On Dec 7, 11:42*pm, David Buttery wrote:
On Mon, 07 Dec 2009 22:04:40 +0000, John Hall wrote:
In article ,
*comp.john writes:
On 2009-12-07, John Hall wrote:

The GFS Ensemble 850mb temps for London are now looking decidedly
chilly:

http://91.121.93.17/pics/MT8_London_ens.png

What do the coloured P numbers mean down the left side of the chart?

Good question. Hopefully someone else will know, as I don't have a clue..

I've always assumed that they're simply a guide to which perturbation is
shown in which colour.

--
Bewdley, Worcs. ~90m asl.

Yes, as far as I know. It's so you can identify which run is which.