circulation during November featured a north-south dipole pattern of
height anomalies over the North Pacific and North Atlantic, with
above-average heights at high latitudes and below-average heights in
the middle latitudes (Fig. E10). Above average heights and
anticyclonic streamfunction anomalies were also evident in the
subtropics over both ocean basins (Fig. T22). In the
extratropics these anomalies reflect the negative phase of the Arctic
Oscillation (Fig. A2.1).
Over the Pacific Ocean these anomaly patterns reflected the
positive phase of the Pacific/ North American (PNA) pattern and
negative phase of the East Pacific (EP) pattern. Over the Atlantic
Ocean they reflected the negative phase of the North Atlantic
Oscillation (NAO) and positive phase of the East Atlantic (EA) pattern
(Table E1, Figs. E7,
E8). Similar phases for each of these
teleconnection patterns were also observed in October. These
circulation anomalies were associated with an eastward extension of
the main Pacific jet stream to well east of the date line, and with a
southward shift of the North Atlantic jet stream to southern Europe (Figs.
E11, T21). Similar anomaly patterns were also evident in the
In both hemispheres the anticyclonic streamfunction anomalies over
the central subtropical Pacific Ocean are seen to flank the region of
enhanced equatorial convection, and are consistent with the
atmospheric response to mature El Niņo
conditions (Fig. T25). The eastward extended Pacific jet
streams in both hemispheres are centered along the poleward flanks of
these circulation anomalies, and are also consistent with ongoing El
In the Northern Hemisphere the prominent temperature anomalies
during November included warmer than normal conditions over western
Canada, Alaska, southern Europe, and most of central Asia, and cooler
than normal conditions over eastern North America and northern Europe
(Fig. E1). Prominent precipitation departures during the month
included a continuation of drier than normal conditions in the Pacific
Northwest region of the United States (Figs. E3,
E5, E6), and
above-average precipitation across the southeastern states and most of
central Europe (Figs. E3, E4).
a. Pacific/North America
The strong positive PNA pattern (+1.6, Table E1) during
November was associated with amplified troughs across the central
North Pacific and over eastern North America, and an amplified ridge
over western North America (Fig. E10). These conditions
contributed to a strong southwesterly flow and above-average surface
temperatures across Alaska and western Canada, with departures
exceeding +5°C (above the 90th
percentile) in southeastern Alaska (Fig. E1).
The amplified trough across the eastern U.S. was also associated
with a large-scale pattern of negative height anomalies that extended
to central Europe. This overall circulation brought anomalous
northerly flow from northern Canada to the south-central United States
(Fig. E11), and resulted in below-average surface temperatures
across eastern North America.
Over the U.S. the primary region of above-average precipitation
during November was observed in the southeast (Figs. E3,
This area was situated immediately downstream of the mean upper-level
trough axis along the right-entrance region of the enhanced North
Atlantic jet stream (Figs. E11, T21). The Gulf Coast and
Southeast regions have recorded above-average precipitation in each of
the last three months (Fig. E5).
Below-average precipitation was observed in the Pacific Northwest
and Midwest during November. The Pacific Northwest has recorded
precipitation deficits in every month since February 2002 (Fig. E5).
This combination of decreased precipitation in the Northwest, and
above-average precipitation and increased storminess and across the
Gulf Coast and Southeast (Fig. E14), is consistent with the
atmospheric response to El Niņo.
b. North Atlantic and Europe
The circulation over the North Atlantic and Europe featured
above-average heights at high latitudes and in the subtropics, and
below-average heights in the middle latitudes (Fig. E10).
Enhanced jet stream winds were also observed across the central
Atlantic in association with a southward shift of the mean jet axis to
southern Europe (Figs. E11, T21). These conditions brought
cooler and drier than normal conditions to Scandinavia, and warmer and
wetter than normal conditions to central and southern Europe (Figs.
2. Southern Hemisphere
The upper-level circulation during November featured a north-south
dipole pattern of height anomalies over the three oceans, with
above-average heights at lower latitudes and below-average heights at
higher latitudes. Above average heights were also observed over the
high latitudes of the eastern South Pacific and across southern
Australia (Fig. E16). This overall circulation was associated
with an eastward extension of the Pacific jet stream to well east of
the date line, and with strengthening of the jet stream winds across
the central South Atlantic (Figs. T21, E17).
In Brazil prominent precipitation anomalies during November
reflected the continuation of suppressed convection in northern and
central sections and enhanced convection in the South (Figs. E3,
E4, T25). Below-average precipitation was also again observed
across eastern Australia, with monthly totals generally below the 10th
percentile. Thee rainfall patterns are consistent with the ongoing El
Niņo conditions. Much of Brazil and Australia were also considerably warmer than normal during
the month, with temperatures exceeding the 90th percentile
in parts of both countries (Fig. E1).