1. Northern Hemisphere
500-hPa height anomaly pattern featured considerable zonal symmetry during June,
with above-average heights prevailing in both the middle latitudes and the polar
region (Fig. E9). Regional anomalies included
above average heights across the southeastern quadrant of the United States,
Greenland, much of the Arctic Ocean, and across northern Europe and
south-central Russia. Above average heights were also evident over the
subtropical North Pacific and North Atlantic Oceans. Conversely, negative height
anomalies prevailed over eastern Canada and central Siberia.
Eurasia, the circulation reflected a strong positive phase (+2.1) of the Polar/
Eurasia teleconnection pattern. Over the North Atlantic, the circulation again
projected onto the negative phase of the North Atlantic Oscillation (NAO) (Table E1, Fig. E7).
The negative NAO signal has been exceptionally persistent since July 2009.
the subtropical Atlantic basin, the 200-hPa streamfunction pattern showed a
pronounced inter-hemispheric symmetry during June, with anticyclonic anomalies
extending from the America’s to Africa in both hemispheres (Fig.
T22). This signal is consistent with
an enhanced west African monsoon circulation (Figs.
main surface temperature signals during June included above average temperatures
across the southeastern quadrant of the U.S., south-central Russia, and Mongolia
(Fig. E1). The main precipitation signals
included above-average totals in the northwestern and north-central U.S.,
portions of southern Europe, and southeastern China, and below average totals in
the mid-Atlantic region of the U.S., south-central Russia, and Mongolia (Fig.
a. North Pacific/
the United States, the circulation during June featured a trough in the west and
a ridge in the southeast (Fig. E9).
This pattern was associated with above average temperatures throughout the
southeastern quadrant of the country, with departures in many locations
exceeding the 90th percentile of occurrences (Fig.
E1). It was also associated with enhanced
storminess and above average precipitation in the Pacific Northwest, northern
Plains, upper Midwest, and Great Lakes regions (Figs.
E3, E5, E6).
Many of these locations recorded more than double the normal June rainfall, with
monthly totals in the upper 90th percentile of occurrences. In
contrast, the mid-Atlantic region experienced ongoing precipitation deficits
during June, following well below average precipitation during both April and
May (Fig. E5).
500-hPa circulation during June featured above average heights across the
central North Atlantic, and below average heights over the northwestern Atlantic
(Fig. E9). This
pattern projected onto the negative phase of the NAO, which has persisted since
July 2009 (Fig. E7).
the subtropical Atlantic, anticyclonic streamfunction anomalies at 200-hPa
extended from the America’s to Africa in both hemispheres (Fig.
T22). This pronounced
inter-hemispheric symmetry to the anomaly pattern was associated with an
expanded area of upper-level easterly wind anomalies that extended across
tropical northern Africa and the tropical North Atlantic (Fig.
T21). It was also associated with an
extensive area of low-level westerly wind anomalies across the tropical Atlantic
These conditions lead to reduced vertical wind shear across the tropical
Atlantic, and are typical of the ongoing high activity era for Atlantic
hurricanes that began in 1995. This combination of conditions is consistent with
an enhanced west African monsoon circulation (Figs.
which was also present during June and has been a prominent feature of the
circulation since 1995.
500-hPa circulation during June featured a north-south dipole pattern of height
anomalies, with above average heights extending from northern Europe to
Mongolia, and below average heights over central Siberia (Fig.
pattern reflected a strong positive phase (+2.1) of the Polar/ Eurasia
teleconnection pattern (Fig. E7). It was associated with
exceptionally warm and dry conditions in south-central Russia, northeastern
China, and Mongolia. The most significant departures were observed in the
vicinity of the Black Sea and Caspian Sea, where temperatures (Fig.
E1) were in the upper 90th percentile
of occurrences and precipitation was in the lowest 10th percentile of
200-hPa cyclonic streamfunction anomalies during June extended from northern
India to eastern China, in association with a reduced strength and westward
retraction of the normal summertime Asian monsoon ridge (Fig.
T22). These conditions contributed to
above average precipitation in southeastern China (Fig.
E3). For China as a whole, precipitation has been
above normal for the past three months (Fig. E4).
2. Southern Hemisphere
500-hPa circulation during June featured a zonally symmetric pattern of height
anomalies, with above average heights in the middle latitudes and below average
heights over Antarctica (Fig. E15).
The main precipitation anomalies were observed in eastern and southwestern
Australia, where totals were generally in the lowest 30th percentile
of occurrences (Fig. E3).
The main temperature signals reflected warmer than average conditions in both
central Argentina and portions of western Australia (Fig.