Pete B wrote:


As I said, these descriptions are based on memories over 30 years old so
should be taken with a pinch of salt. Also, the patterns vary depending
on the time of year due to the changing wavelengths of the upper-air
patterns - most of the descriptions apply to winter though those patterns
with E-W long axes should more consistent through the year. Also, the SST
regime and
atmosphere have changed over the past 30 years and I don't see the
patterns
working as well as they used to.




A very interesting an informed summary. Presumably, this applies to winter
but did you have a similar explanation for summer?


The system also applied to Summer but I can't remember the patterns
associated with each month. As I said above, they do vary.

The reason I am asking is that analysis of:

https://www.fnmoc.navy.mil/PUBLIC/OT...chive2002.html

shows that the SST anomaly for virtually the entire "summer" (JJA) period
of 2003, was extensively and significantly -ve over virtually the entire
Atlantic in a W-E band from the West of Ireland to the Newfoundland coast,
although it did reduce somewhat towards the end of the period. I wonder
how, if at all, that is connected to the development of the type of
pressure pattern that lead to the European heatwave of those months?

I remember at the time not being able to make a connection between the SST
anomalies and the weather we experienced. I can't access the site you refer
to but that at http://www.osdpd.noaa.gov/PSB/EPS/SST/climo_2003.html
doesn't have the cold water extending all the way to Ireland. Looking at
the anomalies I think I might have expected an unsettled, westerly type of
weather.

Another problem I see with trying to use these anomalies is that they are
based on different normals to those used forty years ago. Then we were
using normals based on a period ending in 1960. I believe they were
long-period normals, possibly a hundred years or so. The normals at the
above site are based on data from 1984-93 with some data removed from 91
and 92. Other sites may be using different normals. For this system to work
properly the base SST and atmospheric data should be from the same period.
The next problem would be whether a long period should be used or a
shorter, more recent period limited to the time when satellite data was
available.



--
Graham Davis
Bracknell