Model Output Discussion 01/06/2012

[pyrotech]

Make the most of the warm / hot spell as temperatures tumble for early July as cold air sweeps down from the north

Maxes of just 9c for some! it was warmer on christmas day

Wet as well

Ground frost possible

Why worry about temperatures in Fi, The surface pressure charts for next weekend are still being worked out and subtle differences from the models in that timeframe. Any differences however slight will be massive by 2nd July.

Its fine to look deep in Fi when we have blocking over us, but with such a mobile set up right now , way too much reactive changes to play with.

Discussing any changes in the jet stream over the medium term would probably have a better chance at forecasting likely scenario in Fi

I would concentrate on looking for trends now and towards a building of pressure from the South or not, changes in the Jet, heights over Greenland and what the Azores high does. The models rarely get temperatures accurate at 3 days out unless we are looking at a blocking scenario.

The jet seems to weaken alot towards the end of the Month. We would then likely see high try to ridge North. But so many other issues.

The models have had Tropical Storm Debby move North over Texas initially (ECM 12z 21st June), now fairly broad agreement will move over Florida. Most now have this intensify as heads up NE American Coast. Again then huge differences, Latest GFS is first sign it will make a hit for UK (North) but such variables from large scale powerful storms can make Fi rediculous.

Imho temperatures beyond 5 days in this set up are not even worth looking at, as are rainfall charts, The latter can give indication but accuracy for any place is laughable at this timeframe. This is not always the case thou, these can be a useful tool in less mobile conditions.

Model performance, seems GFS has the better on the tropical storms this year so far, but after ECM changes towards GFS as storms form it then takes over as they head North as the more accurate model. So in my opinion Fi GFS performs pretty well, but in start of reliable timeframe ECM catches up and takes over.

[Aaron]

Make the most of the warm / hot spell as temperatures tumble for early July as cold air sweeps down from the north

Maxes of just 9c for some! it was warmer on christmas day

Wet as well

Ground frost possible

Mins of 3C In July? I doubt it.. away from the frost hollows and high ground, though not unheard of I guess, the temperature has even fallen to 3C in Leeds city centre in the 90s.

[Anthonyb]

Make the most of the warm / hot spell as temperatures tumble for early July as cold air sweeps down from the north

Maxes of just 9c for some! it was warmer on christmas day

Wet as well

Ground frost possible

That's 7 days away which makes it FI

Pointless even thinking that will happen until two days away at the very earliest.

3 days ago the models were predicting a sunny day for most tomorrow and temps up to the mid twenties.

In reality tomorrow will be cloudy and muggy only peaking at 21c at the very best.

[Methuselah]

It may well be 7 days' away, but it's still what the models are saying...

[Snowy Easterly]

That's 7 days away which makes it FI

Pointless even thinking that will happen until two days away at the very earliest.

3 days ago the models were predicting a sunny day for most tomorrow and temps up to the mid twenties.

In reality tomorrow will be cloudy and muggy only peaking at 21c at the very best.

exactly the 06z showed 20c in central areas for tomorrow and now the 12z shows 17c, so things can change at very very short notice

[Summer Sun]

ECM's take for Thursday - By Friday all the warm air gets shifted away

July starts unsettled and cool for the time of year

Edited June 25, 2012 by Summer Sun

[Andy Bown]

All points made are valid on Page 35, however please can I make a request that people don't quote whole posts that include

several charts. The same charts, posted originally by Summer Sun, appear 4 times on page 35 due to quoting!!

[Anthonyb]

It may well be 7 days' away, but it's still what the models are saying...

Absolutely - charts in winter that show a blizzard and harsh temps 7 days away rarely come true. Likewise with charts 'today' that are showing 3c for July.

I'm Pretty confident that the temp will not drop to 3c in central areas in 7 days.

I would also like to add that most models are predicting a pretty wet Wednesday and Thursday across Northern areas when only two days ago there was talk of major thunderstorms across the south with potential flooding and temps up to 27c.

Now we see models and TV media give scattered storms for the South and temps of 25c and possible flooding for the North

Now that's how I know that 3c next week is highly unlikely

[Milhouse]

There looks to be good support now for low pressure to pull away to the north following another unsettled weekend. This should allow the Azores high to extend east into central Europe which should help settle things down, initially across southern parts but possibly more widespread depending on how north the high manages to get. The most likely situation would be a north south split with northern parts most likely to see rain or shower associated with nearby low pressure. However the GFS is indicating there should be some decent dry weather to be had even for northern Scotland and it would be much warmer for the North East with a warm southwesterly developing. For the south of the UK it would become warm and fairly settled with the south east likely to see the best of the sunshine. In these westerly setups we often see contrasting fortunes for the east and west of the country. Eastern areas tend to be very dry and fairly sunny as the rain tends to be light and patchy or fizzle out competely when it reaches here. For western parts it tends to be a lot cloudier and cooler. The models are painting a similar picture to that of August 1998 with a NW/SE split developing. This type of set up does require the jet stream to edge northwards, which the models are suggesting might happen. I just hope that this positive trend does not vanish.

ECM mean at 192h with a definite NW/SE split being shown. Warm and settled for the SE. Cooler and unsettled for the NW.

[snowmackem]

exactly the 06z showed 20c in central areas for tomorrow and now the 12z shows 17c, so things can change at very very short notice

Sorry but you are wrong. As JH and others regularly point out, you should not compare model output between different runs. You are not comparing apples with apples. The data set that produces the runs for 06z is totally different to that which produces thye 12z runs.

The only way you can rightly point out a huge difference in temperatures forecast for example, is by comparing one 06z run with the next 06z run. You will disappear where the sun don't shine if you dont.

Nio wonder newcomers get confused.

[pyrotech]

Sorry but you are wrong. As JH and others regularly point out, you should not compare model output between different runs. You are not comparing apples with apples. The data set that produces the runs for 06z is totally different to that which produces thye 12z runs.

The only way you can rightly point out a huge difference in temperatures forecast for example, is by comparing one 06z run with the next 06z run. You will disappear where the sun don't shine if you dont.

Nio wonder newcomers get confused.

Yes lets educate people on this and your quite right to point this out as it will help people.

I just think we need to be careful how we word these education methods as we were all new on here once and we all want to enchourage new members here and for them to post. We need to make sure we guide and help them rather than shout at them. The amount of times i have seen someone ridicule a newbie about Fi when they call it F1, we need to correct them but we all have a similar interest so lets welcome them here. No aimed at Snowmackem but in general.

On to the models

Alot of us in the past have critisised the GFS, with some biased towards ECM so some observations on the models this year.

Firstly GFS was known to overcook low pressure and it seems they have changed something as it now seems to be more on form.

I did a model comparrison over last 6 days watching the formation of tropical storm Debby.

ECM OPER, ECM MEAN, HWRF and others had it to move North West, only GFS had it moving Eastwards over Florida from day one, the others have gradually moved towards what GFS has consistantly predicted. Might be lucky or it read the weak steering currents correctly.

Looking at the 12z model output and for 5 days ECM and GFS both have alot of agreement.

Then on day six new low south of Greenland is brought in first by ECM, this continues to deepen throughout into fi, but GFS fails to make much of it.

Does GFS now undercook these lows, or has it really got a hold on these features.

Debby (remnants of) appears off NE US coast first on ECM probably running about 30 hours quicker than projection by GFS, but whatever that outcome its GFS that has predicted this path consistantly and ECM was late on picking it up.

Worrying that on all runs by GFS and ECM it appears that the Greenie High is remaining stubborn, Summer is not in sight in the models today and although its deep fi its the consistancy of the models that causes concern. The Azores high does attempt to ridge in but gets pushed too quickly away. Although the models were very late predicting the warm dry spell in Spring.

Four named storms (2 in May, 2 in June, Earliest previous for this was 4 named storms by mid July) pretty much makes this an unusual year. These storms cause major problems early in their formation in regards to strength and depth as well as track. The models will struggle whilst these storms move in to North Atlantic whilst such a mobile scenario is involved. A blocking high would make the situation much more enlightening.

[pyrotech]

Millhouse

I agree the models are trying to bring in a North / South split, but what worries me is they have been playing with this idea on a few runs for the last few weeks. It seems to remain in Fi.

Even if it does come in its an improvement but not really the summer weather we all deserve now.

Obviously for those in the North its worst, but even in the south we would have no sustained clear skies and scorching temperatures, infact cloudy and part cloudy particularly towards South West. But better than current conditions.

I think we will continue to see this scenario show in the models until one day it actually comes into reliable timeframe, as we have higher pressure tantalisingly close to our South throughout most of the runs, but with Greenie high in place i think thats where it will stay apart from the odd day it ridges North. Run after run this is what the models show most consistantly, i just think we jump a bit too quick when we see something that would brighten our lives on a run. I am particularly bad for that as always trying to find what i want to find in the models. Its a human trait to look for what you want to see.

[Glacier Point]

GFS ensemble means continue to signal some slow steady improvement in the coming weeks with pressure increasing to our SW and S, however I suspect a case of two steps forward, one step back for the time being.

[Alex]

GFS ensemble means continue to signal some slow steady improvement in the coming weeks with pressure increasing to our SW and S, however I suspect a case of two steps forward, one step back for the time being.

I've noticed the steady trend of removing heights in the Greenland area which in turn will help knock the jet further north. The MJO is heading towards phase 2 and the composites show a better run of weather than recent times. My worry is that the GWO is still low despite a recent increase. Do you have anything to add on the teleconnections GP?

[Summer Sun]

Wednesday looking odds on to be the warmest day of June now

And with lots of cloud around it will feel very humid

Thursday is back in line with what the beeb were showing on country tracks last Sunday max of 23c

The risk of storms is getting lower as well

Early July is looking mixed on GFS high pressure trys to rise low pressure wins keeping it unsettled

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

Same for ECM

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

[shedhead]

GFS ensemble means continue to signal some slow steady improvement in the coming weeks with pressure increasing to our SW and S, however I suspect a case of two steps forward, one step back for the time being.

Hi Stewart - please don't take this as any sort of critisism, but as June has not exactly gone to plan are you sticking to your overall forecast for July and August?

[Glacier Point]

Hi Stewart - please don't take this as any sort of critisism, but as June has not exactly gone to plan are you sticking to your overall forecast for July and August?

I would disagree there a touch, as we were expecting June to be unsettled, although the rainfall forecast and temperature values will be out.

Looking ahead, I think the theme of steady moderation in the pattern looks to be the call. Noticeably the upper level easterly winds have decreased over the Arctic of late and tropical forcing continues to try fight against the very low angular momentum at present. Sooner or later we should see the GWO bounce eratically from phase 1 to 3 and 4, which will mark the differences with some of the more recent summers where the pattern in June gets locked forthe duration, although there remains no firm indication of sustained warmth, rather more average summer conditions.

[shedhead]

I would disagree there a touch, as we were expecting June to be unsettled, although the rainfall forecast and temperature values will be out.

Looking ahead, I think the theme of steady moderation in the pattern looks to be the call. Noticeably the upper level easterly winds have decreased over the Arctic of late and tropical forcing continues to try fight against the very low angular momentum at present. Sooner or later we should see the GWO bounce eratically from phase 1 to 3 and 4, which will mark the differences with some of the more recent summers where the pattern in June gets locked forthe duration, although there remains no firm indication of sustained warmth, rather more average summer conditions.

Thanks for the prompt reply Stewart, much appreciated.

[bluearmy]

the greenland anomoly remains for the next fortnight according to naefs. i suspect the orientation will be different to what we've seen over the past few weeks which will allow things to improve somewhat in the southern half of the uk as the jet moves a bit to our north from time to time and the depressins take a track further north w - e than they have been (which was generally sw to ne). not wall to wall settled by any means (certainly not for the northwest of the uk) but definitely an improvement in general.

[Glacier Point]

I suspect the NAEFS is hiding something of a split there Nick between GFS and GEM ensembles given the way the GFS suite is trending at the moment. As you conclude, an improvement with some healthy caveats, especially for the north-west.

[Gavin P]

Here's todays model based 8-10 day musing looking at the first week of July;

http://gavsweathervids.com/

Looks like a pretty "average" period coming up, so not terribly exciting, but an improvement compared to June.

Edited June 26, 2012 by Gavin P

[Bobby]

Looks like next week coud end up looking something like this

Might be most unpleasent for us in the middle - damp, grey and dull, the worst summer weather IMO. An improvement for those in the SE at least.

[Downburst]

Looks like next week coud end up looking something like this

Might be most unpleasent for us in the middle - damp, grey and dull, the worst summer weather IMO. An improvement for those in the SE at least.

Really only the mid week period that is very unsettled and that moves past at a fair old pace, so not too bad with and getting better by the end of the week next week although that is FI. I'd bank it at this stage.

[johnholmes]

Sorry but you are wrong. As JH and others regularly point out, you should not compare model output between different runs. You are not comparing apples with apples. The data set that produces the runs for 06z is totally different to that which produces thye 12z runs.

The only way you can rightly point out a huge difference in temperatures forecast for example, is by comparing one 06z run with the next 06z run. You will disappear where the sun don't shine if you dont.

Nio wonder newcomers get confused.

thanks for the mention but as ever in meteorology its got a caution.

At long time scales then your comment is, I feel, quite correct. Once we get down to fairly short time scales, say below T+144 as a ROUGH guide, then it can help to see how each model compares to its previous run and to other models at the same start times. As T+00 approaches all the models will generally slowly become pretty similar.

[johnholmes]

I notice my pc problems are just as marked-I cannot get a reply to have just one quote, this in Google Chrome, I'll pick up in the help thread so please don't clutter this up with well intentioned help?