Interitus
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Posts posted by Interitus
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5 minutes ago, snowking said:
And just in time to try and contradict the above post (entirely unintentional!)
GEFS mean 10mb zonal wind forecast from the last 4 0z runs - note the emerging trend for a much slower recovery of any zonal flow. Still a forecast so we’ll seeThat doesn't contradict it at all
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14 hours ago, Mike Poole said:
Yes, I’m sure GFS and GEFS have predicted 10 of the last 3 SSWs.
Hehe, maybe the best way to visualise variability of model runs is by use of chiclet charts. Here is a form of chiclet covering the whole of the 2019 SSW in GFS forecasts -
It's not annotated, so to explain - it is 10mb 60°N wind speed, red westerly, blue easterly.
Y-axis represents the model time step, T0 analysis at the bottom - what actually happened. T384 forecast at the top. X-axis is the 6-hourly run, 4 times per day, advancing from left to right.
So moving from left to right, forecast winds gradually advance diagonally down to the bottom of the graph and become the actual values.
It can be seen that to the middle or just beyond of runs, accuracy is good and forecast winds progress downwards fairly consistently. But at the top of the graph, there are wild fluctuations in forecasts, from SSW to vortex intensifications, often from run to run giving the vertical stripiness, which don't materialise.
At best it can be suggested that averaged over a number of runs, a weaker vortex and perhaps more particularly, a stronger vortex may be expected from the long range GFS values.
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1 hour ago, ALL ABOARD said:
Do they?
GFS picked this SSW at 384 hours....
And was first not to model a full split.
Yes, they do!
It may well have picked it at 384, it will also falsely pick many others that don't materialise.....
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44 minutes ago, bluearmy said:
Well one just did !
Current events notwithstanding, for example here is a chart of forecasts over a few days last winter, inside 9-10 days the windspeeds progressed forward from run to run, at around 9-10 days they clustered without progressing, and beyond that they diverged all over the place -
Of course not forgetting previous GEFS tendency to overcook wind reduction compared to GFS, here again from a portion of last winter, a day-10 comparison -
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9 minutes ago, SqueakheartLW said:
06z GFS runs and parallel still have the 3rd warming showing. Starting to look a more definite bet now but some of the runs are now showing a double hit warming so a big warmup, then a slight cooldown before another burst of warming shortly afterwards. I have put the double ones first followed by the single ones.
Got the main 3rd warming average peak down below -10 now. This is starting to look like a major warming event and with 19 of those options showing another burst of warming just after the main event then this could be the final blow that sees the vortex destroyed
Are they getting closer though? When consistently seeing peak warmings at 10 days or beyond they have a tendency to stay there, the strength of them doesn't matter so much.
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On 03/01/2021 at 21:58, ALL ABOARD said:
Hi mate,
Top of your head what's the longest reversal we've ever had in terms of days?
Obviously excluding final warnings?
Reversals from MERRA data
Date - days
01/03/84 - 34
24/01/09 - 29
06/01/13 - 22
31/01/87 - 22
26/02/99 - 21
21/01/06 - 19
02/01/19 - 17
12/02/18 - 17
22/03/92 - 15
07/03/89 - 15
11/02/01 - 14
12/03/05 - 12
05/01/04 - 10
27/03/14 - 10
21/02/89 - 9
08/12/87 - 9
22/02/79 - 8
18/03/88 - 7
17/03/80 - 7
22/02/08 - 6
13/03/08 - 6
15/12/98 - 6
23/01/87 - 5
01/01/85 - 5
19/02/10 - 5
24/02/07 - 4
11/02/06 - 4
24/02/84 - 4
30/03/05 - 4
30/12/01 - 4
09/02/10 - 3
29/02/80 - 3
24/03/10 - 3
29/03/08 - 3
20/03/00 - 3
29/03/98 - 3
14/03/88 - 3
05/01/21 - 2
20/01/19 - 2
20/03/18 - 2
25/03/89 - 2
04/12/81 - 2
18/01/03 - 1
29/01/87 - 1
01/02/17 - 1
05/02/95 - 1
25/02/87 - 1
28/03/15 - 1
26/03/05 - 1
04/03/81 - 1
25/03/80 - 1
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14 minutes ago, chionomaniac said:
Hi interitus. What are the x and y on that chart. Otherwise it means nothing to me? Thanks
Y is u m/s, X is time steps of run, pretty obvious really,
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8 hours ago, Catacol said:
We now have 100% ensemble agreement for a 14 day reversal. This will increase.
2 hours ago, s4lancia said:-40 would smash the biggest reversal recorded.
Clearly this would be very much an outside bet currently but it’s still amazing to see it’s not just one rogue run, there are 4 going for it!
This is at 65°N, here is a rough and ready plot at 60°N
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1 minute ago, ALL ABOARD said:
Hi thanks for reply.
I agree there is usually some kind of block but never as weak as it is currently.
Of course green is forecast and 100 hPa is in the strat.
Here's an interesting chart a few days prior to Jan 87 SSW, posted a couple of times before -
Of note, large anticyclonic wave break north of UK. Compare with this forecast for few days time -
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1 minute ago, lorenzo said:
Does this chart worked up by Simon Lee help answer perhaps..
Nothing out of the ordinary there.
From out of the chaos comes order - 3 of the 4 closest 30-day 10mb 60°N wind analogues to 31/12/20 feature an SSW in the following 3 week period -
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1 minute ago, sebastiaan1973 said:
He means 100 hPa.
That's in the strat.
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On 29/12/2020 at 22:35, ALL ABOARD said:
I take it this could be the first time in our recorded history that we have a major SSW with a troposphere that is as weak as it is.
Therefore the papers the theories the wills it's or won'ts it can't be answered.
We can summerize but the weather will make fools of us all.
Its going to be so interesting to dissect this after the event.
No, not really. There is always some tropospheric blocking in advance of an SSW, usually Atlantic side for wave 1 like this.
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On 12/08/2020 at 14:31, Interitus said:
Bit of a downer that weathercast has not had any station data for a couple of days. Noticed that it also affects their app and other meteogroup sites (eg. meteoservices.be) and data from other countries.
Weathercast data seems to be fixed now.
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6 minutes ago, Man With Beard said:
So six successive days 34C, probably for the first time ever.
Shame that this spell may get easily forgotten in the future, I suspect, in the midst of all the heat events of the past few years. Yet for sheer intensity over a sustained period, in the southern counties at least, this period has been top of the tree since 2003, and possibly 1976. Never felt like I was having Spanish weather in the UK before, but I have done in the past six days.
Totally depends on definition of intensity and sustained period - 32°C on 15 consecutive days is the oft trotted out 1976 comparison.
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17 minutes ago, kold weather said:
Whilst I definitely prefer cold weather and snow, I'm more of an extremes wanter today, and this spell definitely ranks up there with some of the most impressive heatwaves. Hasn't quite got the length of a 03/76 but the length of the 34c temperature do put this up in that sort of category.
Bit of a downer that weathercast has not had any station data for a couple of days. Noticed that it also affects their app and other meteogroup sites (eg. meteoservices.be) and data from other countries.
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Very interesting, nice work!
One question however, from near the end of the article re: North shoreline change from 1935 to 2018 on Peninsula Point - there is some variability between the time-samples but overall appears to show a fairly consistent rate of erosion which is at odds with a hypothesis of warming and reduced sea-ice?
Ah: ok re-read your theory now.
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1 hour ago, MattStoke said:
36.3’C at Heathrow.
Iver Water Works 33.9°C at the same time (3pm). The significance? Nobody has seemed to notice that data is available from this other site, but it is barely 3 miles from Heathrow weather station and shows the difference of being semi-rural vs next to carparks, runways and apron.
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On 11/04/2020 at 08:56, knocker said:
Rapidly
Maybe not, the 06z GFS today has +ve 10mb winds til April 28th, then a few days weak reversal then weakly +ve again. Normal reversal by about April 12th, so much for the theory that it happens earlier in years without SSW lol.
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On 16/03/2020 at 20:11, Singularity said:
Yep... big warmth doesn’t necessarily equate to above-normal heights, when the vortex has organised the pressure gradients so strongly as it has this past month.
Going to take a lot to bring it down this spring, especially with the record-low ozone content within the vortex circulation. It’s that which warms majorly in response to UV radiation, helping to weaken the vortex.
Mentioned this before, basically the strength of the vortex is related to the temperature gradient between the pole and the mid-latitudes, so simply put, pole colder than mid-lats = stronger vortex and vice versa. But interestingly, the 10mb zonal wind is more sensitive to temperature gradient at lower levels than at 10mb itself. Using the difference between the 80 and 50°N temperatures from MERRA reanalysis, over all days since 1979 the zonal wind correlation to 10mb temperature is 0.80, but with 30mb temperature it is 0.97 and 50mb it's 0.96. So while seeing a warming appearing at 10mb may hint at an SSW, a wind reversal at 10mb is unlikely if the warming doesn't progress to the 30mb level or below and reversing the temperature gradient there.
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59 minutes ago, virtualsphere said:
Interesting stuff, personally I'm sceptical the weather would have much impact as the majority of people now spend most of their time indoors in a temperature controlled environment at 16 - 22C. e.g. Someone catches the virus at an airport from an overseas traveller, then goes home and passes it on to their family or to colleagues in the office, which would allow international spread without the virus leaving an indoor environment. I guess if we had a warm dry period it would encourage people outdoors, which might help, as long as any restrictions on movement don't prevent this and end up being counterproductive. In less developed countries people probably spend a greater proportion of time outside which might mean the weather is more of a factor in transmission rates?
Yes, exactly this. Corralling people indoors in typical temperature and humidity is the perfect environment for virus transmission. Whilst they survive best in the liquid droplets from coughs/sneezes, it seems slightly counterintuitive but coronaviruses survive drying for some time and remain viable. Being outdoors in the open air reduces chance of transmission and also solar UV quickly inactivates them.
Number of papers written but for example see research on original SARS CoV - https://www.hindawi.com/journals/av/2011/734690/
SARS dried of plastic survived 5 days at 22-25°C 40-50% RH with only slight loss of infectivity.
Seriously should be hoping for some decent weather to help with this but of course dependent on measures on social distancing and self-isolation which come into force.
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3 hours ago, knocker said:
The ecm at 10 & 50mb
The action has been higher up, this chart shows GFS 1mb zonal wind from 8/3 when the forecast splits occurred, to 13/3 and actually wave 1 displacement has been indicated. For a number of days wind reversal stuck around the 240+ hr uncertainty range, but today's 00z and 06z brought it down to 231 and 201 hours respectfully -
Doesn't look like having large effect at 10mb or below at the moment.
edit: Incidentally, does anybody else find those temperature charts slightly distracting with the multiple colour scales and repeated whites?
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On 11/03/2020 at 16:32, mb018538 said:
To dig him out out on a forum that he can't see?
Nah, his tweets are high quality, but splits in particular depend on fairly specific tropospheric patterns which are typically modeled wrongly at the end of a 16-day forecast. Of course it's more than reasonable to highlight the possibilities, but time and again when people make these forecasts in this thread they're invariably incorrect, Maybe because splits are seen as a bit of a holy grail by cold lovers, it's certainly not popular when it is suggested that it is an unlikely outcome!
Stratosphere and Polar Vortex Watch 2020
in Spring Weather Discussion
Posted
Of course this is from a narrow sample of SSW events for any particular day of the winter. So date records now are around 2 S.D. - a 3 S.D. event such as Jan 2009 would give a value today around -26 m/s.