Cold Spell - Feb 7th to 13th 2021 - Technical Discussion

yourdeadwright wrote: »

Is that just for today or do we still expect snow on Thursday in Dublin

He is referring to Thursday/Friday.

Big ECM coming up tonight in regards to Thursday's snow event.

Nqp15hhu wrote: »

That’s not a downgrade. It keeps the mild crap away.

It is a downgrade for snow which most posters here are interested in

A lot of conflicting trends in the models so far but the general theme seems to be a backtracking towards retaining cold air longer (at least in Leinster and Ulster, some parts of Connacht and a few parts of eastern Munster). I get the feeling that this may be part one of a later resolved two-part backtrack to keeping the Atlantic at bay well into next week as well, the maps earlier that showed it coming in somehow looked too weak, like the supposed aftermath of a lightweight knocking out the heavyweight. But I would be the first to say that nobody knows what the outcome will be here, this is just the state of play of this technology, we can't really call medium-range forecasting a science, it's a technology and not a particularly good one compared to others, and that's simply because we don't know what forces actually govern weather systems. If we did, this problem would not exist. A lot of people in meteorology go apoplectic when I make these observations (which I have done for about a lifetime) because they want to be thought of as scientists. And of course there is science involved in "basic meteorology" but basic meteorology is nowcasting plus the limited application of the known science to very short time frames that we call "reliable" even though that varies from situation to situation.

Well then, some might say, there are relatively successful medium term forecasts from time to time, and even relatively good long range forecasts. And some of those are based on science to the extent that on some but not all occasions, enough momentum is built up from the reliable into the unreliable time frame to allow for a bit of confidence about future trends.

Nobody should fool themselves into thinking that somewhere, behind some closed doors, are people who "know" and have access to "information" that tells them what will "actually happen" because there are no such doors, people, information or forecasts.

And shame on anybody who tries to cultivate that image because they are probably fooling nobody but themselves.

Situations like this remind us that there can be and should be pure theoretical research ongoing into turning this technology into an actual science. Let's examine a case where a technology was turned into a science. That would be space travel. In the 1950s, space travel was barely better as a technology than weather forecasting is now. Trial and error was the foundation and it was probably more luck than skill that more catastrophes were avoided. But slowly a science emerged. By science, we always mean one thing -- numerical predictions that may be time sensitive verify routinely. However, a science can have theories and as long as they are identified as such, that is part of the business of science. Weather forecasting models are like theories, and within the forecasting community they are sometimes recognized as such. A theory can be tested out by comparing reality to predictions. Any given weather model is only as good as its latest set of predictions. The fact that the Slovakian 22z nailed the big hailstorm that levelled Omsk in 1987 is no particular help to us as we look at its output for Thursday evening in southeast Ireland.

Until some model is developed that is never wrong (within reasonable limits) then relying on any of them is a mug's game. You can only go with some sort of consensus or a reasoned choice when there is no consensus, and hope for the best. And no amount of self-confident swagger is ever going to change that reality, as people find out one by one at around the age of 25, usually.

Freezing ECM at 48 h rs
Everywhere would see snow even Southcoast

JanuarySnowstor wrote: »

Freezing ECM at 48 h rs
Everywhere would see snow even Southcoast

Much precipitation falling though?

M.T. Cranium wrote: »

A lot of conflicting trends in the models so far but the general theme seems to be a backtracking towards retaining cold air longer (at least in Leinster and Ulster, some parts of Connacht and a few parts of eastern Munster). I get the feeling that this may be part one of a later resolved two-part backtrack to keeping the Atlantic at bay well into next week as well, the maps earlier that showed it coming in somehow looked too weak, like the supposed aftermath of a lightweight knocking out the heavyweight. But I would be the first to say that nobody knows what the outcome will be here, this is just the state of play of this technology, we can't really call medium-range forecasting a science, it's a technology and not a particularly good one compared to others, and that's simply because we don't know what forces actually govern weather systems. If we did, this problem would not exist. A lot of people in meteorology go apoplectic when I make these observations (which I have done for about a lifetime) because they want to be thought of as scientists. And of course there is science involved in "basic meteorology" but basic meteorology is nowcasting plus the limited application of the known science to very short time frames that we call "reliable" even though that varies from situation to situation.

Well then, some might say, there are relatively successful medium term forecasts from time to time, and even relatively good long range forecasts. And some of those are based on science to the extent that on some but not all occasions, enough momentum is built up from the reliable into the unreliable time frame to allow for a bit of confidence about future trends.

Nobody should fool themselves into thinking that somewhere, behind some closed doors, are people who "know" and have access to "information" that tells them what will "actually happen" because there are no such doors, people, information or forecasts.

And shame on anybody who tries to cultivate that image because they are probably fooling nobody but themselves.

Situations like this remind us that there can be and should be pure theoretical research ongoing into turning this technology into an actual science. Let's examine a case where a technology was turned into a science. That would be space travel. In the 1950s, space travel was barely better as a technology than weather forecasting is now. Trial and error was the foundation and it was probably more luck than skill that more catastrophes were avoided. But slowly a science emerged. By science, we always mean one thing -- numerical predictions that may be time sensitive verify routinely. However, a science can have theories and as long as they are identified as such, that is part of the business of science. Weather forecasting models are like theories, and within the forecasting community they are sometimes recognized as such. A theory can be tested out by comparing reality to predictions. Any given weather model is only as good as its latest set of predictions. The fact that the Slovakian 22z nailed the big hailstorm that levelled Omsk in 1987 is no particular help to us as we look at its output for Thursday evening in southeast Ireland.

Until some model is developed that is never wrong (within reasonable limits) then relying on any of them is a mug's game. You can only go with some sort of consensus or a reasoned choice when there is no consensus, and hope for the best. And no amount of self-confident swagger is ever going to change that reality, as people find out one by one at around the age of 25, usually.

Sense prevails!!!

M.T. Cranium wrote: »

...Nobody should fool themselves into thinking that somewhere, behind some closed doors, are people who "know" and have access to "information" that tells them what will "actually happen" because there are no such doors, people, information or forecasts. ...

You mean there's not a Master Forecaster, it's like finding out the Wizard of Oz is not real :D

Looking at an animation on the models of the cold & mild air over the next few days it is like two boxers slugging it out with the captive audience here not knowing who's going to land the knockout punch or do we end up with a messy draw.

I know this chart comes with a load of caveats and model accuracy can vary from run to run or event to event but it's useful to show that models are getting more accurate over time but Day 10, 7, 5 are still a long way off having 100% correlation with the final outcome. It shows anomaly correlation between forecasted and verified outcomes for ECM.

Chalkitdown147 wrote: »

Just curious but is possibly 5cm snow lying on lower levels not excellent for the east of Ireland???

Absolutely. People have no idea what 5cm of snow looks like. We get excited over 1cm.

Perhaps Cork could be marginal and South coast in general. But surely inland Munster and South Leinster are on track for several hours of snow. Like in this country showers of snow lasting 20mins cause trouble but in this case we are talking 7 or 8 hours of snow.
A definite Orange warning minimum for me!!

Re today, very disappointing tbh the lack of proper convection has surprised most of us. It looks like the model ppn charts were quite accurate afterall
I certainly ramped it well beyond what happened

I would take all these updates with a pinch of salt, could well move further north in updates tomorrow. Never seen so much chopping and changes over the course of a couple of days.

quote="TTLF;116223397"]I wish there was an emoji on boards to represent "pain" but i'll just make my own with two separate emoji's instead.

:(

Hopefully all changes and I'm surprised.[/quote]

Well i don't think the idea of a back track to extending the cold well into next week will happen judging by the latest ECM and UKMO. We are going to have to see a dramatic change in their model output overnight for that to happen. Still hopefully some places will see several hours of heavy snowfall on Thursday into Friday

Just watched BBC and they say the mild weather will extend North East on the weekend

M.T. Cranium wrote: »

The fact that the Slovakian 22z nailed the big hailstorm that levelled Omsk in 1987