IRI: International Research Institute for Climate Prediction A Columbia University and NOAA Institute

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Climate Outlook EUROPE July – December 2003

Issued: June 19, 2003

The IRI has prepared the experimental Climate Outlook for Europe for July – December 2003. Of relevance in the preparation of this outlook is the potential for a developing La Nina event. In early March 2003 equatorial Pacific sea surface temperatures (SSTs) returned from above-normal to near-normal in the eastern equatorial Pacific, and they continued cooling through early June reaching values on the order of -2C in the far eastern equatorial Pacific. Weak La Nina conditions are indicated in the SST predictions on which these climate forecasts are based. Warmer than average SSTs continue to dominate much of the tropical Western Pacific and Indian Ocean (SSTs). These are predicted to decrease through the forecast period.
(July-September 2003, August-October 2003, September-November 2003, October-December 2003).

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. 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 sea-surface temperature patterns. D) Other sources of information include NASA’s Seasonal to Interannual Prediction Project (GSFC-NASA) 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 July – December 2003 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 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, and variations within the 3-month season should also be expected.

OUTLOOK –

Precipitation

Enhanced probabilities for above normal precipitation are forecast for mainly northeastern Europe for the period August-October. Enhanced probabilities for below normal precipitation are forecast for varying portions of the Iberian Peninsula for all forecast period: July-December. During the period August-November, this tendency for dryness is indicated also for Italy and vicinity.

Temperature An enhanced probability for above normal temperature is forecast for mainly southern and southwestern Europe


for all forecast period: July-December. An enhanced probability for below normal temperature is forecast for northern Scandenavia for september-november.