What's more, CFS loves to project a very flat jet profile (fits with the tendency to ramp up the intensity), so on those occasions where that jet is fired due east, CFS can end up showing an entire month of blizzard after blizzard . Conversely, if the jet is fired NE, the blocking lasts no more than a few days.
IMO, this is a significant cause of the different climate regimes of multi decadal warming and cooling. The Azores high, affected by the ozone changes caused by the different output by the sun at certain UV levels, either generally, deflects the jet NEwards - or it doesn't.
Makes a lot of sense - perhaps the people behind CFS should focus on very accurate modelling of the Azores High. Trouble is, the overcooking of storm systems and resultant steering of the jet energy NE often leads to more ridging of the Azores High northeastward than is realistic.
When CFS was persistently predicting an extreme March in terms of blocking at the high latitudes, it could be that there was a very strong signal for the Azores High to be supressed or absent, something that no amount of northward bias can overcome.
To be fair on CFS, GFS can be just as bad in the 192-384h range, and ECM is sometimes not much better for 168-240h.
I believe the problem the computer models have is that they transfer energy too efficiently, this being a result of assumptions made in the programming, which were required partly to prevent the modelling becoming so complex that a single run takes more than a day, and partly because some of those smaller details remain poorly understood.
As an example, the models often see all of the energy from a strong thermal gradient (clash of airmasses) being bundled neatly into a large and powerful storm system which then retains a lot of it's energy and makes a lot of progress in whatever direction the steering pattern allows for. Yet the reality is often far less tidy, with energy either forming a more unstable system that breaks apart (disrupting trough) or forming numerous seperate disturbances which interact in a complex manner, making for tricky forecasting. In both cases, progression is usually far more limited as energy is dispersed - it has a lot less 'shove'.
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