Model output discussion - 1st December onwards

[Summer Sun]

Could this be storm Frank?

UKMO for the same time

Edited December 23, 2015 by Summer Sun

[nick sussex]

Some changes now showing up on the ECM 12hrs run compared to the 00hrs.

That lobe of high pressure in the Arctic and its moving towards a positive PNA. Its still reluctant to let go of high pressure to the south but this is still a vast improvement on its 00hrs run.

It shows you just how bad the outputs have been when tonights ECM is a big improvement on this mornings!

 

 

 

Edited December 23, 2015 by nick sussex

[Catacol]

6 hours ago, IDO said:

A 

The BOMM, which was one of the first LR MJO models to pick up the amplified Phase 6 and 7 are now moving away from that. So it is difficult to know how any MJO signal will manifest with the ENSO background noise.

Serious question - why on earth would you go with BOMM as an indicator of potential MJO development? That wild array of squiggles from its members is exactly why I wouldnt give it the time of day. Much more significantly the ECM is more solid of a transition through into phase 7 and towards phase 8 with much less disarray

 

[Captain Shortwave]

Well the ECM also joining in on the stormy outputs.

Some very high gusts over Northern Ireland primarily, but Scotland would face its wrath by the evening.

Some seriously high 850s possible too with the 30th potentially looking like another exceptionally mild day.

This adds to Boxing day which is already forecast to see temperatures again in the mid-teens potentially, 850s of +12C across the south east, if the ECM verified we would be looking at 16/17C widespread potentially which would put us very close to a final CET of 10C.

GFS for Boxing day

 

We may just may see more normal temperatures as we hit New year though with the first couple of days looking rather chilly in a westerly flow.

[nick sussex]

21 minutes ago, Catacol said:

Serious question - why on earth would you go with BOMM as an indicator of potential MJO development? That wild array of squiggles from its members is exactly why I wouldnt give it the time of day. Much more significantly the ECM is more solid of a transition through into phase 7 and towards phase 8 with much less disarray

 

Heres another version of the MJO , its been smoothed out to reduce interference.

I don't normally link to anything with CFS in the title but I liked this forecast! lol

 MacRitchie explains below the reasoning behind this MJO version.

This is modeled after the Wheeler and Hendon (2004) RMM phase space and is most similar to a similar approach that I’ve written about in MacRitchie and Roundy (2012). This approach uses the CFS MJO projections, as used in other figures on this website, to track the MJO. This results in a smoother signal than the WH04 index with less interference from other modes.

I've just put up the abstract of the study.

Previous works have shown that most of the rainfall embedded within the Madden–Julian oscillation (MJO) occurs in large eastward-moving envelopes of enhanced convection known as super cloud clusters. Many of these superclusters have been identified as convectively coupled Kelvin waves. In this work, a simple composite-averaging technique diagnoses the linear and nonlinear contributions to MJO potential vorticity (PV) structure by convection collocated with Kelvin waves. Results demonstrate that PV is generated coincident with active convection in Kelvin waves, but that this PV remains in the environment after Kelvin wave passage and becomes part of the structure of the MJO. Analysis of the Tropical Rainfall Measuring Mission (TRMM) rainfall suggests that 62% of the total rainfall within the MJO occurs within the active convective phases of the Kelvin waves (88% higher than the rain rate that occurs outside of the Kelvin waves), supporting the hypothesis that diabatic heating in cloud clusters embedded within the Kelvin waves generates this PV.

I'm not sure if you followed some of the debate re the MJO versus Kelvin waves, the above might go some way to explaining some of the interplay between the MJO and Kelvin waves.

Edited December 23, 2015 by nick sussex

[Dorsetbred]

4 hours ago, mulzy said:

We can say with some confidence that the broad westerly / south-westerly flow is expected to continue in the medium term - the NAEFS 16 day anomaly chart illustrates this perfectly.

 

 

 I wonder what odds the bookies would give me on the warmest winter ever recorded?

 

 

 

Do it, you have a better chance at that right now than anything, make some money...

[mountain shadow]

23 hours ago, chrisbell-nottheweatherman said:

27 minutes ago, Catacol said:

Serious question - why on earth would you go with BOMM as an indicator of potential MJO development? That wild array of squiggles from its members is exactly why I wouldnt give it the time of day. Much more significantly the ECM is more solid of a transition through into phase 7 and towards phase 8 with much less disarray

 

The composists for phase 8 and 1 in January normally correspond with blocking over Greenland. Why isn't this showing in any output if the MJO is forecasting phase 8?

[nick sussex]

2 minutes ago, mountain shadow said:

 

Good question. I think for the timebeing we're going to have to sit tight and see what the NWP response will be. So far the MJO composites have fitted well with each phase.

If the positive PNA sets up then the amplitude of that eastern USA troughing will determine the movement of the Azores high. Do you remember the time when we used to see northerly topplers? I say that because a true Arctic northerly toppler hasn't been since I could fit into a 34w pair of jeans! lol I think trying to dislodge that PV for a lengthy period of time is going to be difficult however if the MJO can help us then we would have a chance of some nw/n flow. The response to the MJO isn't an exact science, we can just keep our fingers crossed. I just want rid of that Euro high which is seriously getting on my wick now.

[bluearmy]

The Alaskan ridge has been well advertised on the extended modelling for a while.  It doesn't seem to have any effect downstream. re the east Atlantic and Europe. 

[Man With Beard]

I'm still tracking the possible effects of the height rise over Scandi next week. The ECM tonight quickly squashes heights in that region, but the spike in heights still gets into the pole eventually. Leading to this:

Looks to me like Arctic air will pour into Canada/eastern US on this - becoming PM air for us 5-7 days later?

Anyway it's just one run, one possibility, but it just shows how this little rise in heights over Scandi could be significant later on.

[Liam J]

Don't really understand the MJO very much, if it reaches phase 7/8 is that good news? And does this guarantee the UK a certain pattern or could we potentially carry on with the same entrenched pattern we've seen much of December? 

[nick sussex]

6 minutes ago, bluearmy said:

The Alaskan ridge has been well advertised on the extended modelling for a while.  It doesn't seem to have any effect downstream. re the east Atlantic and Europe.

How can you say that it won't at some point? A positive PNA if it came with an amplified eastern USA trough would change the pattern as it would draw the Azores high further west. I think we should keep an open mind to see what plays out re the MJO. At this point I'd just be happy to see the removal of that Euro high.

[The Enforcer]

5 hours ago, mountain shadow said:

No sign of any Northerly blocking but definitely more wintry with more Pm incursions over the next two to three weeks.

850s of -5 will be more of a visitor giving increased snow chances over high ground in the North and West. 

Any Northerly blocking does not now look likely in January either. 

Only if model output can be trusted out to T+936. Also, it's surely far too early to dismiss the Net-Weather Winter Forecast?

[The Enforcer]

21 minutes ago, nick sussex said:

At this point I'd just be happy to see the removal of that Euro high.

Amen to that.

[ANYWEATHER]

Evening all , Looks quite concerning weather between Christmas and New Year, not only with rainfall but with some disruptive stormy winds. It comes to no surprise that this outcome is showing on the operational models, in one way or another its been showing for some time and given the northern hemispheric pattern at the moment with a very strong jet stream and a very strong temperature gradient across the Atlantic, perfect for some very stormy conditions. One thing which may be on a plus side is that it will feel more seasonal than of late with cold air in the mix so a more traditional feel for this time of year, Batten down the hatches everyone......

[phil nw.]

53 minutes ago, bluearmy said:

The Alaskan ridge has been well advertised on the extended modelling for a while.  It doesn't seem to have any effect downstream. re the east Atlantic and Europe. 

It will help to re-enforce the influence from the Greenland trough though Blue.A vortex displacement towards our side of the Arctic forcing the jet further south across our shores.An even more unsettled spell into the new year unfortunately.

We may see temperatures dropping to more seasonal levels in another week or so but by god some areas which are already suffering will see a lot more rain.I do feel for them.

[The Enforcer]

28 minutes ago, ANYWEATHER said:

One thing which may be on a plus side is that it will feel more seasonal than of late with cold air in the mix so a more traditional feel for this time of year, Batten down the hatches everyone......

The benchmark for cold air seems to be the 850 0C isotherm. I don't know if anyone summarises each month on here, but that chart is a pretty good summary of December 2015, which with a few annotations could represent practically any December day:

Edited December 23, 2015 by The Enforcer

[JOPRO]

Surely this is a barttlet set up? We seem trapped in disgustingly mild air, with that dam high pressure eating up our winter. If it looks like a pig,smells like a pig and goes oink.......!!

 

 

 

 

 

 

[BLAST FROM THE PAST]

Hi Team

Just a pop in and bear with me as I'll be editing too.  I know Eva is coming, I know my middle cold didn't work out but something I did mention was a stormy New Year.  Now this is a tad worrying as Eva is just a warm up if this happens, and there has been plenty of hinting in the models so we must watch it

ruddy nora!

 

This ain't cricket.....That is a massive double whammy folks....watch zone

 

BFTP

Edited December 23, 2015 by BLAST FROM THE PAST

[bluearmy]

In case I wasn't clear  with my previous post, I should clarify that the Alaskan ridge, whilst now showing in the output,(and having done so for some time),  doesn't generate much difference downstream in the current extended modelling.  of course that modelling could be wrong but the generally strong +NAO signal persists if you are prepared to accept the output.

[tinybill]

22 minutes ago, BLAST FROM THE PAST said:

Hi Team

Just a pop in and bear with me as I'll be editing too.  I know Eva is coming, I know my middle cold didn't work out but something I did mention was a stormy New Year.  Now this is a tad worrying as Eva is just a warm up if this happens, and there has been plenty of hinting in the models so we must watch it

ruddy nora!

 

This ain't cricket.....That is a massive double whammy folks....watch zone

 

BFTP

very worrying  for the  nw  of the  uk  if the  models are  right

[Cloud 10]

1 hour ago, nick sussex said:

Good question. I think for the timebeing we're going to have to sit tight and see what the NWP response will be. So far the MJO composites have fitted well with each phase.

If the positive PNA sets up then the amplitude of that eastern USA troughing will determine the movement of the Azores high. Do you remember the time when we used to see northerly topplers? I say that because a true Arctic northerly toppler hasn't been since I could fit into a 34w pair of jeans! lol I think trying to dislodge that PV for a lengthy period of time is going to be difficult however if the MJO can help us then we would have a chance of some nw/n flow. The response to the MJO isn't an exact science, we can just keep our fingers crossed. I just want rid of that Euro high which is seriously getting on my wick now.

 

MJO phase 8 composite for January looks a bit of a stinker...

 

 

Phases 7 and 1 i could live with though.

 

7...1...

[lorenzo]

That's a helluva stormy approach to New Years on tonight's 12z !

Then, this extreme evolution

Unsurprisingly the clustering highlights the uncertainty in evolution.

Fingers crossed this one bombs in the atlantic and gets stuck there.

[BLAST FROM THE PAST]

Just now, tinybill said:

very worrying  for the  nw  of the  uk  if the  models are  right

All of us as well if that comes off Tiny

 

BFTP

[chrisbell-nottheweatherman]

11 minutes ago, lorenzo said:

That's a helluva stormy approach to New Years on tonight's 12z !

Then, this extreme evolution

Unsurprisingly the clustering highlights the uncertainty in evolution.

Fingers crossed this one bombs in the atlantic and gets stuck there.

Is a central pressure of 925mB even possible in the UK?  What sort of windspeeds might we expect with something that powerful?