Model Output Discussion Autumn 2024

[Downburst]

 FetchCB 150 kmh would soften your cough early autumn.

[WYorksWeather]

 FetchCB 80-90mph gusts inland are still pretty unusual. It would be a notable storm if it verified.

[TSNWK]

 WYorksWeather with trees in full leaf..

Needs to go next run 

 

[Mcconnor8]

 TSNWK

Unsurprisingly it has vanished on the 12z run

[northwestsnow]

Snow showers into NE Iceland

[Neilsouth]

How's sunday looking? I'm seeing different views on how much rain is coming into the south

[WYorksWeather]

 Neilsouth Rain starts in the SE early on and then seems to track generally NW. Eventually, rain reaches some parts of central and eastern England, and Wales as well by early evening. It does look heavy and thundery though, so possible that many areas may see one or more heavy downpours, and other areas nearby may see little or no rain. That's generally the nature of these types of precipitation events.

 

[stodge]

Evening all

A quick skim through the 12Z output and next week will, in meteorological terms, be as similar to this week as chalk and cheese.

Instead of HP dominated dry, settled and pleasantly warm weather, a much more unsettled LP-dominated regime looks set to take over and we end up between Greenland heights and a Scandinavia trough which means a strong NNW'ly flow and maxima even in the south in the low teens with plenty of rain and showers.

Thereafter, which is basically T+168 onwards so well into FI, signs of a return to a more familiar pattern as heights build into central and eastern Europe and drain out of Greenland as the jet gets going, the PV starts getting organised and we get our old friends, the Atlantic SW'lies back.

[Neilsouth]

 WYorksWeather  Much appreciated!! 

[WYorksWeather]

EC clusters below.

Days 3-4

Increasingly unsettled by Monday and Tuesday, and becoming very cool with winds from the north.

Days 5-7

Cluster 1 (45%) keeps the unsettled northerly from day 5-7. There is a close miss with a deep low at day 7, which drops just to our east.

Cluster 2 (29%) is similar to Cluster 1 overall, but the deep low strikes the south of the UK directly. Very unsettled and perhaps stormy conditions.

Cluster 3 (25%) is again very cool and unsettled, but instead tracks the deep low at day 7 over northern England and southern Scotland. Again, very unsettled and perhaps stormy conditions.

The OP was in Cluster 1.

Days 8-10

Cluster 1 (49%) remains very cool at day 8, but gradually shifts the northerly away to the east. Conditions are mixed at day 10, but winds still from somewhere between W and NW so still somewhat cool.

Cluster 2 (29%) has a similar evolution to Cluster 1 but with a flatter westerly by day 10 - temperatures closer to average.

Cluster 3 (12%) shifts the northerly away to the east, and then builds a strong ridge over the UK, albeit centred slightly to the west. Temperatures probably warm-ish by day but with some cool nights given the position of the high.

Cluster 4 (10%) rapidly flattens off the northerly, but keeps low pressure generally in control. As the blocking retreats towards North America, we instead introduce mild or warm south-westerlies. Very unsettled weather continues, regardless.

The OP was in Cluster 1.

Days 11-15

Cluster 1 (43%) has strong heights generally to the south of the UK, with low pressure running over the top. Warm and dry at times in the south, cooler and wetter further north.

Cluster 2 (33%) has a strong high over the UK at day 11 and day 13, which in conjunction with low pressure to the SW likely brings a plume event. Warm or perhaps even very warm for a time, with a reversion to a more typical NW/SE split by day 15, but likely still on the warm side overall.

Cluster 3 (24%) starts with a flat westerly N/S split at day 11, but quickly builds up a ridge of heights ahead of a stalling low in the Atlantic. Very strong heights over the UK and centred just to the east. A notable plume event would be likely - very warm conditions, perhaps even bordering on hot.

Summary

Some very interesting output this evening, to put it mildly. In the shorter range, we know a cool northerly is on the way - temperatures next week dropping well below average. In the day 5-7 range, we need to keep an eye on a potential storm risk around day 7 - all three clusters going for a deep low in the vicinity of the UK at day 7, and two of these show a direct strike. Clearly far too early to speculate on detail, so a case of watching and waiting for now.

Beyond that, the day 8-10 period looks generally quite typical for the time of year - barring one small minority cluster showing a build of high pressure, all other options generally unsettled, and flatten off the northerly to at least some extent, with winds from the NW, W or SW.

In the extended range, it seems like the ECM is picking up on something this evening - after several days with no real trends at all for the extended output, a big flip to very blocked scenarios with lots of high pressure near or over the UK. Some scenarios also feature cut-off lows leading to plume events. Clearly a potential here for very warm conditions at the start of October - best exemplified by Cluster 3 in the extended, which I have to say bears a striking similarity to something like October 2011. Clearly a long way from saying we're on for a repeat of that, but worth keeping an eye on.

Overall, something for almost any weather preference on tonight's output. Within the reliable, we have much cooler conditions next week, with a potential storm risk to keep an eye on. Early October still a fair way off and very much subject to change.

 

[Weather-history]

Worrying rainfall totals across parts of Wales, Midlands and East Anglia

GFS and UKMO

 

 

GEM is further south

Arperge

 

ICON

Edited September 21 by Weather-history

[LRD]

 Weather-history I'm sure it'll be 'downgraded' (or 'upgraded' depending on how you look at it) but that does look a bit damp to say the least

I know the only extreme weather events you're allowed to like on here is baking heat or snow and cold but I say bring that on. Proper active autumn conditions

PS - mods, could you unpin the summer model thread and pin this one, please? In my bleary-eyed state in the mornings I'm clicking on the summer thread without properly checking! Thanks

Edited September 21 by LRD

[Blessed Weather]

8 minutes ago, LRD said:

PS - mods, could you unpin the summer model thread and pin this one, please? In my bleary-eyed state in the mornings I'm clicking on the summer thread without properly checking! Thanks

Done. Thanks for pointing out.

[LRD]

Thanks for doing that BW

This morning's GFS ensembles. Not often you see precip spikes like this for MBY:

In FI the op goes to the warm side of the pack but it's not unsupported

ECM, day 10,, however reverts back to unsettled after a very brief settling down

 

[near northampton]

That is worrying, Cheltenham and Gloucester rainfall was biblical yesterday, a lot of flooding of roads and property, and it's already raining again this morning, will be watching the storm forecasts for today and tomorrow with interest 

[Downburst]

You know what’s strange, my garden is bone dry, north east Leinster. Just shy of 18mm so far this month. If the low in FI doesn’t make it I shall easily have a sub 30mm month. This is the 5th month in a row with about half normal rainfall. April was last wet month above 37 mm. 

So I’m sure October will settle the score
 

Total accumulation ECM for next 180 hrs. 
 

[northwestsnow]

There is a forecast  warming at 10hPa over NE Canada ..

 

[WYorksWeather]

We can clearly still see from the ECM forecast that the polar vortex is struggling at the moment.

It'll be interesting to see if the forecast for a more 'normal' PV into mid-October comes to fruition or not. Until then, I'd continue to expect fairly wild swings in temperatures with increased likelihood of extremes of warm and cold.

[WinterOf47]

This would be one heck of a blizzard if it was mid January!. As it is, Thursday and Friday will be quite the contrast from last few days in the SE where it has hit 23-25 and I have been on the beach every day! Think I'll get the woodburner ready! Hopefully it will be less dramatic as get closer.

[raz.org.rain]

 WYorksWeather potential for some new October warm records? Fingers crossed. Very yo-yo feel to the weather lately.

[Frigid]

 WYorksWeather Hope it stays negative until March, the synoptics currently would've produced some notably cold weather in winter.

[WYorksWeather]

1 hour ago, raz.org.rain said:

potential for some new October warm records? Fingers crossed. Very yo-yo feel to the weather lately.

I mean there's nothing particularly record-breaking showing up in the ensembles. But it certainly wouldn't surprise me if we get another warm spell following the upcoming cold spell.

54 minutes ago, Frigid said:

Hope it stays negative until March, the synoptics currently would've produced some notably cold weather in winter.

Yep it's definitely a case where the same synoptic in even 8 weeks time or so could have been quite interesting. But a long way off from that yet.

Tonight's GFS 12z has the northerly as expected, but then a much more typical Atlantic-driven setup. Five lows in little more than a week from day 8 to day 16, winds from the SW (one potentially stormy at 975mb). Much more of a standard autumn pattern and quite mild south-westerlies overall.

Accumulated rainfall looks very nasty by day 16. Clearly not to be taken too seriously in terms of the exact spread, but clearly the potential there for some very significant rainfall totals in the first half of October if we move into this type of Atlantic westerly pattern.

All a fair way off and only one OP run, so just need to keep watching for now.

[northwestsnow]

EC looks cold back end of next week ...

Edit ,it is !!

 

[WYorksWeather]

 northwestsnow Yep, sweeps the 0C isotherm in, down to -2C or so further north and -4C not too far to the north of Scotland.

Looks quite similar to the last one - short in duration, but fairly notable cold. I wouldn't expect maxima much above low double figures for most areas, and likely fairly widespread ground frost, with air frost for prone spots.

[WYorksWeather]

EC clusters below.

Days 3-4

Low pressure in control, and becoming increasingly cool, through Tuesday and Wednesday.

Days 5-7

Cluster 1 (49%) has a very cool northerly at day 5, which continues up to day 7, slowly progressing eastwards. Unsettled.

Cluster 2 (31%) is similar, but very slightly slower shifting the northerly further east.

Cluster 3 (20%) deepens low pressure with a direct strike on the UK between day 5 and day 6, but is otherwise similar to Clusters 1 and 2 - very cool and unsettled.

The OP was in Cluster 1.

Days 8-10

Cluster 1 (33%) starts with flat westerlies at day 8 after the northerly, but then builds high pressure to the west of the UK. Gradually turning drier, but also fairly cool with winds from the NW.

Cluster 2 (25%) is flat, westerly and unsettled. Cluster 3 (25%) is broadly similar.

Cluster 4 (16%) is also fairly unsettled, but milder with winds from more of a south-westerly.

The OP was in Cluster 3.

Days 11-15

Clearly, very high uncertainty by this point.

Cluster 1 (35%) has high pressure to the NW, and remaining fairly cool and unsettled with winds mainly from the NW.

Cluster 2 (24%) has a flatter westerly, then turns warmer at day 15 as a ridge builds over and to the east of the UK.

Cluster 3 (22%) has cool and unsettled north-westerlies at day 11 and day 13, but then builds high pressure over the UK, but still centred to the west, by day 15. Becoming warmer by day (especially further west) but potentially quite cool by night.

Cluster 4 (22%) has flat westerlies at day 11 and day 13. By day 15 a large area of high pressure is present from Greenland through much of Europe. Overall, warm temperatures would be expected by day at day 15, but depending on the detail, potentially somewhat cool by night.

Summary

In the short term, a clear picture of the overall pattern, with increasingly cool northerlies through next week. There remains a storm risk around Thursday or Friday next week which needs to be watched carefully.

Beyond that, the trend is for a more typical pattern, with wind direction between SW and NW, around the day 8 to day 10 period.

In the extended range, just hints that we might see weather patterns settling down again. It should be noted that by early October we no longer necessarily expect high pressure to lead to warmth - a lot will depend on the detail of the high positioning. A warm period in early October is possible with some of these charts, but predicting it merely based on the presence of high pressure alone is not possible.