Model Output Discussion - heading into April

[Allseasons-Si]

Day ten and del-monte says yes

Edited May 10, 2020 by Allseasons-si

[Mike Poole]

1 minute ago, damianslaw said:

Direction of travel eventual Atlantic driven pattern, look at jetstream profile forecasts beyond 240hrs, yes 10 dats off but show jet taking a more direct flow to the UK on a westerly trajectory, you can see the stirrings in chart above SW flow incoming. Until then lots of fine settled weather. Not saying it will mark the start of a lengthy unsettled spell, but more so after 2 months of little Atlantic weather there are indications it will make a comeback before month is out.

Then I will beg to differ. That won't happen, in my view. 

[damianslaw]

1 minute ago, Mike Poole said:

Then I will beg to differ. That won't happen, in my view. 

Fair enough, I'll be highly surprised though not to see a south west airstream and frontal activity making inroads into west parts before month is out, east holding onto more settled weather. 

[Scorcher]

5 minutes ago, damianslaw said:

Direction of travel eventual Atlantic driven pattern, look at jetstream profile forecasts beyond 240hrs, yes 10 dats off but show jet taking a more direct flow to the UK on a westerly trajectory, you can see the stirrings in chart above SW flow incoming. Until then lots of fine settled weather. Not saying it will mark the start of a lengthy unsettled spell, but more so after 2 months of little Atlantic weather there are indications it will make a comeback before month is out. Someone also mentioned sst profiles favour rapid cyclogensis south of Greenland through summer, ushering in more unsettled weather to the north, less so in the south. Chart above echoes this, deep low formation in that vicinity of Atlantic.

The thing is, if you say something enough eventually it will happen. I'm sure you mentioned this at least a week ago- I still can't see strong signs of the Atlantic taking over.

[Thundery wintry showers]

I tend to agree with Damianslaw, it looks to me as if we're going to get one last high pressure spell (which in fairness may well last until near the end of May), but there are signs for the long term that the high pressure will slowly get shunted away eastwards and allow those lows to start coming in off the North Atlantic.  It's a long way off though, and certainly high pressure looks set to dominate in what's normally seen as the reliable timeframe.

[weathermadbarnsleylad]

Good signs going forward regarding high pressure/warm temps etc. Trying not to get too excited. Will probably have a bit more confidence after a few more runs. It's a fact the Atlantic will eventually come back but when is anybody guess. But until it does I'm gonna enjoy any fine spells we have and the chase for them. 

[Methuselah]

Anywho, this morning's GFS 00Z looks okay at T+240: anything that puts an end to these repeated outbreaks of cold northeasterlies is fine by me!

    

As I work outside, I always welcome T850s of over around 2C...2m temps anywhere between, say, 14 and 30C are fine. But, hey, comfort zones are a personal thing.

    

Stay safe!

[Guest]

Somehow despite it raining only about 4 times in April we managed an average total for the month down here, if May carries on like this that certainly wont the be case. The cold air at the surface takes an age to shift this week but its dry all the way. ECM, GFS & UKMO all pretty similar @ T144 with a 1025mb high building in from the south west. By T240 GFS starts to give way to the Atlantic, ECM however turns into a superb run and would deliver an exceptionally warm second bank holiday weekend. Either all models looking very, very blocked. 

Amazing how our weather patterns appear to have definitely shifted to getting to a scenario where we get 'locked in' (excuse the term) to either a full blown Atlantic onslaught or a completely blocked setup, with very little in between. Normally this amount of high pressure in Spring would have me fearing for summer, however I'm starting to feel more confident that at least the first half of summer could be , dry, warm and sunny, but lacking in the plume department, as we've come to expect maybe not the best August yet again?

[Frosty.]

Another cracking ECM 0z operational, preety much as recent runs and a lovely day 10 with power to add..no sign of the atlantic!!

[I remember Atlantic 252]

10 minutes ago, JON SNOW said:

Another cracking ECM 0z operational, preety much as recent runs and a lovely day 10 with power to add..no sign of the atlantic!!

Unusual for the Atlantic in charge now, April and May, early June, Atlantic air seems rare

[mb018538]

 

NOAA 8-14 day looks similar too. Perhaps runs this morning not quite as exceptional as the 12z last night, but they still look very decent.

[shaky]

Gfs 06z better and extends the high further north and west at 210 hours!!summer incoming ?

[Zak M]

Incomingggg!! 

      

[weathermadbarnsleylad]

I think the gfs00z had an hangover this morning. But it's 6z brother as shown us the way. High pressure and warmer is the trend. 

[Guest]

GFS 06Z Ops run far more closely aligned with the ECM Ops run from earlier @T240. The chances of lengthy dry and increasingly warm spell appears to increasing. Be interesting to see where this sits in the ensemble grouping, would have been a big outlier in the output just 6hrs ago, will there be a shift in the ensemble grouping post T168.

[Man With Beard]

Just one cluster after D7 this morning on the ECM, but from a quick look through the individual ensembles, the cluster looks reasonably representative. It basically translates into a UK high around D7-D10 (I share some concerns as others, that this looks susceptible to flattening), and then this high retreats slightly west or north as we head towards D12/D13. However, few ensemble members allow a renewed long-fetch draw from the north or build a trough to the east to any great extent, and so on most runs the warmth built up between D7 and D10 is moderated quite slowly. The Atlantic continues to look stuck back west. In general, a good probability of lots of fine days with maximums 18C-25C in the second half of May, east coast regions might get pegged back as the period goes on. 

  

[Singularity]

It's an interesting situation, as the Arctic loses the last of its deeply cold air this week but not into regions that encourage broad and deep Atlantic lows to develop and trouble us.

So we're left with a weaker than usual temperature gradient in the North Atlantic, hence the very 'stuck' weather pattern with little attempt by lows to advance from the west. Even GFS, with its progressive bias, is unable to achieve that convincingly without relying on a large movement of relatively cold air into the N. Atlantic from Arctic parts of Canada. That being a plausible but not likely scenario (a lot has to fall into place).

Cold air is often released from the Arctic in May, as the polar vortex breaks down. For this reason, it has historically tended to be a more westerly-dominated month than April. 

For a few years now, the cold air release has largely avoided the North Atlantic in favour of Europe and/or the USA, allowing for more fully-anticyclonic or easterly weather in May. If the next few behave similarly, that will raise eyebrows. At the moment we can't tell if it's a new climate trend or a fluke of natural variability.

As heat builds to the south, changeable westerlies become harder to avoid in June without major driving forces working in favour of subtropical ridge displacement north-eastward from the Azores.

[Djdazzle]

7 minutes ago, Singularity said:

As heat builds to the south, changeable westerlies become harder to avoid in June without major driving forces working in favour of subtropical ridge displacement north-eastward from the Azores.

Do you think that will be the case this year?

[Djdazzle]

7 minutes ago, Singularity said:

As heat builds to the south, changeable westerlies become harder to avoid in June without major driving forces working in favour of subtropical ridge displacement north-eastward from the Azores.

Do you think that will be the case this year?

[DTHFCJ]

I spy a cheeky 30c bring it on!!

[MP-R]

8 minutes ago, Djdazzle said:

Do you think that will be the case this year?

It might be if we keep having cold air coming down from the north at the same time. Unlikely though in my opinion. It’s more of a problem later in the summer when the jet traditionally moves south again.

 

[Kirkcaldy Weather]

@Singularity an interesting situation indeed have just posted in Scotland thread looks like another snow chance (didn’t expect to say that in May but here we are ) as colder 850s move south again through tomorrow possibly -10 850s in N / NE Scotland again, also New York had snowfall of 9 inches in parts a few days ago and many cold temperature and snow records tied and broken over there and looking at wrf eu looks like various snow chances across Scandinavia in coming days and repeatedly showing quite a bit of snow up toward Lapland at end of run thanks to colder air circulating a low pressure up there all very fascinating for the time of year  

[mb018538]

27 minutes ago, MP-R said:

It might be if we keep having cold air coming down from the north at the same time. Unlikely though in my opinion. It’s more of a problem later in the summer when the jet traditionally moves south again.

 

I take it you mean the ‘formerly known as summer month’ August?

[MP-R]

26 minutes ago, mb018538 said:

I take it you mean the ‘formerly known as summer month’ August?

Absolutely. Augtumn... lol.

[ribster]

13 hours ago, Scorcher said:

The thing is, if you say something enough eventually it will happen. I'm sure you mentioned this at least a week ago- I still can't see strong signs of the Atlantic taking over.

Yes indeed Scorcher, if the cap fits eh?