Model Discussion - 10th March Onwards

[TonyH]

Regionally specific weather guide for the week ahead:

http://forum.netweather.tv/blog/309/entry-4383-weather-guide-easter-sunday-to-saturday-14th-april-2012-west-wales-and-warwickshire-specific/

[Anthonyb]

surprise surprise, king Azores high is back on the ECM in FI

im not normally bad at reading the charts but these synoptics are hard to tell

would there be a high chance of heavy showers this week for my area, or is it likely to stay dry and cloudy like usual, the precipitation charts don't really help as they are not very accurate, i have an allotment so i am desperate for rain, thanks in advance to anyone who answers my question

This is excellent news- bring back the sunshine and warm temps.

[SP1986]

If anyone is still up, take a look at this, highly unusual for April, in fact it only happens on occassions in an average winter.

http://www.wetterzentrale.de/pics/MT2_Manchester_ens.png

Notice how the mean minimum straddles 0C and sometimes slightly below, for maybe 6 days or so straight. Unusual indeed!

[IDO]

Yes it does, and again the GFS 0z today suggests a cool April in FI. However looking at the ensembles, both the Op run and to a lesser extent the control run (T850s London) are at the bottom of the cold options. So this run at the moment would appear to be the worse case scenario. The mean suggests a more average set up for April. Looking at the min temps shows how much of a cool outlier the 0z run is. From the 16th the ensembles have min daytime temps between 5-12c till around the 20th, when the range is between 7-15c (+). Yet the Op run is nearer 0c most of the run in that period (till the end when it finishes around 5c).

So for the next week it looks like starting average then cooling down to below average April temps, with frosts likely where clear skies persist. There looks like spells of rain, but apart from the 9th they look to be hit and miss events. GFS does not appear to be confident from the 15th and I expect ECM are also going to chop and change as HP tries to edge back in. With the synoptics of the PV at the moment, the cooler Op run may not necessarily be far off the mark. So not very confident of April returning to a settled HP outlook (till the last week, maybe, and then poss transient) so suspect this month's CET will be below average by between 1.5-2.5c, balancing out the March gain.

[bluearmy]

Signs on today's 00z ens offerings that this cooler period may not last much beyond mid month. That 'corridor of uncertainty' on the fi naefs spreads shifts back northwards towards the uk and the higher anomalies begin to encompass much of nw Europe, though with less enthusiasm than recent runs. changes in fi naefs from run to run should be treated with caution and although the second week on the ECM ens London also show a warming trend, a few days of model observation wrt any change from a cool regime is probably in order.

[Summer Sun]

Looks like once Mondays rains clears through, it will be a mixed week, some places will avoid the heavy showers altogether and it will feel quite pleasent in the sun whilst some areas will see some heavy showers with thunder and maybe hail, as the week moves on northerly winds look likely to set in this will see the snow level come down even lower for the North, also Gardeners note frost's are likely at times too.

Edited April 8, 2012 by Gavin D

[SP1986]

The outlook is really interesting synoptically speaking, before we go into the nitty gritty I really think it's worth suggesting if the synoptics the GFS showed, happened in December or January, then the intensity of the cold, would perhaps match, if not beat December 2010. Very interesting to see, and whilst some people have theorised the recently occurring patterns are perhaps an annual reshuffle of our normal patterns (for example patterns we normally see, being differently distributed around the seasons), I'm not sure about that, these certainly seem to be some really quite persistent blocking patterns, and although I can't vouch for it's historic frequency, it certainly seems like 'unexplored territory' (it almost certainly is in my lifetime).

As for what this means, well I think we can say such a setup in April would bring a few borderline inland frosts, and some wintry showers to hilly areas, and moderate ridges. I don't think the effect of the cold airmass would be anywhere near as pronounced in mid- April is in Mid-winter contrary to the opinion I have come across in various threads. The chances of wintry weather are subsiding now for most lowland (<300m) and coastal areas.

I think overall perhaps the GFS is overdoing maximums and underdoing minimums in the North, and perhaps slightly underdoing maximums in the south, and placing minimums about right. It'll be interesting to see how it deals with potential wintriness, but a day out to a mountain or high hill, might be the best idea.

[peterf]

frosts are likely right through until the end of May here.

[SP1986]

frosts are likely right through until the end of May here.

Not surprising at all, Durham is of course one of the coolest places in England, fairly inland but still relatively near the cool SST's of the North Sea

[peterf]

it's a bit colder than Durham up here.

[Cheshire Freeze]

Stephen, you raise a point I have tried to labour myself. Blocking patterns over the past few years appear to be setting up and lasting for months. I've not known anything like it. It's as if the whole circulation has become so sluggish. I do wonder if we've breached climate tipping point......something which my geog lecturer is convinced of

Edited April 8, 2012 by CreweCold

[damianslaw]

The outlook is a cold one for the time of year. Heights building over Greenland, jet aligned on a southerly track thanks to the weakening of the PV and its movement to west Greenland - a development many cold snow lovers were hoping to have happened quite some time back. Alas what it all means is a weak trough lingering across the country, meaning spells of rain or showers these heavy and slow moving thanks to the light drift from the north. Northern parts and in particular hilly regions will increasingly see precipitation turning more and more wintry as the week wears on, as cold uppers descend down from the north. High ground will likely see some more general snow cover by the end of the week, conditions in the Highlands and Grampians will be very wintry indeed by next weekend.

Frosts will form very easily as we see light winds, and with lots of cloud temps will struggle to hit double figures in many places especially later in the week.

Longer term - ECM suggests we may see some height rises to our NE which could mean a drier sunnier spell of weather but nothing particularly warm. GFS suggesting more of an influence from the atlantic as we see low pressure and frontal activity from the west..

Given it is April and when northerlies and easterlies reach their yearly maxim thanks to the atlantic being at its quietest coupled with the northern hemispheric signals and teleconnections, I suspect we are likely to see the current pattern wage for quite a while yet, possibly into May, meaning a distinctly chilly April could be the end result in complete contrast to the six period from mid Feb to end Marh, I often say mother nature balances herself out..

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2012040812/gfsnh-0-96.png?12

longest northerly fetch in history

S

[keithlucky]

http://modeles.meteo...snh-0-96.png?12

longest northerly fetch in history

S

Whats the upper temps with this northerly steve?

[Dorsetbred]

http://modeles.meteo...snh-0-96.png?12

longest northerly fetch in history

S

Wow that's certainly very unusual, pity it's so late in the year, it could well have been useful a month or so ago.

[jethro]

Stephen, you raise a point I have tried to labour myself. Blocking patterns over the past few years appear to be setting up and lasting for months. I've not known anything like it. It's as if the whole circulation has become so sluggish. I do wonder if we've breached climate tipping point......something which my geog lecturer is convinced of

I don't think any tipping point has been reached; the pattern of recent years is much more likely to be as a result of the quiet Solar period we are currently experiencing. Mike Lockwood published a paper recently detailing the impact felt during the winter months, whilst the focus was on winter, there is no reason to suppose there won't be an impact during the summer months too.

http://news.bbc.co.uk/1/hi/8615789.stm

[cyclonic happiness]

Stephen, you raise a point I have tried to labour myself. Blocking patterns over the past few years appear to be setting up and lasting for months. I've not known anything like it. It's as if the whole circulation has become so sluggish. I do wonder if we've breached climate tipping point......something which my geog lecturer is convinced of

I agree, we seem to keep getting these weather patterns that last between 4-6 weeks and with next to no weather in them (at least for the Midlands), no doubt the currant spell of wet and cold weather will last until mid may?

Hopefully the next 'phase' will be warm and settled.

[Summer Sun]

ECM ends on a settled note tonight

Edited April 8, 2012 by Gavin D

[SMU]

Whats the upper temps with this northerly steve?

#

-4c for the south -8 for scotland

S

[Cheshire Freeze]

I don't think any tipping point has been reached; the pattern of recent years is much more likely to be as a result of the quiet Solar period we are currently experiencing. Mike Lockwood published a paper recently detailing the impact felt during the winter months, whilst the focus was on winter, there is no reason to suppose there won't be an impact during the summer months too.

http://news.bbc.co.uk/1/hi/8615789.stm

Yeah seen the lockwood study, used it in my dissertation. Solar activity (or lack of) crossed my mind too.

[Anthonyb]

http://modeles.meteociel.fr/modeles/gfs/runs/2012040812/gfsnh-0-96.png?12

longest northerly fetch in history

S

Would have been epic in Jan/Feb, but pretty much useless now. Well for London and the SE anyway.

Would much rather see a lovely Azores High

[Milhouse]

Would have been epic in Jan/Feb, but pretty much useless now. Well for London and the SE anyway.

Would much rather see a lovely Azores High

It'll be back before long. I guess we have to be patient and thankful that we arent seeing these synoptics at the height of summer which would lead to some dreadful cool summer weather.

In the meantime its the persistence of low pressure over Europe that is most notable bringing a northerly airstream throughout the coming week and into the weekend. Despite that, the countryfile forecast showed quite a lot of sunshine for southern parts and temperatures just a bit below average. There will be a scattering of showers around which will be heavy and slow moving from midweek onwards.

[Snowy Easterly]

It'll be back before long. I guess we have to be patient and thankful that we arent seeing these synoptics at the height of summer which would lead to some dreadful cool summer weather.

In the meantime its the persistence of low pressure over Europe that is most notable bringing a northerly airstream throughout the coming week and into the weekend. Despite that, the countryfile forecast showed quite a lot of sunshine for southern parts and temperatures just a bit below average. There will be a scattering of showers around which will be heavy and slow moving from midweek onwards.

i remember last October and November people were saying better to have this mild now rather than in winter and look what happened

[Anthonyb]

i remember last October and November people were saying better to have this mild now rather than in winter and look what happened

Absolutely - whatever weather pattern is happening currently has no effect on what's going to happen in summer 2012.

[damianslaw]

We are about to endure at least a week dominated by a northerly airstream. Nothing unusual for April, this is the time of year when northerlies and easterlies more often than not inch out the atlantic for lengthy periods. The reason why the northerly is going to persist in situ is down to sluggish movement of low heights to our east/southeast and strong heights to our NW - both features are not going to be particularly strong affairs, but with the PV very weak and grinding to a halt to the west of Greenland there is going to be very little movement in the overall pattern - a them we have been used to for so long now it seems, when weather patterns have become unstuck for lengthy periods. Conversely whilst uppers will be very low for the time of year by the end of the week, the lack of any potent trough feature, secondary low development and most importantly strong wind means we are unlikely to see any particularly snowy precipitation away from the hills, if heights could strengthen further to the NW or indeed lower more to our east then we would be in territory ripe for a trough to form in the northerly flow perhaps generating low level snowfall - its a wait and see situation and such a development could still happen by the end of the week.

Longer term - its a tricky set up, but as I said yesterday I can't see the overall pattern changing anytime soon, I suspect GFS is being a little too bullish today with its atlantic attack, and I suspect ECM is overinflating the rise of pressure to our NE, a half way house probably most likely outcome i.e. trough stuck across the country, remaining chilly/cold in a light northerly/northeasterly drift with lots of cloud.