Did you read it? They are admitting it will suck much of the time. "sometimes it will be the worst". I guess one of those times is now, when we are having 100 degree heat and it shows a cold anomaly during our heatwave, which is what, day 4 now? day 5?
Quite the CYA:
Five of the six models predicted the 2021 polar vortex breakdown, with the forecast generated by the Rosenstiel School being the most accurate, according to Kirtman. “But there’ll be times when our model isn’t the best,” he explains. “Sometimes, it’s going to be the best. Sometimes it’s going to be the worst. Sometimes it’s going to be the middle of the pack. That’s the strength of the system.”