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phil nw.

Model Output Discussions 06z 04/11/16

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10 minutes ago, nick sussex said:

Retrogressing highs can only occur with the right upstream signal to help pull those further west and north. You need the jet to dig south and amplify in the mid Atlantic. If the route to cold is going to come through that then we need that amplification initially.

Yes - anything resembling a strong jet anywhere near flat enough to contain a westerly component and the very best you'll do is brief polar Maritime air, / topplers, you need the flow to buckle way before it reaches our shores.

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4 minutes ago, bluearmy said:

The 06z gefs are a bit of a mess looking through them 

any good looking cold solutions ala 00z op quickly become west based and there are even a couple of scandi ridges thrown in

i wouldn't make too many predictions based on that suite 

 

Beat me to it, just flicked through the 216 - onwards range , no long lasting cold really , so many solutions on offer as you say a mess

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The GEFS 6z mean paints an increasingly settled picture from late in the week ahead until deep into week 2 with benign chilly conditions bringing sunny spells, variable cloud and widespread frosts with thick and in places, freezing fog depending on cloud cover which lasts up to around a week before it gradually becomes unsettled and hopefully with snow!

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Edited by Frosty.

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35 minutes ago, nick sussex said:

Retrogressing highs can only occur with the right upstream signal to help pull those further west and north. You need the jet to dig south and amplify in the mid Atlantic. If the route to cold is going to come through that then we need that amplification initially.

That is true nick but I was referring to the part of the jet just between Greenland and scandi. It flattened the euro high and allowed retrogression upstream -

00z

h500slp.png

06z

h500slp-1.png

 

Edited by bobbydog

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As its a quiet time of day I thought I'd bore you with some interesting research re the MJO and its connection with AO/NAO.

Given where we are this might be more relevant, researchers have looked into whether you can correlate phases of the MJO with other teleconnections in the form of clusters.

There is a statistically strong correlation with phase 7 of the MJO and impacts on the AO, the research concluded you have a much higher chance of a negative AO 10 to 20 days after MJO phase 7. The MJO passed through phase 7 between the 8 and 11 November.

Perhaps this gives some added impetus to getting that AO down as we head towards the turn of the month.

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Intrguing model watching at the moment. It seems the uncertainty never ends with regards to the beginning of Dec. I wonder if the meto update will still mention that high level of uncertainty?

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I will say the extended GEFS 6z doesn't look as good (cold) as previously. There was only 1 perturbation worth showing:shok:

Edited by Frosty.

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27 minutes ago, nick sussex said:

I think the problem at the moment is the lack of clarity re the AO, the forecasts don't agree on how negative this will be and for how long. Reading the NCEP monthly forecast done for the USA for December they seemed sure we'd see a tanking AO, their forecast threw up an interesting question:

DESPITE EXCELLENT AGREEMENT AMONG THE DYNAMICAL MODELS THAT FAVOR ABOVE-NORMAL
TEMPERATURES THROUGHOUT THE FORECAST DOMAIN, FORECAST CONFIDENCE IN THE
TEMPERATURE OUTLOOK IS LOWER THAN WOULD BE EXPECTED. THE ARCTIC OSCILLATION
(AO) INDEX HAD ONE ITS MOST NEGATIVE VALUES FOR OCTOBER. A NEGATIVE AO INDEX IS
ASSOCIATED WITH ABOVE (BELOW) NORMAL 500-HPA HEIGHTS AT THE HIGHER (MIDDLE)
LATITUDES OF THE NORTHERN HEMISPHERE. THIS PATTERN RESULTED IN BELOW-NORMAL
TEMPERATURES ACROSS PARTS OF EURASIA. HOWEVER, ABOVE-NORMAL TEMPERATURES WERE
OBSERVED ACROSS MOST OF THE LOWER 48 DURING OCTOBER. AFTER A BRIEF PERIOD WITH
A POSITIVE AO INDEX, THE GFS MODEL REMAINS CONSISTENT THAT THE AO INDEX BECOMES
SHARPLY NEGATIVE ONCE AGAIN DURING LATE NOVEMBER. BELOW-NORMAL TEMPERATURES ARE
TYPICALLY ASSOCIATED WITH A NEGATIVE AO INDEX FROM THE NORTHERN GREAT PLAINS
SOUTHEAST TO THE SOUTHERN ATLANTIC COASTAL STATES DURING DECEMBER. GIVEN THE
LARGE DISAGREEMENT BETWEEN TEMPERATURE COMPOSITES OF A NEGATIVE AO INDEX (BELOW
NORMAL) AND DYNAMICAL MODEL GUIDANCE (ABOVE NORMAL), EQUAL CHANCES FOR BELOW,
NEAR, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST FROM THE NORTHERN GREAT PLAINS
EXTENDING INTO THE SOUTHEAST. ELSEWHERE, ABOVE-NORMAL TEMPERATURES ARE FAVORED
ACROSS NEW ENGLAND AND THE WESTERN CONUS ALTHOUGH PROBABILITIES ARE TEMPERED
DUE TO THE BLOCKY 500-HPA PATTERN OVER THE NORTHERN HEMISPHERE EXPECTED AT THE
BEGINNING OF DECEMBER.

So you can see that on one hand the AO forecast would suggest it should be colder for parts of the USA but the NWP isn't showing that. Which begs the question if the USA doesn't see that cold then the favoured area for that is surely somewhere else in the NH. As we've seen in the past the AOs impact can be a bit of a lottery in terms of which areas are favoured. Hopefully we've got the winning ticket this time in Europe!

Ec 46 looks cold surface temps for the USA in December. 

I think it's the NCEP products that predict not cold

you pays your money etc etc 

Edited by bluearmy

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Changes on each run, wouldn't be surprised if 12z showed ens to be even milder, for the 18z to go complete opposite. time will tell, I think it's probably the second week onwards we need to focus on for cold now. 

 

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2 minutes ago, blizzard81 said:

Intrguing model watching at the moment. It seems the uncertainty never ends with regards to the beginning of Dec. I wonder if the meto update will still mention that high level of uncertainty?

Looking at the spread on the Eps and GEFS temperature graphs, unequivocally YES!!

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4 minutes ago, Frosty. said:

I will say the extended GEFS 6z doesn't look as good (cold) as previously.

Sort of ties in with the latest meto forecast of more unsettled, windy weather as we hit Dec. A bit of a change from a couple of days ago.

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1 minute ago, Connor Bailey Degnan said:

Changes on each run, wouldn't be surprised if 12z showed ens to be even milder, for the 18z to go complete opposite. time will tell, I think it's probably the second week onwards we need to focus on for cold now. 

 

Agreed, ensembles are fickle things, hopefully we will see growing support for a major cold outbreak in early Dec.

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Just now, Frosty. said:

Agreed, ensembles are fickle things, hopefully we will see growing support for a major cold outbreak in early Dec.

I'm beginning to think that any significant UK cold will have to wait until the middle of Dec. The trend with the models has been to delay any early Dec cold and move it back somewhat. On a positive note though, I am looking forward to the seasonal dry, frosty, foggy weather heading our way later this week :)

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Whilst I'm usually a champion for the gfs but certainly not the last week or so. The ECM never bought into sustained height rises over Greenland the way that the gfs did....

Where do we go from here. Well certainly not a bad start, there is still a frost lying here and it's well after midday. In 40 years of watching weather I don't ever remember that in mid Nov (2010 excl). The vortex is very weak and surely as December begins the slightest help from the strat will take it down.

My punt is a few days of atlantic driven weather after this high dissipates before a proper Greenland high bears fruit

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1 hour ago, booferking said:

The 28th-30th Nov seems to be the time to watch.

I remember when the 19-20th Nov was the time to watch 10 days ago across the thread.

Here we are again hoping /watching to see if it's time to watch in 10 days time! 

You couldn't make it up 

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1 minute ago, Ben Lewis said:

I remember when the 19-20th Nov was the time to watch 10 days ago across the thread.

Here we are again hoping /watching to see if it's time to watch in 10 days time! 

You couldn't make it up 

Just par for course with regards to UK winters. Just comes with the territory unfortunately. It isn't even winter yet though :)

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23 minutes ago, bluearmy said:

Ec 46 looks cold surface temps for the USA in December.

I think it's the NCEP products that predict not cold

you pays your money etc etc

Yes but NCEP in doing their monthly forecast use a wide range of models so I would have thought they would include the GEM and ECM. I hope the USA isn't going to steal our cold again!

www.meteo.psu.edu/~sbf1/papers/Riddle.etal.pdf

Lets hope the cluster 4 composite which was associated with the time lagged MJO phase 7 comes to fruition.

Page 7 of the research!

It's similar to this:

AO_Negative_2.gif

 

 

 

Edited by nick sussex

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13 minutes ago, blizzard81 said:

 I am looking forward to the seasonal dry, frosty, foggy weather heading our way later this week :)

I'm sure many of us are but I'm still hopeful we will have a deeper cold spell during the next few weeks rather than just surface cold.

Edited by Frosty.

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1 minute ago, Frosty. said:

I'm sure many of us are but I'm still hopeful we will have a deeper cold spell during the next few weeks.

Me too Karl..

The worry is if we dont get the retrograde in the mid Atlantic ala GFS0z then the high over or near the UK will end up slipping south into europe and that is something i really don't want to happen, 

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15 minutes ago, Ben Lewis said:

I remember when the 19-20th Nov was the time to watch 10 days ago across the thread.

Here we are again hoping /watching to see if it's time to watch in 10 days time! 

You couldn't make it up 

To be fair we have seen hail sleet snow showers since Wednesday Night through to Friday night the hills around me have had snow cover on them since Wednesday Night we have got down to -5 last night and looking the same tonight, the rest of the week is looking rather chilly if not cold with fog and night frost and in some places the frost could linger all day if the fog proves hard to burn off.  Heads up we haven't even entered winter yet hopefully we start seeing consistency around 28th-30th Nov for something more potent and Nationwide.:cold:

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The last decade of November definitely won't be what I hoped for with extreme warmth in many places of mainland Europe. Especially the next two days will be very warm with strong gale here. It's now hard to see any real cold arriving before the end of November so I guess the chase for December cold may as well begin. Hopefully with better ending.

Anyway, it seems the Arctic will get its act together temperature wise over the next week so there will be a lot of cold to tap in.

gfsnh-1-6.png?6gfsnh-1-144.png?6

 

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31 minutes ago, phil nw. said:

It looks like 5/6 days of quiet weather under a mid-latitude high across the UK from around mid week before any further changes.

From what i can see further on is that we have a weaker set of +ve hts across Greenland with the main core moving west towards Canada at day 10.On that basis it's difficult to see a way that any deep cold  will come south to the UK-we do need to see more solid blocking around Greenland for that.

Day 10 Ht anomaly charts

EDH101-240.gifgensnh-21-5-240.png

Those heights do keep the mean path of the jet further south towards us so after the rather cold high at the surface the most likely development is more changeable but rather cold weather as the high fades.

A look at the London graph

 ensemble-tt6-london.gif

shows temperatures dipping to just below  average towards month end.There some colder members but as ever at the later range we need many more showing before we can expect a real cold spell as we go into the new month.

I think the one thing we can take from the latest outputs is that we have no strong signal for a period of mild south westerlies from a traditional early Winter raging jet.

Agreed, no sign of swly mild mush on the horizon apart from a mild interlude tomorrow in the south which is a victory in itself for coldies!

I'm thinking below average temps will tend to dominate during the next 2 to 4 weeks.

ukmaxtemp.png

Edited by Frosty.

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