Checking The 500mb Anomaly Charts Against The Actual One

[johnholmes]

hi

I think it might be a good idea to see how often these charts do verify. I know, with my usual caveats, that I do trust them but let's see what actually happens.

Okay I have not got the time to do this daily and in fact I'm going to try and do it twice weekly, Tuesday and Friday for 10-12 days ahead.

The first one is today.

my summary (I'll do this every time if its possible) for 24 February is:-

Based on the above

Based on the two outputs above on 14 feb expect upper trough 30+ west and upper ridge over UK area with SW 500 flow into uk and surface HP probably NW spain/sw uk

Edited February 14, 2012 by johnholmes

[johnholmes]

well a day late but here are the two issues from Friday 17 February

Brief summary

Both the sets of charts on Friday 17 Feb for around 10 days time, 27 February(Monday) and they appear to me to suggest a continuation of the upper flow predicted on the first set of charts issued on Tuesday 14 February for about 24 February. Showing an upper ridge just SW of the UK with a fairly strong 500mb flow across the Atlantic into the upper ridge where the flow decreases away from the north of the UK where it remains quite strong. This type of ‘diffluent’ ridge is favourable for developing lows in, this case, the Iceland area with developing surface high pressure over/south of the UK (somewhere between SW and SE, just south of the UK).

We will see what the upper pattern is in 10 days time and take a look at the surface features around the UK.

[johnholmes]

My pc problems have stooped the use of pdf so I'll post the text to start and then try and insert the charts-bear with me please?

Check on ECMWF-GFS and NOAA 500mb charts issued Friday 17 February 2012 for Monday 27 February 2012

Both have kept the ridgy look from the last few days with the actual 500mb high centred somewhere s to sw of the UK.

Noaa issue 17th 8-14 for 25 feb-2 mar

This has the +ve centre again in a similar area.

All 3 show a fairly similar 500mb pattern with the upper ridge over the UK and the upstream trough around 60-70 west.

This what I made comment about when I saved the charts

Brief summary

Both the sets of charts on Friday 17 Feb for around 10 days time, 27 February(Monday) and they appear to me to suggest a continuation of the upper flow predicted on the first set of charts issued on Tuesday 14 February for about 24 February. Showing an upper ridge just SW of the UK with a fairly strong 500mb flow across the Atlantic into the upper ridge where the flow decreases away from the north of the UK where it remains quite strong. This type of ‘diffluent’ ridge is favourable for developing lows in, this case, the Iceland area with developing surface high pressure over/south of the UK (somewhere between SW and SE, just south of the UK).

We will see what the upper pattern is in 10 days time and take a look at the surface features around the UK.

The actual 500mb for 00z tue 28 feb was missed 27th due pc problems

So I am showing the first available 500mb chart from Net Wx Extra which is the 00z for Tuesday 28 February 2012.

This shows the upper ridge centred around the meridian with an actual centre of somewhere above 570DM just SW of the UK. It has the upper trough about 45 west.

Looking at the actual and comparing to the prediction how close were they?

The upper pattern around the UK is very close for the ridge and direction of flow at 500mb. The actual height over central UK is shown as somewhat above 570DM whilst the predictions showed 546-552+ so they were not that close. Further afield and the trough on the actual at about 45 west is quite a bit further east than any of the forecast charts suggested, some 10-20 degrees almost. This may well have some bearing on the actual heights being higher than predicted.

Overall I would rate this good guidance for the UK even with the higher heights.

Sadly due to pc problems I have not got the 12z chart for msl and 500mb but if we look at the Exeter Fax chart for 12z today, some 24 hours further on and I don’t think a lot has changed in the situation we can see that surface high pressure is the dominant feature and close by the SW with frontal and low centre activity largely confined to the far NW with the lows running north to north east into the Iceland area from the upper trough around 40 west.

http://www.weathercharts.org/ukmomslp.htm

sorry unable to get it to resize at the moment so use the Met O Fax web site-remember it will update at 18, 00z etc, but hopefully I will have put the actual file in before then-thanks!

now you may see why being able to do things in a pdf format with a mix of text and charts is, to me, so much easier!

If you agree or disagree I would be happy to read your views below this post-thanks.

Its only 3 I now have actual data on the forum for, 2 good and one not. Along with the 60+ lrf issues I made on my web site over the past 2 years I am happy with this use of 500mb anomaly charts but will continue to monitor them through the spring and onwards, doing 1 each week. Having 2 checks running at the same time is too much for my old brain.

Edited February 28, 2012 by johnholmes

[bluearmy]

My pc problems have stooped the use of pdf so I'll post the text to start and then try and insert the charts-bear with me please?

Check on ECMWF-GFS and NOAA 500mb charts issued Friday 17 February 2012 for Monday 27 February 2012

Both have kept the ridgy look from the last few days with the actual 500mb high centred somewhere s to sw of the UK.

Noaa issue 17th 8-14 for 25 feb-2 mar

This has the +ve centre again in a similar area.

All 3 show a fairly similar 500mb pattern with the upper ridge over the UK and the upstream trough around 60-70 west.

This what I made comment about when I saved the charts

Brief summary

Both the sets of charts on Friday 17 Feb for around 10 days time, 27 February(Monday) and they appear to me to suggest a continuation of the upper flow predicted on the first set of charts issued on Tuesday 14 February for about 24 February. Showing an upper ridge just SW of the UK with a fairly strong 500mb flow across the Atlantic into the upper ridge where the flow decreases away from the north of the UK where it remains quite strong. This type of ‘diffluent’ ridge is favourable for developing lows in, this case, the Iceland area with developing surface high pressure over/south of the UK (somewhere between SW and SE, just south of the UK).

We will see what the upper pattern is in 10 days time and take a look at the surface features around the UK.

The actual 500mb for 00z tue 28 feb was missed 27th due pc problems

So I am showing the first available 500mb chart from Net Wx Extra which is the 00z for Tuesday 28 February 2012.

This shows the upper ridge centred around the meridian with an actual centre of somewhere above 570DM just SW of the UK. It has the upper trough about 45 west.

Looking at the actual and comparing to the prediction how close were they?

The upper pattern around the UK is very close for the ridge and direction of flow at 500mb. The actual height over central UK is shown as somewhat above 570DM whilst the predictions showed 546-552+ so they were not that close. Further afield and the trough on the actual at about 45 west is quite a bit further east than any of the forecast charts suggested, some 10-20 degrees almost. This may well have some bearing on the actual heights being higher than predicted.

Overall I would rate this good guidance for the UK even with the higher heights.

Sadly due to pc problems I have not got the 12z chart for msl and 500mb but if we look at the Exeter Fax chart for 12z today, some 24 hours further on and I don’t think a lot has changed in the situation we can see that surface high pressure is the dominant feature and close by the SW with frontal and low centre activity largely confined to the far NW with the lows running north to north east into the Iceland area from the upper trough around 40 west.

http://www.weatherch...rg/ukmomslp.htm

sorry unable to get it to resize at the moment so use the Met O Fax web site-remember it will update at 18, 00z etc, but hopefully I will have put the actual file in before then-thanks!

now you may see why being able to do things in a pdf format with a mix of text and charts is, to me, so much easier!

If you agree or disagree I would be happy to read your views below this post-thanks.

Its only 3 I now have actual data on the forum for, 2 good and one not. Along with the 60+ lrf issues I made on my web site over the past 2 years I am happy with this use of 500mb anomaly charts but will continue to monitor them through the spring and onwards, doing 1 each week. Having 2 checks running at the same time is too much for my old brain.

i saved the naefs and ecm ens means for day 10 from the 17th john

and here is the actual for noon yesterday

[johnholmes]

thanks ba-a quick look without copying and pasting a lager size on to my pc and it looks like not that much difference between the two but I'll go and have a look-thanks again

[johnholmes]

hard to pick the winner it seems to me, what does anyone else think based on those charts ba showed.

I'm not actually lookiong for a winner I'm more interested in the 500mb pattern being predicted accurately enough to give a 'good' feel for the weather at that time scale. If the 3 are pretty similar then I'll stick my neck out if they are 'wobbling' over several days and with one another then I'll say its not possible other than taking the 2 most alike.

[Glacier Point]

For 8-14 day CPC dated 14/02/12:

Forecast

Observed

.. not bad and as a correlation would score highly. Being ultra critical the handling of the Pacific ridge not quite there, but at that range a very solid effort.

[summersnow]

This is a really interesting situation developing! It's really telling the way GFS has moved more towards the recent ECM output but 10 days ago, GFS was actually hinting at something of this nature and this theme has recurred consistently in GFS output, albeit apparently erratic at times.

The aspect of all this I find really interesting is the battle of the air masses - cold block to our NE vs the ever present Azores HP. While it's beginning to look increasingly like the cold air is likely to get the upper hand at least for a while, the Azores HP refuses to be pushed too far away or eroded too much. In all models, it remains a force to be reckoned with and can not be discounted - especially given its track record this winter! While there does appear to be a strong building of pressure in the Arctic, will it materialise or will it yet again be swamped by the power of the Azores HP? Just a few hours ago, GFS was suggesting the latter, so I do believe it to be very much in the balance.

Spring equinox is a prime time of year for pattern change though!

[Suburban Streamer]

hard to pick the winner it seems to me, what does anyone else think based on those charts ba showed.

i'd say close but the naefs seems a little more accurate while the ecm is flatter. seems that both charts underestimated the strengh of the pv.

interesting to see, thanks for saving and posting the charts guys

Edited February 29, 2012 by Suburban Streamer

[bluearmy]

At a 10 day range, one would expect soecific features to be diluted by the inevitable spread of the individual members that make up the mean chart. i would agree that naefs prob shades it due to its slightly larger amplification of the flow and placement of the eastern euro trough.

[phil nw.]

Yes overalll pretty good guidance of the eventual upper pattern i reckon.

I have used these quite a lot in the Winter and on the whole have found them usefull John.Considering they are forecasting 6-14days ahead it would be amazing if they had every little detail spot on.

The trick is to know when to be more cautious in using them when there`s uncertainty in the medium term-often shown up with differences in the 8-10day mean hts from the GFS/ECM operationals.

In general though one of the better medium range tools imo.

It would be good to have some checks on these as you intend doing John just to establish how close they are to reality.

[johnholmes]

Yes overalll pretty good guidance of the eventual upper pattern i reckon.

I have used these quite a lot in the Winter and on the whole have found them usefull John.Considering they are forecasting 6-14days ahead it would be amazing if they had every little detail spot on.

The trick is to know when to be more cautious in using them when there`s uncertainty in the medium term-often shown up with differences in the 8-10day mean hts from the GFS/ECM operationals.

In general though one of the better medium range tools imo.

It would be good to have some checks on these as you intend doing John just to establish how close they are to reality.

yes I hope to do one check each week for several months to build up a list of the times they give good guidance and those when they don't. Of course the trick then is trying to get the surface pattern beneath correct. By having them available on the site then folk can make their own mind up as to which synoptic patterns they seem best at. One of the ideas is to see how good they are at spotting changes rather than a continuation of a similar pattern. I've seen tehm a couple of times do this. One recently when the upper air pattern clearly indicated that a cold spell would only last 2-3 days.

[johnholmes]

check No 3 available in pdf format below

500mb check No 3 started 22feb for 2 mar.pdf

[phil nw.]

check No 3 available in pdf format below

500mb check No 3 started 22feb for 2 mar.pdf

Thanks John,they were indeed a very close match to the actual.

[johnholmes]

check No 4-not a good result for them

No 4-500mb check-for 5 march 12.pdf

[johnholmes]

here is check No 5

good 2-3 days prior to the day of validation but only fair on that day, read why in the pdf.

500mb anomaly checksThis is check No 5.pdf

in the pdf at the end the No should be 6 not 5

Edited March 17, 2012 by johnholmes

[johnholmes]

The latest check No 7 is below, the check on No 6 above is due on Monday 2 April

500mb checks-no 7.pdf

[johnholmes]

here is the issue wrongly numbered 5 its actually 6 with charts and comments about how the 500mb charts fared in terms of accuracy and as a forecast guide to the weather for Monday 2 April

500mb checks-no 6.pdf

[johnholmes]

A day late but here is check No 7-I'd judge it about 60% correct but others may disagree. I will post the 500mb actual chart in 48 hours to see how it matches.

500mb checks-no 7.pdf

[johnholmes]

Check No 8 is below in pdf format-very good correlation this time between the 10 day outlooks on the anomaly charts with the actual showing at 06Z this morning.

500mb-No8.pdf

No 9 will be based on the ouputs from today and checked on 30 April

Edited April 20, 2012 by johnholmes

[johnholmes]

here is the No 9 check, very good guidance this time

500mb-No 9.pdf

No 10 is from today so valid on 10 May for checking.

[johnholmes]

help wanted please!

Has anone got copies of the 500mb chart, Net Wx or Wetter type for the past 1-4 days please?

I would much appreciate them being posted in here if you have-many thanks

jh

[Cloud 10]

The wetterzentrale archive should do the job.

Wetter : Wetterzentrale : Top Karten : Prognose - GFS Europa

Or failing that....

Edited May 10, 2012 by Cloud 10

[johnholmes]

many thanks cloud, just what I needed so thanks again

wetter' do not make charts available for quite some time.

[Cloud 10]

many thanks cloud, just what I needed so thanks again

wetter' do not make charts available for quite some time.

No problem John,i got the charts from the link below,just click on "archiv"

Wetter : Wetterzentrale : Top Karten : Prognose - GFS Europa