Model Output Discussion

[shedhead]

Yesterdays 18hr runs were the 6 or 7th set to show an improvment in the longer term, only to see it diluted or smashed up 6 or 12 hours later. Surely those who keep looking at these runs and hoping they are right will eventually

get the message, until we see a significant shift in the pattern progged here.... http://www.meteo.psu...0z/hgtcomp.html nothing is going to change significantly for the better - whether we like it or not.

johnholmes

• Posted Yesterday, 09:57

It is the model discussion thread so can we discuss that please, there is a thread for discussing the summer forecast?

I doubt the figure of 18C is correct but cannot find the absolute lowest afternoon value for London anywhere?

anyone able to help please?

Edited July 15, 2011 by shedhead

[Methuselah]

More of the same, would be my guess, after looking at this morning's run...BUT, the tentative signs of an improvement later on (for at least the SEern half of the UK) seem to be getting closer (Touch very large plank!)...I'll no be holding me breath, though!

[Thundery wintry showers]

The outlook looks the same as yesterday's to me- a washout weekend (dull wet Saturday, brighter with showers for some on Sunday, while staying dull and wet for others, but also unusually windy). Then next week becomes mostly bright and showery with cool temperatures and slow moving low pressure, though the odd longer outbreak of rain may bring cold damp conditions to some on one or two days of the week.

The GFS and ECMWF into FI look plausible to me, showing a slow mixing out of the cold upper air from the NE which, in a pronounced north to north-easterly regime, usually brings drier conditions which are cold and cloudy by day and warm by night, thinking back especially to a spell of that nature around mid-August 2006. I note that the conditions on the latest GFS run are conducive to warm dry sunny weather eventually by T+384!

[Nick F]

As soon as the trough, which ends up just to our east early next week, moves away - the better our chances of seeing the weather settle down are. Unforuntately for now, the trough doesn't look like moving very far, and stays close to our east through much of next week into the medium range - keeping it cool and unsettled, as the 8-10 day H500 comparisons show:

Perhaps in the longer term we may start to see the Azores high begin to influence the weather more as we head into late July, but this is dependent on amplification in the flow upstream, 00z ECM keeps the flow rather flatter than GFS into the medium range, which would mean further Atlantic depressions could come through later on.

[tinybill]

yes definitely agreed. You just need to look in the south east of France north of Nice it's predicting 10C haha, total tosh!

well looking at the models for the weekend its looking like it wont be far out!!!!

[shedhead]

The 06GFS continues the theme, banging yet another nail into the coffin of July, which to anyone other than an eternal optimist must now look a write off as far as nationwide warmth is concerned. Perhaps of more concern

though is it's hard to see the pattern evolving into anything more setttled looking at the progs post T+300hrs. Admittled the block over Greenland has gone, but the Jet, albeit weak is being fired right at us, with

any Azores ridging only affecting France and N Iberia. Far to early to write August off too, but things do not look that +ive right now imo.

Edited July 15, 2011 by shedhead

[Summer Sun]

As soon as the trough, which ends up just to our east early next week, moves away - the better our chances of seeing the weather settle down are. Unforuntately for now, the trough doesn't look like moving very far, and stays close to our east through much of next week into the medium range - keeping it cool and unsettled, as the 8-10 day H500 comparisons show:

Perhaps in the longer term we may start to see the Azores high begin to influence the weather more as we head into late July, but this is dependent on amplification in the flow upstream, 00z ECM keeps the flow rather flatter than GFS into the medium range, which would mean further Atlantic depressions could come through later on.

I been seeing these charts for a bit now but one thing i've always wondered is where abouts is the UK on that map, sorry for sounding dumb but that type of chart is new two me.

[bluearmy]

I been seeing these charts for a bit now but one thing i've always wondered is where abouts is the UK on that map, sorry for sounding dumb but that type of chart is new two me.

Sorry to say it Gav, but you do sound 'dumb' on this one!! its the NH from above. locate n america, asia, europe and the UK will come into sharp focus - its just left of one of the blue troughs !!!!!

Edited July 15, 2011 by bluearmy

[Typhoon John]

I been seeing these charts for a bit now but one thing i've always wondered is where abouts is the UK on that map, sorry for sounding dumb but that type of chart is new two me.

The charts give an indication of where the average pressure anomalies will be in the 7-10 day range. The ECM output is on the left and the GFS output is on the right. At the moment they're showing a trough likely just to our East and high pressure from the mid-atlantic up to Greenland/Iceland and linking across to the Siberian high at time. In general, a cool and at times unsettled outlook.

Edited July 15, 2011 by Jonathan F.

[snowlover2009]

I always have to tilt my laptop when people posts those charts above, it is easier to understand, but looking from them, they look pretty vile for anyone who wants some settled and dry or warm weather.

[Summer Sun]

Thanks Jonathan

[Thundery wintry showers]

I must admit it's mainly John Holmes's analysis over recent months that has convinced me of the relative reliability of those NOAA outlook charts at the 8-14 day range- nothing is foolproof of course, but their track record does seem better than that of the GFS/ECM operational runs and even their ensemble means, particularly when there's a strong signal (as here).

For warm dry sunny weather we would need the trough in the North Sea to pull out well to the east, with the mid-Atlantic block drifting eastwards towards the British Isles. Generally speaking with these North Sea troughs we start off with sunshine and showers and eventually end up cool and cloudy as the polar air gets mixed out from the north-east, but if the high is close enough to prevent a vigorous north to north-easterly flow from arising then it turns dry and sunny instead.

The main issue I have with that idea is that the most likely way we'd see the North Sea trough displaced further east would be if the jet strengthened again, which would increase the likelihood of Atlantic systems crashing through and the Atlantic block sinking south rather than drifting east.

[feb1991blizzard]

The charts give an indication of where the average pressure anomalies will be in the 7-10 day range. The ECM output is on the left and the GFS output is on the right. At the moment they're showing a trough likely just to our East and high pressure from the mid-atlantic up to Greenland/Iceland and linking across to the Siberian high at time. In general, a cool and at times unsettled outlook.

The main thing to note about those charts is that not only is there high hights to the west and North west but its the deep shades of orange and even red showing very strong blocking which could be very hard to shift.

[bluearmy]

I must admit it's mainly John Holmes's analysis over recent months that has convinced me of the relative reliability of those NOAA outlook charts at the 8-14 day range- nothing is foolproof of course, but their track record does seem better than that of the GFS/ECM operational runs and even their ensemble means, particularly when there's a strong signal (as here).

Ian - if you read the NOAA cpc prose that goes with the 8/14 dayer (only on weekdays), you'll see that those charts are a conglomeration of the various model op runs/ens means from the past 24 hours. different weightings depending on the forecasters assessment. they are generally very reliable although the fact they are a 6 day mean forecast, does allow for small shortwaves/2 day ridges to occur having not registered on the chart. JH, with his experience is able to use them effectively. others may not.

[Thundery wintry showers]

Thanks for that info Bluearmy, I wasn't fully sure on how they were derived- so it sounds like they serve a pretty similar purpose re. the 8-14 day range to the UK Met Office's FAX charts at the 1-5 day range.

[johnholmes]

I hope to post a guide to how useful they are sometime this evening, tips on how to use them for those with and without experience and the usual jh warning-they are ONLY FORECASTS-and like any other can go wrong. But if used as I will suggest, then in my view, a much more reliable guide than the daily GFS output at the time scales involved, ie 10+ usually. This comment also applies to some extent to the ECMWF output at the same time scale. Why not the same as GFS, see the NOAA scores on the doors for 5 and 6 day with ECMWF mostly ahead. Just how well this verifies at 10 days I do not know.

Edited July 15, 2011 by johnholmes

[Summer Sun]

Looks Like Monday will be the last day for the deep area of Low pressure, with it breaking up for Tuesday,

http://www.wetterzentrale.de/pics/Rtavn1021.png

This then leaves us with a spell of Sunshine and showers, temperatures should be around the high teens to low 20's in the east and south, slightly lower on western coast's, so in sunny spells it will feel quite pleasant, wind permitting,

http://www.wetterzentrale.de/pics/Rtavn1261.png

http://www.wetterzentrale.de/pics/Rtavn1501.png

Into the weekend the same pattern continues,

http://www.wetterzentrale.de/pics/Rtavn1741.png

http://www.wetterzentrale.de/pics/Rtavn2041.png

So hopefully not a to bad of a week to come after Tuesday, a typical british summer really with sunshine and showers.

[SP1986]

Looks Like Monday will be the last day for the deep area of Low pressure, with it breaking up for Tuesday,

http://www.wetterzentrale.de/pics/Rtavn1021.png

This then leaves us with a spell of Sunshine and showers, temperatures should be around the high teens to low 20's in the east and south, slightly lower on western coast's, so in sunny spells it will feel quite pleasant, wind permitting,

http://www.wetterzentrale.de/pics/Rtavn1261.png

http://www.wetterzentrale.de/pics/Rtavn1501.png

Into the weekend the same pattern continues,

http://www.wetterzentrale.de/pics/Rtavn1741.png

http://www.wetterzentrale.de/pics/Rtavn2041.png

So hopefully not a to bad of a week to come after Tuesday, a typical british summer really with sunshine and showers.

Agreed, I suspect this is more realistic analysis than the GFS potrays itself currently.

I suspect by next weekend the GFS and other model will tone down the strength of the northerlies so we'll probably end up with sunshine and showers and a pleasant, British summer outlook, with temperatures around average. It's been a typical story of model watching this year, model portrayal of cool, even cold periods relative to the average, then retracting to actually fairly pleasant weather by the time the timeframe in question occurs.

[shedhead]

I'd have to say given what the 12GFS shows next week Gavin, your assessment is, let's call it, a tad optimistic. If the 12GFS were to verify next week will be inherently showery, but it will also be cool, locally very cool.

Moreover the often stiff N wind will make it feel unpleasant at times, especially down the North Sea coast, where occasionally more persistent rain is likely to add to the misery. I certainly would not want to be a beach

based business in Gt Yarmouth next week, or almost anywhere else for that matter.

[Slowpoke]

I don't agree Shedhead. It's mid-July. In any sunshine it'll feel warm and after Tuesday winds are forecast to ease so it shouldn't feel too bad at all. The only exception is the North Sea coasts but I don't agree with your cool statement, even here.

[shedhead]

Even given GFS's perpensity to downgrade maxima, next week will be cool almost everywhere and locally very cool, IF the 12 run verifies.

Edited July 15, 2011 by shedhead

[Swave Snow]

It is very prbably GFS on one of its under cooking temp forecasts by the look of it. But it may come to fruition with such a stubborn low. One thing I do notice is the low is coming in from the north as to what temps it actually brings, I think we have to wait and see. As there is a lot of blocking in the Atlantic and this low could have picked up some much warmer sectors which might not be spotted until the low is over our north and which people like me HATE in the winter months , but it could still make things warmer than what GFS shows.

Edited July 15, 2011 by Swave Snow

[peterf]

cracking growing weather,the precip is most welcome here.

[johnholmes]

It is very prbably GFS on one of its under cooking temp forecasts by the look of it. But it may come to fruition with such a stubborn low. One thing I do notice is the low is coming in from the north as to what temps it actually brings, I think we have to wait and see. As there is a lot of blocking in the Atlantic and this low could have picked up some much warmer sectors which might not be spotted until the low is over our north and which people like me HATE in the winter months , but it could still make things warmer than what GFS shows.

easy to see how warm the air is now without waiting to see what may happen simply by looking at the dewpoint chart on Net Wx?

the link below takes you to Extra and it shows quite well how much 'warmer' air is already tied into the circulation to the south of the surface centre.

http://www.netweather.tv/secure/cgi-bin/premium.pl?action=gfsbasic;sess=e759d1c96f897d41803489270e80f1f2

as promised a page or so back, below is the pdf to help those new to using the 500mb anomaly charts. I know some are unable to access pdf files so it will go into the Guides when I get time as an open file with charts inserted.

500mb charts-how to use 2nd version-15 july 2011.pdf

Edited July 15, 2011 by johnholmes

[January Snowstorm]

It would be good to get an update from GP

I haven't seen him post for a long time.

Even if it's more of the same an update would be welcome