<< While meteorologists and computer models do reasonably well in forecasting severe thunderstorm activity up to a week in advance, their forecasts are less reliable in the 2‐ to 5‐week time frame. >>
AA << develop a technique that can accurately forecast severe thunderstorm activity in this time frame by using knowledge of the current state of weather in the tropics (the Madden ‐ Julian Oscillation). >>
Anne Manning. Researchers rise to challenge of predicting hail, tornadoes three weeks in advance. Colorado State University. Nov 29, 2018.
https://m.phys.org/news/2018-11-hail-tornadoes-weeks-advance.html
Cory F. Baggett, Kyle M. Nardi, et al. Skillful Subseasonal Forecasts of Weekly Tornado and Hail Activity Using the Madden‐Julian Oscillation. Journal of Geophysical Research: Atmospheres. Nov 12, 2018 doi: 10.1029/2018JD029059
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD029059
The Madden–Julian oscillation
https://en.m.wikipedia.org/wiki/Madden%E2%80%93Julian_oscillation