Model Output Discussion 1st Nov.2013

[johnholmes]

I don't agree. Comparing the deterministic with the ensemble mean should be part of the approach.

 

See the (not-unquestionable) Bible here: http://www.ecmwf.int/products/forecasts/guide/user_guide.pdf

 

not seen that before, it looks well worth a good read-thanks for giving the link-NEVER dismiss anything available, use all, assess and decide which seems the most likely then do your forecast. It apllies to professionals and amateurs alike.

[Mucka]

Flicking through GFS 18z ensembles it is the first time I have seen FI show up some potentially cold patterns.

Perhaps GFS and ECM FI are sniffing something of a change for the second half of November? (where did we see that before?)

Here is a selection of charts that look quite different to the endless zonal pattern the models have been churning out even out in FI.

 

 

And plenty more MLB about in deep FI on quite a few runs that won't show up on the graphs yet as cold since the blocking is in FI and obviously we need the block before the cold air arrives, usually a few days later.

 

Straws or genuine hope?

Edited November 3, 2013 by Mucka

[legritter]

Removed my first Straw from its big box tonight ,my pram is fully loaded with toys ,why a post in the middle of night ,our window is in firing line of hvy hail ,and lightning .signs of a possible change in weather type come mid month starting to show up on later output ,but more runs needed .

[IDO]

This morning's ECM flattens the pattern with it's op run.

T240: Whilst GFS op follows ECM 12z:

However the Control run from GFS is zonal from start to finish:

T384: And the GEFS remains status quo:

Some change may or may not be brewing, but at the moment it is a weak signal, so future runs will clarify.

[Frosty.]

Most of the Gfs 00z op run is unsettled with strong to gale force winds at times and temperatures rarely on the mild side, nothing mild in the north, generally close to average but feeling colder than that due to the strength of the winds, generally the winds are from a due westerly point, sometimes a touch south of west and occasionally north of west, the airmass is north atlantic sourced, sometimes mixed with polar maritime, especially further northwest meaning that any precipitation on northern hills and mountains in scotland would be a wintry mix of hail, sleet & snow, cold rain lower down but a wintry flavour at times with max temps in single digits celsius, especially towards the end of the week when winds  begin to ease, firstly in the west as a ridge pushes in allowing a few widespread frosts to develop, again especially in the north. Later in the run we see a big change, high pressure building across the uk bringing increasingly fine but rather chilly weather with a risk of widespread fog and slight frosts.

 

PS...all eyes to the southwest later today as the next spell of heavy rain and gales moves up across the southern half of england and wales.

Edited November 3, 2013 by Frosty.

[Frosty.]

The Ecm 00z op run is relatively chilly and unsettled with heavy rain and gales mixed with brighter, showery interludes, mild is not how I would describe it, I can only see two days on this run where it approaches mild, that's thursday and the following monday, apart from that it would be feeling chilly. occasionally the winds drop and this would bring the risk of frost. As with the gfs 00z, high ground in scotland has a good chance of wintry ppn.

[bobbydog]

The route to cold this November will always be from a northwesterly airflow around the back of an Atlantic ridge and at last this is starting tp possibly show up on the extended anomaly charts.

 

Here is the November expected anomaly composite based on the closest anologue years. 

 

Analog yrs Nov H500.png

 

The GFS 11-16 day anomaly charts are starting to have a similar look about them - so confidence for an Atlantic ridge can grow tentatively for later in the month.

 

12zgfsensCumulative500mbHeightAnomalyNH360.gif

 

THere is a bit of a confusing signal between the MJO and GWO, but the one thing that I can see omnipresent this winter is already showing. That is the strong Pacific ridge.

 

thats something which has caught my eye over a few days. being a little unsure of its implications i've had a quick dig and found this chart which could be of some interest

 

 

apparently, all the years shown are +QBO years except 56-57, 96-97 and 62-63

[johnholmes]

the chart below gives the general upper air pattern likely into mid November

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

all the major 3 show very similar ideas, there is a gradual veering of the 500mb flow over the UK. At the moment there is an area of +ve heights in Europe but the ECMWF-GFS do appear to be suggesting that the veering flow MAY be due to a mid Atlantic ridge trying to develop.

[Summer Sun]

Latest from Gibby

 

All models continue with a very volatile and fast changing period of weather over the coming week. There will be spells of rain or showers throughout the week for all areas with details harder to pin down. However, all of Southern Britain will see a period of heavy rain tonight following early showers. Then after a drier interlude tomorrow another batch of wind and rain followed by showers rushes East through Tuesday and probably again on Thursday and over next weekend. Winds will often be strong with some gales in exposure towards the West and in the North. temperatures through the week will be generally close to average though it will be somewhat colder tomorrow before milder air from the West takes over again before midweek. Frost and fog is unlikely due to the strength of the wind and cloud cover over the week as a whole.

 

GFS then leads us through week 2 with a strong ridge developing over the UK as it moves SE  to be followed with another front and rain. The Higher pressure though does return on larger scale later breaking the current wind and rain pattern and drawing up some mild but dry weather from the South late in the run as the High slips towards SE Europe.

 

UKMO closes it's run this morning with an unstable flow with Low pressure to the North extending well out into the Atlantic indicating at least a few more unsettled and wet days from next Sunday following this coming wet and windy week. Temperatures are shown very close to average in frequent strong Westerly winds.

 

GEM shows unsettled and windy weather too lasting into the start of week 2 before High pressure builds either to the SE or SW and allows for Southern areas at least have a drier spell with less in the way of rain and wind and drier and brighter spells with it never becoming particularly cold.

 

NAVGEM is unsettled throughout with another depression making for another wet weekend as it drifts ESE across Southern Britain on Sunday. This could lead to a weak ridge moving in early in the following week once the Low departs away East on Monday.

 

ECM today continues to look very changeable next weekend and well into the second week with High pressure held at arms length down to the SW allowing rain bearing weather systems to cross East in the strong Westerly flow with rain and showers for all at times along with strong winds. A brief ridge is possible as we approach the close of the run though with the Day 10 profile as it is it would be unlikely to last long.

 

The GFS Ensembles if anything have pointed slightly towards a less mild outcome this morning with the mean for the run now shown very close to the long term mean. There is also a return to slightly more rainfall shown again towards the end of the run than was indicated at times yesterday suggesting that Low pressure may dictate the weather nationwide through the period now and not just in the North. The very mild end to the operational makes it an outlier at the end.

 

The Jet Stream pattern remains locked in it's course over the Atlantic and the UK for the reliable future with the less reliable time still indicating little variation in the track either.

 

In Summary the weather looks like staying basically very unsettled and often wet, certainly through this coming week. There are a few indicators which still suggest a rise of pressure close to the South could mute the effects of the unsettled weather for a time in Week 2 but in general it just puts the terminology of the pattern into 'changeable' rather than 'unsettled' with rainfall never far away from the South from most charts I've seen in week 2 too. Temperatures should remain relatively mild for this time in November but this will be offset by the strength of the wind at times, which could reach gale force at times and because of this, the other twin late Autumn perils of frost and fog will remain a scarce commodity.

 

http://www.norton-ra...is(2859336).htm

[bluearmy]

the chart below gives the general upper air pattern likely into mid November

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

all the major 3 show very similar ideas, there is a gradual veering of the 500mb flow over the UK. At the moment there is an area of +ve heights in Europe but the ECMWF-GFS do appear to be suggesting that the veering flow MAY be due to a mid Atlantic ridge trying to develop.

 

naefs spread at T384 has developed a significant feature just west of the uk. its either a mean deep trough or a block. my money on the latter and its a developing theme for sure.

[Frosty.]

The Ecm 00z ensemble mean shows the uk locked into an unsettled pattern with low pressure to the northwest/north of the uk throughout and high pressure to the south of the BI, a powerful jet stream blasting across with depressions of varied potency chasing each other across the atlantic with just very brief and flat ridges separating us from the next wet & windy spell interspersed by brighter and showery days, a mostly westerly upper flow, strongest early in the period before moderating for a time and then strengthening again later. The temperatures generally close to average, a little below at times, especially further north where showers would be wintry on the higher hills and with a risk snow across the scottish mountain ranges at times, just the occasional mild sector across the south of the uk but soon chased away by cooler oceanic air, even a risk of polar maritime incursions but mostly across the northwest of the BI, a risk of frost in any quieter interludes, quite a lot going on, most of it unsettled with no real sign of any sustained settled weather within the next 10 days, and probably beyond.

[cooling climate]

The route to cold this November will always be from a northwesterly airflow around the back of an Atlantic ridge and at last this is starting tp possibly show up on the extended anomaly charts.

 

Here is the November expected anomaly composite based on the closest anologue years. 

 

Analog yrs Nov H500.png

 

The GFS 11-16 day anomaly charts are starting to have a similar look about them - so confidence for an Atlantic ridge can grow tentatively for later in the month.

 

12zgfsensCumulative500mbHeightAnomalyNH360.gif

 

THere is a bit of a confusing signal between the MJO and GWO, but the one thing that I can see omnipresent this winter is already showing. That is the strong Pacific ridge.

The ridging on the Pacific side will definitely be one of the main features of the

coming winter I think and with increasing wave lengths as we move into the

winter months things should become much more interesting.

[Cloud 10]

the chart below gives the general upper air pattern likely into mid November

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

all the major 3 show very similar ideas, there is a gradual veering of the 500mb flow over the UK. At the moment there is an area of +ve heights in Europe but the ECMWF-GFS do appear to be suggesting that the veering flow MAY be due to a mid Atlantic ridge trying to develop.

 

 

naefs spread at T384 has developed a significant feature just west of the uk. its either a mean deep trough or a block. my money on the latter and its a developing theme for sure.

 

You guys obviously programmed the 06z this morning?. 

 

[MR EXTREMES]

You guys obviously programmed the 06z this morning?. 

 

gfs-0-384.png

now that's a nice looking progression lets get rid of the high heights in Europe lower heights into Europe ridge across the uk or ne or northwest even west block the alantic game on I wonder if we could produce an omega block could be intresting into December.

[Captain Shortwave]

I'm still going to go against the grain here and suggest heights will start more over the UK and Scandinavia rather than the north Atlantic, think there will be a deep trough forming there with some energy leaching into southern Europe over time. Either way there are some signs of drier and potentially colder weather developing from mid-month.

Back to the nearer time frame, this is concerning me quite a bit

This low looks set to hit the south of the UK, more importantly the potential risk of a gale force northerly developing when it clears into the north sea, hope this doesn't coincide with high tide if it did happen.

[Summer Sun]

NAO looks like remaining positive through to at least mid month

 

[bobbydog]

NAO looks like remaining positive through to at least mid month

 

 

yes gav, a weak positive as shown would support mid-atlantic ridging-

 

 

 

[draztik]

The models continue to highlight low pressure dominating the UK weather in the short to medium term. But in saying that, Bright and Blowy seems to be the headline, esp for the North and NW. Was looking at my native area in the east of NI, which is showing sunny skies all week, with little rain, and only then overnight. So very useable weather for northern locations, albeit a touch blowy.

As Gavin has suggested, the NAO remains positive through its forecast period, but the trend is to become weaker as we progress through November, when we should settle down.

gfs 0z showing below average rainfall for NI and much of Scotland.

Edited November 3, 2013 by draztik

[Frosty.]

The Gfs 06z op run is dominated by rather cold weather across the northern half or at least the northern third of the uk throughout the run with an ongoing risk of wintry showers across the hills of scotland with snow higher up in the mountains and perhaps lower levels at times, temperatures really struggling in the mid single digits celsius and lower at times, occasionally a little higher. For the south, it's relatively milder with temps closer to the seasonal average but the cold air further north occasionally digs further southeast and there is actually a risk of sleet and snow across the hills of southern britain at one point in particular. There are a few fine and slightly milder spells but this is totally outweighed by chilly weather and also by spells of strong to gale force winds and heavy rain alternating with sunshine and showers. So, this run really does have a wintry flavour the further north you go and the cold air does make progress further south at times, this is the type of run I like to see at this time of year with more than a few reminders that the meteorological winter is only 3½ weeks away..it's the final countdown  ...

[NorthNorfolkWeather]

I'm still going to go against the grain here and suggest heights will start more over the UK and Scandinavia rather than the north Atlantic, think there will be a deep trough forming there with some energy leaching into southern Europe over time. Either way there are some signs of drier and potentially colder weather developing from mid-month.

Back to the nearer time frame, this is concerning me quite a bit

This low looks set to hit the south of the UK, more importantly the potential risk of a gale force northerly developing when it clears into the north sea, hope this doesn't coincide with high tide if it did happen.

Hi CS,

 

if it happens on the 10th like that, we'll be back to Neap tides, the highest tides this month are in the next 3 days and in 14-17 days time.

 

Interestingly it may start quieting down as the moon gets towards being full.  Sun looks as though it's starting to go rather less spotty as well, it's been relatively active these last 3-4 weeks

[Sean Donoghue]

Yeah we need to sun to sleep now ,,, Presure to build ,,,,,

[TootyFruity]

If there was to be Ridging on the Pacific side what does that mean for winter In the Uk ?

Is it that it would mean blocking of the Alantic thus allowing the Polar air to flood down ?

Thanks

[bluearmy]

If there was to be Ridging on the Pacific side what does that mean for winter In the Uk ?Is it that it would mean blocking of the Alantic thus allowing the Polar air to flood down ?Thanks

 

million dollar question TF.  it likely means we will see a downstream trough over north america making it cold there (too early to say where the mean trough would sit). the main question for the atlantic is does the american trough ignite a strong jet to our west (+NAO and we look for topplers at best) or does the amplified pattern continue with a ridge in the north atlantic/greenland (-NAO  and we could be cold) ??

[Cheshire Freeze]

million dollar question TF.  it likely means we will see a downstream trough over north america making it cold there (too early to say where the mean trough would sit). the main question for the atlantic is does the american trough ignite a strong jet to our west (+NAO and we look for topplers at best) or does the amplified pattern continue with a ridge in the north atlantic/greenland (-NAO  and we could be cold) ??

 

Yep, if recent years are anything to go by we could see the jet amplify our side with ridging up towards Greenland and a Scandi or even European trough. However, as we know, the weather rarely conforms to such simplistic formulae. As ever, time will reveal all.

[TootyFruity]

So what was the pattern in the weather and models pacific side and uk side that gave that great winter snow in 2010 ?

Thanks BA for answering