In article ,
Dave Cornwell writes:
John Hall wrote:
In article ,
Dave Cornwell writes:
It looks like we will have some better idea after that date what the
rest of the month holds. When the ensembles are that split the mean is
meaningless. (excuse the play on words!). At the moment it it is saying
there is about a 33% percent chance of it being either cold, average or
mild from the 8th, which is quite different from assuming an average of
all of the peturbations for which there is little confidence.
Dave
Looking at the 12Z GFS 850mb temps for London, there's a fairly big
spread from about the 5th. That's fairly common. Looks like there's
going to be a fairly chilly day or so around the 4th and a very mild one
24-48 hours later. After that, as you say, there's no clear signal.
------------------
It is very common. Sometimes there is a north or south bias (not
geographically but above and below the mean)within the spread. In this
case although also fairly common, does show cold is just as likely an
outcome in the reasonably near future. I don't really know why I posted
this as it's pretty obvious! I sometimes use this medium so my mental
ramblings have an outlet!
Dave



With the 00Z GFS ensemble there's a definite bias towards mild.

One other thought. When the ensemble mean is close to the long-term mean
there are often more mild members in the ensemble than there are cold
ones. That's because 1 or 2 cold members are often at -10 or -15, whilst
it's rare for a mild member to be as much above the mean as that. So the
ensemble median tends to be rather higher than its mean.
--
John Hall

"The covers of this book are too far apart."
Ambrose Bierce (1842-1914)