Ocean observations improve medium-range weather forecasts

Data collected beneath the ocean surface helps forecasters predict the weather up to ten days ahead. That is the conclusion of a new study by the European Centre for Medium-Range Weather Forecasts (ECMWF), published on 6 November 2026 in the WMO Bulletin (Vol. 75, issue 2).

The team ran a year of daily 10-day forecasts with ECMWF's coupled ocean-atmosphere system, removing one type of ocean observation at a time to see what each one contributes.

Key findings

• Sea-surface temperature from satellites had the biggest impact. Without it, both ocean and weather forecasts lost accuracy over the full 10 days.
• Argo floats improved estimates both below and at the surface. Without them, atmospheric forecasts got worse by about as much as one upgrade of ECMWF's forecasting system improves them.
• Satellite altimetry had a smaller but still significant effect.

The results show that observing systems complement each other and should be assessed together, and that sustained investment in ocean observing pays off well beyond ocean science. ECMWF is now extending the work to fishing vessels, gliders and animal-borne sensors.

Read the full article in the WMO Bulletin: Ocean Observations Improve Medium-Range Weather Forecasts