In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say that because the low pressure today was coming in from the east that made it more difficult to forecast than if had been coming in from the west? I can't get my head round the logic behind that one.

xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say
that because the low pressure today was coming in from the east that made
it more difficult to forecast than if had been coming in from the west? I
can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed, most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

"Brian Wakem" wrote in message
...
xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say
that because the low pressure today was coming in from the east that made
it more difficult to forecast than if had been coming in from the west? I
can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed,
most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


No it doesn't work like that. Computer models "know" nothing about the past.
They are not heuristic models. They simply solve the Navier Stokes equations
on a sphere. It is the forecasters who struggle more as they interpret the
output to get an idea of uncertainty.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Eskimo Will wrote:


"Brian Wakem" wrote in message
...
xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin
say that because the low pressure today was coming in from the east that
made it more difficult to forecast than if had been coming in from the
west? I can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed,
most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


No it doesn't work like that. Computer models "know" nothing about the
past. They are not heuristic models. They simply solve the Navier Stokes
equations on a sphere. It is the forecasters who struggle more as they
interpret the output to get an idea of uncertainty.

Will



Thanks for the info. Surely something can be learnt from decades of data of
things that have actually happened? After all, nobody knew about sting jets
until they were observed in 1987. Maybe I am thinking too simplistically.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

On Tuesday, August 18, 2015 at 3:04:15 AM UTC-4, Brian Wakem wrote:
xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say
that because the low pressure today was coming in from the east that made
it more difficult to forecast than if had been coming in from the west? I
can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed, most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

=============

As Will notes, models don't "learn" per se but they improve (or are improved) through validation, update and resolution.

Meteorological companies and national services, however, use certain methods to "add value" to numerical output, some of which use historical data.

Stephen.

On Tuesday, August 18, 2015 at 9:51:36 PM UTC+1, Stephen Davenport wrote:
On Tuesday, August 18, 2015 at 3:04:15 AM UTC-4, Brian Wakem wrote:
xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say
that because the low pressure today was coming in from the east that made
it more difficult to forecast than if had been coming in from the west? I
can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed, most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

=============

As Will notes, models don't "learn" per se but they improve (or are improved) through validation, update and resolution.

Meteorological companies and national services, however, use certain methods to "add value" to numerical output, some of which use historical data.

Stephen.

"certain methods" eh?

And exactly what value is added? Have you any stats to show that, Stephen?

On Tuesday, August 18, 2015 at 5:14:17 PM UTC-4, Dawlish wrote:
On Tuesday, August 18, 2015 at 9:51:36 PM UTC+1, Stephen Davenport wrote:
On Tuesday, August 18, 2015 at 3:04:15 AM UTC-4, Brian Wakem wrote:
xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say
that because the low pressure today was coming in from the east that made
it more difficult to forecast than if had been coming in from the west? I
can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed, most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

=============

As Will notes, models don't "learn" per se but they improve (or are improved) through validation, update and resolution.

Meteorological companies and national services, however, use certain methods to "add value" to numerical output, some of which use historical data.

Stephen.

"certain methods" eh?

And exactly what value is added? Have you any stats to show that, Stephen?

========

Yes, "certain methods". Downscaling and Model Output Statistics for one, although the industry is moving on from MOS. Bayesian model averaging to calibrate weighted multi-model ensemble output for another.

Stats are available to customers of any reputable private or national weather service.

Stephen.

On Wednesday, August 19, 2015 at 12:28:27 AM UTC+1, Stephen Davenport wrote:
On Tuesday, August 18, 2015 at 5:14:17 PM UTC-4, Dawlish wrote:
On Tuesday, August 18, 2015 at 9:51:36 PM UTC+1, Stephen Davenport wrote:
On Tuesday, August 18, 2015 at 3:04:15 AM UTC-4, Brian Wakem wrote:
xmetman wrote:

In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say
that because the low pressure today was coming in from the east that made
it more difficult to forecast than if had been coming in from the west? I
can't get my head round the logic behind that one.



Perhaps because of all the lows that the computer models have analysed, most
(90%+??) have come from the west, so they find it harder to 'know' what's
going to happen.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

=============

As Will notes, models don't "learn" per se but they improve (or are improved) through validation, update and resolution.

Meteorological companies and national services, however, use certain methods to "add value" to numerical output, some of which use historical data.

Stephen.

"certain methods" eh?

And exactly what value is added? Have you any stats to show that, Stephen?

========

Yes, "certain methods". Downscaling and Model Output Statistics for one, although the industry is moving on from MOS. Bayesian model averaging to calibrate weighted multi-model ensemble output for another.

Stats are available to customers of any reputable private or national weather service.

Stephen.

Such "methods" are only useful if the outcomes are better than other forecasts. Only available for cash? And how does the customer know they are better the others? I know, horrid questions, but questions that need answers, if you are going to say such things as "certain methods to "add value" to numerical output".

So, are your outcomes better than other forecasting agencies, or is it simply Piers territory?

On Tuesday, August 18, 2015 at 7:59:24 AM UTC+1, xmetman wrote:
In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say that because the low pressure today was coming in from the east that made it more difficult to forecast than if had been coming in from the west? I can't get my head round the logic behind that one.

I heard that one too and I'm in the same boat as you Bruce. The models are simply numerically based, so should have no such difficulties. However, forecasting UK weather from the east is an area where MetO forecasters and others have far less experience than forecasting weather from the West - simply because they've been exposed to far less of the former, than the latter, in their careers. Perhaps Alex Deakin was bring this into play?

On 18/08/2015 09:52, Dawlish wrote:
On Tuesday, August 18, 2015 at 7:59:24 AM UTC+1, xmetman wrote:
In Last nights 6.30 weather, I was intrigued to hear that Alex Deakin say that because the low pressure today was coming in from the east that made it more difficult to forecast than if had been coming in from the west? I can't get my head round the logic behind that one.

I heard that one too and I'm in the same boat as you Bruce. The models are simply numerically based, so should have no such difficulties. However, forecasting UK weather from the east is an area where MetO forecasters and others have far less experience than forecasting weather from the West - simply because they've been exposed to far less of the former, than the latter, in their careers. Perhaps Alex Deakin was bring this into play?

---------------------------------------------------------------
I heard that as well and he has been proved right! In the end he plumped
for rain in the North east and possibly as far down into East Anglia as
Suffolk. It's raining here and moving West steadily so certainly further
South and travelling inland further than their best guess was last night.
Dave, S.Essex