WhiteFox
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Posts posted by WhiteFox
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32 minutes ago, Eastnorthwest said:
Unreliable model madness will kill positive debate if things don't improve in the future ,what images shows is what I've been saying all winter ,anything on the models beyond 120 hours can't be relied on is now sometimes down to 96 hours which makes the forecasters job a nightmare ,I look forward to the day when the model performance improve s
I disagree! What you need to do is tune out the noise. The longwave pattern is identical in the two charts that @West is Best posted. The surface analysis is different because it always will be at that range; smaller scale features are enormously complex to forecast.
As far as forecasting goes, IMHO, you can only reliably predict PPN amounts and temperature within a range that broadens as you move further out in time (yes, there are times when the range narrows or widens, generally when a pattern change is occurring). Beyond that, you are simply looking at likelihoods and probabilities; no scientific forecaster will be willing to say if it will rain and what the temperature will be at a particular time on a date more than six days in the future. They may forecast above or below average conditions in a range of categories for a period of time, but I don't think that models going past 6 days were ever intended to be taken literally, but rather as a guide.
Forecasts do bust, with this winter being a prime example. But, on the whole, NWP models are pretty good when it comes to forecasting PPN (not type!), wind direction and overall conditions out to the six or seven day range. Going further out, I only consider a forecast to be a bust if a predicted pattern change hasn't happened or an unforeseen change did happen (e.g. mobile to blocked) and anything beyond day 10 is simply a possibility rather than a likelihood.
A forecast hasn't failed just because a secondary low appeared on one operational output and then does not on the next: that is what I mean by noise.
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50 minutes ago, feb1991blizzard said:
Your never going to be that accurate that far out - its a strongly +AO / NAO setup which it got right.
Yes. It's often said, but look at the overall pattern: the 500mb forecast was largely correct, but it's incredibly difficult to forecast exact conditions closer to the surface at a longer range. Given the range involved, it's pretty good. If you'd looked at the 500mb forecasts you'd have said that the likelihood for the weather in ten days time was unsettled with a high probability of rain at times. And so it transpires.
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17 minutes ago, prolongedSnowLover said:
It’s a parallel universe the GFS-P runs on
I suspect that the GFSp needs more than a little tweaking. I've been following some of the recent storms in the US and its predictions for snow amounts in the north east have been utterly woeful: consistently far too high. To be honest, I haven't paid it much attention, but from the few charts I've seen in here it has a consistent bias towards producing cold and blocked output for Europe. That could be because people only post it when it shows cold, but I get the feeling it does this far more frequently than the live GFS.
I've seen a couple of forecasters in the US say that the whole model needs to be deleted and to start again!
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2 hours ago, Nick F said:
Thanks, I've been guilty on a number of occasions this winter of getting carried away and jumping on the SSW and/or MJO going through 'colder' phases being a definite force for good and WILL change the patterns without addressing the caveats too. Some do of course attach the caveats of caution to the possible benefits of the 'positive' signals, something I will certainly do from now on, after those positive signals have clearly not manifested in the troposphere (such as SSW) or have been overridden by other factors (MJO). Worth pointing out the drivers and teleconnections are still a useful tool, but being too confident in their use to predict more than 10 days ahead can easily end up with too many bust forecasts. This winter has been a good test for those longer range predictions.
Some very good points and the one highlighted is the key. Making predictions based on signals is fine, but it's based on what little we know and always has caveats applied to highlight that they are based on probability and are not definite. I fear that sometimes people choose to ignore the probability side and choose instead to make snide remarks, but that should not out anyone off from making a forecast if they base it on sound analysis.
We still have a huge amount to learn and have very little data to work with; onwards and upwards!
Just to add, it has seemed likely for quite a while now that high pressure setting close to the UK seems the most likely outcome and nothing has changed my view in that respect. The MJO moving into phase 8 means nothing on its own as I posted a few days ago; until the Pacific pattern changes from the current setup there is little to no chance of anything popping up to our north IMHO. I'm interested to know just why the Pacific has been so locked into the same pattern this winter.
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10 minutes ago, winterof79 said:
Waste of effort in the other thread.
Indeed. If you're not pointing out a route to bitter cold you might as well whistle in the wind...
For quite a while it's looked like high pressure builds over or just to east of UK. Chance of some surface cold with a chilly continental flow, or a warmer southerly flow with a chance of an Atlantic incursion. Could even be frost and some fog. What does not look likely is a bitter cold outbreak!
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7 minutes ago, Mike Poole said:
Yes, sensible post. We really can't see much further forward than this from the op runs at the moment, uncertainties quickly creep in in synoptics like this set up, given the trajectory of the MJO in particular, and how it affects us, and there's a lag with this too, so how that factors. All getting complicated for us and for the models, so while I'd not bet my house on a run that shows Narnia at T360, I wouldn't get worried at all if there were 'winter over' runs at that timescale.
A winter dominated by theories and uncertainties, and disappointments for some. Still some more dice to fall before we move on to spring and summer, roll on for a bit more, winter....
The current modelling seems fairly consistent with the projections for the MJO into phase 7. Given the GFS forecast for phase 8 you wouldn't expect that to start showing on output until towards the end of the runs anyway.
If the phase 8 amplitude pans out as forecast on GFS then it would be surprising if we did not see some sort of attempt at ridging towards Greenland. For now, the ECM does not back the GFS at the same sort of amplitude though.
For the moment, I still think some sort of Sceuro high seems fairly probable in the medium range.
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18 minutes ago, alexisj9 said:
Where's the second low going?
I think they're forecast to phase into the main low. Some very unstable conditions hence the likelihood of secondary waves/lows forming over the weekend.
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5 minutes ago, ICE COLD said:
Yesterday’s T168 and today’s T144 . Definitely gone the wrong way . I thought the ecm was king ? Have no confidence in it at all anymore after this winter .
You've got to bear in mind that the overall pattern is much the same. Compare the 500 heights and you will note that the wave pattern is fairly close between the two. At a more local scale, the small differences in the 500 pattern mean fairly large changes locally at the surface. So, it may seem that the model is jumping around a lot, but on this SE two charts they are fairly consistent.
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Excellent satellite picture posted by Marco Petagna on twitter showing the rapid cyclogenesis:
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17 minutes ago, knocker said:
Yes that is true but still a strong jet running south of the trough and exiting the eastern seaboard so how this diverges in mid Atlantic courtesy the ridge/block to the north is just another key element. One thing is for sure it will be interesting to see how the surface analysis pans out with still a fair amount of energy in the mix.
My fly in the ointment was regarding the composites
Yes, the Pacific pattern seems to be favouring the cut off upper low over Canada; conflicting signals from what I can see.
I think that the EN neutral composite probably sits best as we have not seen the PNA swing towards positive and no Aleutian Low.
With the Pacific doing its thing, favouring the low over NE Canada, the Sceuro high seems plausible given the push from the west preventing ridging from building too far north.
If the MJO moves into phase 8 (and that GEFS forecast is a huge amplitude) then we may see some forcing on the Pacific pattern which could open the door to Greenland if the Canadian Low pulls away. But, ECM does not favour such a high amplitude for the moment, so perhaps the Canadian low will stay close to its current position leaving the UK in a coldish anticyclonic flow.
It's all about the amplitude: it seems that it would take something big to change the Pacific pattern and the GFS seems to be providing it...
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9 minutes ago, bluearmy said:
Not sure posters are appreciating the big differences we are seeing within a few days. Suddenly we have a very amplified picture within a week whereas a couple days ago it looked pretty flat ...... go back about ten days and the general feel post the wintry spell was a period of mobility, followed by a push ne of the Azores ridge and the potential for a scandi ridge. take out the week of ‘meh’ nwp and we are getting back to where we thought we could be going.
now add the slider potential (re day 10 ec op and clusters from the 00z) and we could easily arrive mid month with euro low anoms and high anoms to the north ...... it may be a step too far to ask you to have fait( in this but it is making some sense .....
It's been clear all winter that Atlantic systems are struggling to push through the UK on a regular basis. I never bought into the high pressure setting up to the south scenario; given a lack of momentum from the west, north-building ridges always seemed a decent possibility.
Exactly where the ridge ends up depends very much on the upper low over Canada; nudges slightly east or west will have a large impact on the source of the airmass which we receive.
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31 minutes ago, Quicksilver1989 said:
Don't get me wrong it isn't too bad but the Scandi high could whip up some mild air quickly... reminds me of February 2017 and the easterly that occurred then. The wind is also of s SE'y with an anticyclonic curvature so snow showers may be limited in such a setup.
Anyhow a lot of water to pass under the bridge till then.
I've thought for a few days now that surface cold from the continent seems a viable outcome. Without the cut-off upper low moving from Canada there just seems too much pressure upstream to enable heights to build far enough north to deliver a direct easterly feed. In these situations, a cold SE flow is far from out of the question. Surface cold with hints of deeper cold, but nothing like last year I suspect.
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Noticed that the River Loddon had burst its banks in Shinfield on Tuesday morning (5th February).
Can only assume that this is because of snow melt upstream as the river runs from Basingstoke thorough Swallowfield, Shinfield, Twyford and then into the Thames.
Won't take much rain to add to flood risk so worth watching what happens PPN wise over the next few days. Not high enough to cause any damage as it is within its floodplains, but suspect the dry months followed by heavy snow upstream have had a sudden effect.
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4 minutes ago, feb1991blizzard said:
El Nino's do favour a cold late winter / early spring though.
Yes, that's true. But we're barely into EN+ (still neutral by US definition) and it looks like the Central Pacific region warming so that would possibly imply a different effect from a standard EN+. The PNA has not been typical of EN+, so it leads me to believe that we cannot necessarily expect EN+ analogues to verify.
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9 minutes ago, feb1991blizzard said:
That isn't just above average heights - WOW! Thats a stonking big greeny high - the anomaly is so strong.
Yes it is. But, I'd like to be able to look at compound anomalies taking into account QBO, ENSO (both trending rather than developed) and the wildcard that is this year's SSW event. On its own, the MJO chart tells us only that in previous months of February where we have EN+ and an MJO phase 8 amplitude>1 northern blocking is more likely.
Nowhere near enough input in order to gain a clear idea of where we could be given the current setup.
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14 minutes ago, bryan629 said:
What sort of time frames are you thinking ?
Here you go:
High amplitude phase 8 in February during an EN+ implies above average height anomalies towards Greenland. Worth mentioning that this does not take into account the fact that we are in a developing EN+ and that it looks likely to be Modoki.
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1 minute ago, bryan629 said:
What sort of time frames are you thinking ?
Difficult to tell looking at that chart as it's a bit blurry when I zoom in on my phone, but I think it shows high amplitude phase 8 in around 12 days. Add on a few days for lag and say around 20th February.
The forecasts MJO will change, but if it keeps hinting at that sort of amplitude in phase 8 and we don't see any signs of northern blocking close by then goodness knows what it would take!
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20 minutes ago, tight isobar said:
The weekend needs an eye already..
Wouldnt take a great deal of tweeking for snow quite widely in the forecast...ecm 12z...
Already the notions- are noted !!!
I'll keep my motions to myself, but looks like I picked a good weekend to be in Glasgow. A drive to Loch Lomond beckons...
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14 minutes ago, bryan629 said:
Hi BA,
I don`t understand a great deal about the MJO, but looking at the current forecasts going into phase 7 and 8 , shouldn`t we be seeing some sort of HLB in the models by now instead of a raging PV as is been advertised. I do understand there is a lag effect to consider, so when do you expect , if at all, the phase 7 and 8 being picked up by the models?
Is the WAA over Alaska into the pole something to do with it as well ? .
Normally you would expect an MJO moving into a high amplitude phase 7>8 to increase the probability of northern blocking. This winter doesn't seem to repsect the rulebook though...
Anyway, it seems that we need something special from the MJO to make any difference; even a medium amplitude phase 7 implies a much better Atlantic profile than the GFS has been showing. But, MJO forecasts haven't been great this winter; lots of variation in fairly short timeframes. Could it be that the combination of downwelling easterly QBO, developing Modoki EN+ and SSW simply overwhelms any MJO signal?
A high amplitude phase 8 would be a good test, so we shall see.
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28 minutes ago, ICE COLD said:
You say that but it has been the form horse for nearly a year now . The models show a long unsettled spell ahead but in reality it only last for around a week before high pressure comes back on the scene . It’s happened time and time again ever since the ssw last feb/March . Let’s hope we can get high pressure in the right place for a cold spell this time .
I keep saying it, but it's the treacle effect! Time and again we see models throwing powerful systems towards us, only for them to downgrade once they get within the 5-6 day timeframe.
Looks possible this may be repeated which is a little surprising as I thought the ultra cold airmass from the US would push it through this time.
There has been a genuine lack of momentum from the Atlantic since last march; kind of reminiscent of the period in the mid-1990s which saw a prolonged dry spell (and some good summers to boot).
"If onlys" are meaningless, but if only that PV was somewhere else. Of course, it's all part of one pattern, so it is all linked.
Whatever happens, it does not look like we will be stuck under a mild high to the south for any length of time and we seem to keep seeing the jet tracking south.
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3 minutes ago, Danielvn said:
Can we stop using phrases like “I think we deserve it”?
The weather doesn’t respond to what people deserve or not. I mean how does one come to deserve cold weather?
Also, what kind of person goes around telling their family about what the weather’s going to be like based on background signals?!?!?!?
i sometimes tell my wife about possible snow events up to a week out and I end up with egg on my face more often than not.
Ha ha!
I have an email group of some family and friends who are interested in the weather where I post my musings. Always very careful to point out what could go wrong and add estimated probabilities. Never tell those who are not interested in the weather until you are 90% sure! It may seem that it would be great to be seen as a sage for forecasting bitterly cold weather weeks out, but your credibility will bust fairly quickly!
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1 hour ago, Vikos said:
What makes me so currios is the fact, that a couple of days ago there where severe easterly outbreaks predicted by GFS, later EC...both discarted them and turned to an active atlantic within only few runs. The thing I can't catch is: why is this (still only predicted) pre-spring'ish weather seen as final, but winter'ly conditions are completly out of reach? Isn't it possible to see this swingaround in a couple of days again?
I grabbed in a big pile of sh***t when I told near people (friends, family) AGAIN that there will be freezing cold conditions by mid-Feb,
I learnded that I shouldn't predict something for sure these days... this jet is wibbely-wobbely...
The answer to your first question is climatology: on average we have west to east progression of Atlantic systems. Yes, we could see a flip as the NWP models have struggled beyond five days all season. I don't think we will have a locked in period of high pressure over Iberia for an extended period, and there are likely to be some surprises cropping up at short notice. I think the combination of the negative PNA and uncertainty over SSW impacts on the Arctic profile will continue to cause problems.
Throw in some bizarre MJO forecasts and the ingredients are there for flip-flopping. I still think that until we see a more favourable Pacific pattern and consequent shifting of the PV from Canada, we are looking at occasional hints of Scandi blocking or small wedges of high pressure.
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Input appreciated very much from all on here. Just a note as we head into what *should* be a relatively quieter time before the next cold spell.
The extra umph from last week's frigid spell in the upper Midwest looks set to allow the Atlantic to make an appearance this week as the upstream pattern flattens and we see systems start to track towards and across the UK. It's actually much needed PPN down here, so not too many complaints.
The question is whether we become stuck in a pattern where there is high pressure to the south and east and low pressure further north and west. Some signs of this in coming days, yes, but I don't think that we will become stuck under a high drawing southerly winds from north Africa a la 1998 for a great period of time. There is a risk, of course, but the general sluggishness of systems as they approach our treacle in the NE Atlantic may spring a few surprises.
What of northern blocking? As we were really, I feel. There are some signals conducive to blocking teleconnection-wise but we've seen difficulty overriding the stubborn Canadian PV lobe all season so until we see a chart within 48 hours showing the Canadian lobe exiting the stage we continue to look to thread the eye of the needle for easterlies or brief northerly outbreaks. In theory you'd think that the direction of the MJO would help to support some blocking, but there clearly seem to be some overriding influences.
The signal for troughing to our south seems to be receding, but much is dependent on the AO and the overall Arctic profile. The Siberian high seemed keen on heading west for a while, but with the PNA's resolute refusal to turn positive for a prolonged period it seems unlikely that Mr Siberian High will have the resources to visit our shores. We are approaching the time of year when the PV naturally recedes so chances of cold outbreaks may well increase. But, with the Canadian PV clinging on we could end up With a fudge solution where we see some continental surface cold but nothing of any real depth.
Always the chance of some colder outbreaks of cold of course, but I cannot see how any real sustained cold arrives without the Pacific pattern changing, and at the moment there do not seem to be many signs of this happening.
Now I've posted this, expect the next suite of NWP forecasts to show a positive PNA and northern blocking...
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1 hour ago, alexisj9 said:
Not sure why people are so down beat at the min. For us that was a cracking cold spell, very surprising considering it came for on the north. I've had three snowfalls, mostly word only landing in the hills of course. But two had very slight local accumulations. I'm including the first mini cool down in that. The first low, and the third low left slight accumulations here. The last one, even though it rained on top. I think it will warm up this week, then go back down. That cold in the states was just to strong for the Atlantic to hold back.
I think it's the inevitable come down following the snow!
I'm very happy with what I got: lying snow has been very rare here over the past twenty years and this is the fourth morning this year with snowcover in the back garden.
Always a bit sad to see it go though!
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Tuesday 12th March weather observations
in Weather reports
Posted · Edited by WhiteFox
Typo
Days like today are what really drives my interest in the weather! Just look at that perfect squall line that has formed ahead of the cold front:
Anyway, dull and drizzly here with winds gusting to 25mph from SW. Pressure 998.2 falling.
Temperature 9.6, DP 7
Rainfall since midnight 1.4mm.