Model Output Discussion - 15th April Onwards

[Summer Sun]

ECM ends slightly more settled than of late and warmer

[ANYWEATHER]

Even by the Bank holiday weekend , gfs and ecm disagree. To be honest I will slide more to the Ecm, more settled conditions to the North , Unsettled in the South. I Really think this pattern is with us for a Long time!!

[camiscool]

anyweather you obviously havent looked at the end of the ecm? silly conclusion

[Polar Maritime]

anyweather you obviously havent looked at the end of the ecm? silly conclusion

It's hard to come to a conclusion regarding FI.

Even the METO are struggleing.

Edited May 1, 2012 by Polar Maritime

[Frank Trough]

It's hard to come to a conclusion regarding FI.

Even the METO are struggleing.

well, you can look at trends or look across the models -and then take it with a pinch of salt. both the ECM and GFS suggest a trend to warmer more settled weather in FI. Of course the details will change.

i'll say this though. For Thursday (3rd) the GFS consistently predicted a flow from the ne/e/se right from T+384. Yes the exact details have chopped and changed but from my point of view (for planning a fishing a trip) it's been a useful tool.

i'm going to try it again. And it'll probably fail!

[AWD]

Would the ECM FI charts not bring some thundery weather to the South though?

Or is pressure too high for that?

Edited May 1, 2012 by Active Weather Dude

[phil nw.]

Hints in later frames of the 12z output that our stubborn upper trough will finally give way and warm out as we go into week 2.

Early days to be be sure of this but it`s the first real sign of changes to the upper air patterns for a long time but it isn`t untill after the Bank holiday(typical).

Pressure starting to rise around the UK by day8 and both models build a high to our east with some mid-Atlantic low pressure being shown by day 10 bringing the flow more from the warmer south.or south east.

I must say this would be a welcome change after such a protracted dull and wet spell around my region,although i realise it`s been much brighter in other areas.

Just a glance at the ens graph shows the temperature line on the up again after the cold northerly around the weekend.

underlining the modelled changes towards something at least closer to average towards mid-month.

[damianslaw]

Reliable timeframe - becoming cold for the time of year and notably so in the north as we see very cold uppers descend southwards. One good thing with arctic air, is that it does tend to bring lots of sunshine and sparkling visibility, despite the chill the weekend looks a good one for getting out and about with only a few showers in NE parts and possibly eastern coastal areas - wintry as well down to quite low levels in the north.

Longer term - shortwave activity looks likely to our SW as we begin to see heights over Greenland retrogress further westwards. ECM is showing such development. With the jetstream on its current trajectory, I expect low pressure to become slow moving over southern parts with the return of the gusty NE/E wind and the trough going nowhere fast - I don't but into any southern plume as being suggested in the depths of GFS output this evening. We may begin to see the influence of heights rises to our east but not until the second half of the month.

[phil nw.]

I certainly would agree with the outlook for the next week Damian but maybe you are a little pessimistic wrt to a change before the second half of the month as you put it.

Both models do show heights rising across the UK before then and we would see mid-Atlantic low pressure and a warmer regime with high pressure just to our east based on those 12z outputs as we go towards days 8-10.

Certainly no sign of your gusty north east winds by then.

Of course we know these are later frames and could well change but i just wanted to clarify what those charts suggest.

[Thundery wintry showers]

It wouldn't be unusual if this happened- after all we've had major switch-arounds from this sort of pattern before, notably so in early June 1975 when an exceptionally wintry northerly outbreak on the 2nd was followed by southerlies by the 7th as a ridge of high pressure drifted eastwards.

I can't say that the evidence for it is very convincing though- I have a feeling that depressions will continue to slide underneath the block, perhaps not giving as extreme a scenario as Damianslaw outlined but still keeping the weather fairly cool with frequent easterly winds. The model signals are weak as is the current MJO signal (very weakly hovering around phase 1, which has composites suggesting mainly northerly winds).

[ANYWEATHER]

anyweather you obviously havent looked at the end of the ecm? silly conclusion

Whats the point in looking at the end of the run, when the models are struggling with the output way before the end of output runs!!!!

[johnholmes]

below are my thoughts on the 500mb charts as of this morning-not clear to me just which way the upper pattern will be in the lead in to the 3rd week in May but should be by Friday?

wed 2 may

Some changes with ec-gfs starting to show as the major trough in the uk area seems to be declining/filling and both showing some slight indication(gfs more than ec) of a small ridge developing just w/wsw of the uk-in the atlantic the trough is being shown more consistently between the 2 models, not sure if it is actually moving east or just how the models are showing some changes

It may be simply that the pattern is going through a phase where it will settle into what it has been or it may be a change is under way-too early to say

The flow still shows something of a n of west to it with heights very slightly higher than they have been.

Not sure how the 2 tie in with the noaa output from last evening

It showed, as it has for several days, differences in emphasis between the 6-10 and 8-14 day patterns. The 8-14 being rather more like the ec-gfs version even though the 6-10 is closer to the actual period for the ec-gfs time scale; that said and the 8-14 does show a small +ve area, similar to gfs wsw of the uk

I would think by Friday the outlook should be clearer as to which way the upper pattern is going to settle into leading into the 3rd week of may.

[Summer Sun]

The Temperature Outlook continues to offer somthing wamer than of late from the end of next week

Looking drier than of late as well for some

[shedhead]

The Temperature Outlook continues to offer somthing wamer than of late from the end of next week

Looking drier than of late as well for some

I seem to recall you posting similar charts at the beginning of April Gavin, saying despite the progs rainfall across the next 10 days should be near or below average.. I think much of England was shown to be in the 75-100% range. I also said at the time these things can only be used as a guide and it's likely to be much wettern than indicated, the same caveats apply now, but obviously it should be drier and warmer than what we've recently seen over England and Wales at least... that much shouldn't be too difficult to achieve.

[bluearmy]

below are my thoughts on the 500mb charts as of this morning-not clear to me just which way the upper pattern will be in the lead in to the 3rd week in May but should be by Friday?

wed 2 may

Some changes with ec-gfs starting to show as the major trough in the uk area seems to be declining/filling and both showing some slight indication(gfs more than ec) of a small ridge developing just w/wsw of the uk-in the atlantic the trough is being shown more consistently between the 2 models, not sure if it is actually moving east or just how the models are showing some changes

It may be simply that the pattern is going through a phase where it will settle into what it has been or it may be a change is under way-too early to say

The flow still shows something of a n of west to it with heights very slightly higher than they have been.

Not sure how the 2 tie in with the noaa output from last evening

It showed, as it has for several days, differences in emphasis between the 6-10 and 8-14 day patterns. The 8-14 being rather more like the ec-gfs version even though the 6-10 is closer to the actual period for the ec-gfs time scale; that said and the 8-14 does show a small +ve area, similar to gfs wsw of the uk

I would think by Friday the outlook should be clearer as to which way the upper pattern is going to settle into leading into the 3rd week of may.

There does seem to be a trend for a rise in heights close to the uk which then retrogresses west (but within a distance to keep us under its influence as opposed to the recent massive retrogression). the trough has proved resilient and one wonders if it may do so again. like you say john, not enough consistency to have any confidence in any particular solution for mid may as yet.

[Robbie Garrett]

CFS shows week 2 ending may, Southern UK averageing about 5-10mm of rainfall. Week 3 <1mm, Week 4, 3-5mm of rainfall. So a dry trend, but it does look as if come month end more of the same regime, possibly becoming a tad settled during June.

Mean max never goes above 14*C for the UK in May, In June this touches 19*C, In July this touches 20*C, August touches 19*C for the 4 weeks ending 20th August 2012.

End of July/End of August looking very wet. Main problem with any settled weather, and any high pressure builds seems to be the Jet stream, if it does run out of steam, the pattern I can see persisting through summer is an Atlantic high, with low pressure stuck in the bay of Biscay area, and a high pressure belt over Europe.

Edited May 2, 2012 by Robbie Garrett

[johnholmes]

you may be correct Robbie but do treat the CFS output at such time scales with great caution.

It often changes, take it from me watching both versions from September up to Xmas every single day. The predictions were no use whatever as far as I could see, either in predicting the Christmas period, say a 1 week slot in December, or predicting the cold spell in early february. Neither were predicted correctly right down to 2 weeks before each event when I stopped looking at them.

Even looking for trends with CFS I found offered little useful guidance in my view.

[Zenarcher]

Looking at the time period from Monday 7th of May to Friday the 11th next week the GFS ensembles are showing mainly high pressure sticking to our North so generally staying settled there. For Southern parts the trend seems to show low pressure staying for the time being so more wet weather is likely to be on its way there and the wind shouldn't really be an issue as much. Also the ensembles do show the high pressure to our North during this time to slowly weaken.

Start of the week mostly settled,

But quickly changes to more unsettled later,

Also not sure on the ECM run this morning looking at 144 hours it disagrees with the UKMO and GFS meanwhile the UKMO and GFS are very similar to each other.

Edited May 2, 2012 by weathermaster

[Robbie Garrett]

you may be correct Robbie but do treat the CFS output at such time scales with great caution.

It often changes, take it from me watching both versions from September up to Xmas every single day. The predictions were no use whatever as far as I could see, either in predicting the Christmas period, say a 1 week slot in December, or predicting the cold spell in early february. Neither were predicted correctly right down to 2 weeks before each event when I stopped looking at them.

Even looking for trends with CFS I found offered little useful guidance in my view.

Of course mate, not that stupid... but hands down it predicted april as a washout pretty much a month or so beforehand. (when I started looking into them)

So far it's getting May Spot on, pretty much with High pressure never too far away.

[Robbie Garrett]

However I can possibly seeing the jet stream having quite an influence...so yes some brief restbite coming up now and again.

But to Sum may up.

[Summer Sun]

ECM has another unsettled run tonight apart from the very last day where high pressure builds

[Polar Maritime]

ECM has another unsettled run tonight apart from the very last day where high pressure builds

Gav, The very last ECM chart in FI is showing a N/S split propably just below average temps for the very far South, and unsettled for the rest of the uk with below average temp's and showers with a cold Northerly airflow. 0c uppers in the South and -4 uppers over some parts also.

Going off that chart alone in the very far reach of FI, it does look like any hint of high pressure will be quikly shunted away.

Maybe GP can give us his view on the charts and what we can expect over the coming weeks...?

Edited May 2, 2012 by Polar Maritime

[bluearmy]

despite the 12z op ecm developing a potent depression in fi, the ens mean seems keen to settle down with ridging moving up from the sw as we approach the mid month period. the spread shows the ridge more likely just to the west of the uk with some shallow euro troughing to our se.

[johnholmes]

Its quite a different atmosphere in here compared to the frenetic activity in the winter months. Quite peaceful. Yet there is some interesting weather progged by the models. Its a little sad I think that some folk only post in the winter months. As a retired professional and enthusiastic amateur I find there is usually something of interest most days. If not my area then some part of the UK or further afield with the models available for all parts of the world.

Just now what have we got showing on the models?

Still the uncertainty of any depth of cold this weekend, will there be frosts, will any hilly parts get some snow? Further out and the first glimmerings one might say on the 500mb anomaly time scale of a possible wave length change in the upper air that would impact on the surface weather towards mid May. Too uncertain to start making anything of it but its still interesting to see how it plays out. Closer in than that and the models treat a possible developing low in quite different fashions. ECMWF taking a deepening low across the country early - mid next week with GFS making little of it. Well worth looking at the 2 outputs T+72 out to 168 to see the difference and watching how reality will be come that time scale.

4 members + 8 guests and 2 annonymous-my how times change!

Edited May 3, 2012 by johnholmes

[Thundery wintry showers]

Regarding wintry potential, scattered wintry showers are likely to come onshore across E Scotland and NE England on Saturday morning, but they look set to be light and well-scattered, so snow mostly confined to high ground, though if any low-lying areas catch one or two heavier showers there may be sleet/wet snow down to low levels. Sunday looks set to have more extensive shower activity under the weak ridge, but snow confined to northern hills by then IMHO as the cold airmass relents a touch. Frost certainly looks set to be widespread to the north of the Midlands on Friday and Saturday nights, with Saturday night likely to produce a ground frost across much of the south.

There is indeed a lot of uncertainty next week over the track of the southerly tracking lows- wet and cloudy but rather less cold, perhaps even warm in the south on occasion, looks a likely bet for next week. The Bank Holiday Monday is looking very likely to be a wet one for most of us.

The ECMWF ensemble mean is implying that the lows will track north-eastwards at intervals during next week allowing a ridge of high pressure to move in at the end of next week, though it is still somewhat open to change.