The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. The central pressures are exceptionally low. Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.

"Tudor Hughes" wrote in message
...
The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. The central pressures are exceptionally low. Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.


Explosive deepeners often do this. Not had a look in detail but I do know of
at least one of that series was a warm core variety undergoing a seclusion
process (i.e. not classical Bergen school). That process tends to
concentrate the wind field, analogous to a hurricane in tropical waters.
best I can do without pen and paper Tudor!

Will
--

On Feb 12, 10:32*am, "Will Hand" wrote:
"Tudor Hughes" wrote in message

...

* *The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
* * This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. *The central pressures are exceptionally low. *Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.

Explosive deepeners often do this. Not had a look in detail but I do know of
at least one of that series was a warm core variety undergoing a seclusion
process (i.e. not classical Bergen school). That process tends to
concentrate the wind field, analogous to a hurricane in tropical waters.
best I can do without pen and paper Tudor!

There has been a bit of an hangover from that series of blocking highs
a few weeks back.

There was no severe earthquake following the Australian cyclone
either. The Chilean stuff presently being reported is something
probably due to the hold up of the storms leaving North America at the
same time.

Odd behaviour all told.

But I have never watched a blocking high unfold before. Maybe it is a
common theme with them.

On Feb 12, 10:32*am, "Will Hand" wrote:
"Tudor Hughes" wrote in message

...

* *The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
* * This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. *The central pressures are exceptionally low. *Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.

Explosive deepeners often do this. Not had a look in detail but I do know of
at least one of that series was a warm core variety undergoing a seclusion
process (i.e. not classical Bergen school). That process tends to
concentrate the wind field, analogous to a hurricane in tropical waters.
best I can do without pen and paper Tudor!

Will
--

Thanks for that, Will. Each of these storms has had (or
will have) certainly something of a warm core which I noticed but
didn't correlate with the tight hurricane-like centre. I have found
some other information on the web, including Wikipaedia. The central
areas sound quite exciting but, it seems, are confined very largely to
areas over the ocean.

Tudor Hughes, Warlingham, Surrey.

On Feb 12, 3:44*pm, Tudor Hughes wrote:
On Feb 12, 10:32*am, "Will Hand" wrote:









"Tudor Hughes" wrote in message

...

* *The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
* * This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. *The central pressures are exceptionally low. *Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.

Explosive deepeners often do this. Not had a look in detail but I do know of
at least one of that series was a warm core variety undergoing a seclusion
process (i.e. not classical Bergen school). That process tends to
concentrate the wind field, analogous to a hurricane in tropical waters..
best I can do without pen and paper Tudor!

Will
--

* * * * * *Thanks for that, Will. *Each of these storms has had (or
will have) certainly something of a warm core which I noticed but
didn't correlate with the tight hurricane-like centre. *I have found
some other information on the web, including Wikipaedia. *The central
areas sound quite exciting but, it seems, are confined very largely to
areas over the ocean.

Tudor,

Thought I'd add two pence as this is my main area of interest in
weather. The tight hurricane-like centre or "coiled spring" as I
recall seeing in a paper going back to the 80s seems to be associated
moreso with warm-core seclusion "Shapiro-Keyser" type cyclones. At the
other end of the scale are the Bergen-school classical ones. IMHO they
fall on to a continuum of storms types but it's interesting a lot seem
to snap into one category or the other.

David Schultz argued in the late 1990s that the type of formation is
down to whether the storm forms in a confluent or diffluent jet. I
actually tried to build a climatology of whether storms in confluence
or diffluence led to more severe cyclones as identified by maximum
intensification rate of the storm but couldn't actually find any bias
to those in confluence/diffluence.

Of the storms that have hit UK in recent years the 1987 October storm
can be filed under "seclusion" and 1990 Burns Day storm is a "Bergen-
school" type cyclone.

Richard

On Feb 12, 10:30*pm, Richard Dixon wrote:
On Feb 12, 3:44*pm, Tudor Hughes wrote:





On Feb 12, 10:32*am, "Will Hand" wrote:

"Tudor Hughes" wrote in message

....

* *The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
* * This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. *The central pressures are exceptionally low. *Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.

Explosive deepeners often do this. Not had a look in detail but I do know of
at least one of that series was a warm core variety undergoing a seclusion
process (i.e. not classical Bergen school). That process tends to
concentrate the wind field, analogous to a hurricane in tropical waters.
best I can do without pen and paper Tudor!

Will
--

* * * * * *Thanks for that, Will. *Each of these storms has had (or
will have) certainly something of a warm core which I noticed but
didn't correlate with the tight hurricane-like centre. *I have found
some other information on the web, including Wikipaedia. *The central
areas sound quite exciting but, it seems, are confined very largely to
areas over the ocean.

Tudor,

Thought I'd add two pence as this is my main area of interest in
weather. The tight hurricane-like centre or "coiled spring" as I
recall seeing in a paper going back to the 80s seems to be associated
moreso with warm-core seclusion "Shapiro-Keyser" type cyclones. At the
other end of the scale are the Bergen-school classical ones. IMHO they
fall on to a continuum of storms types but it's interesting a lot seem
to snap into one category or the other.

David Schultz argued in the late 1990s that the type of formation is
down to whether the storm forms in a confluent or diffluent jet. I
actually tried to build a climatology of whether storms in confluence
or diffluence led to more severe cyclones as identified by maximum
intensification rate of the storm but couldn't actually find any bias
to those in confluence/diffluence.

Of the storms that have hit UK in recent years the 1987 October storm
can be filed under "seclusion" and 1990 Burns Day storm is a "Bergen-
school" type cyclone.

Richard- Hide quoted text -

- Show quoted text -

It seems to me that far more lows form in diffluent areas ("left
exit") than confluent ones. This is not a serious count but an
impression formed from a lot of Atlantic chart-watching.

Tudor Hughes, Warlingham, Surrey.

On Feb 12, 10:30*pm, Richard Dixon wrote:
On Feb 12, 3:44*pm, Tudor Hughes wrote:





On Feb 12, 10:32*am, "Will Hand" wrote:

"Tudor Hughes" wrote in message

....

* *The deep Low near southern Greenland at 18Z (940 mb) has filled 21
mb in the last 6 hours and will probably lose its identity entirely in
the next 6, though this is probably not particularly unusual in that
part of the world.
* * This Low, like both the previous one and the next one, has had a
very tight centre with the high wind speeds are confined to a fairly
small area. *The central pressures are exceptionally low. *Does anyone
know why this series of Lows are so tight and have not spread
themselves further?

Tudor Hughes, Warlingham, Surrey.

Explosive deepeners often do this. Not had a look in detail but I do know of
at least one of that series was a warm core variety undergoing a seclusion
process (i.e. not classical Bergen school). That process tends to
concentrate the wind field, analogous to a hurricane in tropical waters.
best I can do without pen and paper Tudor!

Will
--

* * * * * *Thanks for that, Will. *Each of these storms has had (or
will have) certainly something of a warm core which I noticed but
didn't correlate with the tight hurricane-like centre. *I have found
some other information on the web, including Wikipaedia. *The central
areas sound quite exciting but, it seems, are confined very largely to
areas over the ocean.

Tudor,

Thought I'd add two pence as this is my main area of interest in
weather. The tight hurricane-like centre or "coiled spring" as I
recall seeing in a paper going back to the 80s seems to be associated
moreso with warm-core seclusion "Shapiro-Keyser" type cyclones. At the
other end of the scale are the Bergen-school classical ones. IMHO they
fall on to a continuum of storms types but it's interesting a lot seem
to snap into one category or the other.

David Schultz argued in the late 1990s that the type of formation is
down to whether the storm forms in a confluent or diffluent jet. I
actually tried to build a climatology of whether storms in confluence
or diffluence led to more severe cyclones as identified by maximum
intensification rate of the storm but couldn't actually find any bias
to those in confluence/diffluence.

Of the storms that have hit UK in recent years the 1987 October storm
can be filed under "seclusion" and 1990 Burns Day storm is a "Bergen-
school" type cyclone.

Richard- Hide quoted text -

- Show quoted text -

The following link may be of interest to people

http://weatherfaqs.org.uk/node/98

Graham
Penzance

On Feb 13, 1:20*pm, Graham Easterling wrote:

The following link may be of interest to people

http://weatherfaqs.org.uk/node/98

Graham
Penzance

Thanks Graham - I'd not noticed this work had been put on the FAQs -
thanks to whoever it did.

Must look again at a climatology of confluence and diffluence across
the Atlantic - my gut feeling (well, Anatol from 1999, Klaus from
2009, Jeanette from 2002, Erwin from 2005, October Storm from 1987,
Nicolas from 2011 that just hit UK/Denmark) is that there are
proportionally more storms that hit Europe are the Shapiro-Keyser type
- i.e. form in confluent jets - although my head says that the jet
"ending" towards Europe typically I'd expect more of the diffluent
sort to produce the classical Bergen-school type lows (e.g. Burns Day
Storm).

What's even more fun is that the S-K type of storms are the ones that
can contain a sting jet. Note can - and even when they do, it's not
always translated down to the surface, so remains enigmatically at
750-850mb or so just above the boundary layer !

Richard

On Feb 13, 4:34*am, Tudor Hughes wrote:

* * It seems to me that far more lows form in diffluent areas ("left
exit") than confluent ones. *This is not a serious count but an
impression formed from a lot of Atlantic chart-watching.

That is my gut feel too - but not per the storms that have hit Europe.
I'll have to dig out what I found when I was at my last job, my memory
is failing me...!

Richard

On Feb 13, 3:36*pm, Richard Dixon wrote:
On Feb 13, 1:20*pm, Graham Easterling wrote:

The following link may be of interest to people

http://weatherfaqs.org.uk/node/98

Graham
Penzance

Thanks Graham - I'd not noticed this work had been put on the FAQs -
thanks to whoever it did.

Must look again at a climatology of confluence and diffluence across
the Atlantic - my gut feeling (well, Anatol from 1999, Klaus from
2009, Jeanette from 2002, Erwin from 2005, October Storm from 1987,
Nicolas from 2011 that just hit UK/Denmark) is that there are
proportionally more storms that hit Europe are the Shapiro-Keyser type
- i.e. form in confluent jets - although my head says that the jet
"ending" towards Europe typically I'd expect more of the diffluent
sort to produce the classical Bergen-school type lows (e.g. Burns Day
Storm).

What's even more fun is that the S-K type of storms are the ones that
can contain a sting jet. Note can - and even when they do, it's not
always translated down to the surface, so remains enigmatically at
750-850mb or so just above the boundary layer !

Richard

It was this low http://www.wetterzentrale.de/archive...ka20080310.gif
which gave the worst gale, and biggest sea, of the century (so far!)
to west Cornwall. It was only Cornwall that was affected (as far as
mainland UK was concerned). The strongest winds being from the NW late
in the day (sting jet?)

Graham
Penzance