There’s a major GFS upgrade (v17) coming in Oct., which includes among many other things upgrades to its MJO forecasting:


The Environmental Modeling Center (EMC) is proposing to upgrade the NWS
operational Global Forecast System (GFS) and Global Data Assimilation
System (GDAS) from v16 to v17 in October 2026. This upgrade will
transition the system to a fully coupled Earth-system modeling framework
for global weather prediction, improved model forecast performance, and
expanded, enhanced products that cover all components of the Earth
system. The NWS is seeking comments on the proposed changes to GFSv17
through May 15, 2026.
GFSv17 introduces a coupled Earth-system model with components of the
atmosphere, land, ocean, sea ice, and waves.

- An increased horizontal resolution from C768 (13 km) to C1152 (9
km)using the Finite-Volume Cubed-Sphere (FV3) dynamic core.
- Introduction of fractional grids along oceanic coastlines.
- Improved atmospheric and land surface parameterization schemes

https://www.weather.gov/media/notification/pdf_2026/pns26-29_Science_for_GFSv17.pdf