lorenzo
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Posts posted by lorenzo
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Just re-posting from the mod. GFS invigorates the LP and it is looking pretty lively to say the least..
In fact very lively..
Somewhere is going to get an absolutely wild time from that..!
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Quite a vigorous low on this run.
Edit - add wind gusts from GFS. Amber warnings from that I would think.
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This entire page, all talk about a potential easterly out in FI. And nothing on the mid term - very cold northerly,Why do people do this?
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What Northerly ? Could be a valid question to ask when comparing the amazing output from the 00z runs on Sunday morning and now looking at the way events are unfolding, through last night 12z and this morning. The main areas affected are certainly being discussed in the Regional thread.
With the model thread catering for the whole of the country, it is logical for folks to look at the potential set up for the rest of the month, I am sure if this Northerly had remained undiluted then it would still be getting the discussion it deserves.
Plus, it just wouldn't be Winter on the model discussion without our annual hunt for an easterly. It's some kind of weird exorcism and catharthis of last years demons created by the ECM.
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Me being no expert on equatorial waves, but I think what actually happens is that the CCKW's do not mimic an OLR signal, they create it. OLR anomalies (outgoing longwave radiation - not sure if that's appearing on the new mouse-over?) is a good proxy for convection in the tropics. CCKW's are a fastish, eastwards moving wave which come with a convective signature that shows up in the OLR anomalies. So the OLR signature is true, and real.I think the issue is that models find it hard to distinguish this from the MJO wave.
(Broadscale) Convection in the tropics can be due to CCKW's, mixed Rossby-Gravity Waves, tropical cyclones, cold fronts, convergence zones, equatorial Rossby Waves, favoured zones of convection due to ENSO state.....and probably a lot more. The above operate on different time-scales and can interfere with each other.
To isolate the contributions of different waves, they run their signals analysis (which I think is a fourier analysis) and try to identify which waves are contributing to the current convection. This can be difficult. It may be especially so when you're dealing with CCKW's and the MJO, because the two behave quite similarly.
The structure of the MJO is often similar to a CCKW, but it moves more slowly.
The models might perk up a bit when the CCKW and MJO are no longer in phase with each other and causing confusion of the signal.
Thanks for the further explanation, it is something I was beginning to look at before being distracted by the Northerly, the above bit in bold was generally what I was trying to say.
The chart I am looking at and getting my head round for this is located here http://www.atmos.albany.edu/facstaff/roundy/waves/hovsdet/0_7.5N/
Latest forecast example
The MJO CPC update comes out each Monday evening. Mike Ventrice site is also an amazing resource of everything in the tropics, can't begin to describe everything here http://mikeventrice.weebly.com/tropical-waves.html
MJO shown in red here with Kelvin Waves in Black
Plotted a couple of composites to try and fathom whether MJO activity would add bearing to the first half of December. Looking at the phase of the GWO, phase 2 Northward momentum transport, a low AAM state and taking into account the neutral ENSO state. These are all dates since 74, filtered for phase 2/3 of GWO and ENSO -1 > 1 values. Then again with MJO filtered for phases 2/3/4.
Not withstanding the west atlantic ridging am unsure about these plots, what is clear from the dates when filtered that there is a healthy split between developing positive NAO regime and the Scandi Block. At present, the positive NAO I believe has the edge. Not great news for folks hunting cold, and hope to be wrong !
Having talked myself out of the Scandi high verifying, for reference this morning 00z normalised Ensemble mean, advertising the Scandi High, this for 14th, which helps change my mind back the other way ! ECM will have to do 'very' well with this to help everyone get over 'that ECM'..
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Well the main models have shifted a fair bit since yesterday morning and the Epic output on offer, 12z last night saw the Eastward shift in the cold plunge, which may be some short term pain for longer term gain as this will serve to give Europe a real chill.
Looking at the impact of the northerly, we are still on course for a solid cold blast, don't let the downbeat thoughts in the model thread kid you.
Thursday Fax from 6am this morning, will see what the 850hPa temps look like on UKMO 12z run later, still a good true Northerly hit, so whilst transient, it is decent.
Few charts from the GFS this morning too..
Snow still on the cards for some, however wind becoming the other main part of the story, with some strong gust profiles being modelled now.
It seems that so far this Autumn / Winter the models themselves are attracting as much debate as the actual output. Yesterday morning runs were at the top end of the scale for what we could get, and this is still a tricky one to call at 84 hrs out. No denying the depth and duration have downgraded since Sunday a.m.
Simply put, the models don't like the vortex shifting around as SK pointed out the in model thread, for me the transfer from Scandi > Canada looks even at present a little quick. Let's hope it slows a little and lets the Northerly extend.
And, it wouldn't be a Winter on Netweather without the annual hunt down the Easterly !!
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Panto was fantastic, much cheerier place to be than looking at the models this evening. Allan Stewart and Andy Gray are superb.
Kids loved it. Only the second show of the run so plenty of stuff going wrong, lines forgotten, props going wrong, timing all out. Added to the fun, won't mention much else as don't want to spoil it for folks who might be going this month.
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See attached example (no longer the latest/valid output, so safe to reproduce for 'education' purposes!!). It's for Thurs. Note polar low signal off W Norway, or at least how the potential was progged in this previous run.
Thanks Ian for the invaluable input this afternoon, a real insight to what is happening with the forecast for this week, and adds another dimension to the excellent discussion already on the thread about this week and also looking beyond. Steve, you're firing on all cylinders today !
I read a lot that Polar lows are never visible on any NWP output, amazing data on that image, couple of notable plots on the control run there, if consistent with a solution, would these be translated to the main UKMO run or are they used to say adjust the Fax output?
Where would we be without Dalmatians and Shannon Entropy !
Also re: GEM, it isn't so bad at 72 hrs, compare with UKM & JMA here.
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Update from fergieweather on snow probabilities & Polar Lows, which by the time you get through the thread to find, will either be in a previous thread or buried in an avalanche, no pun intended, of other posts.
10-20cm possible in places, blizzards & drifting. It had me at 10cm...
Well deserved one of these..
To add, post on the previously mentioned Polar Low threat, W. Norway. This referred to as the Dalmatian Plot.
Some great posts from Fergie today explaining why the met see ECM too amplified and therefore blend in GEM and GFS.
What a period of model watching we have coming up. 12z will be pantomime this evening, going to miss them by being at a real Pantomime!
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Yep Hawesy. I think the real attraction with this is the exceptional depth of the cold. For those of us in the Central Belt. The well advertised wishbone effect. WE can hope for a trough to develop in the flow and the faxes will be getting closely scrutinised, as will the NW coastline of Norway, Polar Low spawning grounds.
Raided the GFS 06z run on NetWx for some of the charts now it has decided to join in the fun as Meto. Winter begins.
Thursday mid-day sees the first advances of cold air making its way south.
Before the above wishbone Northerly becomes apparent.
Can't resist posting up these Potential Equivalent charts... Properly Arctic.
850 hPa temps are just incredible, sorry I may be a stuck record by midweek !
No surprises then with the 0 degree Isotherm, anything falling will be snow. Friday morning minimum temps are brutal.
Closer up on the snow risk chart for Scotland, the Northerly signature is clear.
So, whilst we are hoping for another couple of features to pop up to provide interest for all, the real feature here will be the clean Arctic hit of air.
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Distance to Earth countdown back up and running..
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Fergieweather mentioned the shades of '53, not an event I was aware of, this is a good find in our Regional Thread by Blitzen on that evolution, with Wetter archive Gif. Update, thanks to GU Weather, Blitzen had lifted this from an overnight post in here.
Original charts.
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Welcome to Winter GFS.
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This thread is like a 24 hour garage these days, folks up at all hours posting !! Good stuff.
Winter arriving right on queue, some great cold charts on offer today.
Yes, just over Iceland that IS a -17 850hPa temp reading !!
Looking higher up solid -40 profile, old school colours on the meteogroup one, fits well just looks frozen.
Dust off the satellites and radar, a real Polar Low watch / opportunity!!We have a couple of things to trust, 1) the models are doing very well at picking up on these Northerly hits from a decent range, they wobble here and there en route, but the trend is doing very well at verification.This is going to feel bitingly cold.Edit - add temp chartThis from the 00z GFS, 06z not at the weekend yet, a proper swathe of cold right down into the continent.. which is good for other potential set ups that shall not be named for fear of spooking them...
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Bone chilling blast of cold, sharpest of the Northerly hits so far, great to be seeing proper wintry looking output on 01st December.
Satellite will definitely be worth a watch for non NWP features going by the 500hPa temp profile. Stunning.
Out to mid month and commented on by Nick wrt NAEFS anomaly, the ECM control run in FI also parks this Scandi/Euro Block.
Which would lead to another spell of good model watching, with NWP notoriously wobbly in modelling strong cold blocks, with the addition of frontolysis and fronts getting chewed up. How much colder can this weeks blast get...
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Weather models are not horses !
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Very sad news, thoughts go out to those affected by what is such a surreal accident. A routine shift at work, or a Friday night visit to a pub to see a band impacted by the completely unexpected.
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GLAAM tendency still falling into the low momentum phases.
GEFS forecast sees the orbit through phases 2 and 3
Composites below
Then onwards to
MJO plots for the models are still quite scattered, GFS bringing in phase 2, however ECM and UKMO not in support.
From Adrian Matthews page, only the briefest of forcing which possibly will not qualify as an active MJO.
Saw a good post where it was discussed that some anomalies creating transport on the wheeler diagram for MJO forecasts are a result of CCKW, Convectively Coupled Kelvin Waves, they create a noise signature in the models which mimics OLR and hence we get an MJO forecast. Might need to start looking more closely at OLR - Outgoing Longwave Radiation plots in conjunction with whatever is forecast for verification.
With the above in mind, would be following what the vortex is up to and comparing what is the lead on the 100mb strat charts.
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Just looking at EC ens clusters for 14th December.22/51 members going for Scandinavian High + Mid-Atlantic Trough (looks similar to the GFS 18z chart shown above).
29/51 for Scandinavian Low + Mid-Atlantic High!
Remains annoying that the ECM removed those postage stamps, still saves us all some worry. More sensible odds than the 80:20 split in the ensemble suite last year that left everyone kicking the cat !!
At 168 Colder 850hPA temps dialling in on the UK and Europe getting a proper wintry blast, interesting that this is almost a diluted version of some of the rampant GFS control run charts from a couple of weeks back.
GFS and ECM
Beyond that a couple of control charts from the ECM suite out at 300, to show the easterly flow appearing on the ensembles.
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SOHO scientists announced ISON had vaporized at perihelion.
Then ISON appeared out of nowhere at around 1145 on the C3 Solar observer.
Who knows !!! Looks like it has survived to me.
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A clearer image now of the earlier C3, this the raw image file.
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TInfoil hat and all that - wonder what the predicted trajectory is ? if part of it sheared off and altered this, it looked like this happened in the earlier C2 Image, ( red one) which shows dust cloud well ahead of the position of what is now potentially the reduced nucleus.
Anyone better informed to clarify what was expected?
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Still looking very bright, not sure what trajectory this should be on , if this is a remnant or if the nucleus has popped and this is a fragment??
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/ opportunity!!
In Depth Model Discussion and Summaries
in Spring Weather Discussion
Posted
Yes Weatherbell charts are subscription ones. They occasional appear on twitter from Joe B or Dr Maue.