Model Output Discussion 18z 28/07/13

[johnholmes]

The 500mb anomaly charts are largely as they have been for several days with the upper trough in charge and a fairly strong 500mb flow across the Atlantic.

If one is really searching for signs of +ve height anomalies, small though they are, then NOAA, see below on its 8-14 version last evening

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

 

and this morning the ECMWF-GFS output with GFS having some +ve anomalies showing a bit more than the ECMWF version, even to the suggestion of a VERY slight indication of ridging east of the UK.

The signs are very small so watch how the 3 models deal with this over the next 2 to 3 days before making plans for B-B-Q's!

 

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[summer fun]

Hi everyone,

 

First post in this thread, great to read everyones thoughts on each run and how one person sees something different to what another sees on the same chart. Reaaly good to to read through the discussion.

 

With regards to what john holmes says regarding the upper trough dominating on the anomaly charts, do you think the mjo being forecast to move into a weak phase 8 will play any part in inhibiting a pressure rise over the u.k. Complete novice at all this my question is based on what iv'e read on here over the last year or so.

 

 

[johnholmes]

welcome sf

I am far from an expert on MJO matters but I always take the view that with a low orbit then other factors over rule any effect the MJO has on the northern hemisphere major upper air patterns.

Others may be able to tell you more about this.

Edited August 12, 2013 by johnholmes

[shedhead]

With any possible (and that's all it is) height rise still more than a week away it's fair to say it remains in FI, so whilst perhaps worthy of mention at this point it's not worth building any hopes over imo.  In the short to medium term we're pretty much where we've been across August to date, with bog standard, average, normal (call it what you will) conditions set to predominate initially, before rather more unsettled weather possibly takes hold. 

 

GFS is again the pick of the bunch this morning as far as the most settled conditions are concerned, but even that shows fairly active Atlantic systems pushing their associated frontal troughs southwards across all area at times later this week, with the NW actually looking properly unsettled.

 

 

ECM could probably be called unsettled everywhere come the weekend, with LP being somewhat farther south...

 

 

Meanwhile UKMO tracks the main Low farther NE but at the same time digs a deep trough into the West.

 

Still struggling to see many straws to clutch this morning, but as JH has said the latest 500mb anom charts offer some 'very slight indication' of eventual ridging east of the UK....at least for now!

Edited August 12, 2013 by shedhead

[summer fun]

Thanks John. What would you consider to be our major drivers for the northern hemisphere during summer and do you think that because there has been so little in the way of hurricane development in the atlantic that this has had a positive impact on our summer so far? 

 

Thanks.

[Shuttler]

Latest 00z Ensemble Mean output for days11-15 (23-27 Aug) confirms the likelihood of High pressure dominance, and as we stand centred close to the UK & NW Europe. Breaking it down into individual days for each model suggests this will run throughout the period, indeed the transition point to this pattern seems to commence around the 20th. There is also a consensus on above average temps through this period, though anomalies (both 850 and sfc) are not great, around +1 to +2C overall. So, yes we seems to be heading into a drier, lighter wind and very pleasant possibly sunny phase for the latter third of Aug, but at this stage not a major heatwave.

[johnholmes]

wow, not sure I can honestly answer your question.

The major driver is ENSO and what follows from that, again my knowledge is not high enough to be able to give you your answer. My attempts at longer range forecasting is limited to the 6-20 day time scale. This is why I use the anomaly charts with constant reference to other drivers, ENSO, MJO, AO, NAO although the latter two are more important in winter. They of course simply mirror what the synoptic models may show, high latitude blocking or mobility although they are useful.

For summer and winter I find the 6-15 day range is best served, in terms of the major upper air pattern by using the 500mb anomaly charts. Like any other chart they need to be used carefully and in conjunction with other drivers I've mentioned. When all fit together then one can be resonably confident of the upper air pattern within that time scale. They can and do go wrong just like any other prediction in meteorology but over the 12 months I rate them much higher than the synoptic outputs at that range, something like 70%+ correct in the whole 12 months. That is the upper air pattern and not the surface which is much more diffcult to solve correctly due to a number of factors. One of which is the one that bedevils all attempts at forecasting, even at short time ranges, moisture.

There are two periods when they are less reliable, one is the major change over periods of northern hemisphere summer to winter and the winter to summer period. The other is the next few weeks leading into that first change, the Atlantic hurricane season. Both involve such huge changes in energy within the atmosphere that any model from MJO downwards in time scale finds it extemely difficult to work out how the upper air pattern will be affected.

hope that helps a bit, others will be able to give you more advice about the longer term drivers I am sure.

Edited August 12, 2013 by johnholmes

[Frosty.]

The Ecm 00z ensemble mean shows a nice bump of high pressure bringing a fine and warm spell towards the southeast from midweek onwards with the fine weather lasting until the weekend in the far south/se but progressively more unsettled and cooler the further northwest you go, eventually we all have a cooler, breezier unsettled blip but the southern half of the uk not affected as much as scotland and once the weekend trough clears away to the northeast by early next week, the azores/atlantic anticyclone begins to ridge northeastwards and the weather pattern begins to change for the better with settled, benign and warmer weather slowly gaining the upper hand, the biggest improvements would follow the T+240, just like it does on the Gefs 00z mean, the trend to a settled and warmer last 7-10 days of august and early september is still intact, yes there is some choppy waters to negotiate but later in the month should be smooth sailing into a warm and anticyclonic late summer / early autumn.

[MR EXTREMES]

The Ecm 00z ensemble mean shows a nice bump of high pressure bringing a fine and warm spell towards the southeast from midweek onwards with the fine weather lasting until the weekend in the far south/se but progressively more unsettled and cooler the further northwest you go, eventually we all have a cooler, breezier unsettled blip but the southern half of the uk not affected as much as scotland and once the weekend trough clears away to the northeast by early next week, the azores/atlantic anticyclone begins to ridge northeastwards and the weather pattern begins to change for the better with settled, benign and warmer weather slowly gaining the upper hand, the biggest improvements would follow the T+240, just like it does on the Gefs 00z mean, the trend to a settled and warmer last 7-10 days of august and early september is still intact, yes there is some choppy waters to negotiate but later in the month should be smooth sailing into a warm and anticyclonic late summer / early autumn.

although a very informative post frosty I think beyond t144 hrs is really as far as people should look,

developments beyond this are always possible.

as suggested a few days ago things are starting to slip south with the jet pushing across the alantic towards the uk,

 I think it will be a slow slip into autumn but like I said beyond t144 on any model should really be just to see which model performs the best for long range.

 

but from what im reading id rather not pick out the best bits and just focus on what the charts are really saying.

[Frosty.]

 

but from what im reading id rather not pick out the best bits and just focus on what the charts are really saying.

I wasn't picking the best bits though, I described the whole run from the settled to the unsettled and then the trend to settled which is precisely what the models are showing, a ridge then a trough then an eventual anticyclonic spell, the mean is and has shown a fine and warm outlook for days and days which I think it will continue to firm up on in the days ahead.

Edited August 12, 2013 by Frosty039

[Tamara]

I think the summary above from the West Yorks region is another good one this morning, and as suggested last night, the overall pattern in both the shorter and longer term has not changed much, other than the low at the weekend being perhaps rather more a feature than suggested earlier  However, this is still subject to change as the models have yet to agree on the exact track of it. The overall gist of it though is as explained well just above this post - so little more to add really

 

Best to be wary, as ever, of putting too much stock in operational outputs on a face value basis. The NAEFS height anomalies for about the third day in a row are consistent yet again on pressure build immediately following next weekend, and both the ECM and GFS ensemble means from days 8 to 10 support NAEFS idea of where this pressure rise looks to be as already well illustrated.

 

 

So a rather changeable week, but with southern UK seeing a fair amount of warm weather, then a rather unsettled weekend perhaps more generally, with the heaviest and most persistent rain in the north and west, before the steady improvement from the south and potential late summer warmth still on course to slowly becoming more widespread for the last third of the month

Edited August 12, 2013 by Tamara Road

[shedhead]

although a very informative post frosty I think beyond t144 hrs is really as far as people should look,

developments beyond this are always possible.

as suggested a few days ago things are starting to slip south with the jet pushing across the alantic towards the uk,

 I think it will be a slow slip into autumn but like I said beyond t144 on any model should really be just to see which model performs the best for long range.

 

but from what im reading id rather not pick out the best bits and just focus on what the charts are really saying.

Which is kind of what the MOD is, or should be about.

 

06 GFS takes the weekend low a little farther south and looks rather more ECM like, but perhaps this will ultimately prove to be the trigger for a quicker and stronger pressure rise from the SW next week. Let's see how the remainder of the run pans out.

 

 

 

 

 

Edit - 06 does precisely that and builds pressure significantly across the UK in FI.

 

 

 

 

 

Edited August 12, 2013 by shedhead

[Tamara]

I wasn't picking the best bits though, I described the whole run from the settled to the unsettled and then the trend to settled which is precisely what the models are showing, a ridge then a trough then an eventual anticyclonic spell, the mean is and has shown a fine and warm outlook for days and days which I think it will continue to firm up on in the days ahead.

I agree with you - it was a balanced overview  We can only give an assessment based on the best information we have available at the time. It pretty much is echoed by the High pressure signal the METO have alluded to anyway and this signal has been consistently modelled in the data since the latter part of last week. Therefore it is not 'straw clutching' (I don't like this over-used phrase) to discuss the prospects of it, so long as the signal remains  

[Summer Sun]

Latest met office update continues to move to settled conditions from roughly the middle of next week its set to turn warmer once more

 

http://forum.netweather.tv/topic/64157-meto-uk-further-outlook/?p=2766703

 

[Cleeve Hill]

Just a comment on hurricane season. When we lived in Bermuda I followed the hurricane season pretty closely. There was often a theme that if the hurricane season off the baha peninsular, California was busy (as it is this year) the Atlantic season was very quiet.

It is looking like this for 2013 season, therefore less likely for any ex tropical storms to come our way.

[Summer Sun]

Just a comment on hurricane season. When we lived in Bermuda I followed the hurricane season pretty closely. There was often a theme that if the hurricane season off the baha peninsular, California was busy (as it is this year) the Atlantic season was very quiet.

It is looking like this for 2013 season, therefore less likely for any ex tropical storms to come our way.

 

Thats good to hear the more we can keep away from the UK the better

[MP-R]

Thats good to hear the more we can keep away from the UK the better

 

Having said that, ex hurricanes quite often suck up high pressure underneath them, from a warm direction, more so earlier in the season when the jet is further north than later. From a personal point of view, the main reason I find this weather so boring and frustrating is that the jet is on a NW-SE trajectory rather than a SW-NE, more typical of summer. I would think an ex hurricane would help introduce some much warmer air.

 

Needless to say, there are no indications of such an evolution on any of the models so we just have to stick with what we've got.

Edited August 12, 2013 by Miguel Hugo Roberto

[Frosty.]

The Gfs 06z turns into a cracker of a run with a hot and settled spell developing as high pressure eventually takes total control, it's not a fluke run, this is precisely what the latest mean charts from the ecm & gefs are trending towards with temperatures widely into the mid 20's celsius and some areas into the high 20's c, low to mid 80's F, even this week there will be some warm and fine weather for the second half of this week with high pressure close to the southeast for a while but it looks more unsettled and cooler across the northwest of the uk with sunnier and warmer interludes, then the weekend and start of next week become cooler and more unsettled as a low pushes eastwards from iceland and mainly affects the north with sunday being the nadir although really not too bad at all, certainly compared to the dross we had last summer... then there is a steady recovery which turns into a peach of a settled and very warm spell that dominates the last 10 days of august, with power to add into early september, some great charts here guys...

[Summer Sun]

Another very dry ensemble for London this afternoon also warming up from around mid next week

 

 

The other ensembles also show a drying trend from around the 20th onwards with it becoming warmer as well after what looks to be a cool ish weekend coming up before we get back to normal

 

[Buzzit]

Having said that, ex hurricanes quite often suck up high pressure underneath them, from a warm direction, more so earlier in the season when the jet is further north than later. From a personal point of view, the main reason I find this weather so boring and frustrating is that the jet is on a NW-SE trajectory rather than a SW-NE, more typical of summer. I would think an ex hurricane would help introduce some much warmer air.

 

Needless to say, there are no indications of such an evolution on any of the models so we just have to stick with what we've got.

Generally speaking a very quiet start to the Atlantic Hurricane Season bodes well for a great UK summer... I think I might re-post what I posted five days ago as it is getting closer to fruition  "+384 picture gallery and a massive fat euro high - I am expecting this for the first half of autumn so this would do quite nicely thanks - will be looking to see if we have a bit of change in the general pattern around 16th August as I feel the Azores will encroach a little before we get a full displacement to a Euro high dominated end of August and throughout September, around the same time as I expect the Atlantic Hurricane Season show a bit more life after the middle of this month as well. All conjecture at this point but we shall see..."

[legritter]

I would not like to make a call past this weekend going by current data and charts ,i think outlook up till sunday as been called ok at the moment but past this is all down to positioning of high pressure ,signs yes of a warm week next week [commensing 19th august ]but only signs, i think a few more runs needed before we get out the sun cream and stock up on BBQ food and sun hats .weather seems to be in a quiet mood at the moment ,what is lurking out there gang ,nows the time to put a bet on a white christmas ,cheers all .

[summer blizzard]

Just a comment on hurricane season. When we lived in Bermuda I followed the hurricane season pretty closely. There was often a theme that if the hurricane season off the baha peninsular, California was busy (as it is this year) the Atlantic season was very quiet.It is looking like this for 2013 season, therefore less likely for any ex tropical storms to come our way.

 That effect mainly occurs due to the ENSO cycle however during near neutral seasons there is much less of a correlation. All indications currently suggest an above average season. 

Generally speaking a very quiet start to the Atlantic Hurricane Season bodes well for a great UK summer... I think I might re-post what I posted five days ago as it is getting closer to fruition  "+384 picture gallery and a massive fat euro high - I am expecting this for the first half of autumn so this would do quite nicely thanks - will be looking to see if we have a bit of change in the general pattern around 16th August as I feel the Azores will encroach a little before we get a full displacement to a Euro high dominated end of August and throughout September, around the same time as I expect the Atlantic Hurricane Season show a bit more life after the middle of this month as well. All conjecture at this point but we shall see..."

2003 and 1995 saw two very active seasons, this season to date is technically above average. Its just that they've been mostly crap.

[Buzzit]

 That effect mainly occurs due to the ENSO cycle however during near neutral seasons there is much less of a correlation. All indications currently suggest an above average season. 2003 and 1995 saw two very active seasons, this season to date is technically above average. Its just that they've been mostly crap.

Yes but nothing of any particular note in either year until end August at which point the east coast started to get hit - which is what I meant to suggest rather than to do with frequency / general level of activity - so I apologise for not being more precise

[Summer Sun]

Saturday looks like it will be a breezy old day for many with possibly some gales in exposed northern parts of Scotland

 

 

By Sunday the low is slowly pulling away

 

[MR EXTREMES]

Yes but nothing of any particular note in either year until end August at which point the east coast started to get hit - which is what I meant to suggest rather than to do with frequency / general level of activity - so I apologise for not being more precise

give it time September October November yet for increase hopefully this will put high pressure in favoured spots for winter.

but the point made about a quiet alantic has made a lot of sense and the models do seem to be reflecting on this with a prolonged dry spell warm to so I revise my thoughts and will agree the models are setting up towards more beautiful weather type next week.