Date and Period of Forecast

In June 2006, the IRI prepared a Climate Outlook for July 2006 - December 2006. Here we provide a subset of the June IRI Forecast. The forecasts are updated monthly and can be found in their entirety at http://iri.columbia.edu/climate/forecast/net_asmt/.

Uncertainties

This Climate Outlook is dependent on the quality of the sea surface temperature (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. The procedures, models, and data used to derive this Climate Outlook may be somewhat different from those used by National Meteorological Services in particular regions and may differ from the official forecasts issued in those areas.

Regional Influences

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.

Precipitation Outlook

The Outlook for other regions of the globe for the seasons July-August-September through October-November-December can be found at Net Assessment forecasts.

Maps show expected precipitation probabilities in tercile classes. The maps indicate probabilities that seasonal precipitation will fall into the wettest third of the years (top number), the middle third of years (middle number) or the driest third of the years (bottom). An outlook of climatology "C" (no color) indicates equal probabilities in each class; i.e., there is no basis for favoring the forecast of any particular category. Boundaries between sub-regions should be considered transition zones, and their location considered to be only qualitatively correct. Color shading indicates which tercile class has the greatest probability of occurrence with darker shading indicating greater likelihood as shown by the legend to the right of the plots.

July-August-September 2006 Global Precipitation Probabilities

Temperature Outlook

This forecast consists of expected probabilities of temperature in tercile classes. The terciles refer to the seasonal temperature falling into the warmest third of the years (top tercile), the middle third of years (middle tercile) or the coldest third of the years (bottom tercile). Boundaries between sub-regions should be considered transition zones, and their location considered to be only qualitatively correct. Color shading indicates which tercile class has the greatest probability of occurrence with darker shading indicating greater likelihood as shown by the legend on the bottom of the plots. Note:
The IRI is in the process of implementing new graphics for its forecast products. Currently, global maps only indicate (by shading) the tercile class with the greatest probability of occurrence.
Please consult the regional maps at Net Assessment forecasts for the probabilities of each tercile class.

July-August-September 2006 Global Temperature Probabilities

Ocean Conditions

Of relevance in the preparation of this outlook is a moderately strong likelihood that the present neutral to slightly above average tropical Pacific SSTs will continue, and perhaps rise to slightly farther above average over the coming months. Such neutral to slightly warm and tropical Pacific conditions are indicated in the SST predictions on which these climate forecasts are based. See the IRI's ENSO update for a discussion on the ENSO outlook (see IRI Probabilistic ENSO forecast). Somewhat warmer than average SSTs are now observed in the western and central tropical Pacific, with near average SSTs in the eastern tropical Pacific, and slightly below normal SSTs near the South American coastline. The central equatorial Indian Ocean, and the north tropical Atlantic Ocean, continue to show above-average SSTs (SSTs). The Indian Ocean SSTs are predicted to weaken over the course of the forecast periods, and the north tropical Atlantic SSTs are predicted to slowly change their pattern favoring positive departures from normal near the Gulf of Guinea by northern mid-summer (July-September 2006, August-October 2006, September-November 2006, October-December 2006).

Methods

The following procedures and information were used to prepare this Climate Outlook:

• Coupled ocean-atmosphere model predictions of tropical Pacific SST -- particularly heavy weighting has been given to the NOAA /NCEP, Climate Modeling Branch coupled model
• Statistical forecasts of Indian Ocean and Atlantic Ocean sea surface temperature
• The response of Atmospheric global circulation model (GCM) predictions to the present and predicted SST patterns
• Statistical analyses
• Appropriate Regional Climate Outlook Forum consensus guidance.