Originally Posted by: Gooner

LOL

Just watching the 21:55 telling what the weather will be like tomorrow ( Sunday ) poor , fancy broadcasting Saturday evenings forecast

i guess it’s no different than the Met office LRF using the models of 2 or 3 days ago as they continue to do on s daily basis. 

Originally Posted by: tallyho_83

Well the local spotlight weather is best and mentioned snow down to lower levels Tuesday night for SW but then saw the forecast by Nick Miller who seemed very vague about Tuesday's snow but at least he has the right day and time stamp and or isn't a pre recorded forecast like previous weather presenter Alina Jenkins! But there is still a lot of uncertainty re the snow event for the south on Tuesday so it seems! What is certain in Nick Millers forecast is that it will not turn less cold later this week as previously forecast.

He wasn't remotely vague about Tuesday.  He said snow for many; he also said there was the prospect of further snow later on the week.

Originally Posted by: Stolen Snowman

 

How meaningful though is this? After all it’s just a forecast and the weather will do what it will.

I’ve often wondered of the point of confidence percentages if they’re not verified. There may be some sort of metric that checks back on the number of times the computer was correct (and you’d assume on average 7 out of 10 times in this scenario). But how do you define it. Or is it no better than a ‘gut’ feeling as in ‘we think there’s a higher likelihood of this because the computer says so!’ 

Makes you think.

I would assume the 70% figure relates to clustering of long-range modelling, eg 70% of the perturbations went for a cold scenario.

Looks like mostly rain tomorrow for Exeter and then a rapid change to snow around 3pm looking at that large white blob as forecast by BBC but by 6pm the precipitation would have already cleared but looks like it may linger in central and south eastern areas: - He said accumulations of 2-5cms even at lower levels. However, It depends how heavy precipitation will be for any evaporative cooling at 1500z.

Looks like the south east is where the snow will be the most significant with cold air to the north from another font colliding with the low coming in from the west moving across all of southern England! So looks like a brief transient snow event in Devon between 1500 and 1800 hours but snow lasting perhaps between 1800 and 12:00 am in many parts of the central southern and south eastern areas.

Looks like the cold air has already under cut that warmer sector as it's already snowing as far south as Plymouth by 1500 when most of N.E Devon and East Devon, south SOmerset and west Dorset still sees rain - I will keep you all updated here in Devon tomorrow as the band of snow (if any) from same frontal system will hit Devon first.

However, BBC graphics (as always) are really poor. So will check Met Office rainfall radar,.

SHOW EXTERNAL IMAGES

Edited by user 28 January 2019 10:24:04(UTC)  | Reason: Not specified

Originally Posted by: Stolen Snowman

 

Yes that makes sense.

Easy though to fall into the trap of thinking that 70% of the time this forecast is correct instead. 

That's not correct. Michael found the article and posted in the MO thread. The quote is very specific:

"He estimates a 70% chance of a severe cold spell around the end of January/early February."

https://www.theweatheroutlook.com/twocommunity/default.aspx?g=posts&m=1079493#post1079493

Originally Posted by: tallyho_83

Looks like mostly rain tomorrow for Exeter and then a rapid change to snow around 3pm looking at that large white blob as forecast by BBC but by 6pm the precipitation would have already cleared but looks like it may linger in central and south eastern areas: - He said accumulations of 2-5cms even at lower levels. However, It depends how heavy precipitation will be for any evaporative cooling at 1500z.

Looks like the south east is where the snow will be the most significant with cold air to the north from another font colliding with the low coming in from the west moving across all of southern England! So looks like a brief transient snow event in Devon between 1500 and 1800 hours but snow lasting perhaps between 1800 and 12:00 am in many parts of the central southern and south eastern areas.

Looks like the cold air has already under cut that warmer sector as it's already snowing as far south as Plymouth by 1500 when most of N.E Devon and East Devon, south SOmerset and west Dorset still sees rain - I will keep you all updated here in Devon tomorrow as the band of snow (if any) from same frontal system will hit Devon first.

However, BBC graphics (as always) are really poor. So will check Met Office rainfall radar,.

1428 BBC News had quite a long piece on – South East and south Midlands the sweet spot with all-snow events on both Tuesday evening and Thursday – but stressed uncertainty. 

SHOW EXTERNAL IMAGES

Originally Posted by: moomin75

The stupidity of some of these forecasters really annoys me. BBC local radio in my area this morning, Bee Tucker comes on and says, we are waking up to no frost today as temperatures are only just below freezing? Say what? Listen to what you are saying!!! Temps below freezing = frost. My window was very iced up on my car. Think before you speak!!!

Just because it is below zero doesn’t always mean you will get visible frost. If the air is dry then surfaces still might not reach the dew point and so no frost. (It’s like that here this morning, a tiny bit of white in places on the grass but no frost on cars etc.)

Sounds like they were talking rubbish though!

Edited by user 29 January 2019 08:06:23(UTC)  | Reason: Not specified

CPF January update

February to April

Temperature summary

For February and February-March-April as a whole, below-average temperatures are more likely than above-average temperatures. The likelihood of impacts from cold weather is greater than normal, particularly earlier in the 3-month period. Overall, the probability that the UK-average temperature for February-March-April will fall into the coldest of our five categories is 25%, and the probability that it will fall into the warmest of our five categories is around 15% (the 1981-2010 probability for each of these categories is 20%).

Full forecast: https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-fma-v1.pdf

Precipitation summary

For February and February-March-April as a whole, above-average precipitation is more probable than below-average precipitation. The probability that UK-average precipitation for February-March-April will fall into the driest of our five categories is 15% and the probability that it will fall into the wettest of our five categories is around 25% (the 1981-2010 probability for each of these categories is 20%).

Full forecast: https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-precip-fma-v1.pdf