How to be led astray by NWP
 

A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

How to be led astray by NWP
 

On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value.. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

The one thing that does seem to be coming thru is a high probability of some kind of blocking scenario, the met office 30 day forecast hints at this as well. But as you say the ensembles are all over the place. At least the ingredients are in place for something more interesting.

But it does seem more than one outlier hinting at something more interesting. I'll eat my hat if this follows thru to something like this ;) -

http://www.wetterzentrale.de/maps/ar...85010800_2.gif

How to be led astray by NWP
 

On 31/12/2016 12:12, Alan [Guildford] wrote:
On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

The one thing that does seem to be coming thru is a high probability of some kind of blocking scenario, the met office 30 day forecast hints at this as well. But as you say the ensembles are all over the place. At least the ingredients are in place for something more interesting.

But it does seem more than one outlier hinting at something more interesting. I'll eat my hat if this follows thru to something like this ;) -

http://www.wetterzentrale.de/maps/ar...85010800_2.gif



I still think something cold is on the cards, but the devil is in the
detail and of course again we are doing that party dance again "Move to
the right shuffle".

I would be interested in Will's thoughts as I'm sure Haytor is tropical atm.

--
Keith (Southend)
"Weather Home & Abroad"
http://www.southendweather.net
Twitter:@SS9Weatherman

How to be led astray by NWP
 

On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

Hear Hear!

Making something out of nothing: How to be led astray by NWP
 

On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:


A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable. The
operational runs of any model beyond about 5 days are getting into fantasy
land.

It all began with chaos and spin
Jive talkin', you're telling me lies, yeah
Jive talkin', you wear a disguise
Jive talkin', so misunderstood, yeah
Jive talkin', nope NWP no good

Some people will never know
Just what charts say
Is what the world does
They're gonna take away the energy

With all their
Jive talkin', they're not telling lies, yeah
Around t 72 all of those highs
Nobody believes what they say
It's just jive talkin' that gets in the way


With all your
Jive talkin', you're telling me lies, yeah
Jive talkin', you wear a disguise
Jive talkin', so misunderstood, yeah
Jive talkin', you just ain't no good

Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

How to be led astray by NWP
 

On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value.. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr



On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value.. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

Stay on your soapbox and shout it even louder, especially the penultimate sentence. This is rather a contrast with the introduction of "long-range" forecasts in the 60's which, as far as I can remember, the Met Office did not want to publish but simply use them for internal research. They were persuaded to publish them by various political/social forces even though they knew, and so did the users, that they were not much good.
I have read some theoretical investigation that says that the position, intensity etc of individual synoptic features are intrinsically unforecastable after a period of about 20 days even if a tendency to a particular pattern may persist. This is due to random effects, i.e. chaos, which cascades up to synoptic scale. This had been predicted by Lorentz some time earlier anyway.

Tudor Hughes, Warlingham, Surrey.

How to be led astray by NWP
 

On Saturday, December 31, 2016 at 9:38:30 PM UTC, Tudor Hughes wrote:
On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr



On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

Stay on your soapbox and shout it even louder, especially the penultimate sentence. This is rather a contrast with the introduction of "long-range" forecasts in the 60's which, as far as I can remember, the Met Office did not want to publish but simply use them for internal research. They were persuaded to publish them by various political/social forces even though they knew, and so did the users, that they were not much good.
I have read some theoretical investigation that says that the position, intensity etc of individual synoptic features are intrinsically unforecastable after a period of about 20 days even if a tendency to a particular pattern may persist. This is due to random effects, i.e. chaos, which cascades up to synoptic scale. This had been predicted by Lorentz some time earlier anyway.

Tudor Hughes, Warlingham, Surrey.

I'd agree with just about everything said above. In winter, for many, it's just wishful thinking at the slightest hint of something cold.

Also, I'd hate accurate forecasts a week or more ahead. It's the unexpected that makes life.

Anyway, Happy New Year everyone.

Graham
Penzance (wet)

How to be led astray by NWP
 

Yes, there is often a fine line with NWP solutions, and what we call a "Flip-Flop" solution between runs is quite common.
Of course it may be a distant signal that the NWP is hinting that the UK and NW Europe could be in some sort of battleground of air mass types at the temporal limits of the deterministic forecast.
Now that would be interesting from day to day.

How to be led astray by NWP
 

On Saturday, 31 December 2016 11:56:09 UTC, Norman Lynagh wrote:
A good number of pundits, including some of the saner variety, have been
getting quite excited by recent operational runs of the GFS showing a very
cold spell setting in during the second week of January. There's been quite a
bit of hope/wish-casting. The 00z operational run today predicted strong E'lies
over the southern half of the British Isles from 11th-16th Jan. In very sharp
contrast, the 06z operational run today predicts strong SW'lies over the
country during the same period. The pundits have gone very silent.

A casual glance at the ensembles recently shows that beyond about 5 days there
is so much divergence that the situation is effectively unforecastable to any
useful level of reliability beyond 5 days. The fact that the model is routinely
run out to 16 days ahead doesn't mean that its predictions have any value. The
operational runs of any model beyond about 5 days are getting into fantasy
land, especially as they are quite often warm or cold outliers when compared to
the ensembles. Unfortunately, it's not easy to build uncertainty into the apps
that are so prevalent these days.

Medium-range NWP output is a tool for meteorologists, not end-user material for
Joe Public.

I'll get off my soap-box now :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org
@TideswellWeathr

Always happens. Every year.

How to be led astray by NWP
 

On Sunday, 1 January 2017 10:08:22 UTC, Graham Easterling wrote:



Also, I'd hate accurate forecasts a week or more ahead. It's the unexpected that makes life.



Graham
Penzance (wet)


A very subversive thought, that, and one I share entirely.

Tudor Hughes, Warlingham (only a bit wet), Surrey.