Yesterday’s global atmospheric angular momentum index forecast transitioned the current strong positive phase to negative phase in 10+ days. (Well, the GFS did. Other models are not as strong). The transition of an intense convection phase of the Madden Julian oscillation (which triggered Cat-5 Typhoon Surigae) across the equatorial Pacific releasing heat poleward as it weakens in the Atlantic/Africa tropics in early May is a likely explanation for the GLAAM phase change. If you look at 500 MB heights right now they are LOW in the northern latitudes and there are 7-9 short/long wave troughs across the middle latitudes of the northern hemisphere within an energetic mid-latitude jet stream. The MJO eastward shift and weakening releases heat pole ward causing the northern hemisphere to warm. Less thermal latitudinal gradient implies a slower jet stream in 10+ days. The slower upper level flow is representative of the -GLAAM phase change.