nick sussex

Overall model rating 6/10. Longevity and depth of cold isn’t really there and although there is some wintry potential it looks marginal for most areas . It could be worse but best to temper expectations until nearer the time when more accurate 850s will be known .

I don’t want to be a grinch but you have to factor in issues around shortwave modeling this far out near Iceland . What can often look like a clean flow this far out can get interrupted by shortwaves . So in terms of 850 values really far too early to say .

Just got in reading the last few pages and you won’t be surprised to see that NCEP note a lot of uncertainty . This was the 00hrs discussion . The ECM should hopefully clear things up ! NCEP update again later so more then .

Looking very unsettled in the run up to Christmas . I think a se correction is needed though and shortwaves near Iceland won’t be picked up this far out . In terms of wintry potential still too far out to be sure of as the GFS does have a cold bias in this type of set up . I give the GFS 6/10 .

In terms of the medium term and any initial nw n flow still uncertainty there as much depends on the set up in the eastern USA and Canada . This from the morning NCEP extended discussion . Guidance/Predictability Assessment... Model guidance continues to be agreeable with the southern stream upper low system into Friday, but model spread rapidly increases into the weekend. Models have been waffling over the last few days with the strength and track of a northern stream shortwave likely moving southeast through the northern Plains Friday. This feature may combine with the southern stream upper low in the east-central U.S. in some way, and most models from the 12/18Z model suite and now the incoming 00Z have trended toward some sort of combination. GFS runs indicate the northern stream energy dropping south to become part of the upper low, while the ECMWF and CMC create more of a phased trough for a time before additional southern stream energy comes in to help close off a low (with different timing between the two). These differences aloft create ample differences in models and ensemble members for a resultant surface low track and strength. A day ago, GFS runs (with some GEFS member support) were the fastest and farthest north to bring the low track across Florida. Now the GFS runs have slowed but still look to be on the west side of the spread (resulting in more QPF onshore in the Southeast). Meanwhile the 12Z and newer 00Z CMC switched to the faster side of the spread in bringing a low north. The 12Z ECMWF seemed to be a good middle ground in track/timing but the 00Z ECMWF is even stronger and faster in bringing the low north as a nor'easter. Confidence is very low in the low track and QPF given the models are in such flux. The northern stream shortwave is currently over the northeastern Pacific, a classic data-devoid region that leads to uncertainties in the models downstream. Interesting that they also mention data issues in the ne Pacific .

I’d be wary of outputs that take the PV eastwards at longer range . We have seen this before and then as the time counts down a chunk is left over ne Canada . You really need to see this modelled at closer range . Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4974743

The ECM has now decided to phase the eastern seaboard low with shortwave energy heading south out of Canada at day 7 . You need the low to now deepen even more and run ne helping to pull some of those low heights away from Greenland . Still a bit too flat upstream . The low needs to be more inland before the phasing .

I’d be wary of outputs that take the PV eastwards at longer range . We have seen this before and then as the time counts down a chunk is left over ne Canada . You really need to see this modelled at closer range .

This is a slower evolution from the GFS moving most of the PV east. But it will end up more interesting . Problem is of course the longer it takes the more variables can pop up . Let’s hope for the favourable topple later towards Scandi . The GFS has other ideas with some shortwave energy running around the high .

The GFS used to have a fiat bias upstream and had difficulty with phasing of northern and southern arms of the jet so it would be a surprise to see it beat the ECM and UKMO . The ECM 06 hrs control run however did nudge towards the more amplified upstream pattern at T144 hrs and the ICON 12 hrs has followed suit so it sets up an interesting evening . The bellwether is that low eastern seaboard . Deepening and running ne is what we want to see .

The low on the eastern seaboard needs to develop further and run ne but its a start at least . Certainly it’s more amplified . The plot thickens !

Before the afternoon runs come out , the ECM 06 hrs control run was slightly more amplified over Canada at T144 hrs . The 12hrs ICON is trending towards the GFS upstream pattern .

The GFS 06 hrs run is flatter upstream and fails to develop the low over the eastern USA . Its still different from the ECM but without the deeper low running ne upstream the ridge is flatter and the cold flow downstream will be shunted further east . Its not looking good for the GFS 48 hr cold snap which is turning into a blip! I’d give it one more run tonight to see whether there’s any more mileage in what on the face of it is hardly the Day After Tomorrow but would at least have given a bit of interest !

The GFS remains isolated with its 48 hr cold snap . The rest aren’t interested and even if the GFS is correct in its more northerly push of the high more than likely it would edge the pattern further east with time . Unless that is there’s a background signal to hold the high further north and west . So in effect its a bit of a squabble over tickets to see an aged band of has beens! Given the paucity of excitement on offer I can understand a crappy band night out is better than watching One Man And His Dog. Younger members may need to google this . The oldies will be aware of this hub of excitement! Anyhow for want of anything interest let’s indulge the GFS . Unusually it’s the more amplified over the USA and Canada . It normally used to be the flattest solution historically. The key timeframe which is day 7 into 8 means we should get a resolution soon . This isn’t like a shortwave drama near the UK and if the GFS is correct I’d expect a shift to that by this evening . Of course the reverse applies also . Below is part of the latest NCEP extended forecast discussion . This explains in good detail why we are seeing the model differences . Guidance /Predictability Assessment... Namely, the GFS/GEFS suite lately has been interacting/combining the preexisting southern stream upper low and this shortwave, which forms an east-central U.S. trough that supports a strong and faster moving surface low in the Gulf and progressing northeastward. This is opposed to the remaining majority that keeps the northern stream shortwave progressive and north of the southern stream upper low. Without the phasing of these features, the southern stream upper low will be slower and the only dynamical support for surface low pressure, so the surface low forms/strengthens later and stays more suppressed. WPC has been generally favoring the more suppressed and slower track given it is the larger cluster with multiple model suites (the ECMWF and CMC). Ensemble members tend to favor with their operational runs but do show a lot of spread. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4974168

The GFS remains isolated with its 48 hr cold snap . The rest aren’t interested and even if the GFS is correct in its more northerly push of the high more than likely it would edge the pattern further east with time . Unless that is there’s a background signal to hold the high further north and west . So in effect its a bit of a squabble over tickets to see an aged band of has beens! Given the paucity of excitement on offer I can understand a crappy band night out is better than watching One Man And His Dog. Younger members may need to google this . The oldies will be aware of this hub of excitement! Anyhow for want of anything interest let’s indulge the GFS . Unusually it’s the more amplified over the USA and Canada . It normally used to be the flattest solution historically. The key timeframe which is day 7 into 8 means we should get a resolution soon . This isn’t like a shortwave drama near the UK and if the GFS is correct I’d expect a shift to that by this evening . Of course the reverse applies also . Below is part of the latest NCEP extended forecast discussion . This explains in good detail why we are seeing the model differences . Guidance /Predictability Assessment... Namely, the GFS/GEFS suite lately has been interacting/combining the preexisting southern stream upper low and this shortwave, which forms an east-central U.S. trough that supports a strong and faster moving surface low in the Gulf and progressing northeastward. This is opposed to the remaining majority that keeps the northern stream shortwave progressive and north of the southern stream upper low. Without the phasing of these features, the southern stream upper low will be slower and the only dynamical support for surface low pressure, so the surface low forms/strengthens later and stays more suppressed. WPC has been generally favoring the more suppressed and slower track given it is the larger cluster with multiple model suites (the ECMWF and CMC). Ensemble members tend to favor with their operational runs but do show a lot of spread.

Regardless of the 850s a flow with a se element in December should help develop some surface cold . It’s also more likely to be clear . So high positioning and orientation is important .

The GFS 06 hrs still displaces the Azores high but it’s a weaker effort with the wrong orientation and associated Scandi trough set up . The later output is wildly different over the NH . You can always rely on the GFS to throw up all manner of solutions in FI with 4 runs a day ,

The GFS op still wants to bring in a northerly towards day ten . So it’s been pretty consistent with this over the last few days . This is more from the Azores high displacing nw and not from a Greenland block so an extension post that would need the favourable topple towards Scandi and enough energy supporting that over Southern Europe . The GEM develops some interest with some ringing extending ne towards Scandi . The start of the evolution to colder conditions is now within range of the ECM op so we await that to see whether it’s interested !

The best that can be said for the ECM is the weakening and fragmenting of the PV . At least the monsoon rains will come to an end with the country having a chance to dry out.

High pressure looks like moving in after the latest deluge . The positioning varies between the models and with it the weather on the ground . The GFS brings the high further north so eventually some surface cold developing towards day 9 to 10. The ECM would remain on the mild side with the high centred further south . Not a lot to get excited about although the PV blob of doom doesn’t seem to want to set up longer term to the north and shows signs of weakening later . So at this point I’d take that as a win !

Woeful ECM op . The mini Scandi high tease of the 00hrs blown into the next galaxy by the PV blob of doom . The GFS scrapes some interest towards day ten by trying to develop a high sufficiently north to develop some faux cold , yes that infamous term is being wheeled out for the first time this winter . The blob of doom is of course terrifying to coldies and for good reason. Those who’ve been around here for a while should at least take some solace in that I haven’t wheeled out the film analogies ! Thats normally a very bad sign !

The PV shape , rounded at day 10 with no dig into the Atlantic. Energy will just pile over the top . Perhaps the ECM might sharpen things up in future runs . We’ll see if there’s any more mileage in this over the next few runs .

Some ugly looking charts for coldies barring the ECM which wants to try and squeeze a ridge ne towards Scandi day 9 into 10. Unfortunately the attempt fails . You really need that deep troughing to remain sharp , so that the jet can bounce ne and then back sw . Day 9 gave some hope which sadly didn’t materialize as any dig into the Atlantic is lost as the pattern flattened day 10. Barring the Scandi high longshot it’s looking pretty grim for coldies .

Looks like another fail from the ECM op. The others not interested in taking the next low more se between day 4 and 5 and now the op is beginning to backtrack . Its recent performance has been very poor .

The Siberian high needs to do one if it’s just going to block low pressure from clearing the UK . Another GFS run with low pressure filling over the UK . Cold air to the north trapped there .