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Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

 Daniel*

UKV is broadly similar I think - perhaps not quite as cold . Cold limited to Scotland and Northern England early tomorrow and Tuesday, then some pretty cold nights across all area beyond that. Friday morning looks the coldest. As you say air frost is possible in some areas - UKV is unlikely to pick out frost hollows and other local features.

image.thumb.png.d1a9870b3bb8c573b82cf9e826edb508.pngimage.thumb.png.e054155603e7476929f5740acfaac9ff.pngimage.thumb.png.7adafef720c03db1bbfce460e86deb86.pngimage.thumb.png.52e20a1c0874b9cef4d048e202da79a9.pngimage.thumb.png.5a56410009fd01b6e599065625357d21.png   

 Frosty. T+2598 - just outside the reliable timeframe. Not to be taken too seriously at this stage. More runs needed 😀

  • Like 3
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted (edited)

EC clusters below.

Days 3-4

Northerly still in control on Wednesday and Thursday - (very) cool and unsettled.

image.thumb.png.69e26777fceba29559ca5a4c6f4904ad.png

Days 5-7

Cluster 1 (29%) has high pressure moving in from the west on Friday (day 5), then building over the UK. Wind direction is westerly or south-westerly. Warm by day, but probably somewhat cool by night.

Cluster 2 (27%) builds high pressure in from the west at day 5 and day 6, but by day 7 a secondary low drops in over the UK so turning more unsettled. All fairly westerly and unremarkable temperature-wise.

Cluster 3 (20%) also builds high pressure from the west at day 5, and sustains it up to day 7. Warm with winds from the SW.

Cluster 4 (16%) builds high pressure in from the west, and by day 7 this is a strong build of pressure with an extension from the mid-Atlantic up to Scandinavia. Warm, perhaps becoming very warm by day 7 as the wind direction shifts to an easterly.

Cluster 5 (8%) has a very messy pattern. Fairly warm with winds from the east, but the trough to the SE is close enough to bring some showers.

The OP was in Cluster 1.

image.thumb.png.9552a68e92045a7f930347fdae0ebfcb.png

Days 8-10

At this point, tropical developments are likely to become more significant - we are now expecting at least two tropical cyclone formations in the next 7 days. Hence, uncertainty is higher once again.

Cluster 1 (43%) has high pressure centred to the west of the UK at day 8 with mixed conditions for the UK itself. This high gradually moves eastwards and strengthens, leaving the UK under a broad area of high pressure covering much of northern and western Europe. Warm or very warm. The tropical storm visible on the bottom left of the chart should be noted.

Cluster 2 (33%) has strong high pressure over and to the north and east of the UK from day 8-10. A low to the SE aids in pumping heat. Warm easterlies or south-easterlies.

Cluster 3 (24%) has low pressure over the UK at day 8, but then builds the Azores high in from the SW. Becoming warm with south-westerlies.

The OP was in Cluster 2.

image.thumb.png.33a2e82bac1aa6cf332e8313c6887cd5.png

Days 11-15

Read the comment I put above about day 8-10, but doubly so for this look at the extended range.

Cluster 1 (41%) has a NW/SE split at day 11 and day 13, though the more unsettled side of the split is really limited to the far NW of the UK. Overall warm with winds from the SW. By day 15 high pressure pulls out into the Atlantic turning things cooler and more unsettled more widely. Winds from the NW. Note the tropical cyclone on the left of the chart.

Cluster 2 (39%) has high pressure generally centred to the north of the UK from day 11-15, but in control over the UK as well. The orientation of the high brings warm easterlies or south-easterlies. Consistently warm, perhaps very warm. Dry.

Cluster 3 (20%) has high pressure centred just NW of the UK at day 11. Warm but probably cool by night. Moving towards day 15, high pressure moves further NW, eventually leaving eastern areas in particular exposed to a cool or very cool northerly. Still dry though up to day 15 as the high is still in control. As with Cluster 1, tropical storm developments on the left of the chart should be noted.

image.thumb.png.77cc414a9d066c0b44c8c808c314e4c9.png

Summary

Confidence about the coming week now appears to be relatively high. Almost all models show northerly winds dominating until around Thursday or Friday, before high pressure moves in. Most of the ensemble keeps the settled weather through the weekend, though about a third does turn a bit messy with secondary lows.

Everything beyond that, though, comes with huge caveats. Tropical cyclone development now looks very likely over the next few days. By day 8 and beyond, modelling is trying to forecast the position and strength of cyclones that don't even exist yet, and could have huge implications for our weather going forward.

With that being said, at this stage, modelling is generally in favour of dry outcomes at day 8-10, though with some disagreement over whether the wind direction is more of a warm south-westerly or a possibly very warm easterly.

In the extended range, again with even more caveats, modelling does become a bit more split. Roughly speaking, 40% warm and dry with winds from the SW before a cool northerly. Another 40% is consistently warm and dry. The final 20% is a cool high, potentially becoming quite cold towards the end with a northerly. In short, not much of a signal, which is expected given the tropical uncertainty.

The key point is that this upcoming week is fairly clear. The following week is enormously uncertain and will remain so for some time.

 

Edited by WYorksWeather
  • Like 2
  • Thanks 3
Posted
  • Location: Farnham, Surrey
  • Weather Preferences: Cold, Sunny and Dry with a Hard Frost.
  • Location: Farnham, Surrey
Posted

I was looking through the Fax output for the coming week, when this particular image struck me. There are fourteen separate pressure systems on this for the coming Friday. That's pretty impressive for the size of the area covered on the map. There probably has to be an upper end to the number of featured pressure systems that can actually fit into the north Atlantic basin and western Med. Anyway, just something that caught my eye......

image.thumb.png.847cd0a12f43b3fd7db22f4e170c2639.png

  • Like 9
Posted
  • Location: Ireland - East Coast
  • Location: Ireland - East Coast
Posted

@Cambrian many thanks for that analysis. 

On the Operational runs, I must say as crazy as it is to be looking at day 10, the ECM and GFS are in some agreement, low heights south central europe and reasonable robust heights in Scandi with link into or about these parts. Chance of an EX Tropical storm entering the fray too. So after this short polar inclusion perhaps a chance of more pleasant September weather for a while

ECM

image.thumb.png.3d8514832a21985fb2d028f21eea115b.png

GFS

image.thumb.png.f5fbad251850b9f0ac786afdf18595dd.png

 

Now in saying that the low heights to the north and north west, and fresh after reading Cambrians observation, the likely hood is perhaps that we get deeper lows and a failure to link any Azores ridge with Scandi heights, a story of the summer just gone.

Like this image, would that low probably be lower, to the north west of Ireland.

image.thumb.png.a51ed7c8da92a6bfc1114b3f24ab6030.png

  • Like 4
  • Thanks 1
Posted
  • Location: Northern Ireland
  • Weather Preferences: Proper winter/Proper summer
  • Location: Northern Ireland
Posted

 Cambrian this is an excellent post which explains so well why so many  times this Summer optimism was replaced by gloom.

  • Like 3
  • Thanks 1
Posted
  • Location: Southern Finland, Nurmijärvi or Northern Savo.
  • Location: Southern Finland, Nurmijärvi or Northern Savo.
Posted

 Downburst is this something like 2010 July, but too late in the season. 

Posted
  • Location: Chessington, Surrey
  • Weather Preferences: Snow, Hot and Sunny but not opressive
  • Location: Chessington, Surrey
Posted (edited)

Quite happy with the UKMO so far and especially the Gem . GFS is tricking out late on meteociel.

would be nice to have a nice settled spell in mid September.

 

E01BCE2F-547E-4414-9DA8-648FF26029D5.png

 

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Edited by Mr Marky Marky
  • Like 6
Posted
  • Location: Lancing
  • Weather Preferences: Sun, Snow and Storms
  • Location: Lancing
Posted (edited)

image.thumb.png.5df201a5a2b003b0f5e5999c66f41592.png

image.thumb.png.8505c99dc16864cd41d009e1ec526953.png

We've been here before this Summer to see it watered down, very nice from the GEM as well today.

Edited by Mcconnor8
  • Like 2
Posted
  • Location: Chessington, Surrey
  • Weather Preferences: Snow, Hot and Sunny but not opressive
  • Location: Chessington, Surrey
Posted

No no no ECM , don't you dare !!! 

AED2A75F-EBF7-40BC-AC79-BEC198C3C5A5.png

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  • Like 2
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

 Mr Marky Marky It does get to a solid high in the end, but not until day 9 and 10. Always irritating to see high pressure pushed back.

image.thumb.png.344d42975cbb3837f326455e2ff73983.pngimage.thumb.png.3762703f603633e4d91581465a3be6da.png

However, the resulting plume does look quite interesting for the time of year.

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  • Like 1
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

Latest UKV shows some very cool nights over the next few days - Friday morning definitely qualifies as cold! Air frost possible for some upland spots and a widespread ground frost in northern England and Scotland.

image.thumb.png.2748f3ca3f19473c1c1bec56c978c45e.pngimage.thumb.png.82e1fa24940b513fc7ee42ece308431d.pngimage.thumb.png.9ae56517be1795b03de027e2d18a2788.png

Milder air returns by Saturday morning.

image.thumb.png.27a37f8e76d9f7a8c0b87ce576728c37.png 

  • Like 1
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

EC clusters below

Days 3-4

Northerly winds on Thursday. High pressure beginning to move in from the west on Friday.

image.thumb.png.be6b667da4fccbdd1cd795fc1609922a.png

Days 5-7

Cluster 1 (29%) has high pressure on Saturday (day 5). By day 6, a trough moves in from the north and leaves fairly mixed conditions. By day 7, high pressure is to the west, north and east, but conditions for the UK remain fairly fixed.

Cluster 2 (27%) also shows high pressure at day 5, but makes less of the trough at day 6, which passes mostly to the north of the UK. High pressure quickly rebuilds across the UK by day 7.

Cluster 3 (20%) has a stronger high at day 5. Low pressure at day 6 makes very little impact except perhaps in the far north. By day 7, the high rebuilds strongly, bringing fairly warm south-westerlies.

Cluster 4 (16%) has an extension of heights from the Azores to Scandinavia through the UK consistently from day 5-7. Warm and dry.

Cluster 5 (8%) is similar to Cluster 1 in that it is settled at day 5, but then makes more of the low pressure at day 6, and conditions remain mixed at day 7.

The OP was in Cluster 1.

image.thumb.png.ef41ef77f51e11c8bc4851b5efd3b2fb.png

Days 8-10

Increased uncertainty from this point due to tropical developments.

Cluster 1 (47%) has strong high pressure at day 8-10. A low to the SE likely aids in bringing warm air to the UK from the SE. Warm, perhaps very warm. Note the tropical feature at the bottom left of the chart.

Cluster 2 (29%) starts with a mixed and flat westerly setup at day 8. A ridge builds from the Azores at day 9, but it is transient and by day 10 conditions are fairly mixed again. On the dry side overall though, and fairly warm.

Cluster 3 (24%) has a very strong high over the UK and centred just to the north and east of the UK. Likely very warm.

The OP was in Cluster 1.

image.thumb.png.f2e00bf6ace946f2a0372656f813d63a.png

Days 11-15

Even more uncertainty of course by this point.

Cluster 1 (39%) has warm easterlies  at day 11 and day 13, with low pressure held fairly static to the west. However, at day 13 a deep low sits in the Atlantic just to the west - unclear whether it strikes the UK between day 13 and day 15. Generally continuing fairly warm though, with a lot of easterlies, which are still reasonably warm at this time of year.

Cluster 2 (29%) has very warm south-easterlies at day 11, before high pressure starts to retrogress at day 13, potentially introducing cooler air from the NW, though a complicated pattern with low pressure to the east likely keeping southern areas fairly warm. By day 15 we have high pressure directly over the UK again - warm by day and cool by night.

Cluster 3 (24%) has a strong high over and to the east of the UK at day 11 and day 13. Warm, perhaps very warm. By day 15, signs of a more typical N/S split setting up with a flat westerly.

Cluster 4 (8%) has the Azores high into the south at day 11 with south-westerlies. A complex pattern at day 13, with high pressure to the south possibly keeping southern areas fairly warm, but the orientation of the high likely exposes northern areas to a cool or very cool northerly. By day 15, the pattern reverts to a south-westerly, with fairly warm and dry conditions in the south closest to high pressure, but cooler and more mixed in the north.

image.thumb.png.3f4ed4cf844017240b4aa1812ad80fa6.png

Summary

The day 5-7 period has suddenly got a bit more uncertain again - some differences in how much is made of a trough passing close to the north of the UK around day 6. The ECM OP was on the more unsettled side, along with about a third of the ensemble. The other two-thirds made much less of the low, having it both weaker and further north, meaning very little impact for the UK.

Beyond that, the day 8-10 period is pretty uncertain due to tropical developments, but at the moment it does look fairly warm and dry with lots of high pressure around.

In the extended, which is of course even more uncertain, perhaps support for some rapid switches in weather conditions. Plenty of options showing a continuation of warm and dry conditions, whereas others see high pressure retrogressing and become significantly cooler again.

Overall, a very cool few days to come, but then the pattern is mainly high pressure dominated according to the majority of the ensemble..

  • Like 4
Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
Posted
12 hours ago, Cambrian said:

Notice too that at both timeframes we get regions predicted to have above normal heights and below normal pressure e.g. US Midwest at day 2. Now that might be a better candidate for being a climate change signature i.e. despite below average surface pressure, there is so much warmth in the atmosphere between the surface and 500mb, that the geopotential height can be above normal. It’s reasonable to speculate that the reference long term heights averages may well be adjusted in time to accommodate this warming-related upward drift and to more accurately reflect the heights that are these days in reality associated with just below average surface pressure.

This is an important point.  When I look at the seasonal model output, one regularly finds above average 500 hPa height anomalies pretty much everywhere nowadays, simply due to the world being warmer now.  These are starting to give a misleading picture of what the weather might actually be like on the ground, so while I might be most interested in the heights averaged over a month or 3 months from the seasonal models, I always check the surface pressure anomaly charts as well, because these are not affected by the warming world that affects the heights.

Anomaly charts are easily misinterpreted anyway, so we are rather overdue an update in the averages they are based on for the 500 hPa charts.

  • Like 1
  • Insightful 1
Posted
  • Location: Wilmslow, Cheshire
  • Location: Wilmslow, Cheshire
Posted

 Coldilocks Temperatures barely getting into the teens are not at all normal in the first half of September. Much more normal to have 20C+ temps.

  • Like 6
  • Thanks 1
Posted
  • Location: London
  • Weather Preferences: Warm Springs/Summers, Chilly Autumns , Cold Winters
  • Location: London
Posted

 Scorcher Last year we got 7 days of 30c+ weather in September and that's not normal.

  • Like 2
Posted
  • Location: Longden, Shropshire
  • Location: Longden, Shropshire
Posted

 Scorcher Whilst this week will certainly see below average temperatures for all, I think perhaps we have got used to September being an extension of summer in more recent years, rather than early autumn?  This September is looking to perhaps be more 'variable' with warm summer like periods alternating with cool autumnal spells?

  • Like 5
Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl
Posted (edited)

An interesting outlook synoptic wise, not the normal westerly atlantic flow dominating. A chilly NW flow next few days, significantly below average.

The weekend sees a ridge try to topple in but some form of trough feature could produce some rain in the NW.

Next week forecast is for heights to the east to build west with heights over the UK, either an easterly or southerly flow looks likely with the atlantic trough held out west.

If this was winter it would be a very wintry outlook,heavy snow showers, severe frosts then a snowy breakdown, brief thaw then possible very cold continental airflow. Alas its September and will bring a swing from cold to warm. 

 

Edited by damianslaw
  • Like 4
Posted
  • Location: Home: Chingford, London (NE). Work: London (C)
  • Weather Preferences: Winter: cold and snowy. Summer: hot and sunny
  • Location: Home: Chingford, London (NE). Work: London (C)
Posted

Well if anyone else feels a shock this morning at how cold it is for mid September, and longs for a return to some dry and sunny weather, then the models this morning should cheer you up. 

Very chilly for the next few days, showery for many, before high pressure builds back in on Friday and looks to sustain. Could become very pleasant indeed if these charts verify. 

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