– November 2014
1. Northern Hemisphere
The 500-hPa circulation during November
exhibited two distinct anomalous wave patterns (Fig. E9). The first was a 3-celled
pattern extending from the central North Pacific to eastern North America. The
second was a 4-celled pattern extending from the central North Atlantic to
central Siberia. Regional aspects of this circulation included a highly
amplified ridge-trough pattern across North America, and a blocking-type
pattern centered over Scandinavia.
The overall height anomalies projected
onto a record positive phase of the East Pacific (+3.2) teleconnection pattern,
and also onto strong positive phases of the East Atlantic/ Western Russia
(+1.1), and Scandinavia (+1.8) teleconnection patterns (Table E1, Fig. E7).
The main land-surface temperature signals
during November included above-average temperatures in Alaska and Europe, and
below-average temperatures across central Canada and the eastern half of the
United States (Fig. E1).
The main precipitation signals included above-average totals in the northwestern
and southeastern U.S. and southwestern Europe, and below-average totals in the
central and northeastern U.S., northeastern Europe, and western Russia (Fig. E3).
a. North Pacific/ North America
The mean 500-hPa circulation during
November featured an anomalous wave pattern with above-average heights over western
North America and below-average heights over the central North Pacific and the
eastern half of North America (Fig. E9). These anomalies reflected a record positive
phase of the East Pacific (+3.2) teleconnection pattern, which exceeded its previous
record strength (+2.1 observed during November 1976) by more than a full
standard (Table E1,
Fig. E7, ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/epnp_index.tim).
Regional features of this pattern
included an amplified ridge over western North America extending into the polar
region, and a very strong Hudson Bay trough. This combination was associated
with an extensive and sustained flow of polar air into central North America (Figs. E8, E10), resulting in well below-average temperatures
across central Canada and the eastern half of the United States (Fig.
E1). The most significant departures were
observed in the midwestern U.S., where monthly mean
temperatures were in the lowest 10th percentile of occurrences.
The precipitation patterns across
the North America also reflected the strength and position of the mean
ridge-trough axes, with above-average totals observed in the southeastern U.S.,
and below-average totals recorded in Alaska, western Canada, and the central
and northeastern U.S. (Fig. E3).
According to the U.S. Drought
Monitor, a massive area of exceptional drought continued in central/ southern
California and western Nevada, with extreme drought extending northward into
Oregon. Exceptional or extreme drought was also observed in northeastern Texas
and south-central Oklahoma.
b. Europe/ Russia
The 500-hPa circulation featured an
anomalous wave pattern extending from the eastern North Atlantic to central
Russia, and included a blocking ridge over Scandinavia and amplified troughs
over the eastern North Atlantic and central Russia (Fig. E9). This pattern projected onto the
positive phases of the East Atlantic/ Western Russia (+1.1) and Scandinavia
(+1.8) teleconnection patterns (Table E1, Fig. E7)
This pattern impacted surface
temperatures and precipitation Europe and western Russia. For example, the
associated enhanced southwesterly flow of mild marine air across Europe
contributed to well above-average surface temperatures, with many parts of
Europe recording departures in the upper 90th percentile of
occurrences (Fig. E1).
Central and southern Europe were situated downstream of the mean trough axis,
and recorded above-average precipitation with departures in the upper 70th
percentile of occurrences (Fig. E3). In contrast, monthly precipitation totals were
well below average in northeastern Europe and western Russia, regions located
downstream of the mean ridge axis.
2. Southern Hemisphere
The mean 500-hPa circulation during
November featured above-average heights over southeastern Australia, the high
latitudes of the central South Pacific, and south of Africa, and below-average
heights across the high latitudes of the Indian Ocean and in the vicinity of
New Zealand (Fig. E15).
In eastern Australia, the amplified
ridge led to a continuation of well above average surface temperatures, with
much of the region recording departures in the upper 90th percentile
of occurrences (Fig. E1). Most of southeastern and eastern Australia also
recorded a continuation of exceptionally dry conditions in response to
anomalous sinking motion downstream of the mean ridge axis (Fig. E3).
The South African rainy season
lasts from October to April. Rainfall for the region as a whole was below
average during October and November 2014(Fig.
with the largest deficits recorded in the northeast including northern
Mozambique and Madagascar (Fig. E3).
The Antarctic ozone hole typically develops during August,
reaches its peak aerial extent in September and October, and dissipates by
early December. Overall, the 2014 ozone hole was slow to develop during August,
was near the 2004-2013 mean size during September through November, and
dissipated at the end of November (Fig. S8, top). This near-average size follows two
consecutive years in which ozone hole was smaller than average.