Model Output Discussion - 15th April Onwards

[Cheshire Freeze]

Looking at the last few GFS runs, I'd say that should the pattern come off with heights around Greenland, then frosts will be fairly prevalent as we move into May. Looking at the 12z, that Greenland high looks robust!

ECM 32 day is apparently suggestive of a settled early May...probably as a result of HP around Greenland defleting lows suffiiently south before a wetter second half....extrapolating from this suggests the block gradually gets eroded and we see LP once again ploughing into the UK.

Edited April 27, 2012 by CreweCold

[SP1986]

I notice the latest EC 32 dayer is painting a fairly average picture for May! ( according to Matt Hugo )

High pressure early may with temps around average, low pressure returning mid may with temps below average!

Sounds like anything but average to me! Sounds pretty squarely below average; although I can't as such recall a prediction which involves such persistent Northeasterlies.

[Summer Sun]

GFS 12z,

High pressure stays during the opening week of May, rainfall amounts should be much less than of late, although temperatures won't be anything special it should still feel pleasent in any sunny periods

http://www.jp2webdes...o.uk/ds/gfs.htm

UKMO,

Its not working on Wetterzentral tonight we just get a white screen,

Netweathers UKMO only goes to 120h (Wetterzentral goes to 144h) but that looks settled

Edited April 27, 2012 by Gavin D

[Cheshire Freeze]

Yes settling down next week. However, Sunday looks like it has the potential to see another 25mm of rain quite widely

The 144hr UKMO chart perpetuates the notion of retrograde with a trough to the NE dropping slowly south over time.

Edited April 27, 2012 by CreweCold

[Gordon]

GFS 12z,

High pressure stays during the opening week of April, rainfall amounts should be much less than of late, although temperatures won't be anything special it should still feel pleasent in any sunny periods

http://www.jp2webdes...o.uk/ds/gfs.htm

UKMO,

Its not working on Wetterzentral tonight we just get a white screen,

Netweathers UKMO only goes to 120h (Wetterzentral goes to 144h) but that looks settled

by Early April , I assume you mean early May otherwise you have taken Long Range Forecasting to a whole new level

[Summer Sun]

ECM 12z is looking more unsettled later next week just in time for the bank holiday weekend

[summer blizzard]

Wow.. ECWMF12z looks pretty horrific for warm weather.

[Bottesford]

Oh I don't know - if we compare T+24 to the whole rest of the run (bar that FI northerly at the end) then the uppers are all higher than we've been used to lately and rising as the week goes on.

With less rain around, more chance of sunshine and slightly warmer temperatures it will feel like heaven - even if it won't really be that warm, especially at night.

Of course North Sea low cloud will probably become a problem but still - at least the rain will stop!

T+24: http://cdn.nwstatic....ecmt850.192.png

T+96: http://cdn.nwstatic....ecmt850.096.png

T+168: http://cdn.nwstatic....ecmt850.168.png

[Robbie Garrett]

Wow.. ECWMF12z looks pretty horrific for warm weather.

If those -10/-15 uppers get any closer, this place is going to explode. Fairly good chance of some convective snowfall I would have though at this time of the year, if the surface temperature can be anything but remarkable.

Not sure how a May type snowfall would work, but hey... if it does continue this way as we get further into May, I'd put a bet on one of the coldest May's since record began. If you look at recent times, the amount of extremes and odd weather we have been having, a Cold Spring month wouldn't surprise me.

NAO looking to go negative pretty much... and it wouldn't suprised me to see a pretty cold May, if the Greenland block in Lala land gets the go-ahead.

Edited April 27, 2012 by Robbie Garrett

[Thundery wintry showers]

Convective snowfalls can and do happen in May but it helps if there is a prominent Scandinavian trough bringing cold air/troughs at 500hPa, promoting deep instability. Under those circumstances heavy wintry showers occur- the starkest example in the last 50 years was probably in early May 1979:

http://www.wetterzen...00119790503.gif

A north to north-easterly type with a weak Scandinavian trough tends to mean shallow convection and a scattering of light to moderate wintry showers for the north and east, as happened in the Mays of 1995 and 2010.

http://www.wetterzen...00119950512.gif

However the current model outputs (apart from this morning's GEM and this evening's ECMWF at T+216-240) suggest that high pressure will be more dominant if we get a northerly into early May, and so the outcome will probably be dry, quite sunny, and chilly with night frosts.

[A.J]

Robbie, with due respect what charts are you viewing if you think that 'this place is going to explode' ??.....-10 or lower T850's don't get within 500 miles of any part of the UK at any stage in either GFS or ECM 12z outputs...Right out in the extreme FI of both runs there is just the chance of wintry showers on the Scottish mountains and that's just about it...The outlook in FI (which by it's very name is unlikely to verify) is for generally dry anticyclonic weather and cool, certainly not cold

[TonyH]

Looks like a decent week here in the west, things dry up after Tuesday, plenty of sunshine, which feels strong and warm in May, even if temperatures are close to average.

[A.J]

Robbie, with due respect what charts are you viewing if you think that 'this place is going to explode' ??.....-10 or lower T850's don't get within 500 miles of any part of the UK at any stage in either GFS or ECM 12z outputs...Right out in the extreme FI of both runs there is just the chance of wintry showers on the Scottish mountains and that's just about it...The outlook in FI (which by it's very name is unlikely to verify) is for generally dry anticyclonic weather and cool, certainly not cold

...just to add, in case my post has come over in the wrong light, I'm not having a pop Robbie, I think personally your enthusiasm is great, it's this 'coldest May' hyperbole, it's driving me nuts!...lol

[SLEETY]

Why couldn't we have had this sort of charts we are seeing now during the Winter now gone.This place would have gone in to meltdown

Typical

[damianslaw]

Short term - another very wet period as we see low pressure from the near continent migrating northwards with its associated potent warm front. The front looks like stalling over northern england later Sunday and into Monday, so these regions could end up with a very wet 24-36 hrs indeed.

Next week - no sign of any warm up, models want to develop a very robust string greenland high which will pull down arctic air by the holiday weekend and potential for heavy showers in NE parts, with very cold nights and potential for some wintriness in any showers over northern areas with a bit of height.

As I said last night, the charts have an air of May 96 about them, strong heights to our NW can be very stubborn at this time of year thanks to the atlantic being at its weakest. What has been notable this month has been the absence of any southwesterlies, April 2012 is likely to go down as a very 'northerly' month.

Just watched the BBC forecast and had to laugh at Darrens remarks that early next week could get 'very warm' in SE parts but only temporarily, mmm maxes of 16 and 17 degrees possibly 18 degrees in London in my book should never be described as 'very warm', we saw low 20's in late March regularly and the BBC hardly used the word very warm then..don't know hwy they bothered saying this, the milder temps as they said will be very shortlived and barely noticed under the cloud and wind.. it shows the SE bias, the rest of the country will remain locked in low teen temps. The BBC do annoy me.

Edited April 27, 2012 by damianslaw

[SP1986]

Sunday is an interesting potential for quite an unusual event. An air inversion under low pressure in heavy rain in late April is rather unusual. I'm not sure whether I buy this idea of just 4C in central areas with the potential for +5C 850hPa air spreading over that layer, seems a little iffy to me, especially given the weather conditions. Maybe I'm wrong though; but a Max of 4C seems a little optimistic for cold; considering the setup.

[davehsug]

Very disappointing set of models again. Don't mind the rain so much, but would be delighted if it rained a bit warmer! It looked like we might get something a little better, but it's back to the Northerlies again. A bit of sunshine would help of course. It's been nothing but grey cloud & rain here for days.

Edited April 27, 2012 by davehsug

[SP1986]

GFS FI once again taking it to the extreme, should we believe these FI outputs? Not so sure, however the GFS will soon be getting a reputation as the 'ice age model' if it keeps up these charades. GFS seems to want to show Europe in a similar state to winter when those exceptional cold periods were shown; basically it literally wants to freeze Europe in May (at night).. seems a little silly in my opinion.

I do believe it pretty much overdoes everything it predicts outside the reliable timeframe; although someone with more knowledge of the models workings might be able to tell us why that is that everything is 'extremified' as it goes into a lower resolution?

[Thundery wintry showers]

The ECMWF ensembles have shifted towards a full-on northerly which would probably be of the "sunshine and scattered light-moderate wintry showers" type, so the possibility of a brief early-May snowfall in central and northern areas is approaching the "worth keeping an eye on" category, though still an outside bet at this stage IMHO due to it being a long way out (T+168 onwards). The GFS 18Z precipitation outputs highlight the fact that some pretty hefty wintry showers are possible from such a setup if low pressure is prominent over Scandinavia. However I still think the most likely outcome is the more anticyclonic, dry/sunny in west, cloudier in east scenario.

The charts do look quite reminiscent of those of May 1996, but are also nothing unusual for May. What made May 1996 unusual was the exceptional persistence of such synoptics during the first 20 days of the month- normally there would be at least some interruptions, be it via lows tracking across to the north cutting off the supply of Arctic air, warmer air mixing in from the SE or ridges of high pressure. For this reason I think the odds are strongly against May 2012 being comparable to May 1996.

[Roger J Smith]

Instead of a Spanish plume, looks like a Spanish hose. At least you don't have to pay.

[mushymanrob]

awful charts this morning unless you like cool cloudy and often wet weather. the fax shows fronts straggling the country into midweek and with an easterly flow it wont be warm.

i note the mjo suggests a shift towards phase 8 into may, but the 500 annomoly charts dont agree with the may phase 8 synoptic .... or am i (likely) missing something? lol

Edited April 28, 2012 by mushymanrob

[WhiteFox]

I don't mind cool and cloudy. We're not ino summer yet and I'd be exceptionally surprised if there isn't a warm and settled spell at some stage.

The fax charts highlight my concerns from earlier in the week. The raw GFS did not suggest unbroken sunshine and there was always a chance of fronts hanging around as the influence of the HP is not strong enough. In fact, these setups can sometimes give Significantly more rain than Atlantic LPs. By the time you get to early May, LPs tend to be at a higher pressure (if that makes sense) which is what made Wednesday's low so notable. Furthermore, you don't need a 1050 high over Greenland to block systems; 1030 will do in late spring/early summer.

Edited April 28, 2012 by WhiteFox

[Polar Maritime]

Very cold charts from the GFS this morning, nothing remotely warm showing.

If anything FI gets colder, -8 uppers over all but the South from quite a potent Northerly. Some very interesting chart watching over the next few days to see how this evolves.

[Anthonyb]

It's 7 days away - it will not happen. We may be in a cool regime but -8 uppers look unlikely, if you are a model watcher in winter you will know that charts 7 days away that show cold/colder weather never pan out -ie downgrade.

[summer blizzard]

Stunningly cold outputs for May at the moment with the output dominated by clear showery northerlies and maxima suppressing easterlies. Synoptics for a cool May probably could not get any better.