Model Output Discussion

[Stormyking]

At the risk of boring long time users of NW, stormy, following models in what some call FI range is not very productive comparing run to run. Its better, down to T+144 maybe T+168 to compare 12z with 12z or 00z with 00z etc!

Oh ok so basically I will start saying T+ . Thankyou for the tip if it was a tip to me lol.

Im still trying to learn all the basics and find it fun looking at each Model as there is so much to it.

[ANYWEATHER]

The "benign" weather continues for the Uk for the forseeable future with most of any precip confined to Scotland which could turn wintry later this weekend. True to say ,the weather in this part of the Uk has been pretty dry ,to date only 13mms of rain so far and no rainfall in anytime in the near future with high pressure continuing to control. Next week even in the south if models are correct could well see some potent frosts so watch those delicate plants!!! :excl:

[Snowyowl9]

Looking a tad chilly in just over a weeks time.

Theres no blossum here for any air frosts to knock off yet.

http://www.wetterzentrale.de/pics/Rtavn1622.png

http://www.wetterzentrale.de/pics/Rtavn16217.png

This pattern we have now is just a reminder of what`s happened all winter and even twice this spring..

With today`s E/NE-ly.

Edited April 13, 2010 by Snowyowl9

[Thundery wintry showers]

Indeed- thinking back to a point Reef has made recently, this spring so far has felt pretty uneventful, I think the main issue is that for the most part any warm weather has been cloudy & wet and any cold weather hasn't been particularly snowy, with the exception of parts of northern & western Britain which saw the wet snowstorm at the end of March and the sunshine with 18-20C over the last few days. Still, there's been more in the way of talking points so far than with last year's offering.

The northerly has been toned down on the latest set of runs- I think high pressure is progged to be too close to allow wintry showers to develop on Sunday away from northern and north-eastern Scotland.

[Frosty.]

The GFS 12z continues the theme of the 6z with a noteworthy cold snap for the uk, mostly for scotland and especially for northeast and n.isles, the 12z is not the full on N'ly of the 6z but still potent enough for snow & hail showers in the far north and for frosts to become widespread from sunday onwards, a further wintry reload is indicated for the far north but it lacks much of a sting and warmer weather looks like developing in the south by the end of next week which is in line with the latest meto update. So, a more wintry feeling spell ahead, offset by the strong april sunshine but with a chilly wind to remind us of the great winter we had and then hints of some proper spring warmth later.

[damianslaw]

Strong indications from all the models that the northerly which has been projected for a few days now will manifest itself as we are reaching the reliable timescale when it is due to appear i.e. Saturday.

Question as ever with northerlies is how potent will it be, the depth and position of the developing low pressure over Iceland which will be the trigger for the colder northerly airstream is unknown and will be the determining factor.

GFS keener on developing a deeper low which is set to track closer to the north east of the country than the ECM which would result in some wintry showers for the NE but the rest of the country escaping with a slightly less wet and milder outcome. UKMO sitting inbetween the two perhaps erring more towards the GFS. The BBC stuck their necks out just now in their forecast showing the weather for Sat suggesting quite a direct northerly feed.

Longer term - AO and NAO staying negative - gosh we have been in a long period now with a combined negative NAO and AO, both have hardly been in positive territory all year. This will mean a southerly tracking jet for the foresseable future and no azores ridging and south westerly airstream. Looks a fairly dry outlook in the main with pressure quite high and often to the north of the country meaning winds from between north and east and never that mild, this is not the time of year when the atlantic stirs into action, in fact the outlook is very typical mid spring weather, northerlies and easterlies often dominate, and this is very much often the driest time of year for the north west in particular.

[Frosty.]

The GFS 00z looks generally rather chilly for the time of year, especially in the north with high pressure tending to be to the west of the uk with low pressure to the northeast over scandinavia, the N'ly has been watered down somewhat for this weekend with only the far northeast likely to catch some wintry showers, the ukmo 00z only shows the N'ly penetrating into NE Scotland and a ridge from the main high extending across most of the uk by sunday. The rest of this week should be fairly settled with some sunshine but large areas of cloud floating around and a cool NE'ly breeze, rain in the far north by late fri / early saturday then colder & showery and then next week looks cool and unsettled with rain and showers and snow on northern mountains plus some overnight frosts, mostly in the north.

[johnholmes]

This morning both 00z model runs have, at T+240, gone for the colder option. They both are varying at times but the main 'signal' does appear cold not warm at the latter end of April.

NOAA 500mb anomaly charts have lowish 500mb contour heights as does the ECMWF-GFS version for 10 days ahead, even more than NOAA really. With AO and NAO shown as being on the -ve side along with the PDO on the +ve side then it would be a very brave person who went against the idea of cold not warm as we move towards the 3rd week and month end.

Nor do events as they are predicted to be around the tropics suggest anything really much different. So we may have to wait a while for any major synoptic pattern change.

[Milhouse]

Nice little high appeared at 120h on the ecm. So a continuation of the settled theme looks likely for some time yet. from mid week onwards it all goes downhill but as has been said its beyond the reliable timeframe.

[ANYWEATHER]

Ecm paints a very cool outlook especially for Scotland with some elavated snow at times, but most other areas hanging on to a lot of dry settled weather, as high pressure will have the most influence. The only bugbear for the southern half of the Uk is given any long clear spells overnight ,frost will be problamatic. :unsure:

[SP1986]

frost will be problamatic. :unsure:

It hasn't been so far under the clear skies of the last few days for many parts of Western England and Wales. I wouldn't worry about that.

[Frosty.]

There is no doubt the Ecm has veered towards the gfs in FI although it could easily flip back again such is the fickle nature of the models but the gfs seems to have come out as the winner this time with regard to next week. It does look like a very cool and unsettled spell will take control from the weekend onwards with snow likely on northern hills and mountains and frosts where skies clear but mist and fog is unlikely.

[Frank Trough]

There is no doubt the Ecm has veered towards the gfs in FI although it could easily flip back again such is the fickle nature of the models but the gfs seems to have come out as the winner this time with regard to next week. It does look like a very cool and unsettled spell will take control from the weekend onwards with snow likely on northern hills and mountains and frosts where skies clear but mist and fog is unlikely.

i really hope the ECM veers towards the GFS 06z in early FI! nice southerly flow with a much better positioned high with some warm temps. I would love to think it's right! On a personal note i'm rather glad to see the weekend northerly get somewhat downgraded but i still think it will be far too cold to make the decision to go camping look anything other than rather silly.

[snowmadchrisuk]

This morning both 00z model runs have, at T+240, gone for the colder option. They both are varying at times but the main 'signal' does appear cold not warm at the latter end of April.

NOAA 500mb anomaly charts have lowish 500mb contour heights as does the ECMWF-GFS version for 10 days ahead, even more than NOAA really. With AO and NAO shown as being on the -ve side along with the PDO on the +ve side then it would be a very brave person who went against the idea of cold not warm as we move towards the 3rd week and month end.

Nor do events as they are predicted to be around the tropics suggest anything really much different. So we may have to wait a while for any major synoptic pattern change.

I'm loving this chart , I will be in Felixstowe in Kent that week So would love it if that came off . With the Nao and Ao likely to be on the negative side rather than positive I have little chance of that coming off I guess. If it did I would be in the perfect place to record the highest temp.

Edited April 14, 2010 by snowmadchrisuk

[Bluebreezer54]

I'm loving this chart , I will be in Felixstowe in Kent that week .........

You might want to get yourself a sat-nav Chris

[mushymanrob]

i think theres a lesson to be learned here for any newbies viewing the charts. the gfs 00z suggested a very cool mixed outlook in fi (beyond c t+180) the 06z has totally flipped this and suggests a very warm and mainly settled fi... thats great uncertainty, in fact the runs could hardly be different! so dont believe fi .... its only a slight chance of happening. i reckon the eventual outcome will be somewhere between the cold 00z and warm 06z...lol

[snowmadchrisuk]

You might want to get yourself a sat-nav Chris

I'll stick with my train timetable lol ,(it's near Kent then haha) I meant to say Suffolk mind you I am taking my mountain bike on the train with me .

There has been a growing trend IMO for pressure to rise in the South East during that period , but why it remains in FI and because of Johns reasoning I will just have to live in hope , cause with the setup at the minute , heavy showers could easily set it self up to move up from the South.

Edited April 14, 2010 by snowmadchrisuk

[Frosty.]

i really hope the ECM veers towards the GFS 06z in early FI! nice southerly flow with a much better positioned high with some warm temps. I would love to think it's right! On a personal note i'm rather glad to see the weekend northerly get somewhat downgraded but i still think it will be far too cold to make the decision to go camping look anything other than rather silly.

The problem with the GFS 06z is that it has no support from the latest meto update just issued, the update seems to follow the gfs & ecm 00z so I would assume the 6z is a warm outlier for the crucial early FI period, next week is still looking cold and unsettled in the north and cool and changeable in the south.

[Frank Trough]

The problem with the GFS 06z is that it has no support from the latest meto update just issued, the update seems to follow the gfs & ecm 00z so I would assume the 6z is a warm outlier for the crucial early FI period, next week is still looking cold and unsettled in the north and cool and changeable in the south.

yes, im drooling over it and hoping but i don't actually believe it. I would be very surprised if it was anything other than at least on the warm side of the ensembles. I think i'm right in saying that 06z yesterday really ramped up the weekend northerly only to drop it again today? I didn't see the 12z's however.

[SP1986]

I dont think there's much to suggest a change on the way. I think we may have to sit out these cold, dull easterlies which have a possibility of lasting into May. One of the main things we can be sure of though is that April will most likely come in below average.

I do wish it would warm up (with higher humidity) but there isn't much to offer myself or anyone else any hope at this moment in time except FI's that change everyday

[Derp Patrol]

I'd love some warm weather.. so far we've had a week of pleasant warm, sunny weather the whole Sping, but not any real warmth yet. I would love for the GFS 6Z to come true, but it is changing every run. The only positive I can see out of a cool April is that the last time we had one in 2006, we got a brilliant summer. If I could get rid of all of the SWerlies and easterlies now in return for a summer without them, I would.

[Ben_Cambs]

Suprisingly the GFS 06z wasnt a outlier, but the models are chopping and changing every run and the GFS 00z was fairly cool, and a major difference from the 06z. The other thing aswell is the -ve NAO which is keeping the Jet stream southwards and tracking over North Africa/Med which with its LP systems cant allow HP to build from South and Eastern Europe where you would have to get a warm southerly flow from. We want the Jet to be tracking North of the UK for the scenario that 06z is suggesting, so IMO, this run is not going to verify and there will be changes on the 12z run

[Frosty.]

yes, im drooling over it and hoping but i don't actually believe it. I would be very surprised if it was anything other than at least on the warm side of the ensembles. I think i'm right in saying that 06z yesterday really ramped up the weekend northerly only to drop it again today? I didn't see the 12z's however.

Yes you are correct, the 6z yesterday showed a full on Northerly for this coming weekend and a reload N'ly for next week, I think the reality will be similar to the 00z runs but I think it's only the far north which is likely to have another taste of winter and the scottish mountains, and that goes for the next couple of weeks although the south should escape with just cool to average conditions.

[Nick F]

The other thing aswell is the -ve NAO which is keeping the Jet stream southwards and tracking over North Africa/Med which with its LP systems cant allow HP to build from South and Eastern Europe where you would have to get a warm southerly flow from. We want the Jet to be tracking North of the UK for the scenario that 06z is suggesting, so IMO, this run is not going to verify and there will be changes on the 12z run

The -ve NAO is a symptom of a southerly tracking jet rather than a cause. The NAO has actually been +ve these last few days, though trending -ve:

... I guess down to presence of low pressure near Iceland and ridging towards the Azores currently/recently, there is actually a fair bit of energy and low pressure towards the arctic with a large PV near the North Pole, though the AO has been close to neutral slightly +ve recently.

We are stuck under a mid latitude block which is being under cut by quite an active southerly jet over the Atlantic, but also there is a fair bit of jet energy going around the top of this high and then returning SW across Europe:

Eventually it looks like the northern stream of jet to our north will plunge more NW to SE towards the UK, introducing winds from a more northerly sector.

[johnholmes]

true Nick

Although I think that some posters are using the term regarding the jet being displaced well south a touch out of context at times.

To see just what is happening it needs one to look at the TWO jet flows into north America. One is the Polar jet and the other is the Sub Tropical jet. Only by looking at the jet pattern for the whole earth, or rather that part covering north and south America out into the mid/far east is that totally clear at times.

As Nick illustrates, on the chart in his post, there are times, often as well in the past winter when the Polar jet swings way south. At other times the jet some are quoting as the Polar jet is in fact the Sub Tropical jet. Through to about T+168 the two are clearly visible. beyond that, on the 00z GFS, and they do tend to intermingle.