Winter Model Discussion 18Z 8/1/13. The hunt for cold (is closer).

[andy_leics22]

*tears hair out*

Damn you 06z Gfs!!! I worried that this might happen. I think it may just be a mild outlier after t144 but i'm not confident about that. If the 12z ECM sticks to its guns then it will be a little more promising. At this stage though it could swing either way, If the 06z gfs run turns out to be correct... We will have gone from what seemed like a prolonged cold spell to a 2 day cold snap!

[NO LONGER POSTING]

One word..Bad episode of tereits on here

[bradymk]

Key period coming up on the 6z GEFS ensembles. Look out for that shortwave.

[pyrotech]

Historically speaking what are the % chances of shortwaves being downgraded vs being deepened, once they have been picked up?

Historically really does not matter here as the atmosphere is not in an average state, we do have an SSW ongoing propogating through the layers, When it reaches the troposphere it will effect blocking and shortwaves. Blocking becomes more likely, shortwaves shallower. FACT

However that does not mean a shortwave can not form and spoil this for us, but i would suggest that it very likely GFS without the extra baloon data has missed a key part of the puzzle.

If GFS is correct then blocking is again over Russia and we would possibly be in a pre xmas state and flooding an issue.

[Wivenswold]

Shortwaves are perhaps the most volitile feature on these models. To be worrying about 1 run on 1 model that is upset by such a feature is jumping the gun somewhat. Especially as the Met Office have been ignoring GFS in the last week.

[TEITS]

Just returned from the Doctors and I see the 06Z has put the cat amongst the pigeons. Lets be honest here I cannot remember the full detail of the 0Z run but synoptically the difference between the 0Z & 06 is so different its laughable. The difference in how the models handle the LP at +120 is farcical really. We have the GEM that takes this SE and phases with the SW tracking SE. We have the ECM we takes this directly S and the UKMO takes this SE. Finally the GFS 06Z moves this E and phases with the LP in the Atlantic. Basically the models are useless beyond +120.

I will add though that one thing that irritates me is the general attitude of cold runs always downgrade and mild runs are more likely. Sorry but are members so busy focussing on what may occur in the medium range that they have missed what is being projected at +72. The +60, +72, +96 charts have upgraded significantly over the past few days which is why we have seen the risk of snow on Saturday upgrade followed by snow showers on Sunday.

Finally I very much doubt the ensembles will help us out. We are going to need the 12Zs to sort this out and even then I will await tomorrow 0Zs.

[Frosty.]

For the very few mild lovers out there, the gfs 06z is a dream in FI with a long draw swly and springlike temps towards the end of the month, a lot of average/mild weather before then too but i'm going to suggest this run will be at the warmer side of the ensembles, not good news for the majority who want a freeze but we still have the ecm..for now.

[snowmadchrisuk]

Good grief even I didn't expect something this dismal from the GFS 06hrs run.

The thing I don't like with all this constant chopping and changing is that as you get to within 144hrs theres less room for changes so when the final chop comes we'd better hope its for cold and snow and not the underwhelming picture painted by the GFS.

I would have thought theres always room for changes until at least +72 hours , especially regarding SW's . The SSW will signal a blocking pattern to develop very soon , If that effects the UK is always open to question , but it will not be the p/v driven flat pattern that the 6z shows . As Steve M said , it will be a long wait until the 12z's . Also r.e. this weekend , the GFS continues to forecast a spell of heavy Snow for southern UK . Chris

[garbagebags]

If im not mistaken despite all the excitement over it does a SSW not statistically actually make mean UK ground temps go UP? im sure ive seen that posted a few times (and quickly swept under the carpet)

[warrenb]

That is not going to happen, the 6z has just put the PV back together and plonked it back over Greenland, I think what is happening here is a reaction the to initial SSW warming, but no account for downwelling has been taken in.

[Weathizard]

Just to add a sense of realism, its practically all models VS the GFS here, all 144 charts

GFS

ECM

UKMO

GEM

BOM

JMA

CFS

NO support for GFS.

Edited January 9, 2013 by Weathizard

[JP1972]

At this time any news from upstream which rubbishes the GFS is fine by me! So this is the best I can do at the moment!

SATURDAY NIGHT...LATEST MODELS DEPICT A WAVE LIFTING NORTHEAST

THROUGH THE BAROCLINIC AXIS WELL TO THE SOUTHEAST WHICH WOULD

SPREADING LIGHT PRECIPITATION INTO IL...AND POSSIBLY INTO SE IA. THE

GFS IS AN OUTLIER WITH A MUCH STRONGER AND MORE NW TRACKING SYSTEM...

WHICH RESULTS IN OUR FORECAST KEEPING CHANCE POPS FOR LIGHT SNOW

ACROSS THE SOUTHEAST.

That nw tracking system is the one that heads towards western Greenland and phases with troughing in the west Atlantic.

SUNDAY INTO TUESDAY...COLD HIGH PRESSURE BUILDS OVER THE REGION

WHILE THE UPPER LEVEL TROUGH TRANSITIONS EAST OVER THE AREA. THIS

WILL RETURN TEMPERATURES BACK TO NEAR OR BELOW NORMAL. MODELS

DIVERGE EARLY IN THE WEEK...WITH THE GFS DEPICTING A LONGWAVE UPPER

TROUGH OVER THE CENTRAL U.S. AND ANOTHER SYSTEM BRUSHING PAST TO THE

SOUTHEAST BY MONDAY NIGHT...WHILE THE ECMWF IS LESS PHASED WITH MORE

OF A SPLIT FLOW PATTERN...KEEPING SYSTEMS WELL TO THE SOUTHEAST.

I should also add though that NOAA didn't think much of last nights ECM operational run in terms of what it did with the PV in the USA.

LATE DAY 6 TUE THRU DAY 7 WED FOLLOW A 70/30 WEIGHTING OF THE 12Z

ECMWF/18Z GEFS MEANS GIVEN ROBUST ENSEMBLE MEAN AGREEMENT AND

VERIFICATION CONSIDERATIONS IN FAVOR OF THE 12Z ECMWF MEAN. THE

12Z ECMWF BRINGS ITS NRN CANADA VORTEX WELL SWD OF CONSENSUS BY

WED.

Hi Nick,

I've noticed you always go to the trouble of sharing this info with us, however for the thicker people on here (me!) would you be so kind as to put some more flesh on the bone with maybe a few words to translate what this info means for us?

Thank you.

[nick sussex]

I would have thought theres always room for changes until at least +72 hours , especially regarding SW's . The SSW will signal a blocking pattern to develop very soon , If that effects the UK is always open to question , but it will not be the p/v driven flat pattern that the 6z shows . As Steve M said , it will be a long wait until the 12z's . Also r.e. this weekend , the GFS continues to forecast a spell of heavy Snow for southern UK . Chris

The full downwelling of the SSW hasn't occured yet, the outputs though have probably been effected by the slowing and then reversal of the zonal winds above 60N.

I'd say tonights 12hrs will at least reach agreement within 144hrs in terms of whether we can at least jump the first hurdle.

The GFS signal to flatten the jet will either be sent packing or we'll see a rather sad thread.

Theres little middle ground here, you either get energy undercutting a ridge to the north or the energy piles east and pushes the Azores high with it.

[Ian Brown]

Not surprised at the 06z, given the ensemble scatter we could have seen this solution shown on the 0z or any of the runs yesterday.

It’s no more or less plausible than the other solutions, but has to be upgraded to more plausible because as I’ve said, if it can go wrong for the UK, then invariably it will.

[Jason H]

If im not mistaken despite all the excitement over it does a SSW not statistically actually make mean UK ground temps go UP? im sure ive seen that posted a few times (and quickly swept under the carpet)

Ian posted yesterday that 70% of the time a SSW decrease temperatures.

[Iceaxecrampon]

06Z

Cumbrian ensembles bottoming out at 14th Monday - chilly....

METO Mountain forecast for Saturday having none of it although freezing temps altitude lowered ...

Saturday

Mainly dry but cloudy, although some sunny spells develop especially in the western fells. Light northeasterly winds. Freezing level 500m.

Sunday

Dry but cloudy throughout the day. The best of the cloud breaks in the eastern fells around Helvellyn. Light winds, mainly northwesterly. Freezing level down to 350m

Bonkers - who is right? - we are getting so near the reliable....!

Ian

Edited January 9, 2013 by Iceaxecrampon

[ChartViewer]

Never did like this model

CMA144...goes the way of the pear afterwards..Must be being drawn by the fella who draws the 06Z

[TAFKAP]

If im not mistaken despite all the excitement over it does a SSW not statistically actually make mean UK ground temps go UP? im sure ive seen that posted a few times (and quickly swept under the carpet)

Yes that does, on the face of it appear to be the case re: SSWs. However from what I've seen posted the temperature rise is less than one degree C and none of the figures I've seen posted have explained those figures in the context of seasonal influence and broader tropospheric conditions. Furthermore I don't think anything is being 'swept under the carpet' as this isn't some top secret forum with an evil agenda to hide information. There is no conspiracy going on here, perhaps your tinfoil hat is on a little too tight!

[pyrotech]

If im not mistaken despite all the excitement over it does a SSW not statistically actually make mean UK ground temps go UP? im sure ive seen that posted a few times (and quickly swept under the carpet)

I can not say thats not written somewhere, but generally a SSW increases the likelihood of a Cold outcome for the UK but does not guarantee a cold outcome.

It just increases the chance.

I have now added a quote from Met office, if any one needs a link let me know -

"We normally expect our weather to come in from the west – with a flow of relatively mild air coming in off the Atlantic.

When an SSW brings easterly winds this tends to alter our weather patterns slightly, weakening areas of low pressure and moving our jet stream further south. This leads to high pressure over the North Atlantic, ‘blocking’ that flow of mild Atlantic air and dragging in cold air from the continent to the east. Exactly how cold it might be depends on the details of where the air comes from.

SSWs don’t always result in this outcome – but a cold snap follows more often than not, so the SSW greatly increases the risk of wintry weather."

[TAFKAP]

Not surprised at the 06z, given the ensemble scatter we could have seen this solution shown on the 0z or any of the runs yesterday.

It’s no more or less plausible than the other solutions, but has to be upgraded to more plausible because as I’ve said, if it can go wrong for the UK, then invariably it will.

Come on Ian, the only reason you think it is being updated to more plausible is to support your own mild biased agenda.

[fergieweather]

Shortwaves are perhaps the most volitile feature on these models. To be worrying about 1 run on 1 model that is upset by such a feature is jumping the gun somewhat. Especially as the Met Office have been ignoring GFS in the last week.

They most certainly haven't ignored it but in 00z analysis for longer-term end by saying "NCEP-GFS considered unlikely and ECMWF preferred." Anyway, they won't consider 06z GFS in next update and only refer to midnight and midday runs.

[TEITS]

I would have thought theres always room for changes until at least +72 hours , especially regarding SW's . The SSW will signal a blocking pattern to develop very soon , If that effects the UK is always open to question , but it will not be the p/v driven flat pattern that the 6z shows . As Steve M said , it will be a long wait until the 12z's . Also r.e. this weekend , the GFS continues to forecast a spell of heavy Snow for southern UK . Chris

Exactly right. What I have found in all the years of model watching is +72 and below is when the models show much greater consistency. When you go from +72 to +144 this begins to fall away especially between +120 & +144. Obviously it also depends on the projected pattern because sometimes the consistency can vary between this period. So based on this we still have plenty of time for the models to trend either way.

Just to illustrate my point about +72 and im sure some of you like me have told friends and family about impending cold spells which have gone pearshaped? Now in recent years I have learn't to keep quiet and I never tell anyone until a cold spell is being projected at +72. This makes sense really because apart from the BBC weekly forecast on Sunday they rarely forecast beyond 3 days.

Back to the models and another scenario which nobody has mentioned is just maybe we shall see a blend of the ECM/GFS. Now you may ask how can we have a blend when they are so different. Well my answer is possibly we could see a brief return of milder weather into next week which is swiftly replaced by a return to colder weather.

[fergieweather]

Ian posted yesterday that 70% of the time a SSW decrease temperatures.

Yup: it was in an internal email with a link to the data.

[SMU]

That CMA is a snowfest. Like the 00z control run.

As said & repeated many times now-

until something gets to t60 it has time to go t*ts up-

the 12's will be very telling, but *IF* we end up with anything close to the 06z past day 5 it will be a big kick in the teeth for us that has used the strat to forecast with & and all cold winter Jan forecasts will be bust...

lets hope not- this is the pivotal point of winter I feel the next 48 hours in terms of where we go from monday onwards..

S

[ITSY]

THE MEAN at +144

All of England, Wales and Scotland in sub-5 till at least Tuesday with enough heights for numerous midlands eastwards snow events sat-tues.

No need to hit panic mode, YET.