The IRI has prepared this Climate Outlook for Europe for January - June 2000. Of relevance in the preparation of this Outlook has been the current La Niņa conditions (lower than average sea-surface temperatures (SSTs) in the central equatorial Pacific Ocean) that have been amplifying through the end of 1999. Thus La Niņa conditions are in effect for the first season of the forecast, January-February-March 2000, and are expected to decline slowly through the second season of the forecast period, April-May-June 2000. The SSTs of the western tropical Indian Ocean were assumed to remain near-normal, and the above-average SSTs of the eastern tropical Indian Ocean are expected to return to normal during the forecast period. The forecast of tropical North Atlantic SSTs suggests a cooling trend through June 2000.

METHODS -

This Outlook was prepared using the following procedures and information:

A) Coupled ocean-atmosphere 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 the continuation of La Niņa conditions. The persistence of colder that average conditions in the central and eastern equatorial Pacific is consistent with most other numerical and statistical forecasts.

B) Forecasts of the tropical Indian and Atlantic oceans using statistical models developed by the IRI and CPTEC respectively.

C) Global atmospheric circulation model (GCM) predictions of the atmospheric response to the present and predicted sea-surface temperature patterns.

D) Other sources of information include ( 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 January - June 2000 is dependent on the quality of the SST predictions. For the tropical Pacific, these predictions can be expected to provide useful information, but there is some uncertainty concerning the detailed evolution of SSTs. Spread in global SST predictions is a source of uncertainty in the Outlook provided here.

It is stressed that the current status of seasonal-to-interannual 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. For further information concerning this and other guidance products, users are strongly advised to contact their National Meteorological Services.

OUTLOOK -

This Outlook covers two seasons: January - March 2000 and April - June 2000. 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). 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 experiencing their dry season (less than 15% of annual precipitation) and for which less than 5cm of precipitation typically occurs over the season. Otherwise, for example, in the case of England in January - March 2000 (Map B), 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 near-normal third of the years, and a 40% chance that the precipitation will be in the driest third of the years.

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 25-40% 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 40-50% 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.

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 below-normal.

Boundaries between sub-regions should be considered as transition zones, and their location considered to be only qualitatively correct.

January - March 2000:

PRECIPITATION

The following regions of enhanced probabilities of precipitation anomalies are indicated:

P.A) slightly enhanced probabilities of below-normal precipitation over much of the United Kingdom, France, Germany, Switzerland, Belgium, and the Netherlands;

TEMPERATURE

The following regions of enhanced probabilities of temperature anomalies are indicated:

T.A) enhanced probabilities of above-normal temperatures over the United Kingdom, the Netherlands, Denmark, and southern parts of Norway and Sweden, extending towards the western portions of Lithuania, Latvia, Estonia;

T.B) slightly enhanced probabilities for above-normal temperatures over most of western Europe west of about 30E, and south to the Mediterranean including Italy and Sicily;

April - June 2000:

PRECIPITATION

No coherent regions of enhanced probabilities of precipitation anomalies are indicated:

TEMPERATURE

The following regions of enhanced probabilities of temperature anomalies are indicated:

T.i) slightly enhanced probabilities of above-normal temperatures over the United Kingdom, northern France and Germany, and southern areas of Norway and Sweden;

Cutoffs and Max/Min extremes for JFM and AMJ.

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