On Dec 11, 5:52*pm, Dave Cornwell wrote:
how accurate (in %age terms) is the GFS at 120h ?

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Who knows for sure? 60% ??
Dave









The secret with GFS is not to take any particular frame literally, but
to monitor the time period you are interested in on a run by run
basis. The general trend on the previous three runs is for an intense
low to be somewhere over northern Scotland between 18Z Thursday and
06Z on Friday.

The 12Z run has the centre a little further south, but the low centre
continues to be forecast at below 950mb (and maybe 940 for a time).

Therefore I would say that the accuracy on a slightly larger spatial/
time scale is higher than 60%, maybe as high as 80 in this case.