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Climate Diagnostics Bulletin
Climate Diagnostics Bulletin - Home Climate Diagnostics Bulletin - Tropics Climate Diagnostics Bulletin - Forecast

 

  Extratropical Highlights

  Table of Indices  (Table 3)

  Global Surface Temperature  E1

  Temperature Anomalies (Land Only)  E2

  Global Precipitation  E3

  Regional Precip Estimates (a)  E4

  Regional Precip Estimates (b)  E5

  U.S. Precipitation  E6

  Northern Hemisphere

  Southern Hemisphere

  Stratosphere

  Appendix 2: Additional Figures

Extratropical Highlights

JUNE 2021

Extratropical Highlights June 2021

 

1. Northern Hemisphere

The 500-hPa circulation during June featured above-average heights across the western United States, the North Atlantic Ocean, and Scandinavia, and below-average heights extending eastward from northeastern Canada, across Greenland to the Arctic Sea (Fig. E9). Over the Atlantic basin, the circulation reflected a positive phase (+0.77 std. dev.) of the North Atlantic Oscillation (NAO) (Fig. E7, Table E1).

The main land-surface temperature signals during June were predominantly well above-average temperatures across most of the U.S., Canada, Europe, and Siberia (Fig. E1). The main precipitation signals included above-average totals in the southeastern U.S., southern and eastern Asia, the Mediterranean, and eastern/western Europe, and below-average totals in central North America and central Europe (Fig. E3).

 

a. North America

The 500-hPa circulation during June featured above-average heights across the western U.S. and Canada (Fig. E9). This pattern was associated with an amplified ridge, with areas under this ridge recording departures in the upper 90th percentile of occurrences, and contributed to record breaking surface temperatures across the western and central U.S. (Fig. E1). Multiple states experienced all-time high temperatures that exceeded 100 degrees Fahrenheit for 6 consecutive days. This heatwave led to a Class-1 degradation to the already Extreme- to Exceptional- intensity rating for drought conditions in the region according to the U.S. Drought Monitor.

The above conditions also contributed to below-average precipitation in the north-central U.S., with many areas recording departures in the lower 10th percentile of occurrences (Fig. E3). The southeastern U.S. saw above-average precipitation and early tropical cyclone activity due to enhanced divergence and trade winds in the Atlantic (Figs. E3, T20, T23).

 

b. North Atlantic/ Scandinavia

The 500-hPa height pattern featured above-average heights across the North Atlantic Ocean and Scandinavia, and below-average heights over the Hudson Bay, Greenland and the Arctic Ocean (Fig. E9). This pattern reflected a positive phase (+0.77 std. dev.) of the NAO (Fig. E7, Table E1). This pattern contributed to exceptionally warm surface temperatures across Scandinavia and Europe (Fig. E1), with many areas recording departures in the upper 90th percentile of occurrences. It also contributed to an east-to-west tripole pattern of precipitation in Europe, with above-average totals in east and west Europe and below-average totals in central Europe (Fig. E3).

 

2. Southern Hemisphere

The mean 500-hPa circulation during June featured above-average heights over New Zealand, the Indian Ocean, and the South Atlantic Ocean, and below-average heights over the Southern Ocean near the Drake Passage (Fig. E15). In the Sahel and Southern Africa, precipitation totals were above-average while precipitation was near normal in northeastern Australia, and below-average in northeast Brazil (Fig. E3).


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Page Last Modified: July 2021
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