Model Output Discussion 31/03/14 onwards.

[Summer Sun]

hmm some big differences between the GFS Op (right) and control run (left) this evening with the control going for a steady rise in the 850's from day 10 the driest weather always looks to be the further north you are

 

[Mark Canning]

It does look as though the weather will rapidly deteriorate after the weekend, which for most will be the warmest of the year so far owing to a fair amount of warm air advection. At the moment there is a degree of uncertainty around whether or not some pretty heavy isolated storms may break out in the S/SE by Saturday, so it might not be BBQ weather for all!Regarding post Monday though there is still a large disparity between the models, so confidence is low as to what to expect... EC det allows for cyclogenesis in the bay of biscay, which would lead to most of next week being pretty wet and windy. MOGREPS is too spread the the moment to have anything more than low confidence in the solutions (though some do allow for building a high for the bank holiday weekend).

[phil nw.]

One thing i struggle with as someone fairly new to model reading is knowing where the weatherfronts will be. Tonights ECM for example looks quite dry to me, but some posts above are saying some rain will be about.

 

I know that the fronts are where the airmasses meet, so as an example below, am i reading it correctly that the charts below from tonights ECM show a front to the north west of Scotland, along the green band?

 

 

Just seen this Winter Cold-yep you pretty much got it.

Fronts on the fax charts are the boundary of the warm and cooler air masses along the Polar front.

I usually find the 850hPa charts show these up quite well.

If we compare the fax and the 850hPa charts below we can see this.

 

see the frontal systems running along the 0C isotherm on the temperature chart.

 

Hope that helps.

[Winter Cold]

Just seen this Winter Cold-yep you pretty much got it.

Fronts on the fax charts are the boundary of the warm and cooler air masses along the Polar front.

I usually find the 850hPa charts show these up quite well.

If we compare the fax and the 850hPa charts below we can see this.

http:////f1.nwstatic.co.uk/forum/public/style_images/tctc91_simplify/attachicon.giffronts1.gifhttp:////f1.nwstatic.co.uk/forum/public/style_images/tctc91_simplify/attachicon.giffronts 2.gif

 

see the frontal systems running along the 0C isotherm on the temperature chart.

 

Hope that helps.

 

Top stuff

Thanks very much Phil, thats a good clear example!

[IDO]

Looks like agreement on the trough over the UK has been reached, though the position of the low remains fluid, T144:

 

Navgem:  JMA: 

 

UKMO:    GFS:  ECM: 

 

The GEFS are also variable on this count: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

 

No doubt its positioning will be a guide to the surface conditions.

 

Cannot fathom at the moment whether the trough will fill, mix or slide away, following the seemingly inevitable pressure rise in our locale showing in the GEFS FI. There are lots of spread and various clusters. Though around D12 appears the tip point for about 50% of the GEFS for that pressure rise, predominantly from a Scandi High cluster, then the AH ridging NE. 

 

As we would expect the Atlantic is asleep throughout FI, so plenty of opportunity for a HLB to build in-between the declining slack flow of the PV.

Might be more lucky next time and get some of the hot temps Eastern Europe will reach next week:

 

 

 

 

 

[ANYWEATHER]

After a few fine days, the weekend is the turning point for more unsettled conditions for all eventually....

[ANYWEATHER]

Out to T+168 there is general consensus of a cyclonic spell of weather, so some warm sunshine to be had but there will be some heavy slow moving showers, so a convective outlook is likely...

[Frosty.]

It looks like turning unsettled by sunday across most areas, the southeast corner being the last place to see the change but in the meantime, becoming very warm with a lot of sunshine and light winds for the south of the uk and especially the southeast where temperatures look like soaring into the low to mid 20's celsius, around 75 F and perhaps a notch higher in and around london on saturday, progressively cooler and more unsettled the further northwest you are, especially for n.ireland / n & w scotland and the isles but with occasional fine spells.

 

The Ecm 12z op run shows a trough swinging southeast from greenland / iceland and sliding just to the west of the uk but gradually taking control of our weather with a growing risk of showers, heavy, thundery and slow moving but with warm sunny spells too, quite a cyclonic looking outlook for next week with sunshine and heavy showers and longer periods of rain, cooler when it rains but warm in the sunny spells.

[knocker]

The ECM Anomaly has a deep pool of cold air centred just to the west of the UK with the intense high to the east next week A situation that is almost stationary for the time. Equally the surface cyclonic weather is the same Giving unsettled conditions with average temperatures

,

Edited May 13, 2014 by knocker

[knocker]

The ENS means. The ECM has the cold air somewhat deeper and more east with the GFS giving a glimmer of hope that the high pressure will infiltrate.

Edited May 13, 2014 by knocker

[Vorticity0123]

With the buildup of high pressure from the southwest, it seems like an end will come to a prolonged wet period. More settled conditions will prevail for the next few days over the UK. How will the weather situation evolve after that? A look at the synoptics and uncertainties will be given.

 

Current synoptics

 

After the low pressure, which was over the UK at May 11, had moved away to the east, a high pressure cell (mainly an extension from the Azores high) has been building to the west of France. This can be seen in the weather map below:

 

GFS MSLP + 500 hPa height T0 (12Z)

 

Along with the buildup of high pressure, a weak upper level ridge (at 500 hPa) has developed just to the west of Ireland edging northward toward Iceland (this can be seen with the orange/yellow colours pointing northward, indicating of relatively high heights and thus high pressure).

 

Furthermore, a trough of low pressure is apparent over Scandinavia toward Switzerland (green colours/low heights edging southward). This trough is associated with a low pressure area with multiple centres near Finland.

 

The high pressure area development has led to a cool northwestern flow developing over the UK. Along with this flow, cool 850 hPa temperatures of close to 0*C are being transported toward the UK. The image below shows these 850 hPa temperatures:

 

GFS 850 hPa temperatures T0 (12Z)

 

Of a side note (based on WinterCold's question), there is also a sharp temperature gradient present to the southeast of the low to the west of Iceland. Such sharp temperature gradients are often a good guide to locate fronts. For example, check the precipitation chart of 6 hours later: (the chart of the initial time was not available):

 

GFS precipitation forecast T6 (12Z)

 

Comparing the two charts shows that a front is located near the 0*C isotherm following the temperature gradient (a cold front in this case, as colder air is located behind the front). The isotherms don't exactly match with the position of the cold front. Still, a pretty accurate prediction can still be made of the position of fronts with only looking at the 850 hPa temperatures.

 

Short- to mid-term forecasts

 

In the short term, a strong area of high pressure will become dominant from the west of Ireland all the way to Finland. This is located alongside a ridge of high pressure (dark red colours extending northward) extending into France. The high pressure area on the surface connects to a high over Nova Scotia, making it a very impressive sequence! See the GFS-pressure chart of 66 hours out:

 

GFS MSLP + 500 hPa heights (T66)

 

Another notable feature is the existence of two cut-off lows, one to the north of Greece and the other one just to the south of Nova Scotia. This can be seen by the low (sub-552 decametre heights; green colours) being surrounded by higher heights (i.e. yellow colours).
 

However, it appears that the key to the weather in the extended period lays to our northwest, to be more exact the beginnings of a trough to the northwest of Iceland. This can be seen in the GFS forecast chart of T120 (5 days from now):

 

GFS MSLP + 500 hPa heights T120 (12Z)

 

The weak trough, previously located just to the southwest of Iceland, has dipped southward and deepened, to become situated to the west of Ireland. The trough can be seen by the green/blue colours to the west of Ireland. 

 

The position of the trough seems to be pretty certain, as can be seen at the 6-10 day 500 hPa height anomalies from NOAA:

 

50

6-10 day 500 hPa heights (green lines) and anomalies (red and blue dashed lines) as forecasted by NOAA.

 

The trough is also rather vigorous, as can be seen by the sharp negative height anomalies (blue dashed lines). This will most likely start another period of rather unsettled and possibly cool weather.

 

Thereafter, the uncertainty starts to increase markedly. 

 

Long-term forecasts

 

In the long term (about 8 days out), the uncertainty starts to increase, as could be expected. The main uncertainty lies within the question whether the trough will become a cut-off low over France (as forecasted by the ECMWF operational run), or whether the trough will stay in the vicinity of the UK (as forecasted by the GFS operational run). For the UK, the difference will be small, as both types will result in unsettled conditions.

 

To gain a better insight at the uncertainty, a look will be taken at the 8-14 500 hPa heights forecast from NOAA:

 

8-14 day 500 hPa heights (green lines) and anomalies (red and blue dashed lines) as forecasted by NOAA.

 

What can be seen is that even though a negative height anomaly is forecast near the UK (indicative of a trough), the uncertainty is much greater than in the 6-10 day period, as the negative anomalies are weak at best. Furthermore, some uncertainty exists about the longitudinal (east-west) position of the trough.

 

Although the impact of the exact position of the trough is not very large for the UK, for the Netherlands, this exact position has a large influence at the weather. To show this, the ensemble temperatures of the Bilt will be given below:

 

De Bilt ECMWF ensemble forecasts of temperature.

 

What can be seen is that the uncertainty in maximum- and minimum temperature in about 7 days gets very high. A slight displacement to the east/west might be the difference between unsettled and settled conditions. Furthermore, a slight displacement north/southeast might alter the wind direction between southwest (maritime air), and southeast (continental, hot air). Once again, note that this ensemble prediction is of the Netherlands, and not of the UK. 

 

Any remarks/suggestions/improvements are always welcome! 

 

Sources:

http://www.wetterzentrale.de/topkarten/fsavneur.html

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

http://www.weerplaza.nl/15daagseverwachting/?type=eps_pluim

Edited May 13, 2014 by Vorticity0123

[Captain Shortwave]

Well I wasn't expecting this from the GFS, a shift west

Sunday and Monday would be warm, especially in Eastern areas if this came off.

Given how small shifts west or east can greatly effect the surface conditions, getting anything beyond Saturday still looks to be difficult.

 

In the more reliable timeframe, some talk from the metoffice/BBC about showers on Saturday, GFS showing some decent cape for the late afternoon.

Could get some decent storms. There is also a risk of isolated showers/storms on Friday as well though lower than Saturday.

 

Interestingly the NAVGEM also corrects west.

Edited May 13, 2014 by Captain shortwave

[Frosty.]

The Met office are going with an unsettled outlook once the fine spell ends by sunday night across the south and east, much sooner than that for the north and west. With a large complex trough dropping anchor to the southwest of the uk next week, the west and especially the southwest are likely to see the most persistent rain and potentially stronger winds but for most of the uk it looks showery, most on the heavy side with thunder but with decent sunny spells and feeling warm.

[Geordiesnow]

The Met office are going with an unsettled outlook once the fine spell ends by sunday night across the south and east, much sooner than that for the north and west. With a large complex trough dropping anchor to the southwest of the uk next week, the west and especially the southwest are likely to see the most persistent rain and potentially stronger winds but for most of the uk it looks showery, most on the heavy side with thunder but with decent sunny spells and feeling warm.

 

I think that also shows that low pressure does not fully mean it will turn significantly cooler, in any sunny moments, temperatures could still be around average if not above. Although it does look likely low pressure will become more of an influence, there is not too much out there to suggest the trough will park itself right over the UK but its certainly a possibility. 

 

On a side note and in relation to Karyo's status, look at all that hot air over Russia and potentially later on into Scandinavia, absolutely ridicules for this time of year, could be another hot and dry summer there? 

[The PIT]

Latest GFS shows it staying fairly warm with low pressure system staying out to the north west allowing warm air to move north. Later another low pressure system develops over Spain keeping the warm feed going. Some showery rain around but looking better than previous runs.

[shaky]

My god where did that gfs run come from!!big changes in just a short time frame!!very warm and humid will be the standard over the next week if gfs is right!!ukmo slightly further west and south but still more unsettled!!just when we thought we saw model agreement!!

[knocker]

Well all change. The train standing at platform five is the 00z GFS to “that fooled youâ€.

 

The 500mb anomaly on the18z run has the centre of the trough well to west of Scotland with the Scandinavian high reaching its tentacles into the North Sea. Spot the difference with the 00z run leading to a somewhat different evolvement of the surface analysis. The net result of this, in summation, is that high, or very high temperatures will persist at least until Wednesday with Tuesday showing temps in the high 70s.

 

What are the synoptics?

 

Saturday

A low SW of Iceland and a transient high over the Scilly Isles and the UK in an area of slack pressure except for northern Scotland that is in the SW flow from the depression.

 

Sunday

A complex area of low pressure NW of the UK bringing SW winds to the west with the east under the influence of a southerly from the high pressure to the east. The front is lying western Ireland to Stornoway, Art the same time the UKMO has the low west of Ireland with the front from Stornoway to Cornwall.

 

Monday

It’s as if Tommy Cooper has appeared. The low to the north west has relocated way NE of Iceland.leaving a slack area of low pressure stretching from northern Spain to the UK with the east, just, still under the influence of the high.

 

Tuesday

The low to the SW of Cornwall has deepened to 994mb with a frontal trough over Cornwall and generally SE unstable conditions to the UK.

 

Wednesday

The low now over the Bristol Channel with another low developed near NW Spain. Again a light SE and mainly dry.

 

At this range hopefully the models will be singing from the same hymn book but don’t hold your breath.

Edited May 14, 2014 by knocker

[shaky]

Even ecm has the low backed further west at 96 hours and very similar to the gfs and not the ukmo!!Although I know eventually that low will come across us but if it gete delayed there is better chance of things going wrong for the good hopefully!!

[Polar Maritime]

Yes, The GFS this morning is showing some very warm Spring-like Temps from Friday through until Tues.

 

[Captain Shortwave]

I think the nail fell out last night 

Decent agreement on trying to get low heights south west of the UK, the Euros going for low pressure close to South west England whilst the American models have the low further south in the Bay of Biscay. All output suggests warm weather for the start of next week with temperatures in the low/mid twenties. Question is how unsettled will conditions be. 

Mean 850 temperatures for my area have gone from +1/2 to +8 in 12 hours. Enough said really.

 

I must add kudos to the GEM, it never really backed down from this scenario (if of course this is the right solution)

Edited May 14, 2014 by Captain shortwave

[Summer Sun]

UKMO this morning at t144 showing +8 850's in the SE at t144 (t120 850's currently not updated) away from the west  and Scotland Tuesday looks like another warm day though unsettled

 

 

ECM however is much warmer for all at t144 looks pretty wet in parts of the west

 

 

GEM remaining consistent from previous runs by also keeping the warm air in place at t144 GEM keeps it mostly dry

 

 

And finally GFS also keeps the warm air over the UK on Tuesday

 

 

So this morning its UKMO which is on its own for the 850's with all the rest going against it

 

 

[bluearmy]

Fwiw, the spreads on ECM ens yesterday had the track of the lowest heights where the op takes them on the 00z.

Don't make the mistake of only looking at the heights and ignoring the surface pressure. Looks impossible to avoid the rainfall next week, even though temps may be reasonable

[Frosty.]

Yes, The GFS this morning is showing some very warm Spring-like Temps from Friday through until Tues.

 

Yes PM it's looking FAB-U-LUS

[IDO]

Yes the GFS op is a nice run but looks like an outlier. Temps for Manchester:  

 

By the 21st the op is 5c higher than the mean: 

 

The placement of that low within the trough looks like it remains the main variable.

 

Lots of spread by D6:  

 

The ensembles are split 50:50 with regard to the op sending the low further south into the Bay of Biscay. Within that cluster there are some that cut off this low, some that allow a warmer flow and some with a cooler flow. The other 50% keep the low more towards Ireland:

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=150

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=0&ech=150

 

Whatever happens to the low we have support for the  UK trough next week and that remains a wet 5-6 days on the whole though it is split whether it is cool or warm rain.

 

As for GEM nailing the pattern, many of their runs had the 1017 pressure line straddling the UK:

 

12z 12th:  0z 12th: 

 

Even today's warmer GFS op run has this pressure line a long way eastwards across the North Sea!

Edited May 14, 2014 by i'm dreaming of...

[knocker]

The ECM, as already mentioned, is also developing low pressure to the west of the UK. The anomaly mean has the Scandinavian ridge extending into the UK.