Jump to content

Welcome To The Netweather Forum!

Sign In or Register for full access to the community - including the regional forums.

Photo

GFS Checks For T+168 Hours


  • Please log in to reply
149 replies to this topic

#21 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 12 December 2004 - 21:49

Hi
part of this is from the Christmas 2004 forecast but applies to this thread.
On the other thread I am running, T+168 checks. Its almost certain that the 8th consecutive run over the past 8-10 weeks is going to show a pretty close pic to the actual. The next one could be even more interesting as it will go to 20 December.
I'll post this also in the other thread. Mods if this is wrong pse delete just one!
thank you
John
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#22 Shiny_Bottom_1

Shiny_Bottom_1

    Bimbostratus - The Dizzy Cloud

  • Members
  • 7,031 posts
  • Gender:Male
  • Location:Derby - 46m (151ft) ASL

Posted 12 December 2004 - 21:59

Wow.

It seems quite consistant for T+168. It will be quite interesting when (or if :) ) the cold weather enters that time frame.

Thanks for the update John.
  • 0
This weeks cheese is...Manchego.

Yellow in colour, and tangy in flavour.

#23 Paul B

Paul B
  • Members
  • 11,344 posts
  • Gender:Male
  • Location:Manchester

Posted 12 December 2004 - 22:07

Thanks John.

The GFS is doing quite well really at the T+168 timeframe.
  • 0
Paul B
Have you ever stopped to think, and forgot to start again?

#24 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 15 December 2004 - 14:48

Hi folks
Well amidst all the mounting excitement over will it/ won't it be white at Christmas, let us not forget what enables us to even begin to try to forecast that far ahead. I give you, ladies and gentlemen, the GFS T+168 forecast check.

This one runs from the start time of 12Z Monday 6th December 2004 to T+168 on Monday 12Z 13th December 2004


I suppose it is possible, if you want to, to 'nit-pick' at this to find some fault. Personally I find it very good at this time frame for reasons I've regularly posted about.

The wind flow, even its main source, and the flow strength, are all accurate by my measuements.
Hopefully by clicking on the attachment below you will be able to see for yourself what I mean.

So I now have eight checks on GFS T+168 from late October to now, most with differing synoptic start situations, and all accurate.

The next check will have to be over 144 hours as I go away next Wednesday morning, it will run from 12Z today until 12Z Tuesday next week.

regards
John


  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#25 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 15 December 2004 - 14:49

okay Mods pse tell me how i get the attachment to open please??
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#26 Snowrules!!!

Snowrules!!!
  • Members
  • 127 posts
  • Location:Yeovil, Somerset

Posted 15 December 2004 - 15:22

John holmes your not confident for a cold christmas are you!
  • 0

#27 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 15 December 2004 - 15:35

hi snowrules
what makes you say that?
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#28 Snowrules!!!

Snowrules!!!
  • Members
  • 127 posts
  • Location:Yeovil, Somerset

Posted 15 December 2004 - 15:39

Just by the way you seem to be saying about the situation?
  • 0

#29 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 15 December 2004 - 16:49

Hi Snowrules
pse read my Xmas forecast link. I'm not daft enough at 16 days to say with certainty that it would be a white Christmas, but I think, if you read ALL the thread then you will agree I have been more leaning towards a cold Christmas,long before you could read anyone else about it. My latest thoughts with a real effort to face the 'White Christmas' issue I hope to have ready by about 6.30pm this evening. At the moment I am slowly dowmloading and trying to assimilate the 12Z data from GFS.
cheers
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#30 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 21 December 2004 - 15:46

hi folks
away from the unfolding drama of Christmas 2004 I have continued to do this check.
This one runs from Tuesday 13 December until today 21st, so just for 144 hours.
It is again, if not 95% right like almost all the others, its a good 80% correct in my view, so another undoubted success.
The major high (Azores) is in the right place and intensity with about the right orientation of the isobars around it. On the Depressions, they are a little out, but only in so far as the main one, predicted to be just ne of Iceland when it is actually well ne of Iceland.
The isobars round Britain were predicted to be wsw'ly, quite fresh, especially in the north but are actually more wnw'ly, but with the air of much the same origin.
The next check will start on Tuesday 28th December and run for the full T+168 hours.
regards
John
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#31 Paul B

Paul B
  • Members
  • 11,344 posts
  • Gender:Male
  • Location:Manchester

Posted 21 December 2004 - 16:48

Thanks John...another good performance from the GFS. :)
  • 0
Paul B
Have you ever stopped to think, and forgot to start again?

#32 P.K.

P.K.

    Sir Michael Fish

  • Members
  • 3,072 posts
  • Location:Watford

Posted 21 December 2004 - 16:50

:lol:

Should be good when they start using 0.5 degree grid boxes all the way to T+384. :)
  • 0
This winter we shall be using the OAP model.

TORRO Member
http://www.torro.org.uk

#33 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 04 January 2005 - 17:18

Hi Folks
well just finished the last check. Its the 10th done since late October and yet another brilliant predict from GFS.
below is my summary, and sorry no pics, I promise I will eventually sort this out so that you can compare the T+168 and its T+00 as well as my ramblings.

here we go
The T+00 is almost identical to the last run and most others, even down to the low in the Atlantic, around 52/53N and 40W; trough as before, perhaps just a touch less marked but flow over uk spot on. 850=0=spot on, -5=almost identical to T+168. Comparing T+168 to T+00, and LP near Iceland is 5mb out!! And about 60miles further wsw. HP 1035 in the Med is about 100 miles wsw of T+168 predict. New low developing about 53N40W is spot on but is 15mb higher than T+168 suggested. The trough over the UK is less sharp and instead of Scilly Isels to Wick was, say, Plymouth to about 60N 03E. As a result of the trough being less well marked the 500mb trough is also smoothed out from the T+168 predict.
My conclusions: stunningly accurate yet again. Now checked 10 runs and NOT ONE has been essentially wrong, this one right from T+168 has been very very accurate.

enjoy
John
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#34 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 12 January 2005 - 10:50

hello folks
Back to the day to day trivia!
This is the GFS check from Tuesday 4th January at 12Z to Tuesday
11 January 12Z


This is the first gfs run in 11 checks since October which cannot be considered a success! When we remember what has happened over the past 48-96 hours this is perhaps hardly surprising. After two of the worst storms within 72 hours of one another there was no sign of this on the T+168, nor indeed until T+96 when it first started to show these developments. Nevertheless, wrong though T+168 was, GFS did better than most other models in first picking up the two major lows.

At T+168 all that gfs had, as some possible indication of what actually happened, was an elongated trough from off the nw Scottish coast thence trailing to be off the sw coast of Ireland. The 500mb flow and the several high pressure systems to the south of the UK were all pretty well positioned. But not the low pressure systems over and west of us, or the 850mb temperatures over the UK.

so 10 out of 11, not bad, eh?

No check for two weeks now as I'm off to ski in Switzerland, so the next check will start, probably, Monday 31st January 2005.
bye for now
John
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#35 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 08 February 2005 - 22:03

hi people
This is the next GFS check, number 12: period Tuesday 1st to Tuesday 8th February 2005.

Not the best but still not too bad.
Summary:
At T+168= utterly wrong, ie nely which is in fact 180 deg out = sswly at T+00 over the UK. From about T+120 it settled down to what it has shown since T+96; ie a sw or sswly over the UK with 850mb temps below zero deg C over all the UK. Its main High and Low pressure centres being in about the same place and similar pressure with each run.

I have e mailed the NOAA site with questions about GFS. Principally why after such a superb run from October into December, including picking up the November snow situation and, of course, its spot on forecast for Christmas. This was indicated as early as 15 days before the event and, very largely was continued throughout the period. I remember it well, I've never spent so much time in front of a computer! Now, from early January, starting with the severe storms in north Scotland it has not been anything like as reliable. Why for the past 4-6 weeks has it, dare I say it, reverted to its old ways of last winter? I have not yet received a reply but hope that I will. If I do then I will post their response.

The next check is Tuesday 8-15th february 2005.

regards
John

Edited by johnholmes, 08 February 2005 - 22:04 .

  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#36 J10

J10
  • Site forecast team
  • 17,262 posts
  • Gender:Male
  • Location:Tycoch, Swansea 162m asl

Posted 08 February 2005 - 22:12

It will be very interesting to see what they have to say.
  • 0

All Comments made are entirely my own opinion

 

 


#37 Thundery wintry showers

Thundery wintry showers

    Cumulonimbus Incus

  • Long range forecast team
  • 27,698 posts
  • Gender:Male
  • Location:Sandhutton near Thirsk, N Yorks

Posted 09 February 2005 - 00:22

Same here, I have noticed a downturn in GFS accuracy rates, although in its defence the GFS has not really fallen below the level of the other models.
  • 0

"There is always an easy solution to every human problem - neat, plausible, and wrong." - H L Mencken

Weather records for Cleadon, 1993-2011:
http://tws27.50webs....ther/index.html
My new blog relating to humanitarian issues, which will serve as an update to my ageing manifesto from a decade ago:

http://freedom-and-r...blogspot.co.uk/

The old manifesto is still available here (but bear in mind that I have refined a lot of my ideas since I wrote this):
http://tws27.50webs.com/index.html
My upcoming modification for Doom 3 (updated 2013-06)
http://enemymountain....com/index.html

'Views and opinions expressed in this or any other of my posts are my own'


#38 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 15 February 2005 - 12:07

latest GFS run
Sorry folks, due to a variety of circumstances I have not been able to follow this week's output, so no post for this week. I'm starting the next one tonight, so 12Z Tuesday 15th for 12Z Tuesday 22nd February. We all know what the current excitement is about so it should be interesting to see what the actual shows next Tuesday.
I mentioned last time that I had e mailed NOAA with comments and asking for their ideas. Sadly I have had nothing back, in spite of two repeats to them. I will wait for Paul to return fom Canada and ask him to re send my thoughts. Perhaps they will reply to him.
regards
enjoy any snow!
John
  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#39 johnholmes

johnholmes
  • Members
  • 31,215 posts
  • Gender:Male
  • Location:just south of Doncaster, Sth Yorks

Posted 25 February 2005 - 22:08

hi folks
bit late with this but been rather busy with the Forecast side of things this week:

check number 14:
T+168 check from 15th February 2005 to 22 February 2005 for 1200Z
It set off with low pressure over north Italy and High Pressure over Greenland. This gave a north easterly flow over the UK with 850mb temperatures of all well below ms 5C.

Throughout its run the overall pattern remained the same for both low and high pressure. 850mb temperatures also remained well below ms 5 C. If anything these values were lowered later in the runs.

My assessment is that this T+168 was an excellent prediction for surface centres, 850mb temperatures and the overall position of ridge and troughs at 500mb. So, maybe, GFS is returning to its run of good forecasts from late last year.

You may remember that I mentioned having attempted to get a response from NOAA regarding these checks. I suppose it was rather conceited of me to expect much response. I did eventually get a reply but it really just reaffirmed my comment to them that with Europe being so far from the USA that what happened with us was of no direct importance to them! What I did get was a link to their site explaining how they arrive at their run and what changes they make. As an ex senior forecaster in the UK Met Office Iím afraid I failed to understand about 40% of it. Perhaps the younger computer weather experts may get more from it.

This is their reply
NCEP's Hydrometeorological Prediction Center does write a model
discussion each day discussing the current run's strengths and
weaknesses. It is one of many weather discussion products. It can be
found here: http://www.hpc.ncep....l/discuss.shtml Click on
Model Diagnostic Discussion. However, as you correctly surmised, since
predicting weather over Europe is not in our day-to-day mission, and
Europe is not upwind of the U.S., not a lot of notice is given to the
model's performance over that continent.

There is some documentation about the Global Forecast System available
here: http://www.emc.ncep....el_changes.html
You'll find many links with documentation of the model.

Just reading the model discussions, even though they will be Western
Hemisphere-centric, may give you some insight into what the forecasters
believe are its weaknesses or strengths.

I hope this is helpful.

Sincerely,

Lauren Morone
National Centers for Environmental Prediction

the next check is out to Tuesday 1st March 12Z

regards
John

Edited by johnholmes, 25 February 2005 - 22:10 .

  • 0

I no longer have a web page

please take care with sunbathing-it can give problems years down the line with skin cancer as I discovered


#40 Paul B

Paul B
  • Members
  • 11,344 posts
  • Gender:Male
  • Location:Manchester

Posted 26 February 2005 - 09:25

Thanks for that John.

To be honest its about the sort of reply which I expected, and I certainly don't understand a lot of it either.
  • 0
Paul B
Have you ever stopped to think, and forgot to start again?




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users