GFS output and checks on them

[johnholmes]

Hi everyone

For some time I have thought that a realistic assessment of GFS 12Z surface /500mb products would be a good idea.Say to start from 7 days and run down each 24 hour output at 12Z From it we could all learn about how accurate, or otherwise, these products are in different weather scenarios.

To start I have been checking the 12Z runs from 18th October for today, Tuesday 26th October to see how each run compared to the previous one and, ultimately, how these compared to the actual for 12Z 26th October.

Unfortunately I forgot to store the http code for each run so you will have to bear with my assessment but in future, if it seems those of you out there are interested I would include those as well as my assesment.

Perhaps, before I put the first one on the Forum you could give me some feedback? this being especially true of the 'Mods'

I'll put my ideas of this run out early this evening unless there is a deafening silence!

regards

[Paul]

I think thats a great idea John, I'd be very interested to see the results of that

[johnholmes]

Hi again

Thanks for that Paul I'll try and issue this first one early this evening. The next one I will try and follow will be the T+168 prog for 12Z today.

[johnholmes]

Hello

Well here goes with the first issue:

The forecast run at 12Z(T+168) gave a dumbell type low, with the main centre off NW Ireland below 990mb, this extended into a low in the North Of the North Sea of 995mb with a slackish WSW flow over England and Wales, but stronger over Eire.

By the 12Z run Tuesday 19 October the low centre was <995Mb and approximately 500 miles SW of Eire with a slack SW'ly over much of the UK.

The 12Z run On the next day showed a similar scenario.

By 12Z on Thursday 21 October it had deppened the low to <985mb, slightly further NE and with a secondary centre West of Ireland. A light to moderate W to SW flow covered most of the UK.

I was away from mid Friday until mid Monday so only saw the following:

00Z on Friday was totally different, it had the low off Eastern Scotland, centre<990mb with a ridge over SW Eire and a strong NW'ly flow over most of the UK.

By Monday 12Z it had reverted back to a similar story to that of 12Z on Thursday.

Now to the actual today 12Z Tuesday 26 October 2004:- Low 982 at 46.5N and 20W with a slack SW'ly flow over much of the UK, with a secondary low of 995 with associated fronts over SW Eire.

Now, its easy to be critical, but I would love to be as accurate as that out at T+168. In my experience GFS does handle these patterns quite well. Its the blocking situations it has trouble with more than about T+84?

To the 'mods'; is there any way these subjective treatments can be stored for any of us to be able to look at them at a later date please?

[Paul]

Thanks John, yep sure, they will be saved in this forum area anyway as everything in here is saved

I'll try and make a point of saving the images for you too

[Guest Mrs murphymoo]

Great idea! Thanks for that John

[Shiny_Bottom_1]

Excellent thread peeps.

Look forward to the next instalment

Regards,

SR

[johnholmes]

Hi

I am away this next weekend so will start the next check using the 12Z on Sunday 31st October for T+168 hours(7 days), which takes us to the 7th November. Currently GFS shows a large High covering the whole UK with central pressure >1030, centre just off SW Scotland.