Model Output Discussion 1st Nov.2013

[nick sussex]

So in terms of the uncertainty upstream heres the latest update from NOAA, for newbies I've highlighted the important bits that have a big knock on effect in Europe:

 

THERE IS GENERAL AGREEMENT WITH GUIDANCE SHOWING DISTINCT NRN ANDSRN STREAM FLOWS TRANSPORTING AMPLE HEIGHT FALLS/TROUGH ENERGYALOFT AND COLD AIR INTO WRN NOAM THIS WEEKEND IN AN AMPLIFYINGPATTERN.  FORECAST CONFIDENCES WANE BY EARLY NEXT WEEK WITH THESEPIECES OF ENERGY AND SURFACE REFLECTIONS AS EMPHASIS AND PHASINGPOTENTIAL BECOMES INCREASINGLY VARIED WITH MAIN MID-UPPER LEVELMEAN TROUGH PROGRESSION OUT TO THE EAST-CENTRAL US.  THIS INCLUDESTHE HANDLING OF SIGNIFICANT CANADIAN COLD AIRMASS SURGES DOWNTHROUGH THE CENTRAL THEN ERN US IN A QUITE WINTERLIKE FLOW PATTERNFOR MUCH OF THE NATION.THE WEST WILL COOL AND BECOME INCREASINGLY UNSETTLED INTO THEWEEKEND WITH DIGGING IMPULSES SPREADING QPF INCLUDING SOME LOCALLYHEAVIER TERRAIN ENHANCED SNOWS WITH APPROACH/PASSAGE.  THEDOWNSTREAM TIMING OF MAIN FRONTAL PUSHES THIS WEEKEND AND EARLYNEXT WEEK...ASSOCIATED PERIODS OF ENHANCED POST-FRONTAL UPSLOPEFETCH AND LEAD FOCUS FOR ORGANIZED AND LOCALLY HEAVIERRAINS...SOME WRAP-BACK NORTH-CENTRAL US SNOWS AS DEEPER MOISTUREFEEDS EVER INLAND FROM THE GULF OF MEXICO AND FURTHER DOWNSTREAMINTO THE SRN/SERN US ALSO FROM THE ATLANTIC...WILL LIKELY FLUXUATEOVER THE COMING DAYS UNTIL GUIDANCE SETTLES IN BETTER WITH SUPPORTSPECIFICS.  THE ECMWF HAS BEEN RECENTLY PROMOTING A DEEPER COLDINFULTRATION THAN THE THE CANADIAN/UKMET AND TO A LESSER EXTENTTHE GFS.  WHILE COLD AIR OFTEN WINS IN THESE TYPES OFPATTERNS...FORECAST SPREAD DOES OFFER SOME REASON TO QUESTIONECMWF EMPHASIS.  ACCORDINGLY...PREFER A SOLUTION BLENDING THEQUITE COMPATABLE 06 UTC GFS ENSEMBLE MEAN AND 00 UTC ECMWFENSEMBLE MEAN THAT TRENDS WPC FORECAST SUITE GUIDANCE WELL IN THISCOLDER DIRECTION...BUT NOT TO THE MAGNITUDE OF THE ECMWF. 

So we have that amplified pattern upstream which is one tick for cold, the more south that cold air digs into the USA the more amplified the pattern is, basically you cant have that transport of cold with a flat jet, the American forecasters are still a bit dubious to the amplification shown by the ECM but have used that blended solution to go for a bit more amplification than shown by the UKMO/GEM/GFS. Because of some uncertainty with phasing this adds another difficulty regarding low pressure moving east so we have to assume that we will see some changes to both amplitude and depth of any low pressure.

 

I should add this update doesn't include tonights models, we may well see a different tune tomorrow regarding which model to follow from NOAA.

 

PS! Does anyone have a link for the ECM postage stamps? My current link says no access, when it was working fine a few days back, not sure perhaps the scrooges at ECM have pulled this free sample.

Edited November 12, 2013 by nick sussex

[The PIT]

LOL everybody getting over excited and some getting over aggressive over deep FI charts that may or may not happen. Happens every year. Still it's nice to have a bit of polar vortex. Possibly.

 

[Frosty.]

I think the Ecm 12z op is a peach of a run from early next week onwards, a decent cold plunge south of arctic air, a risk of snow in places, especially the north and over hills but wet snow to low levels in the heavier ppn, widespread frosts with max temps well down into low single digits celsius and soon turning sub zero during the evenings with widespread sharp frosts as time goes on. Later in the run, although we lose the very cold uppers, we retain surface cold with more frost and probably fog, after a few days of high pressure at the end of the run I can imagine another reload of cold from the northwest soon after.

[tinybill]

all i say  if this happens  this place  will go   into melt down!!

[Summer Sun]

Latest from Gibby, colder for a time then becoming milder in the north?

 

All models shows the UK under a ridge of High pressure with light winds and frost overnight. Tomorrow will see the ridge cling on over the South while freshening Westerly winds bring rain and strong winds into the NW late tomorrow, moving quickly SE across all parts overnight and followed by strong NW winds and showers in the North and East. Through Thursday and Friday things calm down again across the South as High pressure builds again. Over the weekend the weather slowly changes again from the NW as freshening Westerly winds bring a trough down over the North on Saturday and the South on Sunday.

 

GFS then shows a cold Northerly flow for a day or two as we approach midweek next week with showers, wintry in the North. Pressure quickly builds though and milder air topples over the UK in a fresh Westerly wind with a lot of cloud and largely dry weather. Another cold surge sinks South behind a cold front attached to an intense Northern European Low pressure with another spell of squally wintry showers. Late in the run milder air again returns as each new High cell to the West sinks SE and opens the door to Atlantic milder conditions with a North/South split developing at the end of the run.

 

UKMO closes it's run with Low pressure moving SE close to Northern Scotland with a trough crossing East over the UK through Monday with rain and freshening winds for all in average temperatures.

 

GEM tonight also shows Low pressure slipping SE over the UK with cold and windy weather developing with rain giving way to wintry showers and probable night frosts. Conditions in the West would be better as High pressure moves in over these areas later with the addition of fog into the wintry mix by night and morning.

 

NAVGEM shows Low pressure slipping SSW over the UK early next week ending close to the SW of Britain with a chilly and cyclonic flow over the UK bringing rain bearing troughs and showers across the UK, perhaps wintry in the North.

 

ECM shows a cold Northerly flow developing behind a Low pressure area sinking South just to the East of the UK early next week. The weather will be unsettled with rain or showers at times and it will be cold enough for a time for wintry showers over the hills and maybe some lower ground in the North for a time. Late in the run as Low pressure fills and moves away from the South a ridge of High pressure develops over the UK with fog, dense and freezing in places becoming the likely weather issues for a time ahead of milder air poised to move in from the West over Northern areas following Day 10 

 

The GFS Ensembles show nothing overly exciting for mild or cold lovers tonight as despite alternating milder and colder days the end result seems to be a very close to average mean for the run for areas North and South. Rainfall amounts though common are never particularly excessive and often of a showery nature. The operational was one of the colder options especially for Northern locations.

 

The Jet Stream shows the flow migrating North over the Atlantic over the coming days before the flow turns South over the UK early next week. In the longer term there is no clear cut indication of where the flow might lie beyond the middle of next week from tonight's output.

 

In Summary tonight the weather looks pretty likely to turn colder next week with a spell of unsettled weather when most observers will be looking for their first flakes of snow of the season. However, away from higher ground rain is more likely in the form of showers but over the hills of the north a covering is possible. It looks like it would only be a matter of days before the flow is cut off as pressure builds over or to the SW of the UK bringing the threat to a return of milder air into the North while Southern regions look likely to become under threat of some cold and foggy weather if High pressure remains close by. Frosts though will become a good deal more widespread and frequent in all areas than we have seen so far this Autumn.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[HammerJack]

Could someone tell me the difference between MLB and HLB. I guess this has something to do with high pressure over Greenland in the next week or so? Thanks

[joggs]

Blinkin eck,finally got through that lot lol,very interesting model output and to be honest couldnt of wished for better if its cold your after seen as where we were a few days ago.If people have difficulty of topplers,try and think of the high been like a ballon and the low pressures hand squeezing gently at it,the high wont topple/sink whilst been nipped at from Italy lol nor will it go ne towards scandy's fingers,it will dent on the top from Icelands fingers(as that moves east)then squash through the gap to the west-north-west (the weak spot to join its weaker bro)over the top o the se tracking hand from the eastern seaboard lol,hope that helps.

Edited November 12, 2013 by joggs

[joggs]

Leigh,thats mid lat blocking and high lat blocking, with hlb reserved for high lattitudes(pole,Greenland etc) and mid lattitude over us/atlantic.

[Zenarcher]

My view on the models tonight and where each one stands.

 

Firstly the next 3 days (next 72 hours) in a bit more detail,

 

Wednesday -

 

 

Generally a cloudy day with scattered showers thanks to low pressure sitting to the North West, higher pressure will remain over Southern parts giving drier and brighter conditions. Gale force winds in the West and some low temperatures in the morning especially in the South West where 0c to 2c is likely.

 

 

Thursday -

 

 

A much drier day but still remaining cloudy for most however England and Wales can expect some sunshine from time to time. A strong North Westerly wind which will touch severe gale force over Northern exposed parts will make it feel much colder in the wind and some wintry showers will occur over the Scottish Highlands. Low temperatures will be mainly in the Northern parts between 0c and 3c.

 

 

Friday -

 

 

High pressure covers the UK bringing calmer conditions than the day before with the strong winds easing but it will be cloudy, dry and dull. Inland parts of England and Scotland are looking cold on Friday morning between -1c to 2c.

 

 

Going to compare the GFS, ECM, UKMO, JMA, GEM, NAVGEM and CMA.

 

96 Hours Saturday

 

Nothing major stands out apart from a few minor details first of all the UKMO is the only model to develop a 980mb low to the far North of the Faroe Isles no other model shows this.

 

UKMO below

 

 

Compared with the ECM

 

 

Next the models are dealing with a massive storm over Northern Norway as well some have it down to 945mb while others have it at 955mb, the NAVGEM model goes a step further than any other model by going off the scale which you can see clear on the Northern Hemisphere chart,

 

 

So the models don't know where exactly the low is going to track yet there are some very large differences between all of them on today's run and this will surely have an effect on trusting anything too serious after this point until they show agreement.

 

120 Hours Sunday

 

First of all large differences on each model again on how they handle the big storm over Northern Norway, for example the UKMO and the ECM have the center over about 750 miles apart by this time.

 

Five models do agree on forming a low around Iceland but the GFS and CMA don't.

 

An example of this between the GFS

 

 

And GEM

 

 

144 Hours Sunday

 

Most models by this point start building up pressure in the Atlantic or at least try to towards Greenland.

 

The five models that had a low develop off Iceland the day before now have it over the UK as GEM shows,

 

 

But the GFS says no to it and forms nothing like it,

 

 

Overall - There are some good and bad charts out there tonight it will be interesting to see how things develop over the next few days just remember to always look for a trend and not take each run very serious and say its game over. I personally think we will see a cold snap towards the end of the month or at least average temperatures staying on the colder side, this is good interesting model watching at the moment a time for everyone to continue to learn about a subject they love and should look forward to whatever the outcome if nothing happens its not winter over by any means we still have plenty of time to see cold weather.

Edited November 12, 2013 by weathermaster

[Mark Neal.]

Leigh,thats mid lat blocking and high lat blocking, with hlb reserved for high lattitudes(pole,Greenland etc) and mid lattitude over us/atlantic.

 

Mid Latitude blocking is blocking around our locality, Mid Atlantic Ridge is the block as we head into next week. High Latitude blocking is blocking in the Northern Hemisphere which we spent alot of the last few months with, until a few weeks back, 

[NorthernRab]

Mid Latitude blocking is blocking around our locality, Mid Atlantic Ridge is the block as we head into next week. High Latitude blocking is blocking in the Northern Hemisphere which we spent alot of the last few months with, until a few weeks back, 

 

Quick correction - both HLB and MLB (high-latitude blocking and mid-latitude blocking respectively) are examples of Northern Hemispheric blocking, but HLB is simply in the more northern parts of the Northern Hemisphere, so up towards Greenland and the Arctic.

[bluearmy]

             

 

 

a couple of charts that will put frosty's ecm ens mean output into some perspective later.   high heights in the se greenland/iceland locale is the favoured day 10 solution with the large spread on uppers over greenland to back this up.  

 

for those wanting to preach that this is just an old fashioned toppler - well it might turn out like that but if you believe this then you're using instinct rather than the output. the ecm ens say that this will be a more sustained cool/cold spell.

Edited November 12, 2013 by bluearmy

[Iceni]

People ususal define toppling by the fact that high pressure ends up back over the UK or south of the UK-

 

At day 10 The high has gone from the classic ridge shape ( stretched ) to a bit more circular ) as the low over the pole moves east along its northern flank)

 

however look at the energy over the eastern seaboard- its going SSE not NNE - which means that area will soon fill with pressure & that high will once again move back NW, as it does it will pull back a Northerly flow-

a double dip outlook -

 

There will of course be a milder wedge at somepoint as cold is replaced by mild then replaced by cold again-

 

So is it a toppler- well not by most peoples definition, is the first phase of cold going to result in a greenland HLB- no, however the second phase has a much higher chance due to the energy flow off the eastern seaboard being south as opposed to North east when the first high tries to get to greenland-

 

you could say the high pressure ridges North, then gets sheared across the top which allows a slight topple EASTWARDS then the expectation would be migration back NW....

 

anyway I dont know how many times I can write this in different ways- thats the forecast from day 7 to day 14.- 16

 

S

 

 

Thank you Steve. I wish you had an assistant who could do a little animation for us. I get it but then I don't get it IYSWIM.

 

Please don't go to the bother of a diagram, I'll just read your post again a few more times so my addled brain can visualise what you're getting at.

[Catacol]

EEM1-240.gif              EEM0-240.gif

 

 

a couple of charts that will put frosty's ecm ens mean output into some perspective later.   high heights in the se greenland/iceland locale is the favoured day 10 solution with the large spread on uppers over greenland to back this up.  

 

for those wanting to preach that this is just an old fashioned toppler - well it might turn out like that but if you believe this then you're using instinct rather than the output. the ecm ens say that this will be a more sustained cool/cold spell.

 

Yes - agree with that. ENS output does indeed suggest something more dramatic than a toppler, and this NH image shows it even more clearly. The blocking pattern to our NW looks pretty impressive

 

 

 

The question I suppose is - how does this tie in with other signals? But before Chio raps my knuckles that is probably for another thread.

 

Very interesting, and not quite what I expected for the latter third of November. Not that I'm complaining! - but still not totally convinced that this kind of pressure rise will occur quite like this.

[shaky]

EEM1-240.gif EEM0-240.gifa couple of charts that will put frosty's ecm ens mean output into some perspective later. high heights in the se greenland/iceland locale is the favoured day 10 solution with the large spread on uppers over greenland to back this up. for those wanting to preach that this is just an old fashioned toppler - well it might turn out like that but if you believe this then you're using instinct rather than the output. the ecm ens say that this will be a more sustained cool/cold spell.

maaan your getting me excited now bluearmy!!!cant believe we could be looking at a prolonged cold spell when just a few days ago the models were not showing anything cold at all!!this is winter model watching at its best!!

[Summer Sun]

ECM ensemble shows the -5 850's getting no further south than Scotland this evening

 

 

Compared to this mornings runs the cold has backed off, -5 850's got down to the far north of England

[bluearmy]

I did post 'more sustained than just a toppler'. That doesnt mean weeks at this stage! Also, i said cool/cold. We could be looking at a prolonged cold spell but just as the models dont say toppler, they also dont say that either. One cannot take issue with those painting a picture at the not cold end and then do the same in the opposite direction.

[chionomaniac]

Fwiw, I don't think that it is a toppler but I do think that as we see the high rebuild to the NW it will bang straight back into the polar vortex, so that it is unlikely to lead to a full HLB over Greenland with classic undercutting. More likely that we will see the Atlantic ridge reform bumping up towards Greenland, but not completely enveloping it. And with that we can see some repeated cold shots - not necessarily like some previous year but those in the north west will have a chance of some white stuff - though not the type that lasts for days on end.

 

 

The NAEFS anomalies highlight this well - 

the 6-10 day cumulative charts show the stong Atlantic ridge

 

 

By days 11-15 there is still promise - note the weak anomaly bridge between the Pacific and Atlantic sector (could this grow?) and how the Atlantic sector of the PV relocates towards Svalbard - just not far enough in my opinion.

 

 

The pattern is most definitely tropospheric led but is not without precedent in wQBO, moderate solar, ENSO neutral years. Here is the composite again for those years - the thing that surprises me is that the formation of the Atlantic ridge for mid month was so predictable.

 

 

this looks very close to the NAEFS 6-10 day ensemble mean.

 

There is still a window of opportunity for perhaps something stronger to grow into Greenland before the stratospheric influence does become too strong. But for that to occur I suspect that we may want to see a strong Mountain torque, and perhaps a North American one at that, to reinforce the block through lower strat wave breaking - so that will be worth watching.

 

 

Otherwise the favourable positioned positive AAM anomaly may just fade away.

 

 

And we wouldn't want that would we?

Edited November 12, 2013 by chionomaniac

[SMU]

Remember Chiono ( I know you know) the 11-15 Mean will be diluted by the runs that dont see any blocking....

 

S

[chionomaniac]

Remember Chiono ( I know you know) the 11-15 Mean will be diluted by the runs that dont see any blocking....

 

S

.....which could be offering the correct solution, Steve!

 

Also to edit that will be tempered somewhat in the NAEFS full 5 day anomly suite as no doubt some members will be over estimating the blocking as well.

 

However, at least we have something to discuss!

Edited November 12, 2013 by chionomaniac

[SMU]

yep + the reanalysis site is working again...........

 

thats a bonus as it was down last time I looked...

 

S

[bluearmy]

i guess my earlier post could be viewed as being euro centric from model point of view. maybe we should check out naefs for day 10 then

 

 

convinced yet ?

Edited November 12, 2013 by bluearmy

[garbagebags]

Is it wrong that I prefer a NW wind to a NE wind? Where did I get that from? It's just that easterlies have never produced for me. 

[chionomaniac]

yep + the reanalysis site is working again...........

 

thats a bonus as it was down last time I looked...

 

S

I constructed that chart back in September - and have been waiting to see if it came into fruition for two months!

 

Also, we have yet to see anything on any 100hPa charts suggetsing a split in the vortex over Greenland. That concerns me as previously that has always been shown by now if something was in the offing there.

[Mr_Pessimistic]

some great posts tonite from the gurus, been waiting all year for this!

 

off topic, but hey, maybee ill get away with it being a newbie.

 

keep up the good work lads (and ladetts)..