I'm not sure I've seen this one. Only caught the back end of it about
meandering jet streams and SSW events but it looked pretty good. One
thing did catch my attention which I thought was a nice concise epigram
was that "being uncertain doesn't mean we know nothing". Will have to
watch it all on catchup.
Dave

On Thursday, July 17, 2014 9:00:52 PM UTC+1, Dave Cornwell wrote:
I'm not sure I've seen this one. Only caught the back end of it about

meandering jet streams and SSW events but it looked pretty good. One

thing did catch my attention which I thought was a nice concise epigram

was that "being uncertain doesn't mean we know nothing". Will have to

watch it all on catchup.

Dave

Not a repeat Dave as far as I know.
I only watched the first half hour as I had to turn off due to TS in vicinity.

It seemed a reasonable programme trying to examine what made the jet stream so strong last winter. It debunked one theory about the lack of hurricanes last year leading to higher SST and therefore a greater latitudinal temperature gradient between pole and tropics.

I will have to watch the second half on iPlayer sometime.

Len

"Len Wood" wrote in message
...
On Thursday, July 17, 2014 9:00:52 PM UTC+1, Dave Cornwell wrote:
I'm not sure I've seen this one. Only caught the back end of it about

meandering jet streams and SSW events but it looked pretty good. One

thing did catch my attention which I thought was a nice concise epigram

was that "being uncertain doesn't mean we know nothing". Will have to

watch it all on catchup.

Dave

Not a repeat Dave as far as I know.
I only watched the first half hour as I had to turn off due to TS in
vicinity.

It seemed a reasonable programme trying to examine what made the jet stream
so strong last winter. It debunked one theory about the lack of hurricanes
last year leading to higher SST and therefore a greater latitudinal
temperature gradient between pole and tropics.

I will have to watch the second half on iPlayer sometime.

Len

=========================================
Yes, it is a brand new program.

"Horizon - 2013-2014: 12. What's Wrong with Our Weather?
Physicist Dr Helen Czerski and meteorologist John Hammond make sense of
Britain's extreme weather and discover that recent extreme winters are
connected by the jet stream."

http://www.bbc.co.uk/iplayer/episode...th-our-weather

In the good old days, everyone complained about the dumbing down of Horizon,
but I don't think that charge could be put to this program. It considers the
effects of (or the lack of) hurricanes, the QBO, SSWs and Arctic sea ice on
the jet stream and British weather.

Cheers, Alastair.

On Friday, 18 July 2014 14:19:28 UTC+1, Alastair wrote:

"Horizon - 2013-2014: 12. What's Wrong with Our Weather?

Physicist Dr Helen Czerski and meteorologist John Hammond make sense of
Britain's extreme weather and discover that recent extreme winters are
connected by the jet stream."

http://www.bbc.co.uk/iplayer/episode...th-our-weather

In the good old days, everyone complained about the dumbing down of Horizon,

Has Helen Willets bin and gorned?
Things went to hell in an handbasket when Bill Giles was screwed out of a job there.

None of my business now that I don't pay TVtax.

On Friday, 18 July 2014 14:19:28 UTC+1, Alastair wrote:
"Len Wood" wrote in message

...

On Thursday, July 17, 2014 9:00:52 PM UTC+1, Dave Cornwell wrote:

I'm not sure I've seen this one. Only caught the back end of it about



meandering jet streams and SSW events but it looked pretty good. One



thing did catch my attention which I thought was a nice concise epigram



was that "being uncertain doesn't mean we know nothing". Will have to



watch it all on catchup.



Dave



Not a repeat Dave as far as I know.

I only watched the first half hour as I had to turn off due to TS in

vicinity.



It seemed a reasonable programme trying to examine what made the jet stream

so strong last winter. It debunked one theory about the lack of hurricanes

last year leading to higher SST and therefore a greater latitudinal

temperature gradient between pole and tropics.



I will have to watch the second half on iPlayer sometime.



Len



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

Yes, it is a brand new program.



"Horizon - 2013-2014: 12. What's Wrong with Our Weather?

Physicist Dr Helen Czerski and meteorologist John Hammond make sense of

Britain's extreme weather and discover that recent extreme winters are

connected by the jet stream."



http://www.bbc.co.uk/iplayer/episode...th-our-weather



In the good old days, everyone complained about the dumbing down of Horizon,

but I don't think that charge could be put to this program. It considers the

effects of (or the lack of) hurricanes, the QBO, SSWs and Arctic sea ice on

the jet stream and British weather.



Cheers, Alastair.


Trouble is Alastair there is nothing wrong with our weather. Full stop.

On 18/07/2014 14:19, Alastair McDonald wrote:
"Len Wood" wrote in message
...
On Thursday, July 17, 2014 9:00:52 PM UTC+1, Dave Cornwell wrote:
I'm not sure I've seen this one. Only caught the back end of it about

meandering jet streams and SSW events but it looked pretty good. One

thing did catch my attention which I thought was a nice concise epigram

was that "being uncertain doesn't mean we know nothing". Will have to

watch it all on catchup.

Dave

Not a repeat Dave as far as I know.
I only watched the first half hour as I had to turn off due to TS in
vicinity.

It seemed a reasonable programme trying to examine what made the jet stream
so strong last winter. It debunked one theory about the lack of hurricanes
last year leading to higher SST and therefore a greater latitudinal
temperature gradient between pole and tropics.

I will have to watch the second half on iPlayer sometime.

Len

=========================================
Yes, it is a brand new program.

"Horizon - 2013-2014: 12. What's Wrong with Our Weather?
Physicist Dr Helen Czerski and meteorologist John Hammond make sense of
Britain's extreme weather and discover that recent extreme winters are
connected by the jet stream."

http://www.bbc.co.uk/iplayer/episode...th-our-weather

In the good old days, everyone complained about the dumbing down of Horizon,
but I don't think that charge could be put to this program. It considers the
effects of (or the lack of) hurricanes, the QBO, SSWs and Arctic sea ice on
the jet stream and British weather.

Cheers, Alastair.



Agreed, I thought it was well put together.

Regarding the hurricanes, although the effect of hurricanes on Atlantic
SST is too small to significantly affect the poleward temperature
gradient, there is a significant negative correlation between Atlantic
hurricane activity and UK winter storminess, particularly in
ENSO-neutral years.

On Thu, 17 Jul 2014 21:00:52 +0100
Dave Cornwell wrote:

I'm not sure I've seen this one. Only caught the back end of it about
meandering jet streams and SSW events but it looked pretty good. One
thing did catch my attention which I thought was a nice concise
epigram was that "being uncertain doesn't mean we know nothing". Will
have to watch it all on catchup.
Dave

A few things caught my attention.

(1) How does excess rainfall in the Philippines affect the position of
the jet-stream over the Pacific and USA? That seemed a bit of a weird
idea to be dashed off without more explanation. In fact, the warm sea
in the NE Pacific during Summer and Autumn could have led to predictions
of a cold winter in the eastern USA.

(2) John Hammond referred to the jet stream as being straight last
winter, when we had the wet winter, and buckled and weaker in the
previous years of cold winters here. Trouble is, it was only straight
whilst it was over the Atlantic but very buckled upstream. It's the
positions of the buckles that's important.

(3) John also mentioned something about how we've only got 30 years of
records of rapid Arctic warming and thinning ice so can't judge the
effect this will have on the jet stream. Actually, there was rapid
warming before WWII with reported thinning of the ice.

(4) The theory that weakening temperature contrast between the Tropics
and Arctic is weakening the jet stream and producing slow-moving
meanders and hence, long spells of extreme weather. Unfortunately, I
remember that it's a strong jet-stream that produces a small number of
meanders that a slow-moving or quasi-stationary. A weak jet produces
more meanders but they tend to be more mobile.

(5) About 65 years ago, a study on the weakening temperature contrast
between the Arctic and Tropics in the first half of C20 showed that it
produced a strengthening of the upper winds instead of a weakening.
Thus, we may get slow-moving buckles in the jet-stream and prolonged
spells of extreme weather due to Global Warming but because of a
strengthening of the jet, not a weakening.


--
Graham P Davis, Bracknell, Berks. Mail: 'newsman' not 'newsboy'.
"Minds are like parachutes. They only function when they're open". -
Lord Dewar (1864-1930)

On Sunday, July 20, 2014 9:43:42 PM UTC+1, Graham P Davis wrote:
On Thu, 17 Jul 2014 21:00:52 +0100

Dave Cornwell wrote:



I'm not sure I've seen this one. Only caught the back end of it about

meandering jet streams and SSW events but it looked pretty good. One

thing did catch my attention which I thought was a nice concise

epigram was that "being uncertain doesn't mean we know nothing". Will

have to watch it all on catchup.

Dave



A few things caught my attention.



(1) How does excess rainfall in the Philippines affect the position of

the jet-stream over the Pacific and USA? That seemed a bit of a weird

idea to be dashed off without more explanation. In fact, the warm sea

in the NE Pacific during Summer and Autumn could have led to predictions

of a cold winter in the eastern USA.



(2) John Hammond referred to the jet stream as being straight last

winter, when we had the wet winter, and buckled and weaker in the

previous years of cold winters here. Trouble is, it was only straight

whilst it was over the Atlantic but very buckled upstream. It's the

positions of the buckles that's important.



(3) John also mentioned something about how we've only got 30 years of

records of rapid Arctic warming and thinning ice so can't judge the

effect this will have on the jet stream. Actually, there was rapid

warming before WWII with reported thinning of the ice.



(4) The theory that weakening temperature contrast between the Tropics

and Arctic is weakening the jet stream and producing slow-moving

meanders and hence, long spells of extreme weather. Unfortunately, I

remember that it's a strong jet-stream that produces a small number of

meanders that a slow-moving or quasi-stationary. A weak jet produces

more meanders but they tend to be more mobile.



(5) About 65 years ago, a study on the weakening temperature contrast

between the Arctic and Tropics in the first half of C20 showed that it

produced a strengthening of the upper winds instead of a weakening.

Thus, we may get slow-moving buckles in the jet-stream and prolonged

spells of extreme weather due to Global Warming but because of a

strengthening of the jet, not a weakening.





--

Graham P Davis, Bracknell, Berks. Mail: 'newsman' not 'newsboy'.

"Minds are like parachutes. They only function when they're open". -

Lord Dewar (1864-1930)

--------------------------------------------------------------------------
Yes Graham, it worries me that forecasting these climate anomalies on the scale of weeks and months ahead has not really improved over recent decades.
We of mature years are witness to this.

Recent focus has been higher in the atmosphere, to include sudden stratospheric warmings (in winter). This has had rather patchy success.

Forecasting the wiggles in the jet stream is a can of worms.

Weaker zonal winds favour slower Rossby waves (reduced phase speed).

One thought is that high amplitude patterns in the jet stream are associated with extreme weather as the waves move slowly.

This, as you point out in (2) is at odds with John Hammond explanation of last winter's wetness. It is all to do with position and number of waves.

Theory is all very well but the fact is the wiggles in the jet stream are baroclinic waves (depressions) influenced by the Rossby effect.

So there is plenty of feedbacks on various scales which make forecasting with any certainty difficult.

Len
Wembury. SW Devon