How Well Can We Predict Seasonal Climate?

This map shows where IRI 3-month forecasts are consistently good at predicting seasonal rainfall for at least one season of the year.

Specific patterns of rainfall that can be predicted 3 months in advance are strongest in the tropical regions, which you can see on this map. If you are in a red or yellow area, we recommend monitoring seasonal forecasts all year long for current confidence levels in predicted rainfall.

Explanation

• Red areas show where forecasts can be generally skillful, and so it is possible for us to indicate high confidence for forecasts of unusually wet or dry seasons in these locations. Seasonal forecasts in red areas may be most useful for early warning.
• Yellow areas indicate where forecasts have some skill. These are also areas worth monitoring, although we will only occasionally indicate high confidence for these forecasts.
• Grey locations are places with little or no skill. Any forecasts of unusual rainfall in these locations will usually only show low confidence and early warning opportunities would likely be limited.

The map categories are calculated as follows:

Assume a simple model, in which you will break even over many years if you ignore the forecast and prepare evenly for below-normal, normal, and above-normal rainfall. If you don’t ignore the forecast and instead invest preparedness resources according to the forecast probabilities of each category, based on this simplified model, you would

• Have a return of 10% in “good skill” areas.
• Have a return of 5-10% in “some skill” areas.
• Have a return of less than 5% in “little or no skill” areas.

These categories are based on the Effective Interest Rate which is derived from the Likelihood Score. Detailed information on these skill scores is available on IRI’s Seasonal Forecast Verification Webpages.

How to navigate between maps

Switch to another map: Select the dropdown menu at the top of the page, to the right of the blue “Forecasts” heading.

Return to the menu page: Click the blue link called “Forecasts” at the top left corner of the page.

Dataset Documentation

Helpdesks

Contact help@iri.columbia.edu with any technical questions or problems with this Map Room, for example, the forecasts not displaying or updating properly.