circulation during July featured above-average heights over the high latitudes of the North Pacific (Fig. E9). Overall, surface temperatures remained well above average in Alaska, western Canada, and much of the continental U.S. Precipitation was above average across the midwestern U.S. (Fig. E3), where area-average totals exceeded the upper 90^th percentile of occurrences (Fig. E5).

According to the U.S. Drought Monitor, exceptional or extreme drought continued across central and southern California during July, while extreme drought developed in portions of northern Georgia and northeastern Wyoming. Severe drought was evident in central Mississippi, central Georgia, portions of central Texas, and portions of New England. Moderate drought was evident in eastern Oregon, the southern half of New Mexico, and western Arizona.

 

b. Europe/ western Russia

The 500-hPa circulation during July featured above-average heights over Greenland, southern Europe and northwestern Russia, along with below-average heights over the high latitudes of the eastern North Atlantic (Fig. E9). This pattern was associated with anomalous upper-level westerly winds across central Europe (Fig. E10). Overall, surface temperature were above normal across Europe and western Russia, with the most significant departures exceeding the 90^th percentile of occurrences in eastern Europe and northwestern Russia (Fig. E1).

 

c. Northern Africa

The West African monsoon, which lasts from June-September, has been well above average so far this year (Fig. E3). Area-averaged totals during both June and July were near the 100^th percentile of occurrences (Fig. E4). Another indication of the enhanced west African monsoon system was a core of negative velocity potential anomalies and divergent wind anomalies centered over subtropical northern Africa (Fig. T24).

 

2. Southern Hemisphere

 

The mean 500-hPa circulation during July featured generally above-average heights across the Indian Ocean and east of Australia, and below-average heights in the area poleward of Australia (Fig. E15). Surface temperature signals during July included above-average temperatures in eastern Australia (Fig. E1).