Model Output Discussion

[johnholmes]

Whilst the 1000-500mb thickness is used, and the 'magic' 528 line is oft quoted. It is in fact needed to be 522 or below really, its the 1000-850mb thickness which is often more important-below 1290 and better if below 1282Dm. That is along with 850mb temp, zero isotherm, dewpoint and wet bulb all needing to be within the parameters commented on in the Guides. of course the first need is precip. Slight and even if other things are in its favour and it can still fall as drizzle or rain. Moderate to heavy can help with the evaporative cooling effect. Also height also helps.

So lots for any forecaster to have to take into consideration.

An interesting week trying to get the precip type correct!

[winterof79]

Whilst the 1000-500mb thickness is used, and the 'magic' 528 line is oft quoted. It is in fact needed to be 522 or below really, its the 1000-850mb thickness which is often more important-below 1290 and better if below 1282Dm. That is along with 850mb temp, zero isotherm, dewpoint and wet bulb all needing to be within the parameters commented on in the Guides. of course the first need is precip. Slight and even if other things are in its favour and it can still fall as drizzle or rain. Moderate to heavy can help with the evaporative cooling effect. Also height also helps.

So lots for any forecaster to have to take into consideration.

An interesting week trying to get the precip type correct!

Thanks John,perhaps i should have used the word possible.Certainly looks like some could get a good fall though.

[mountain shadow]

Nothing much changed overnight.

A wintry feel to the weather. Mostly rain to low levels with the odd place getting snow. Low pressure to be situated of the south west approaches in five days. After that, who knows?

The jet being so far south is working against us, a little further north and it would pick up the trough and move into the continent feeding in the frigid air to the north east.

No real guidance in the ensembles.

[Weather-history]

faxwise, the snow potential for tues is slightly downgraded on the T84 compared to the T96 due to the angle of approach of the fronts being more nw/se than w/e. however, what should be noted is the sqeeze of pressure to the se T72 which holds up its progress and could well spring a surprise or two.

I would say the downgrade is much more than slight for the FAX charts, there is a mild sector involved and its not phased out until it reaches the far SE, so for lot of people its going to be largely rain.

[bluearmy]

I would say the downgrade is much more than slight for the FAX charts, there is a mild sector involved and its not phased out until it reaches the far SE, so for lot of people its going to be largely rain.

sorry kev - terribly imby post !!!

expect most of the advisorie will be removed later this morning then.

[Duane S.]

Hmmm. The general concensus does seem to be an annoying loitering LP over the UK for next week. I'm still struggling with this

Viewing the UKMO run I was surprised NOT to see the trough drop further south @ +144 after the +120 chart GFS gives us a half-hearted Northerly as it moves the low, eventually, back NNE. Blizzard conditions likely for Eastern Scotland next weekend if that transpired I expect. The problem, IMO, in this case, is that because of the indecisive wishy-washyness of our trough throughout the week, the Iberian Low just says "right, I've had enough of you dilly dallying around, you're not coming to see me I'm coming to see you!" and just sweeps up from the SW later on and marches straight in with very little resistance and no real battleground scenario, leaving the door wide open to mild. Fairly firm agreement of the GEFS ens but then we know that that doesn't always mean a lot.

The good news though is that the ECM continues its thoughts of the 12z. I wasn't expecting it after viewing the others beforehand and although it is not quite as bullish as the 12z in terms of dropping our resident trough out of harms way and bringing in colder air, the fact it tries (and does to an extent) to is a good sign.

[TEITS]

Well still we have much uncertainity in the model output. The GEM/GFS and recent GEFS ensembles have thrown a ridge of HP N in the medium range with LPs tracking NE. The ECM follows similiar to last nights 12Z with the phasing of the LPs. Unfortunately as the UKMO only goes out to +144 its difficult to tell how this would trend. Interesting to note the UKMO has the cold pool to our N pushing further S compared to the GFS.

ECM ensembles continue to trend cold with the mean only a couple of degrees above freezing.

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

I will add though that I cannot see these widespread snow events that some are promising for next week.

[cooling climate]

Following other guidance I remain totally unconvinced by the 06 GFS output.

The UKMO imo is on the right track in building heights to the northeast we then

need to see a trend for the low to track east south east.

The ECM this morning shows signs of doing both so hopefully we will see the

Euro models continue this trend.

As for the GFS it will probably continue on its merry way for a while before the

penny drops so to speak.

Just to add on the GFS t168 plus charts it shows part of the vortex setting up

where the ECM stratosphere forcasts show warming to occur.

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=town&alert=1

[stewfox]

An interesting week trying to get the precip type correct!

The marginal set ups next week ,more to do with synoptics or time of year

As we reach the later stages of February

[Frosty.]

No wonder it's so quiet in here today, next week is looking less wintry with every run, the 6z is very disappointing for cold and snow lovers with temps rising through next week to near average and plenty of rain with snow becoming restricted to hills in scotland. The ecm 00z still offers some hope with cold air pushing southwest but compared to the 12z yesterday it looks like this idea is fading with just northern scotland catching some snow.

[TEITS]

The marginal set ups next week ,more to do with synoptics or time of year

As we reach the later stages of February

If you don't mind me answering I would say both are responsible.

Although next week doesn't look that promising I still believe Tues could see some snowfall. At the moment based on the fax charts the greatest risk IMO is for E areas where the front may actually stall before weakening.

At the moment I would say E Anglia/E Midlands and then E areas further N. The greatest risk for the heaviest snowfalls is E Anglia/E Midlands because this is the location that the occluded front may stall over.

http://www.wetterzentrale.de/pics/brack2a.gif

However this is still subject to change and will be until the day itself.

Moving onto the longer range and im unconvinced by the model output. When we have disagreement at +144 between the models my confidence is very low. When you combine this with the unusual synoptics I feel its a case of wait and see.

[MP-R]

Ooo dearie me what another disappointing run. This really is rather messy for next Friday:

http://www.wetterzentrale.de/pics/Rtavn1441.html

Troughs all over the place and eventually the Iberian low transfers eastwards into Europe, allowing a high to take its place over Spain and by Mon 22nd we're into a more Atlantic flow. Thank heavens is well over a week away and much can change before then. I think I would rather see a continuation of this dry, bright and cold rather than wet and cold to be honest.

[TEITS]

The only positive about the 06Z is the eye candy in F.I is very plausible and could be the pattern that dominates much of March. The signals for March do suggest blocking to continue around Greenland with a very cold pool to our NE.

Obviously in March we're not going to see endless days of lying snow due to the strength of the sun. However the possibility of snow events remains and from my own perspective this is what im now looking for. I have seen plenty of days with lying snow in Dec and now im after a big event!

Still before looking that far ahead we have Tues to be focussing on. Tne 06Z suggest temps around average whereas the Met O have released an advisory suggesting snow for E areas on Tues & Wed. This makes perfect sense and im glad I didn't misread the fax chart.

[MAF]

The only positive about the 06Z is the eye candy in F.I is very plausible and could be the pattern that dominates much of March. The signals for March do suggest blocking to continue around Greenland with a very cold pool to our NE.

Obviously in March we're not going to see endless days of lying snow due to the strength of the sun. However the possibility of snow events remains and from my own perspective this is what im now looking for. I have seen plenty of days with lying snow in Dec and now im after a big event!

Still before looking that far ahead we have Tues to be focussing on. Tne 06Z suggest temps around average whereas the Met O have released an advisory suggesting snow for E areas on Tues & Wed. This makes perfect sense and im glad I didn't misread the fax chart.

was just about to comment on the change in the Meto warning Dave. and say that you previous post had already pre-empted the chance that your area and the east side of UK would be most favoured for any snow on tues/Weds

[D KARLSON]

Inference; I think at the moment there is low confidence past 120hrs and ceratinly past 144hrs , that said the models still suggest rather cold if not cold weather persisting especially over scotland , but further ahead is not really worth commenting save for a 50% chance of another cold outbreak.

As for the fax charts showing the cold front pushing south east monday ,tuesday going from previous similar events i think there will be some lowland snow produced from this front as the intensity and timing could well bring things on the right side of marginal certainly the potential for some heavy wet snow.

[MisfitDog3]

Hmmmmm...very interesting set up for Tuesday through to Wednesday onwards starting to show up on the models. Who'd be a forecaster having to call that one?!

I do have to laugh at the number of times I see postings that seem to assume as as soon as we approach Valentines day the potential for sustained very cold weather has gone. Can memories really be that short? It was only 3 years ago we had an extended cold spell well into March! It's a very interesting 10 days coming up.

[bluearmy]

http://www.meteogroup.co.uk/uk/home/weather/services/ensemble_forecast.html?eps=leuven

love to see the run that brings those temps to belgium.

check out the london temps - definitely a cooling trend longer term and the tues/wed precip of 20mm occurs with temps no higher than around 3c. could be very interesting chilterns way if that verifies.

[johnholmes]

I've put my ideas on how the next week may evolve and why in the link below

http://forum.netweather.tv/topic/61410-will-it-snow-at-low-level-next-week/page__st__17__gopid__1773791&

[Duane S.]

http://www.meteogroup.co.uk/uk/home/weather/services/ensemble_forecast.html?eps=leuven

love to see the run that brings those temps to belgium.

check out the london temps - definitely a cooling trend longer term and the tues/wed precip of 20mm occurs with temps no higher than around 3c. could be very interesting chilterns way if that verifies.

Ignoring that one mental 'day after tomorrow' member , pretty good ens long term, certainly leaving open the possibility of a further cool down into Feb.

Clearly different charts at the point where the GFS and the ECM go their seperate ways...

[yamkin]

The only positive about the 06Z is the eye candy in F.I is very plausible and could be the pattern that dominates much of March. The signals for March do suggest blocking to continue around Greenland with a very cold pool to our NE.

Obviously in March we're not going to see endless days of lying snow due to the strength of the sun. However the possibility of snow events remains and from my own perspective this is what im now looking for. I have seen plenty of days with lying snow in Dec and now im after a big event!

Still before looking that far ahead we have Tues to be focussing on. Tne 06Z suggest temps around average whereas the Met O have released an advisory suggesting snow for E areas on Tues & Wed. This makes perfect sense and im glad I didn't misread the fax chart.

FI is showing some eye candy Easterlies which is very interesting.

I'm confused with the MetO Fax Chart http://www.wzkarten3.de/pics/brack2a.gif MetO advisory is showing snow for the East and Northwards, but their latest SE outlook for Monday to Wednesday states the following: Tuesday sleet and snow is expected, with some accumulations possible. Wednesday outbreaks of lighter sleet or snow.

[cooling climate]

Just been reading over on Eastern US and the with the AO index standing at -4.7 yesterday

(record tying 8th consecutive day) and another - 4SD reading expected today this will apparently

break the record set in 1969.

70% of the US is snow covered with a large swathe of snow around the 30 degree latitude

and snow forcast into Florida today and tomorrow.

Despite this amazing blocking to the north the UK have only seen rather cold weather

since the latest phase of the very negative AO with the very cold weather missing us to the

southeast.

I think we in the UK would have to be very unlucky to miss out on another very cold and wintry

spell of weather with the amount of blocking just to our north plus with the warming expected

to our north at the 30hpa level and the down-welling negative zonal winds from the MMW.

Maybe patience is the key and we will have to wait until nearer the months end but seeing the

way the Euro's are starting to trend I think the return of real winter weather will be sooner rather

than later.

[johnholmes]

FI is showing some eye candy Easterlies which is very interesting.

I'm confused with the MetO Fax Chart http://www.wzkarten3...ics/brack2a.gif MetO advisory is showing snow for the East and Northwards, but their latest SE outlook for Monday to Wednesday states the following: Tuesday sleet and snow is expected, with some accumulations possible. Wednesday outbreaks of lighter sleet or snow.

I hope the blog I've done might answer the query about their Fax chart and the country being mainly in Polar Maritime showery air by late Tuesday.

[Snowyowl9]

It`s going to be a right mix of rain/sleet and snow next week and on the cold side,looks like above 200metres does get a covering going by this.

http://www2.wetter3.de/Animation_06_UTC/120_35.gif

[Duane S.]

Just been reading over on Eastern US and the with the AO index standing at -4.7 yesterday

(record tying 8th consecutive day) and another - 4SD reading expected today this will apparently

break the record set in 1969.

70% of the US is snow covered with a large swathe of snow around the 30 degree latitude

and snow forcast into Florida today and tomorrow.

Despite this amazing blocking to the north the UK have only seen rather cold weather

since the latest phase of the very negative AO with the very cold weather missing us to the

southeast.

I think we in the UK would have to be very unlucky to miss out on another very cold and wintry

spell of weather with the amount of blocking just to our north plus with the warming expected

to our north at the 30hpa level and the down-welling negative zonal winds from the MMW.

Maybe patience is the key and we will have to wait until nearer the months end but seeing the

way the Euro's are starting to trend I think the return of real winter weather will be sooner rather

than later.

I agree with that. And perhaps it highlights how off kilter what we have experienced so far this winter is for the UK. That time we got lucky.

[Winter Monsoon]

Just been reading over on Eastern US and the with the AO index standing at -4.7 yesterday

(record tying 8th consecutive day) and another - 4SD reading expected today this will apparently

break the record set in 1969.

70% of the US is snow covered with a large swathe of snow around the 30 degree latitude

and snow forcast into Florida today and tomorrow.

Despite this amazing blocking to the north the UK have only seen rather cold weather

since the latest phase of the very negative AO with the very cold weather missing us to the

southeast.

I think we in the UK would have to be very unlucky to miss out on another very cold and wintry

spell of weather with the amount of blocking just to our north plus with the warming expected

to our north at the 30hpa level and the down-welling negative zonal winds from the MMW.

Maybe patience is the key and we will have to wait until nearer the months end but seeing the

way the Euro's are starting to trend I think the return of real winter weather will be sooner rather

than later.

I really hope your right. With my limited knowledge all i have seen is constant downgrading this month especially with this current event. And i would have thought we would have to be very lucky to get FI into the reliable without downgrading along the way. When things look to be going right for us the uk always seem to end up on the wrong side, aside from the occasional lucky strikes.

FI looking good at the mo but lets see if it continues....perhaps a small westward shift would be better?? Fingers crossed its a new trend/signal that doesnt go the way of the pear as it moves towards +96.