Model Output Discussion 06Z, 13 Sep. 2013 ---->

[Summer Sun]

High pressure building in for Friday

 

 

Temps lower than what the beeb had but GFS does have a tendency to under cook them by 2 or 3c at times

 

 

It could be cloudy in the east still on Friday with some light rain or drizzle possible

 

 

By Saturday pressure is building in more so any thread of rain will continue to fade away

 

[Captain Shortwave]

GFS still calling next weekend to be fair, high pressure slap bang over the UK

 

 

Humberto looking pretty harmless to the UK, hard luck Iceland. Also I'm liking that cut-off low developing.

[Summer Sun]

Nice

 

 

In the words of frosty Bank!

Edited September 15, 2013 by Summer Sun

[Cheshire Freeze]

GFS still calling next weekend to be fair, high pressure slap bang over the UK

 

 

Humberto looking pretty harmless to the UK, hard luck Iceland. Also I'm liking that cut-off low developing.

 

Yes but we also have to remember we'll be nearing the end of September by this point. Any HP over us will result in a rapidly cooling ground level and thus any warm uppers (such as shown) will result in mist and fog forming overnight. Temperatures would probably be supressed in some locations from the 21C shown as any mist and fog may be more stubborn to clear than it would have been a few weeks ago. There will be a crossover sometime in October where HP will mean cooler than average.

 

If it was a southerly flow shown (such as late Sept 2011) it'd be a different story

Edited September 15, 2013 by CreweCold

[Summer Sun]

As you were from UKMO with high pressure building in just in time for the weekend

 

[Cheshire Freeze]

Here's an interesting chart which would raise Steve Murr's interest levels from a synoptic POV

 

Edited September 15, 2013 by CreweCold

[ANYWEATHER]

High pressure building in for Friday

 

 

Temps lower than what the beeb had but GFS does have a tendency to under cook them by 2 or 3c at times

 

 

It could be cloudy in the east still on Friday with some light rain or drizzle possible

 

 

By Saturday pressure is building in more so any thread of rain will continue to fade away

 

There is no consensus among the models for next weekend though. "Humberto" is stirring some interesting , but potentially  misleading output by next weekend, indeed its FI, though given the timesscale, but I expect gfs will be showing something completely different in a day or twos time. Its certainly a possible scenario, but as yet it has now weight behind its output, and these ex hurricanes/tropical storms often confuse computer models at this time of year... 

[Captain Shortwave]

There is no consensus among the models for next weekend though. "Humberto" is stirring some interesting , but potentially  misleading output by next weekend, indeed its FI, though given the timesscale, but I expect gfs will be showing something completely different in a day or twos time. Its certainly a possible scenario, but as yet it has now weight behind its output, and these ex hurricanes/tropical storms often confuse computer models at this time of year... 

The metoffice and bbc are starting to feel confident on high pressure building in on friday and into the weekend.

GEM into the hat too

GEM has uppers of 14C over a fair part of the country

No matter what model you look at the forecast for next weekend is dry and probably sunny for many 

Edited September 15, 2013 by Captain shortwave

[Summer Sun]

There is no consensus among the models for next weekend though. "Humberto" is stirring some interesting , but potentially  misleading output by next weekend, indeed its FI, though given the timesscale, but I expect gfs will be showing something completely different in a day or twos time. Its certainly a possible scenario, but as yet it has now weight behind its output, and these ex hurricanes/tropical storms often confuse computer models at this time of year... 

 

UKMO and ECM seem to be handling Humberto better

 

 

ECM (00z)

 

 

GFS is overcooking it by miles at present when compared to UKMO and ECM

 

[Cheshire Freeze]

The metoffice and bbc are starting to feel confident on high pressure building in on friday and into the weekend.

GEM into the hat too

GEM has uppers of 14C over a fair part of the country

 

Please don't fall into the trap of putting too much emphasis on uppers during late September. They're much less relevant than they were a few weeks back. We'll be past the equinox by then with added implications of overnight mist/fog (depending on situation of HP). Will feel pleasant during the day in the sun though.

Edited September 15, 2013 by CreweCold

[Steve C]

Here's an interesting chart which would raise Steve Murr's interest levels from a synoptic POV

 

From what I've seen of his posts, wouldn't he be more likely to say, 'GFS, a long way out, therefore bin it'?

[Cheshire Freeze]

UKMO and ECM seem to be handling Humberto better

 

 

ECM (00z)

 

 

GFS is overcooking it by miles at present when compared to UKMO and ECM

 

 

A deeper Humberto = a sturdier ridge thrown over the UK ala GFS. A weaker Humberto would probably lead to 2-3 fine days then unsettled once more. If you think that the GFS is overcooking Umberto then I wouldn't get carried away over any settled weather shown by the GFS.

Edited September 15, 2013 by CreweCold

[Cheshire Freeze]

From what I've seen of his posts, wouldn't he be more likely to say, 'GFS, a long way out, therefore bin it'?

 

I didn't mean that it was a likely route we'll take synoptic wise per se. It's the chart itself that's interesting, regardless of how far ahead it is

[summer blizzard]

The overall model consensus is pointing to a very decent spell of warm settled weather by next weekend, indeed, by friday, the azores high will have built north through the uk and most areas look dry and sunnier with temps close to 21c in the south, then warming up even more through next weekend into the first half of the following week with temps well into the 70's F, superb for late september and untold riches after those dismal and wrong ecm op runs recently showing 10 consecutive days of very cool unsettled weather with persistent NEly winds. So it could become very warm for the time of year with winds sourced from southern europe and temps into the mid 20's celsius.

 

That's being the case since about the 20th August but has all too often (bar that one weekend) fallen apart as the models have shifted to a more unsettled pattern. Certainly ten consecutive days was a touch too far at this time of year but i suspect that warm interludes will be just that, short interludes. Infact this one appears to be driven by Humberto. With the tropics looking less active afterward and no MJO activity i suspect we will revert to the dominant pattern of recent weeks which has been for a N/S split with troughs finding it easy to make it east of the UK.

[Summer Sun]

A deeper Umberto = a sturdier ridge thrown over the UK ala GFS. A weaker Umberto would probably lead to 2-3 fine days then unsettled once more. If you think that the GFS is overcooking Umberto then I wouldn't get carried away over any settled weather shown by the GFS.

 

The reason I think GFS is overcooking the low is because of the ensemble mean (06z)

 

 

As ever only time will tell what we get but a 2 or 3 day settled spell looks the best bet currently

[summer blizzard]

Yes but we also have to remember we'll be nearing the end of September by this point. Any HP over us will result in a rapidly cooling ground level and thus any warm uppers (such as shown) will result in mist and fog forming overnight. Temperatures would probably be supressed in some locations from the 21C shown as any mist and fog may be more stubborn to clear than it would have been a few weeks ago. There will be a crossover sometime in October where HP will mean cooler than average.

 

If it was a southerly flow shown (such as late Sept 2011) it'd be a different story

 

An excellent point, pressure of 1020mb+ from late October invariably means cool surface temperatures (Nov 05 being a stunning example). For now it's worth bearing in mind that even without the inversions for most (though no doubt valleys starting to become prone to mist and fog) the lapse rates have decreased so high twenties becomes the best you can hope for,

[Captain Shortwave]

A deeper Humberto = a sturdier ridge thrown over the UK ala GFS. A weaker Humberto would probably lead to 2-3 fine days then unsettled once more. If you think that the GFS is overcooking Umberto then I wouldn't get carried away over any settled weather shown by the GFS.

Thing is take the UKMO chart for day 6

 

The Atlantic is going to struggle to push east with an elongated high stretching from Iberia to Northern Scandinavia, UKMO would also show Humberto tracking harmlessly towards Iceland. I think the ECM run will help see where we might be heading, but I wouldn't be surprised if the settled spell which looks odds on to happen next weekend gets extended well into next week. The bbc week ahead forecast is already hinting this.

Of course we need a proper southerly flow to get the maximum from the potential shown, but I wouldn't be surprised if we got a couple of degrees higher than 20-21C currently suggested. One thing I noted earlier that even the 2011 spell the temperatures were undercooked by a good 5 degrees out at a similar distance to verification as this currently is.

Edited September 15, 2013 by Captain shortwave

[No Balls Like Snow Balls]

In regards to the ECM showing 10 days of unsettled not so long back while this is true the flipside to this is the GFS has been doing the complete opposite of late and showing endless days of very warm temps and endless sunshine but in reality it never has happened like that since July. Basically all models show a load of rubbish at some point, the GFS does it more than others.

[Cheshire Freeze]

Thing is take the UKMO chart for day 6

 

The Atlantic is going to struggle to push east with an elongated high stretching from Iberia to Northern Scandinavia, UKMO would also show Humberto tracking harmlessly towards Iceland. I think the ECM run will help see where we might be heading, but I wouldn't be surprised if the settled spell which looks odds on to happen next weekend gets extended well into next week. The bbc week ahead forecast is already hinting this.

Of course we need a proper southerly flow to get the maximum from the potential shown, but I wouldn't be surprised if we got a couple of degrees higher than 20-21C currently suggested. One thing I noted earlier that even the 2011 spell the temperatures were undercooked by a good 5 degrees out at a similar distance to verification as this currently is.

 

The 2011 spell was courtesy of a deep seated southerly with saturated, warm air at all levels (due to a slight tropical maritime influence). Hence temperatures held up in the high twenties by day and held up well at night.

 

 

Notice the HP centred to the east of us.

 

The UKMO shows the high to be centred well to our NE and much slacker winds across the UK courtesy ridging directly across us. LP is held slightly further west.

 

 

Although differences look minimal there would be a fairly fundamental difference at ground level. Without that southerly flow (which held further west), there is little to mix the warm uppers to ground level. Hence with nocturnal ground cooling and warm uppers, the temperature differential would almost certainly lead to mist and fog development. This could complicate matters somewhat. Though as I've said, in the sun during the day, low 20s is likely to be had in some locations.

[Paul]

Just as a reminder / a notice - we have a zero tolerance policy on personal digs / snipes and petty point scoring in this part of the forum now. Anyone doing this sort of thing, or generally posting in such a way that is against the spirit of the forum will be stopped from posting in here for a period of time without any further notice, so please ensure you self moderate your own posts before hitting submit. Some posts today (which have been removed) are treading a dangerously close line...

[Scorcher]

Please don't fall into the trap of putting too much emphasis on uppers during late September. They're much less relevant than they were a few weeks back. We'll be past the equinox by then with added implications of overnight mist/fog (depending on situation of HP). Will feel pleasant during the day in the sun though.

 

What trap? The uppers are still hugely important, as they are at any time of year. They still dictate how warm it will get in the daytime and in any prolonged sunshine temperatures can easily get well into the 20s if the uppers support it. What happened in 2011? That spell showed what was possible right into October. It wouldn't have been possible without the very warm uppers, and if the setup is right we can get the warm temperatures right into October.

 

Another point is that that spell in 2011 was pretty fog free, certainly where I was at the time and the temperature held up very nicely at night time even with the longer nights. Many places were having minima in the mid to high teens in that spell. I'm not suggesting we're heading into a spell like 2011, but I think it just showed what is possible with the right setup.

[Cheshire Freeze]

What trap? The uppers are still hugely important, as they are at any time of year. They still dictate how warm it will get in the daytime and in any prolonged sunshine temperatures can easily get well into the 20s if the uppers support it. What happened in 2011? That spell showed what was possible right into October. It wouldn't have been possible without the very warm uppers, and if the setup is right we can get the warm temperatures right into October.

 

Another point is that that spell in 2011 was pretty fog free, certainly where I was at the time and the temperature held up very nicely at night time even with the longer nights. Many places were having minima in the mid to high teens in that spell. I'm not suggesting we're heading into a spell like 2011, but I think it just showed what is possible with the right setup.

 

See my post above. I'm not rubbishing the potential for any warmth at all. However, given the time of year, there are many more variables to take into account when talking about potential max temperatures and weather at ground level etc. Come September 22nd the sun will be in the same position in the sky as it was on March 21st. You have to take these things into consideration.

Edited September 15, 2013 by CreweCold

[Scorcher]

See my post above. I'm not rubbishing the potential for any warmth at all. However, given the time of year, there are many more variables to take into account when talking about potential max temperatures and weather at ground level etc.

 

Yes sorry I didn't see that post, that's a good explanation and we know the odds have got steeper on a very warm spell. Nevertheless low 20s is still very easily achievable but the chance of cold starts with overnight fog is certainly greater than it was in August.

[Captain Shortwave]

The 2011 spell was courtesy of a deep seated southerly with saturated, warm air at all levels (due to a slight tropical maritime influence). Hence temperatures held up in the high twenties by day and held up well at night.

 

 

Notice the HP centred to the east of us.

 

The UKMO shows the high to be centred well to our NE and much slacker winds across the UK courtesy ridging directly across us. LP is held slightly further west.

 

 

Although differences look minimal there would be a fairly fundamental difference at ground level. Without that southerly flow (which held further west), there is little to mix the warm uppers to ground level. Hence with nocturnal ground cooling and warm uppers, the temperature differential would almost certainly lead to mist and fog development. This could complicate matters somewhat. Though as I've said, in the sun during the day, low 20s is likely to be had in some locations.

To be honest I know the UKMO chart would not be that warm, actually that was my thoughts on the slower movement of Humbert and suggesting the UKMO would be suggesting a start to more settled conditions with the elongated high. As you say we need the perfect conditions not just in uppers but in the correct continental flow. My post was to suggest that I feel temperatures predicted by the GFS/GEM are probably a little lower than what they will actually be. 

Either way next weekend looks pretty sunny after some cool and perhaps misty mornings in place and well I will take that in September to be honest

By the way, I hope the long rangers are right about winter.

Edited September 15, 2013 by Captain shortwave

[bluearmy]

The reason I think GFS is overcooking the low is because of the ensemble mean (06z)

 

 

 

As ever only time will tell what we get but a 2 or 3 day settled spell looks the best bet currently

 

gav, the ens mean at day 7 will rarely show a mean deepening ex TD. (especially when the models are all over the place with it). too many variables. fwiw, around 25% of the gefs deepen it significantly.  will our ridge be a 2/3 day wonder, become a sustained feature or be flattened before it gets going ?