Climate Outlook
EUROPE April  September 2013
Issued: March 2013
The IRI has prepared this experimental Climate Outlook for Europe for April  September 2013.
Of relevance in the preparation of this outlook is a good likelihood that the western tropical Pacific SSTs will be slightly above average while the eastcentral part will be slightly below average during all four lead times, but weakening toward average with increasing lead time. The eastern part will be somewhat below average, particularly for the first lead time, but not enough so to indicate weak La Nina conditions. Such tropical Pacific conditions are indicated in the SST predictions on which these climate forecasts are based (SSTs). See the IRI's ENSO update for a discussion on the ENSO outlook (see IRI Probabilistic ENSO forecast). Slightly above average SST is predicted over much of the equatorial Indian Ocean during the first forecast period, weakening toward average between thereafter. During all four forecast periods, SSTs in the tropical Atlantic are predicted to be near average, except to be somewhat above average in the northwest quadrant (in Caribbean) and southeastern quadrant (Gulf of Guinea). (AprilJune 2013, MayJuly 2013, JuneAugust 2013, JulySeptember 2013).
METHODS 
This Outlook was prepared using the following procedures and
information:
A) Coupled oceanatmosphere model predictions of tropical Pacific SST
covering the forecast period. Particularly heavy weighting has been
given to predictions from the coupled model operated by the NOAA
National Centers for Environmental Prediction, Climate Modeling Branch.
This model suggests a continuation of nearaverage conditions during the
first forecast season. The forecast for nearneutral conditions is
consistent with some, but not all, numerical and statistical forecasts
of central and eastern Pacific SSTs.
B) Forecasts of the tropical Indian ocean using a statistical model
developed by the IRI.
C) Global atmospheric general circulation model (GCM) predictions of the
atmospheric response to the present and predicted seasurface
temperature patterns.
D) Other sources of information include
NASA's
Seasonal to Interannual Prediction Project (GSFCNASA)
and also seasonal prediction research at COLA.
The procedures, models, and data used to derive this Climate Outlook may
be somewhat different from those used by the national meteorological
services in the region. Thus, this product may differ from the official
forecasts issued in those areas. The Climate Outlook for
April  September 2013
is dependent on the accuracy of the SST predictions. For the
tropical Pacific, these predictions can be expected to provide useful
information, but there is some uncertainty concerning the evolution of
SSTs. Spread in global SST predictions is a source of uncertainty in the
Outlook provided here. Note that even if perfectly accurate SST
forecasts were possible, there would still be uncertainty in the climate
forecast due to chaotic internal variability of the atmosphere. These
uncertainties are reflected in the probabilities given in the forecast.
It is stressed that the current status of seasonaltointerannual
climate forecasting allows prediction of spatial and temporal averages,
and does not fully account for all factors that influence regional and
national climate variability. This Outlook is relevant only to seasonal
time scales and relatively large areas; local variations should be
expected, and variations within the 3month season should also be
expected. For further information concerning this and other guidance
products, users are strongly advised to contact their National
Meteorological Services.
OUTLOOK 
This Outlook covers four seasons: AprilJune 2013,
MayJuly 2013, JuneAugust 2013 and JulySeptember 2013.
Maps are given showing tercile probabilities of
precipitation and temperature. The maps for precipitation indicate the
probabilities that the seasonal precipitation will fall into the wettest
third of the years (top number), the middle third of the years (middle
number), or the driest third of the years (bottom number). The color
shading indicates the probability of the most dominant tercile  that
is, the tercile having the highest forecast probability. The color bar
alongside the map defines these dominant tercile probability levels. The
upper side of the color bar shows the colors used for increasingly
strong probabilities when the dominant tercile is the abovenormal
tercile, while the lower side shows likewise for the belownormal
tercile. The gray color indicates an enhanced probability for the
nearnormal tercile (nearly always limited to 40%). As before, numbers
and their associated histograms show the probabilities of the three
terciles. In areas with lots of spatial detail, there may not be
sufficient room on the map, to allow histograms for each region. In
those cases, some idea of the probabilities may be gained from the color
alone. A qualitative outlook of climatology ("C") indicates that there
is no basis for favoring any particular category.
Areas that are marked by "D" represent regions for which less than 3cm of
precipitation typically occurs over the season.
Otherwise, for example, in the case of
AprilJune 2013 (Map A), there
is a 25% probability that the precipitation will be in the wettest third
of the years, a 35% chance it will be in the nearnormal third of the
years, and a 40% chance that the precipitation will be in the driest
third of the years in Tuvalu, in the tropical Pacific.
Maps of temperature show expected probabilities that the seasonal
temperatures will fall into the warmest third of the years, the middle
third of the years, or the coldest third of the years
(Map A) . The numbers for each region on the temperature maps
indicate the probabilities of temperatures to fall in each of the three
categories, above, near, and belownormal.
An additional precipitation
map
is provided for the first season indicating probabilities for extreme
precipitation anomalies. Extremes are defined as anomalies that fall
within the top and bottom 15th percentile of the observed records. A
priori, there is a 15% probability of being within the extremely wet
category, and a 15% probability of being within the extremely dry
category, leaving a 70% probability that the precipitation will not be
extreme. The maps indicate areas of increased risk of extreme
precipitation totals. Three levels of increased risk are defined:
slightly enhanced risk, enhanced risk, and greatly enhanced risk. For
slightly enhanced risk, there is a 2540% probability that precipitation
will be within the indicated extreme, i.e. wet or dry. This represents
an approximate doubling of the climatological risk. For enhanced risk,
there is a 4050% probability that precipitation will be within the
indicated extreme. This represents an approximate tripling of the
climatological risk. For greatly enhanced risk, the probability that
precipitation will be within the indicated extreme exceeds 50%, i.e. the
indicated extreme is the most likely outcome. A similar map is provided
in the first season indicating probabilities of
extreme temperature
anomalies.
Boundaries between subregions should be considered as transition zones,
and their location considered to be only qualitatively correct.
AprilJune 2013 through JulySeptember 2013
The following tables summarize the precipitation and temperature probability forecasts:
Summary of PRECIPITATION forecast for Europe
Leads 1, 2, 3, and 4 refer, respectively, to the upcoming seasons:
AprMayJun MayJunJul JunJulAug JulAugSep
A nonenhanced probability for above or below normal is 33%.
(There is a nearnormal category whose nonenhanced probability is also 33%.)
The following countries or regions out of the 36 in Europe
have at least half of their area under a PRECIPITATION forecast for:
At least At least
Substantially slightly slightly Substantially
enhanced enhanced enhanced enhanced
probability probability probability probability
(>48%) for (>38%) for (>38%) for (>48%) for
below normal below normal above normal above normal
Summary of TEMPERATURE forecast for Europe
Leads 1, 2, 3, and 4 refer, respectively, to the upcoming seasons:
AprMayJun MayJunJul JunJulAug JulAugSep
A nonenhanced probability for above or below normal is 33%.
(There is a nearnormal category whose nonenhanced probability is also 33%.)
The following countries or regions out of the 36 in Europe
have at least half of their area under a TEMPERATURE forecast for:
At least At least
Substantially slightly slightly Substantially
enhanced enhanced enhanced enhanced
probability probability probability probability
(>48%) for (>38%) for (>38%) for (>48%) for
below normal below normal above normal above normal
ALBANIA
leads 1,2,3 and 4
ALBANIA
leads 3 and 4
AUSTRIA
leads 1,2,3 and 4
AUSTRIA
leads 1,2,3 and 4
BELGIUMLUXEMBURG
leads 1,2,3 and 4
BELGIUMLUXEMBURG
leads 1,2,3 and 4
BELARUS
leads 1,2,3 and 4
BELARUS
leads 1,2,3 and 4
BOSNIA HERZG
leads 1,2,3 and 4
BOSNIA HERZG
leads 3 and 4
BULGARIA
leads 1,2,3 and 4
BULGARIA
leads 2,3 and 4
CROATIA
leads 1,2,3 and 4
CROATIA
leads 1,2,3 and 4
CZECH REP
leads 1,2,3 and 4
CZECH REP
leads 1,3 and 4
DENMARK
leads 1,2,3 and 4
DENMARK
leads 1,2,3 and 4
ESTONIA
leads 1,2,3 and 4
ESTONIA
leads 3 and 4
FINLAND
leads 2,3 and 4
FRANCE
leads 1,2,3 and 4
FRANCE
leads 1,2,3 and 4
GERMANY
leads 1,2,3 and 4
GERMANY
lead 1
GREECE
leads 2,3 and 4
GREECE
lead 3
HUNGARY
leads 1,2,3 and 4
HUNGARY
leads 1,2,3 and 4
ICELAND
leads 1,2,3 and 4
ICELAND
leads 1,2,3 and 4
IRELAND
leads 1,2 and 3
IRELAND
leads 1 and 2
ITALY
leads 1,2,3 and 4
ITALY
leads 1,2,3 and 4
LATVIA
leads 1,2,3 and 4
LATVIA
leads 1,2,3 and 4
LITHUANIA
leads 1,2,3 and 4
LITHUANIA
leads 1,3 and 4
MACEDONIA
leads 1,2,3 and 4
MACEDONIA
leads 3 and 4
MOLDOVA REP
leads 1,2,3 and 4
MOLDOVA REP
leads 1,2,3 and 4
NETHERLANDS
leads 1,2,3 and 4
NETHERLANDS
lead 1
NORWAY
leads 1,2,3 and 4
NORWAY
lead 4
POLAND
leads 1,2,3 and 4
POLAND
leads 1,3 and 4
PORTUGAL
leads 1,2,3 and 4
PORTUGAL
leads 1,2,3 and 4
ROMANIA
leads 1,2,3 and 4
ROMANIA
leads 2,3 and 4
SLOVAKIA
leads 1,2,3 and 4
SLOVAKIA
leads 1,2,3 and 4
SLOVENIA
leads 1,2,3 and 4
SLOVENIA
leads 1,2,3 and 4
SPAIN
leads 1,2,3 and 4
SPAIN
leads 1,2,3 and 4
SWEDEN
leads 1,3 and 4
SWEDEN
lead 4
SWITZERLAND
leads 1,2,3 and 4
SWITZERLAND
leads 1,2,3 and 4
TURKEY
leads 1,2,3 and 4
TURKEY
leads 1,2,3 and 4
UK
leads 1,2,3 and 4
UK
leads 1 and 2
UKRAINE
leads 1,2,3 and 4
UKRAINE
leads 1,2,3 and 4
YUGOSLAV FR
leads 1,2,3 and 4
YUGOSLAV FR
leads 3 and 4
OBSERVED CLIMATOLOGY DATA for AprMayJun,
MayJunJul, JunJulAug and JulAugSep
CLIMATOLOGICAL AVERAGE:
TERCILE THRESHOLDS (33%ile & 67%ile):
EXTREME THRESHOLDS (15%ile & 85 %ile):

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