Model Output Discussion - 15th April Onwards

[Robbie Garrett]

...some limited suggestion here that with angular momentum falling back to a more Nina like pattern, the ridge might build over the top of the trough week 2-3 settling things down finally for the north of the UK to start, these more settled conditions heading southward over time.

CFS week 3 & 4 height anomalies:

http://origin.cpc.nc...120419.z500.gif

Those charts put my neck in a weird position to find the UK ahha!

I take it, this is because the trough is trying sink further south??

[Scorcher]

Those charts put my neck in a weird position to find the UK ahha!

I take it, this is because the trough is trying sink further south??

Interesting that GFS wants to do that too, with the trough sinking south, starting around the 29th.

[MP-R]

I wonder if such a continental drift will provide the right conditions for some thunderstorms such as 10th-12th May 2006. In such an instance, temperatures were also above average.

Though it wouldn't take much for a warm, dry easterly to become a cloudy, cool or cold one like in May 2008 and 2010. The GFS 12z showed that with an easterly with a northerly source.

[J10]

Latest Ski Blog out, with Polar Maritime airflow set for the Alps over coming days, remaining rather unsettled and cold with further snow over higher slopes.

[Milhouse]

Encouraging signs for HP to build from the north next weekend and then slip over the continent to possibly bring some warmth our way. I'm not expecting any settled conditions to last much longer than a couple of days but the conveyor belt of deep lows looks to be coming to an end.

http://www.wetterzentrale.de/pics/Rz500m9.html

[A Winter's Tale]

A look at what the models have instore:

So far, other than the absence of heat, this April has been great but of course as we enter May we'll all want the days to become progressively warmer. But what are the models showing, what impact could it have on the drought situation, how does it compare to the synoptics of 2012 so far and where are we heading for the weather in the coming weeks. Let's have a look.

00hrs - Right now there is an area of low pressure centred around the North Sea coast of the UK. The air is pretty chilly with a cool with an easterly wind and uppers of around -2C. This means that the East may see some showers of rain, hail and perhaps with a bit of thunder in them though with sunny spells inbetween. Elsewhere, the synoptic picture is different from what we had from January to March as the Azores High has disapeared and high pressure is more abundant further west and north. There's still a lot of cold air to our north although warmer air is now appearing further south. The UK is sandwhiched inbetween these two airmasses.

22nd April - Little has changed with cool, unsettled air situated over the UK and with high pressure and warmth on either side.

23rd April - Still cool and unsettled over the UK. A cooler NWly lies to the west of the UK thanks to high pressure out in the Atlantic. In Eastern Europe it's warming up nicely and even more so over N Africa. In the Arctic, winter continues.

24th April - A cooler situatuon though still unsettled with winds from the NE. With this synoptic pattern in place, the UK will struggle to find itself in warmer and settled conditions that are found elsehwere other than the North. And if winds do turn more northerly, there's still enough cold air to bring wintryness to northern areas. And this chart shows exactly that with cold NNEly winds and uppers bordering on -5C uppers for the Shetland Isles.

25th April - High pressure looks set to move to a Cold Greenland. Another anti-cyclone is situated much further east of the UK. Low pressure on this chart remains centred to the SW of the UK which allows cold Nly winds to reach Scotland and bring hill snow.

26th April - The NEly resumes with the potential for wintry showers in the north. Low pressure is situated nearer the south of the UK. It seems that the Scotland that was the warmest place in parts of Europe in February looks set to be the coolest with a synoptic that is so different from earlier in the year.

27th April - An interesting chart this is. Cold northerlies are still present over Scotland. However to the SE of the UK, warmer air isn't too far away. And the high pressure out in the Atlantic is moving slightly south.

28th April - The UK remains cool and unsettled but again things look like changing with the high pressure adjusting its position out in the Atlantic and warmer air getting closer.

29th April -High pressure had moved eastwards to the UK to make things more settled and warmer. Northerlies still look possible to the north. A real mixed picture.

4th May - The start of May looks more settled and warmer but High Pressure is again lurking out in the Atlantic. This means that further cooler and unsettled weather could be possible.

Overall, it's a very unsettled and cool outlook but that isn't a problem as long as we don't get endless days of low, thick cloud cover. A mixture of weather types and enough sunshine will keep plenty members on here happy as we get some typical April weather. If this pattern were to resume into May then it could be a problem is there's a lack of warmth and too cool. But a mixture of warmth and cooler and varied weather types with lots of sunshine will keep may happy. For gardners, frosts are probably now becoming more unlikely and in the southern drought zones, rainfall will become more common. The synoptic picture is different from winter where we had the Azores High, now high pressure has moved a bit NWrds. As we enter May, I think we'll see High pressure move towards the UK but the potential for Northern Blocking remains. But I doubt that we'll see continued, dull, wet and cool weather this May as it's looking like a changeable and transitional month - just like March I suppose. The drought situation may improve slightly with an increase in rainfall but I feel that May will see periods without rainfall. So this year of weather is evolving in a very interesting way and there have been many good moments as we've moved through Spring. But there'll be more twists and corners as we move into summer where these changes will be felt. It all depends on what May is like, whether a pattern looks fixed or is likely to move on. I feel that summer will start off cool but warmer periods are likely and I believe that warmer and sunnier periods will be more common than last summer and the latter part of the season could see something more prolonged interms of good summer weather. And of course, all of this has an impact on what autumn and winter will be like to complete the 2012 UK weather picture.

[phil nw.]

Yes signs at last that our upper trough will warm out after the next week as pressure builds in from the north west.

The 8-10 day mean heights from the 00z runs show the demise of the low pressure as it eases away.

Although the recent April showers setup with dramatic skies has been very interesting i would welcome some fair weather at least for a while with some warmer days to enjoy outdoor activities.

The 006z Gefs does promise something a little warmer as we go towards month end.

[TonyH]

Regionally specific weather guide blog for the coming week:

http://forum.netweather.tv/blog/309/entry-4389-weather-guide-sunday-22nd-to-saturday-28th-april-2012-west-wales-and-central-midlands/

[johnholmes]

A look at what the models have instore:

. And of course, all of this has an impact on what autumn and winter will be like to complete the 2012 UK weather picture.

You spoilt yourself with that last sentence. No one has ever shown me anything that proves such a link. I'd be happy to accept convincing evidence. Overall, and I am NOT being condescending, a pretty good comment on the model you used. If only others would follow suit? Posts like yours really do help newcomers get a better understanding of what the models show and how that is linked to what sort of weather to expect.

Edited April 21, 2012 by johnholmes

[MP-R]

The GFS 06Z, 00Z and last night's 18Z have all shown encouraging signs of a southwesterly showery spell on Wednesday and Thursday which would majorly favour those who have missed out from a storm point of view these last few days.

Overall the unsettled theme continues, though tentative signs of a warmER spell of weather to start May. How long it lasts if it happens at all is open to question. From a personal and probable point of view, I think May will continue unsettled but with more influence from the continent rather than the north and northwest like April.

[Summer Sun]

Signs of less rain as we enter May

[azores92]

Signs of less rain as we enter May

there hasnt been all that much rain ya know, there is more than high pressure anyway, back on topic, and it looks like an end to the unsettled stuff temporarily, more sunshine and respite next week

[Summer Sun]

ECM ends on a settled note tonight

I hope this does happen there is some catching up to do in the Garden now

[johnholmes]

That chart does not imply settled weather Gavin, upper trough to the north, a suggestion of a possible thundery trough to the south with ridges east and west. IF it turns out exactly as that chart then don't expect dry weather and unbroken subshine for most of the country.

[SP1986]

Th e 0z GFS is alarming for it's persistence of very cool weather well on into May. I'd have to say it's almost fantasy to believe the 0z is correct, I think it is a very cool run, and I am having a difficult time believing that will actually occur. As I don't have time to post charts; I will describe it by saying very persistent northerly regime, with temperature under the rain perhaps nearer 0C in some parts than 10C (looks a little realistic from the temperature pattern distribution too). That said if it did turn out to be the case then certain I have never seen anything like it synoptically - I have heard of such, but surely not this cool.

Time to dig out the record books.

Haven't got time to view the ECM but I'm sure it's not as cool as the GFS outlook.

[Summer Sun]

Well next week parts of Europe will become nice and warm if not hot whilst the UK will struggle to get out of sigle figures

This continues through much of FI with the UK becoming cooler rather than warmer

Edited April 22, 2012 by Gavin D

[johnholmes]

The last 24 hours have shown the 500mb anomaly charts diverging in how they deal with the pattern in the UK area. When this happens I am never very confident in using them; 2 out of the 3 suggest something of a 500mb flow from e of south with an upper cut off in the Iberia area, and with rising heights both west and north of the UK. The other has dropped the rising heights to the north, makes less of the cut off low and shows a more marked flow from n of west.

None suggests any really settled weather but 2 would perhaps indicate some rise in temperature over the time scale, 7-15 days, whilst the 3rd would not.

[ANYWEATHER]

Th e 0z GFS is alarming for it's persistence of very cool weather well on into May. I'd have to say it's almost fantasy to believe the 0z is correct, I think it is a very cool run, and I am having a difficult time believing that will actually occur. As I don't have time to post charts; I will describe it by saying very persistent northerly regime, with temperature under the rain perhaps nearer 0C in some parts than 10C (looks a little realistic from the temperature pattern distribution too). That said if it did turn out to be the case then certain I have never seen anything like it synoptically - I have heard of such, but surely not this cool.

Time to dig out the record books.

Haven't got time to view the ECM but I'm sure it's not as cool as the GFS outlook.

It would certainly "not" surprise me to see the 00z gfs verify! After months of well above average and indeed record breaking warm months,mother nature will compensate us and balance things out and at the time when most folk are looking forward to seeing Summer! Its not to say the 00z is correct and that there will not be any decent weather to enjoy, im sure there will be, but if the Cfs is correct unsettled conditions look to prevail for a long time!!

[Alex]

The models this morning are the worst I have ever seen them for early May , we should expect something a bit better! Temps struggling to get to 11/12c and copious amounts or rainfall, ridiculous!

I know its probably stupid to write May off but nothing seems to be changing upstream so we seem to be left in a rut, we are paying severely for a dry winter! I just hope summer isn't a writeoff again especially after the rubbish endured last year!

[Thundery wintry showers]

There is the chance of something warmer heading in from the SE but the majority of model outputs, as far as I can see, keep us on the western side of the trough into the latter part of next week giving us generally northerly winds. The "April showers" regime will continue until at least Tuesday for most, though with some rather more persistent rain in the south on Monday, and some coastal parts of E Scotland and NE England missing the showers and staying dry with some chance of low cloud off the North Sea. Today looks set to be the "peak" day of the three for thundery activity with the Midlands and northern England favoured for storms this time.

During the latter part of next week it becomes very complicated as we see a battleground between an Arctic northerly regime (sunshine and scattered showers, possibly wintry in the north) and continental air, associated with warm wet conditions. It is likely that Scotland will remain bright and showery with an increasing chance of sleet/snow in the heavier showers, but much of England and Wales, especially towards the south, will end up with some heavy and persistent rain at times.

For the long-term, it is quite possible that we may end up with a rather more 'settled' regime but not necessarily any sunnier or warmer, just drier and less changeable, as those setups with high pressure centred to the W and SW have a habit of sending a lot of cloud in off the north Atlantic. There are also indications that we might end up with a more changeable north-westerly type if the high sits well out to the W/SW.

[Robbie Garrett]

Looking at the model runs, for early May I can actually agree with coldest in 100 years. Who actually came up with that idea??

If you want fairly decent warmth and sunny days, the high pressure is in the wrong place. Needs to be over Europe not to the west or over us.

[Snowyowl9]

Fax charts for a few cold wet easterlies this week,from channel lows,more than normal for this month.

http://www.wetterzen...ics/brack0a.gif

http://www.wetterzen...ics/brack2a.gif

[Scorcher]

It looks like we may end up with the coldest April since 1989 and looking at the models perhaps we will see the coldest May since 1996. I can't really see it beating 1996 but it could come close given the start to the month that looks likely. The 00Z GFS is a horror show for those wanting a warm, settled start to May.

The only hope for the warm fans is that GFS has been swinging hugely from day to day- only yesterday it was showing high pressure dominating in FI. I'm just glad I'm escaping to Germany and Austria from May 3rd-8th as it seems I may see some warm settled weather there.

[Summer Sun]

GFS 06z isn't too bad for early May there arn't as many deep low pressure systems heading our way, but temperature's arn't anything special for the time of year

http://www.null/ds/gfs.htm

[Cloud 10]

The last 24 hours have shown the 500mb anomaly charts diverging in how they deal with the pattern in the UK area. When this happens I am never very confident in using them; 2 out of the 3 suggest something of a 500mb flow from e of south with an upper cut off in the Iberia area, and with rising heights both west and north of the UK. The other has dropped the rising heights to the north, makes less of the cut off low and shows a more marked flow from n of west.

None suggests any really settled weather but 2 would perhaps indicate some rise in temperature over the time scale, 7-15 days, whilst the 3rd would not.

Latest ensemble means from ECM and GFS both hinting at the NW flow option as we head into the start of May.

ecm> gfs>

Today's met office forecast updates talking of more cool and unsettled weather,and even

a mention of wintriness on northern hills and a frost risk.