On Saturday 16 Jan 2010 23:15, Yokel scribbled:
"Martin Rowley" wrote in message
news
|
| Until these seasonal forecasts can be shown to have significant
| skill, they
| should be clearly labelled "Experimental" or - like some machines in
| the old
| "penny arcades" - "For amusement only - no prizes". Of course it is
| possible that the variability of our local climate and weather is
| such that
| reliable seasonal forecasts cannot be issued with technology likely
| to be
| available any time soon. If this is the case, let's hold our hands
| up and
| be honest about it.
|
|
|
| ... for those of us who were around in the 1960s, all this is a bit
| "Déjà vu" ! Good grief, that was half-a-century ago :-)
|
Those forecasts were produced by the "analogue" method. Basically, they
looked for similar months (analogues) to the one which has just gone and
worked on the basis that similar weather would follow. So if you had 4
Decembers like the one just gone and the 4 Januarys that followed were
similar, you would use the weather in those Januarys as the basis for your
January forecast. If the months following the analogues had different
types of weather, you issued a forecast on the lines of "dry spells, some
rain in places" and hoped no-one noticed.
There was a lot more to it than that. That was the simple version that was
either supplied to the media or the only bit they could understand from a
more detailed briefing.
Before the monthly forecasts were issued, there were several meetings, each
dealing independently with an aspect of the atmospheric and surface
conditions. These were then brought together with a final meeting. I used to
take part in the one which dealt with surface conditions, ice, snow, SST
anomalies, etc.
As you doubtless recall, this method was not a winner then. If climate
change is real, it is even less likely to be a winner now as going back to
the past will not be comparing like-with-like any more.
Agreed. Even what I thought was the most reliable contribution to the
forecast, the SST anomalies, seems less reliable now, perhaps due to GW,
though it's worked really well this season.
--
Graham P Davis, Bracknell, Berks., UK. E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."