Model Output Discussion 12z 20/04/13

[NeilN]

Looking gooood

 

Honestly today hasn't been too bad. Breezy when I left to go out, warmed up in the afternoon - sunny, even walked it from the post depot to my flat!

[Methuselah]

 Very good to see the ecm sticking to it's guns from the earlier 00z with high pressure gradually taking control during the course of the bank holiday weekend with the trough being squeezed by high pressure and then setting up a very settled outlook as per the ecm 00z ens mean, we are still on course for a prolonged fine spell and a warming trend.

Oh dear. That does raise the spectre of North Sea haar, fret, mizzle, or whatever one wants to call it...looks a bit like 1974?

Edited April 27, 2013 by Rybris Ponce

[Gibby]

Hi folks. Here is tonight's look at the midday output from GFS, UKMO, GEM, NAVGEM and ECM for today Saturday April 27th 2013.

All models show a ridge of High pressure sinking South over England and Wales overnight followed by a trough of Low pressure moving SE behind it to reach Southern Britain by tomorrow evening. Thereafter a cold NW flow with showers and sunny spells will be prevalent over the UK with the showers becoming more restricted to the far North by the middle of the week with a lot of dry and bright if not overly warm conditions elsewhere but with a continued risk of frost at night.

GFS then shows that away from the far North of the UK the period up to and including the Bank Holiday Weekend will be largely fine and bright with temperatures gently recovering to near to average values and perhaps a little on the warm side in any prolonged sunshine. The far North will probably stay more cloudy with some rain here at times as troughs brush past. Soon after the holiday a trough to the SW brings some rain for a time before FI brings High pressure back on the scene settling across the North of the UK and linking to Scandinavia with a NE flow over the South with fine conditions for all but cool and murky near the East Coast with the best of the sunshine to the far West and NW. Some thundery rain could affect the far SW for a time from Low pressure over France.

The GFS Ensembles tonight show a steady warm up over the coming week to levels slightly above normal and with not much rain about for much of the time high pressure will never be far away.

The Jet stream shows the flow gradually becomes less organized as we move through next week before settling down again on a West to East course across the UK by next week. A weak flow continues to track East over Southern latitudes across to North Africa.

UKMO tonight shows High pressure building NE across the UK squeezing the life out of the weak Low pressure close to NW Scotland. Increasingly settled and warmer conditions will slowly develop as we approach the weekend though at this stage frost at night will still be possible.

GEM tonight shows a depression over NW Britain taking control at the start of next weekend before weakening and replaced by drier and brighter conditions to end the holiday.

NAVGEM shows the same Low to the NW of the UK to end next week with a SW flow over the UK with warmer and drier weather for England and Wales while Scotland and Northern Ireland will be close enough to the Low to see some cloud and rain at times.

ECM tonight is being less favourable to start the weekend bringing the low into the UK where it becomes a slow moving and cut-off feature meaning a showery Bank Holiday with heavy showers with hail and thunder possible. Late in the weekend and towards the end of the run the showers would become more isolated and restricted to the South as the low fills up and pressure builds from the North and West leaving the end of the run with a chilly NE flow near the East Coast.

In Summary tonight the weather looks like staying a little on the cold side for the next week while many Southern areas stay largely dry with just the odd shower the North will see somewhat more rain at times. Frost at night remains a big risk over the coming week. Through the Bank Holiday the weather is leaning towards a dry one with some sunny spells and if not exactly heat wave status it could be very reasonable for many. there are a few caveats to that as ECM stubbornly shows with a showery Low hung up over Britain early in the weekend. The trend thereafter is continuing to suggest fine and dry conditions with somewhat higher temperatures overall.

[Frosty.]

Looking closer at tomorrow, the southeast corner of england might get away with a fine day tomorrow with a sunny start after a widespread frost with the weak ridging just about hanging on for long enough, almost a carbon copy of last sunday's london marathon weather and then more unsettled weather over most of the uk spreading down to the southeast by the evening, scotland and n.ireland becoming colder and showery after a wet and breezy start, thereafter the north-south split comes into effect although monday will only see a slow improvement for the south, much better for the south on tues/wed in particular.

Edited April 27, 2013 by Frosty039

[Frosty.]

Oh dear. That does raise the spectre of North Sea haar, fret, mizzle, or whatever wants to call it...looks a bit like 1974?

Hi RP, to be honest i'm just wanting to see high pressure take over for all areas and hope the high ends up in a more favourable position, no point fretting just yet.

[Milhouse]

Its quite certain now that high pressure will become a more dominant feature of our weather from the early part of next week onwards. Initially it will be quite a flabby affair with a lot of dry and settled conditions and temperatures where we would expect them for early May. From then on its a case of seeing where high pressure will build and the liklihood is still that it will be to the east of the UK. It is nice to not have to worry about low pressure, whose influence looks to be rather minimal, but still the ECM has low pressure still a small feature to provide a bit of convective activity, but thankfully no endless wind and rain of last May.

Edited April 27, 2013 by Milhouse

[phil nw.]

Thanks to Frosty and Gibby for your regular and informative summaries-much appreciated by many of us i am sure.

The trend to a more anticyclonic regime from the end of next week continues with areas further south settling down to some fine weather first and extending more widely into week 2.

Some promising looking mean outputs for the BH weekend

http://modeles.meteociel.fr/modeles/gens/run/gens-21-1-192.png?12

http://www.meteociel.fr/modeles/ecmwf/runs/2013042712/EDM1-192.GIF?27-0

Any showery activity dying out by then as the remaining upper cold pools around the UK warm out.

The ens show this predominately dry spell continues well into May.

[Cloud 10]

Thanks to Frosty and Gibby for your regular and informative summaries-much appreciated by many of us i am sure.

The trend to a more anticyclonic regime from the end of next week continues with areas further south settling down to some fine weather first and extending more widely into week 2.

Some promising looking mean outputs for the BH weekend

http://modeles.meteociel.fr/modeles/gens/run/gens-21-1-192.png?12

http://www.meteociel.fr/modeles/ecmwf/runs/2013042712/EDM1-192.GIF?27-0

Any showery activity dying out by then as the remaining upper cold pools around the UK warm out.

The ens show this predominately dry spell continues well into May.

 

 

For some reason the ECM ensemble mean charts are not showing up on Meteociel at the moment,only the operational runs.

 

Wetterzentrale mean charts are working though,and are showing the settling down trend you 

describe in the 7-10 day timeframe.

 

 

 

Tonight's CPC 8-14 day anomaly chart looking good for a rise in pressure close to the UK as well.

 

[shaky]

For some reason the ECM ensemble mean charts are not showing up on Meteociel at the moment,only the operational runs.

Wetterzentrale mean charts are working though,and are showing the settling down trend you

describe in the 7-10 day timeframe.

Reem1921.gif Reem2401.gif

Tonight's CPC 8-14 day anomaly chart looking good for a rise in pressure close to the UK as well.

814day.03.gif

Close to the uk??more like well over the uk according to that cpc chart

[SP1986]

18z showing a familiar pattern of recent, starting unsettled and cool, gradually warming up with High pressure taking charge in general.

 

The 18z moves to the ECM in that it brings in a cut off low, but actually the low starts the ball rolling with regards to an anticyclonic easterly flow, the low then moves south and becomes 'relegated' to Northern Spain, this would mean the potential for some storms around the south coast?, anyway High pressure scenario still very much on the cards.

 

GFS FI wants to bring in a potent northerly, but this can be discounted for a number of reasons (the main one being no members has actually showed this scenario yet), and also given the amount of relatively warm air the 18z pumps across western Europe, it is inconceivable that cold air with that much geographical influence will suddenly pop up from nowhere.. anyhow.. positive 18z runs if you discount the latter part of FI.

Edited April 27, 2013 by SP1986

[Frosty.]

A north-south split next week according to the 00z models with northern britain cool and generally unsettled with a mixture of persistent rain and sunshine & showers, wintry on higher hills/mountains and with overnight frosts where skies clear. Southern britain a mostly fine week with high pressure ridging across for most of next week with long sunny spells and max temps into the low to mid teens celsius but cold nights with slight frosts. The unsettled weather in the north then spreads to all areas either later on friday but more especially during the weekend with cool cyclonic conditions and a mix of sunshine and heavy showers, however, this looks brief because it then looks like generally rising pressure will squeeze the life out of the trough and a large mass of high pressure will take control of our weather by early the following week, the gfs and ecm 00z show high pressure and pleasantly warm weather (mid 60's F) dominating for at least a week and potentially longer than that from the ecm 00z  BUT the gfs 00z has a big shock in store, a deep low forming around the southern tip of greenland  pushes southeast, carving it's way through the flabby high like a knife through butter and brings an unusually cold and prolonged plunge of arctic air (by mid may standards) to the uk for several days with widespread wintry showers and night frosts. 

[mushymanrob]

im far from convinced about a settling down, it keeps getting pushed back or/and downgraded to a breif ridge before another trough brings cool unsettled back.

 

the anomaly charts are in total disagreement this morning, ecm high pressure over us, gfs deep low.so they offer no firm indication. to me within a reliable timeframe and hinting beyond, its looking unsettled and cool.

[IDO]

The ECM this morning moves closer to the GFS with Bank Holiday Monday being the day the ridge moves into the UK:

Sunday: Monday:

The high then migrates NE hinting at a further trough moving in for latter that week, T240:

UKMO also similar/close to ECM, with a low over the UK next Sunday:

GFS was the first to pick up on that shortwave, delaying the rise in pressure and others are now following.

This morning's GFS (in FI) has for the third weekend in a row, another weak trough: Saturday 11th: , following on from the 18z. The GEFS 2m temps ensembles showing no clear signal for any warmth in early-mid May:

Too early to call but as the 500hPa GFS ensembles stamps show (at T384) only four have HP as the major influence over the UK: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=384. Most are trough orientated so a dry HP dominated spell not showing just yet.

Next week looks settled, Tuesday-Thursday for the south with average temps but below average nights. Rainfall for the south in the next 8 days is nominal but north of Manchester, above average amounts (GFS):

GFS goes with the cut off low again for next weekend and Bank Holiday, so better prospects for the north and Scotland Monday week:

Dry at least. GEM also now going with the cut off low: so one to watch on latter runs to see if ECM follows suit.

[Gibby]

Hi everyone. Here is my look at the midnight output from GFS, UKMO, GEM, NAVGEM and ECM for today Sunday April 28th 2013.

All models show a NW airflow developing over the UK behind a cold front crossing SE over the UK in association with Low pressure crossing East towards Scandinavia to the North of Scotland. Occasional rain on the front will clear to leave a lot of dry weather for Southern areas over the coming few days with a more showery flow to Scotland. Through Tuesday and Wednesday a 'Col' area develops over the UK with High pressure close to the east and to the West with Low pressure well to the South and North of the UK. Central areas will stay dry and bright while extreme Southern areas and Northern parts could become cloudy by Thursday with occasional rain. With inherently cold air over the UK daytime temperatures will slowly recover a little while the nights will be cold with a touch of frost where skies clear.

GFS then takes us through the Bank Holiday weekend with Low pressure slipping slowly South down over the UK from the NW to be to the South of the UK by Holiday Monday. A showery spell looks likely over the long weekend with some heavy showers with hail and thunder a probability, the highest risk transferring to the South only by Monday as high pressure builds strongly across the NW. Through FI today the shower risk continues in the South with a chilly and haar filled flow off the North Sea for a time on Eastern English coasts with showers extending to other areas later as winds back Northerly and High pressure is pulled further West out into the Atlantic maintaining cold North winds and the risk of touches of overnight frost and further showers to end the run.

The GFS Ensembles put the operational above as both a warm and cold outlier in the second part of the run as well as being one of the wettest for a time too. The general average between the group suggest nothing better than fairly average temperatures and there are some rather chilly options showing up again this morning, especially later in the run. Rainfall outside the operational run is shown scattered about throughout the run but much of it being from showers.

The Jet Stream shows the flow still crossing East over the UK weakening and edging North as we move through the coming week. In addition a Southern arm strengthens slightly next weekend as it heads east over the Atlantic towards Spain and Portugal.

UKMO starts the Holiday weekend with Low pressure edging East across the far North with showery troughs likely to be crossing the UK early in the weekend with a SW breeze. The SE would see the best and driest conditions for longest whereas the West and NW sees the heaviest showers.

GEM today has the Low at the weekend further South and becoming a slow moving filling feature over the South before it finally fills up early in the following working week. There would be heavy and slow moving showers with local hail and thunder scattered about over the UK each day before the filling Low dissolves leading to a NE flow with the best and warmest conditions to be found in the NW of the UK as we move through the following week.

NAVGEM today at first glance looks OK for next weekend with High pressure much closer in and less in the way of a closed centre of Low pressure than the other models. However, a cold upper pool does transfer South over the weekend with showers each day gradually transferring to more Southern areas later in the weekend as the weather becomes set fair from the NW though never overly warm.

ECM shows the Low up over Northern areas early in the weekend close enough to turn the weather unsettled with showers for all. Through the weekend the low fills and it's influence diminishes as high pressure builds across the UK settling things down for the end of the weekend before the High quickly migrates to Scandinavia setting up a chilly ENE feed across the South with scattered showers and East Coast cold conditions with sea mist and low cloud becoming prevalent. The best weather would then be found to the NW of Britain.

In Summary today it looks like this week will be fairly benign for most with a lot of dry weather though never overly warm. Nights could be chilly with frost locally under any overnight clear skies. Late in the week the far South and North may become cloudier with some rain for a time before the rain in the North extends to other areas in the form of showers over the Holiday Weekend with temperatures fairly subdued. It won't be a write off weekend though and no doubt some areas may miss the showers altogether. Beyond the break and into the following working week an Easterly looks like a highly likely proposition and from this morning's output Low pressure to the South could throw some showers up into Southern areas at times while the NW stay dry, bright and possibly reasonably warm by day. North Sea coastal mist and low cloud could become a problem later and extend well inland at times. Frosts at night cannot be ruled out even at this stage in May under any clear skies and probably most likely in the clearer NW later.

[NeilN]

Typical....

I just hope the flabby low goes away. Just wish there was a way to block these cold fronts.

[Summer Sun]

Looking at the ECM ensemble it shows BH Monday to be fairly decent

 

 

Then just after the BH the high really starts to build

 

 

The GFS ens also shows BH Monday to be fairly decent

 

[Frosty.]

Very good news from the latest ensemble mean from the gefs  & ecm 00z, they both show a major anticyclonic spell evolving beyond the week ahead with a pleasantly warm and settled spell for all parts of the uk once the trough to the northwest is sent packing. It's very interesting to note that the gefs 00z mean supports the gfs 00z operational for a cold northerly later in FI with an atlantic blocking high up to greenland and a trough to the northeast but the best news is there continues to be a strong signal for a fine and relatively warm spell in the not too distant future, and the week ahead looks pretty decent across southern britain with a mainly dry week with sunny spells and temps recovering to average but cold nights, scotland and n.ireland look cooler and more showery and then the Bank Holiday weekend could be cool and cyclonic for all of the uk before the big improvement arrives.

[Milhouse]

Subtle differences in the models compared to a couple of days ago. Firstly the return to milder temperatures has been brought forward further to Tuesday with a ridge of high pressure nosing in to deliver settled conditions to all but the far northwest. However the chances of an unsettled end to the week have increased with the UKMO still sticking to an extended period of high pressure. The build of high pressure to the east of the UK is still there though from the weekend onwards. So essentially 2 high pressure spells to look forward to with a unsettled and cooler period inbetween.

[Milhouse]

Once again the ECM op seems to be overdoing the low pressure at the weekend with the mean indicating that pressure should be starting to build to the south of the UK by the middle of the weekend. However the op still has us under the influence of low pressure.

 

[Frosty.]

The Gfs 06z is a rather cool run throughout, we never tap into any warm air source but at least pressure becomes generally high beyond the next week or so and next weekend we slowly lose the trough after an unsettled start but then the trough gets squeezed by high pressure to the east and west, the high never gets into a good position but at least there would be spells of strong sunshine and temps into the low teens celsius but chilly nights with a touch of ground frost, again, as with the gfs 00z operational, there is a risk of even cooler and unsettled weather spreading southeast later in FI but much less of a threat on this run, this run does not do justice to the far superior ensemble mean charts in FI.

[Gibby]

Subtle differences in the models compared to a couple of days ago. Firstly the return to milder temperatures has been brought forward further to Tuesday with a ridge of high pressure nosing in to deliver settled conditions to all but the far northwest. However the chances of an unsettled end to the week have increased with the UKMO still sticking to an extended period of high pressure. The build of high pressure to the east of the UK is still there though from the weekend onwards. So essentially 2 high pressure spells to look forward to with a unsettled and cooler period inbetween.

While you are right it should also be noted that temperatures are never particularly high and many people are intrerested as much in night temperatures as well as day ones at this time of year and as I hinted at in my report earlier the risk of frost at night cannot be removed from important status over the coming period.

[Frosty.]

Hopefully this is what we can look forward to in a little over a week from now, dominant anticyclonic weather for all.

[Guest pjl20101]

Seems to me that ECM have a bug at the moment and that it needs to be fixed. I would say the GFS 6Z are correct at this stage.

[skifreak]

I quite like the scenario being toyed with just now where it snows each day this coming week on the Scottish Mountains, then slam - high pressure lands on top Highland Scotland for the Bank Holiday weekend! Yes please...

[snowmadchrisuk]

Looks warm and settled to me 16-17 in the SW by Wednesday , and 21 deg by day 7 , which is often underdone so low 20's probably likely . Hottest day of the year in some parts will likely happen next week on the latest Gfs .