ARCS Dry Spell Forecasts

The forecast maps on this page show predictions of dry spells based on ECMWF's extended-range forecasts and a reference climatology-based model. They provide an early indication of dry spell risks, helping farmers and decision-makers prepare for periods of limited rainfall. The first two maps represent the likelihood of at least one dry spell occurring over a specific time period according to the two models. Areas with higher probabilities (indicated by colour) are more likely to experience dry spells. The last map shows the differences between the model predictions. More information is provided below the maps.

Instructions

The forecast page is updated daily. The three maps show the likelihood of one or more dry spells occurring during the selected period. From left to right, the maps display the forecast based on ECMWF's extended-range (subseasonal) forecast model, a forecast based on climatology, and the difference between the two (ECMWF minus climatology).

Blue colours in the last maps indicate areas where dry spells are less likely than normal during this time of the year. Conversely, red colours indicate areas with a heightened chance of dry spells compared to other years.

You may select options from the dropdown menus:

• Region: Select the zoom level, currently East Africa, Ethiopia, Malawi, or Madagascar.
• Resolution: Choose between the model's native resolution (0.4 degrees) or 1.5 degrees, the resolution of the data freely available through the S2S project.
• Forecast Initial Date: This is the date that the forecast was initialised. There is currently a two-day embargo period for the 1.5-degree forecasts. Hence the latest available forecast is two days old.
• Forecast Period: The maps display predictions for the following two or three weeks. The forecasts show the likelihood of one or more dry spells occurring during these periods.
• No Rain Threshold: The forecast maps consider rainfall levels below a certain threshold (e.g., 1 mm per day) to identify dry spells. Any day with less than the threshold amount of rain is considered a no-rain day.
• Dry Spell Length: The maps show the likelihood of dry spells that last for at least 5, 7, or 9 days.

The forecast maps were produced by Erik Kolstad at NORCE for the ARCS project (funded by NORAD; grant RAF:23/0006).

A validation paper is published in Climate Dynamics. If you have any questions or feedback, please contact Erik.