There has been low activity so far in the Tropical Atlantic and I wonder whether this heralds another quiet season.

http://www.nhc.noaa.gov/

http://www.cpc.ncep.noaa.gov/products/outlooks/

Did anyone see Operation Cloud Lab on BBC 2 last night?

Towards the end they got on to discussing Atlantic hurricane frequency and intensity, saying how the frequency and intensity had increased in recent years.

They blamed it on rising sea surface temperatures (a gross simplification).
They showed that polluted cloud had more smaller droplets (this has been known for yonks by us oldies) and therefore reflected more solar which gave a net cooling at the surface.
Then had a graph of yearly Atlantic hurricane activity 1950-2012 which showed low activity from about 1960 to 1990.
This was due possibly to all the air pollution that was around then. Since everyone (?) has cleaned up their act since then, Atlantic hurricane activity has returned to the high levels pre- 1960.
All a bit tenuous.

I cannot find the precise graph they showed on the programme but here is a link to something similar showing hurricane frequency and sea surface temperature variations.

http://www.cpc.ncep.noaa.gov/product...mmary_2011.pdf

Len
Wembury, SW Devon

On Thursday, July 17, 2014 12:41:26 PM UTC+1, Len Wood wrote:
There has been low activity so far in the Tropical Atlantic and I wonder whether this heralds another quiet season.

==========

Likely a little below average. Seasonal hurricane forecasts don't have the best predictability (see last year) but, subjectively at least, the problems seem to be more when more than average *should* develop.

This year we have emerging El Niño which usually suppresses tropical Atlantic tropical developments, and on top of that SSTs are below average so this hinders Cape Verde developments.

However, high SSTs in the west Atlantic might promote "home grown" developments like Arthur up the Eastern Seaboard.

Sub-tropical ridge might steer storms into the Gulf of Mexico rather than hitting the SE.

Stephen.

Len Wood wrote:

There has been low activity so far in the Tropical Atlantic and I wonder
whether this heralds another quiet season.

http://www.nhc.noaa.gov/

http://www.cpc.ncep.noaa.gov/products/outlooks/

Did anyone see Operation Cloud Lab on BBC 2 last night?

Towards the end they got on to discussing Atlantic hurricane frequency and
intensity, saying how the frequency and intensity had increased in recent
years.

They blamed it on rising sea surface temperatures (a gross simplification).
They showed that polluted cloud had more smaller droplets (this has been
known for yonks by us oldies) and therefore reflected more solar which gave a
net cooling at the surface. Then had a graph of yearly Atlantic hurricane
activity 1950-2012 which showed low activity from about 1960 to 1990. This
was due possibly to all the air pollution that was around then. Since
everyone (?) has cleaned up their act since then, Atlantic hurricane
activity has returned to the high levels pre- 1960. All a bit tenuous.

I cannot find the precise graph they showed on the programme but here is a
link to something similar showing hurricane frequency and sea surface
temperature variations.

http://www.cpc.ncep.noaa.gov/product...mmary_2011.pdf

Len
Wembury, SW Devon

While it is certainly true that the number of North Atlantic tropical cyclones
has increased markedly in recent years the annual Accumulated Cyclone Energy
index has decreased over the same period. This suggests that either the average
intensity has decreased or the average duration has decreased.

It's also interesting that it's now 10 years since the Brazil hurricane of
March 2004 and, to my knowledge, there has been no hint of a repeat. Was it a
direct result of atmospheric/oceanic warming or was it just a random one-off
event? It's probably too soon yet to pass judgement on that.

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

On Thursday, July 17, 2014 5:58:40 PM UTC+1, Norman wrote:
Len Wood wrote:



There has been low activity so far in the Tropical Atlantic and I wonder

whether this heralds another quiet season.



http://www.nhc.noaa.gov/



http://www.cpc.ncep.noaa.gov/products/outlooks/



Did anyone see Operation Cloud Lab on BBC 2 last night?



Towards the end they got on to discussing Atlantic hurricane frequency and

intensity, saying how the frequency and intensity had increased in recent

years.



They blamed it on rising sea surface temperatures (a gross simplification).

They showed that polluted cloud had more smaller droplets (this has been

known for yonks by us oldies) and therefore reflected more solar which gave a

net cooling at the surface. Then had a graph of yearly Atlantic hurricane

activity 1950-2012 which showed low activity from about 1960 to 1990. This

was due possibly to all the air pollution that was around then. Since

everyone (?) has cleaned up their act since then, Atlantic hurricane

activity has returned to the high levels pre- 1960. All a bit tenuous.



I cannot find the precise graph they showed on the programme but here is a

link to something similar showing hurricane frequency and sea surface

temperature variations.



http://www.cpc.ncep.noaa.gov/product...mmary_2011.pdf



Len

Wembury, SW Devon



While it is certainly true that the number of North Atlantic tropical cyclones

has increased markedly in recent years the annual Accumulated Cyclone Energy

index has decreased over the same period. This suggests that either the average

intensity has decreased or the average duration has decreased.



It's also interesting that it's now 10 years since the Brazil hurricane of

March 2004 and, to my knowledge, there has been no hint of a repeat. Was it a

direct result of atmospheric/oceanic warming or was it just a random one-off

event? It's probably too soon yet to pass judgement on that.



--

Norman Lynagh

Tideswell, Derbyshire

303m a.s.l.

http://peakdistrictweather.org

Tropical cyclones are one thing Norman.
But the focus here was on hurricanes.
In fact an increase in intensity, or in other words major hurricanes, presumably meaning cat 3 and above.

The record is highly variable and too short to say anything about a trend.
They will try though.

Len

On Thursday, 17 July 2014 12:41:26 UTC+1, Len Wood wrote:
There has been low activity so far in the Tropical Atlantic and I wonder whether this heralds another quiet season.



http://www.nhc.noaa.gov/



http://www.cpc.ncep.noaa.gov/products/outlooks/



Did anyone see Operation Cloud Lab on BBC 2 last night?



Towards the end they got on to discussing Atlantic hurricane frequency and intensity, saying how the frequency and intensity had increased in recent years.



They blamed it on rising sea surface temperatures (a gross simplification).

They showed that polluted cloud had more smaller droplets (this has been known for yonks by us oldies) and therefore reflected more solar which gave a net cooling at the surface.

Then had a graph of yearly Atlantic hurricane activity 1950-2012 which showed low activity from about 1960 to 1990.

This was due possibly to all the air pollution that was around then. Since everyone (?) has cleaned up their act since then, Atlantic hurricane activity has returned to the high levels pre- 1960.

All a bit tenuous.



I cannot find the precise graph they showed on the programme but here is a link to something similar showing hurricane frequency and sea surface temperature variations.



http://www.cpc.ncep.noaa.gov/product...mmary_2011.pdf



Len

Wembury, SW Devon

Lets be fair, they make it up as they go along with a succession of contradictory reasons all usually with a an AGW narrative. Its the sea temps that did it Guv, and they will again.

On Thursday, 17 July 2014 14:16:14 UTC+1, Stephen Davenport wrote:
On Thursday, July 17, 2014 12:41:26 PM UTC+1, Len Wood wrote:

There has been low activity so far in the Tropical Atlantic and I wonder whether this heralds another quiet season.



==========



Likely a little below average. Seasonal hurricane forecasts don't have the best predictability (see last year) but, subjectively at least, the problems seem to be more when more than average *should* develop.



This year we have emerging El Niño which usually suppresses tropical Atlantic tropical developments, and on top of that SSTs are below average so this hinders Cape Verde developments.



However, high SSTs in the west Atlantic might promote "home grown" developments like Arthur up the Eastern Seaboard.



Sub-tropical ridge might steer storms into the Gulf of Mexico rather than hitting the SE.



Stephen.


Super El Nino is a now El Nono

Len Wood wrote:

On Thursday, July 17, 2014 5:58:40 PM UTC+1, Norman wrote:
Len Wood wrote:



There has been low activity so far in the Tropical Atlantic and I wonder

whether this heralds another quiet season.



http://www.nhc.noaa.gov/



http://www.cpc.ncep.noaa.gov/products/outlooks/



Did anyone see Operation Cloud Lab on BBC 2 last night?



Towards the end they got on to discussing Atlantic hurricane frequency and

intensity, saying how the frequency and intensity had increased in recent

years.



They blamed it on rising sea surface temperatures (a gross
simplification).

They showed that polluted cloud had more smaller droplets (this has been

known for yonks by us oldies) and therefore reflected more solar which
gave a

net cooling at the surface. Then had a graph of yearly Atlantic hurricane

activity 1950-2012 which showed low activity from about 1960 to 1990.
This

was due possibly to all the air pollution that was around then. Since

everyone (?) has cleaned up their act since then, Atlantic hurricane

activity has returned to the high levels pre- 1960. All a bit tenuous.



I cannot find the precise graph they showed on the programme but here is a

link to something similar showing hurricane frequency and sea surface

temperature variations.




http://www.cpc.ncep.noaa.gov/product...mmary_2011.pdf



Len

Wembury, SW Devon



While it is certainly true that the number of North Atlantic tropical
cyclones

has increased markedly in recent years the annual Accumulated Cyclone Energy

index has decreased over the same period. This suggests that either the
average

intensity has decreased or the average duration has decreased.



It's also interesting that it's now 10 years since the Brazil hurricane of

March 2004 and, to my knowledge, there has been no hint of a repeat. Was it
a

direct result of atmospheric/oceanic warming or was it just a random one-off

event? It's probably too soon yet to pass judgement on that.



--

Norman Lynagh

Tideswell, Derbyshire

303m a.s.l.

http://peakdistrictweather.org

Tropical cyclones are one thing Norman.
But the focus here was on hurricanes.
In fact an increase in intensity, or in other words major hurricanes,
presumably meaning cat 3 and above.

The record is highly variable and too short to say anything about a trend.
They will try though.

Len

Since about 1995 there have been more major hurricanes than during the period
1970-1995 but between about 1950 and 1970 there were as many as there have been
in recent years. During the period 1944-2008 the year with the most major
hurricanes (8) was 1950. In joint second place with 7 were 1960 and 2005. I
don't have figures immediately to hand for the years since 2008 so I'm not sure
if there is any year that has reached or exceeded 8 major hurricanes in that
period.

As you say, it's impossible to say whether what we are seeing in recent years
is the start of a trend or just part of a cyclical fluctuation.

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

On Thursday, 17 July 2014 21:55:08 UTC+1, Norman wrote:

As you say, it's impossible to say whether what we are seeing in recent years
is the start of a trend or just part of a cyclical fluctuation.

And that's even before you tackle the thorny problem of how many of them go on to make landfall. The conventional wisdom up until recently was

- Atlantic multidecadal oscillation fluctuates the SST (i.e. warm since 1995)
- More storms in the basin with higher SSTs
- More storms therefore available to make landfall

Recent work in 2011 has suggested that when SSTs are warmer, hurricanes are predisposed to form further east as the warm water stretches further east and is able to instigate cyclogenesis from African Easterly Waves earlier, which means that have more chance of recurving north well before reaching the US mainland.

This sort of work has probably been instigated to work out why we've had active hurricane "basins" but no major landfall since 2005 - 8 consecutive seasons without one which is unprecedented in the relatively short [reliable] historical record we have of hurricanes.

Richard