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 2011

Beginning with this month, all anomalies reflect departures from the 1981-2010 base period.

1. Northern Hemisphere

The 500-hPa circulation during June featured above average heights over the Gulf of Alaska, Greenland, the polar region, and western Siberia, and below average heights over the western U.S., Great Britain, and south-central Russia (Fig. E9). At 200-hPa, enhanced troughs over the tropical and subtropical central Pacific in both hemispheres reflected a lingering response to La Niña (Fig. T22).

The main surface temperature signals during June included above-average temperatures across the southern U.S., much of Europe, central Siberia, and large portions of eastern Asia, and below average temperatures in the northwestern U.S. (Fig. E1). The main precipitation signals included above-average totals in the northwestern U.S. and southwestern Canada, and below-average totals across the southern tier of the U.S. (Fig. E3).

a. North Pacific and North America

In the lower latitudes, the 200-hPa circulation during June featured amplified mid-Pacific troughs in both hemispheres (Fig. T22). This pattern is linked to the lingering La Niña-related pattern of tropical convection (Fig. T25).

In the extratropics, the mean 500-hPa circulation during June featured an amplified ridge-trough pattern extending across the Gulf of Alaska and the western U.S. (Fig. E9). This pattern was associated with cooler (Fig. E1) and wetter (Fig. E3) than average conditions in the northwestern U.S. and southwestern Canada.

The circulation also featured a persistent ridge across the southern U.S., which contributed to exceptionally warm and dry conditions across the southern and mid-Atlantic states (Figs. E3, E6). June marks the 9^th consecutive month of well below average precipitation for both the Southwest and Gulf Coast regions of the U.S. (Fig. E5). Also, both the southeastern and mid-Atlantic regions have recorded generally below-average precipitation for the past year. According to NOAA’s U.S. Drought Monitor, extreme-to-exceptional drought conditions were evident at the end of June extending from southeastern Arizona to central Georgia, and also covering southern Florida and eastern North Carolina.

b. North Atlantic and Eurasia

The 500-hPa circulation during June featured an amplified ridge-trough pattern that extended from Greenland to Great Britain (Fig. E9). This pattern was associated with a continuation of enhanced southwesterly winds across Scandinavia, along with a continued strong poleward heat transport into the high latitudes of Eurasia. It was also associated with warmer than average conditions across much of Europe (Fig. E1).

For the past four months, the circulation has featured an extensive southwesterly flow of mild air into the high latitudes of Eurasia (Fig. E9). These conditions led to an early snow-melt, and to a continuation during June of well above average temperatures in central Siberia.

2. Southern Hemisphere

All anomalies reflect departures from the 1981-2010 base period.

In the subtropics, the upper-level (200-hPa) circulation during June reflected an amplified trough across the central South Pacific, and a westward retraction of the mean South Pacific jet stream to west of the date line (Figs. T21, T22). These conditions are consistent with the lingering La Niña-related pattern of tropical convection.

The 500-hPa circulation during June featured above average heights over the central South Pacific and over the high latitudes of the South Atlantic, and below average heights over the high latitudes of the eastern South Pacific and South Africa (Fig. E15).  The most significant surface temperature (Fig. E1) and precipitation (Fig. E3) signals were observed in Australia, where exceptionally warm and dry conditions prevailed in the southeast, and exceptionally cool conditions prevailed in the north.