Model Output Discussion - Summer 2024

[carinthian]

Morning all. The German fax chart has the formation of The Genoa Low on Thursday into Friday. This phenomena often forms when a cold ❄ polar flow pushes into the Northern Alps. Its exact positioning determines which parts of the Alps get the most precipitation. So the latest fine mesh model has the risk of greatest snowfall across the Northern Eastern Alps with my location in Salzburgland right in the mix. The current prediction is of 50 cm fresh snowfall by Friday morning at 2000m plus and for the snowline to drop to possibly to 800m. If this comes off, it will be recorded as a impressive "early winter cold snap ". The colder air likely to remain in place for a few days at least as the low drifts slowly east and pressure builds to the North and West.  I am so excited at the prospect of having a wander in the wonderful white stuff from heaven ! What can go wrong ?  Will provide another update in the morning.

C

[minus10]

Yes...after this cooler unsettled week the gfs 0z bringing in some decent Autumnal weather...indeed pretty warm at times with east to south essterly wind direction ..

..as early as Friday high pressure is coming back in..

..it then goes onto build to the east/north east to scandi acting as a block to westerly troughs..

..a reasonable signal from the gefs for above average temps for good part of september after this week...

...and higher pressure..

h

.. geps also showing higher than average 850s..

..gefs anomalies showing the heights to  the north east extending towards the uk...

..while obviously things could change, particularly with the anomalies as has been previously covered and also the unknown  factor with increasing risk of tropical storms in the mix...i would say this is a fairly reasonable signal for the weather to improve after this week with september getting back on track to be a decent month..

 

 

[emmett garland]

 carinthian my wife is heading to lake garda on Saturday  for a week if you can fit in conditions the other side of the alps I would be grateful 

[carinthian]

 emmett garland Some of the models not yet decided which part of the Alps will get the most rainfall/snowfall but some showing a lot of precipitation. Sure think Lake Garda will get a spell of wet weather but the worst of conditions passing away to the east by Saturday. So maybe not to bad the following week but probably a bit cooler than recent weeks past. Hope that helps .

C

[Mcconnor8]

GFS 6z is a very good run for an extended period of time as well, looking pretty nailed on that we will finally get a true 'UK High' for at least some of next week.

[Scorcher]

 Mcconnor8 I certainly won't believe this is actually happening until a couple of days out.

I'm going to assume that the models will flatten the high as we get closer to the time- which has happened constantly for the last 2 years now.

Although this would be very welcome, there would be a feeling of 'too little, too late' for me, given it will be mid month by that point.

[baggielad]

 Scorcher

Quote

I'm going to assume that the models will flatten the high as we get closer to the time- which has happened constantly for the last 2 years now.

I'm hoping this time it will be different as, although I've not been keeping a really close eye on the models, it does appear to be trending the other way over the last few days so perhaps this suggest the signal is getting stronger - for a change!

[Mcconnor8]

 Scorcher Currently it looks like the models are upgrading the strength of the high as we approach it, but of course there is still time for that to change. 

Obviously would have preferred this a month or two ago but rather it now and squeeze out some more warm sunny weather while we can.

The ensemble pack on the GFS 6z seems to be firming up on it but the 0z EPS was less sure.

Edited September 10, 2024 by Mcconnor8

[Scorcher]

 baggielad Yes the trend is certainly a good one. I'm going to err on the side of caution though as we've been burned enough times this year with potential builds of high pressure.

I will be delighted to be wrong on this.

[danm]

1 hour ago, Mcconnor8 said:

Currently it looks like the models are upgrading the strength of the high as we approach it, but of course there is still time for that to change. 

Obviously would have preferred this a month or two ago but rather it now and squeeze out some more warm sunny weather while we can.

Yes I’ll still take it, late September can still bring some pleasantly warm and sunny weather. 

[emmett garland]

 carinthian Thanks so much 

[Downburst]

 Scorcher Yes, I am afraid "nailed on" for something you are looking for in meteorology is asking for trouble, a week away. But the mean is backing the OP, just that the low to the nrth west, lots of spread there

[Downburst]

Combined monthlies are out. Picking December for the brave snow addicts on here

 

Pressure

T850

 

Temps

 

Rain (was expecting this a little wetter)

 

SST (here I selected prob. of being in top 20%, to give an indication of actual value rather than, high, low etc. Sure bet to be in the upper tercile.

 

Can we have a mild mid winter without too much rain? Could this be nice and produce the odd cold break for the addicts, I hope so. 

[Scorcher]

And right on cue, the GFS 12Z significantly weakens the high compared to earlier on. The number of times this has happened over the last 2 years is astonishing- this year in particular.

[Mcconnor8]

 Scorcher

GEM and UKMO look good at day 6, let's see what the ECM says.

The GEM is beautiful.

Edited September 10, 2024 by Mcconnor8

[SunChaserWales]

14c tomorrow and the day after which will be a shock to the system, about 5c below average which will make it very cold for the time of year. But I'm looking forward to it because we've got three days of bright sunshine on offer which I think will be a really nice change!

After that, without wanting to jinx anything, we might actually be looking at a warm, dry, high pressure dominated second half of the month? Extraordinary scenes for 2024. Especially considering the last 10 days of September is when most summers tend to fall apart.

[Mcconnor8]

ECM at day 6 is a big improvement on yesterday's equivalent at day 7, hopes rising for at least a spell of high pressure. It probably doesn't look quite as good as the GEM or UKMO that I posted earlier but better than the GFS on this set of runs.

ECM day 7 and we are in business.

Edited September 10, 2024 by Mcconnor8

[LRD]

The GFS 12z - from about the 16th or 17th until virtually the end of the run; what a wintry pattern that would be if it occurred from around mid/late Nov to mid/late March

But, this time of year, dry and pleasant. I don't think it'd be overly warm though except maybe early next week in the west and north

Edited September 10, 2024 by LRD

[LRD]

An E'ly setting up on ECM too. Not as pronounced as on the GFS though

[Mcconnor8]

 LRD We must be record holders around the world in getting the right synoptics at the wrong time of year over here, won't be any easterlies to be seen come Winter 

[damianslaw]

 LRD Yes, correct, not an overly warm source, with heights projected further north then west, with the airflow from NE Europe. ECM trending same way.

These are interesting model runs against the normal westerly grain at a time when westerlies typically dominate. More akin to synoptics in Spring. 

[Mike Poole]

 Downburst Yes, pretty thin gruel from the seasonals this month in terms of winter prospects.  The appears to me to be a short window of opportunity in December where the models see an Atlantic ridge, into new year and it looks +NAO, but perhaps not wet and stormy, some of the models showing higher than average pressure for the UK.

GloSea6 continues to promote a weak vortex early on, but trending to strong for the second half of winter, so again a hint that it is December that holds some promise, here’s the 10hPa zonal wind plot:

The only thing with this is the model climate mean is similar to the prediction early winter - both well lower than climatology but this does suggest the model may have a bias to a weaker early winter vortex.

Have to say, I had hoped for a better update, but we’ve still got 3 months to go…

[danm]

Looking good again on the models. Settling down nicely and turning warmer. No heatwave but pleasantly warm, losing that northerly chill from Friday. 
 

How cold is this spell for September? The deep dive explains…

 

[raz.org.rain]

6 hours ago, Downburst said:

Can we have a mild mid winter without too much rain? Could this be nice and produce the odd cold break for the addicts, I hope so. 

Really hope so, it would make for a really curious climatic event. It seems to be among the rarest combinations you can get in this country, I believe 1989 was the last time we saw the fabled mild and dry winter combination? It would be really interesting to see how it would be replicated under current conditions. It would also make for a very usable season.

[Mcconnor8]

The AIFS 12z run also looks pleasant, 14c uppers across the country is very much welcome.