Beginning with this
month, all anomalies reflect departures from the 1981-2010 base period.
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).
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.
a. North Pacific
and North America
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.
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.
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 9th 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.
North Atlantic and Eurasia
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.
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
anomalies reflect departures from the 1981-2010 base period.
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.
These conditions are consistent with the lingering La Niña-related pattern of
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.