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Baroclinic Cyclones
Transcript of keynote speech by Donald
Burfitt-Dons (continued)
The
second type occurs through cyclogenesis and is known as baroclinic cyclones.
I’m sure Frank Burrow could do a much better job than me in describing
the mechanism of formation, but without going into it too deeply, they
form along frontal zones initially at the upper levels where the jet
stream dwells at around 30,000 feet.
As pilots we are always interested in where the jet
stream runs because we use it to ad between 100 and 150 knots to our
ground speed when flying eastbound and like to hop aboard, when we can.
It’s very high energy air with dramatic wind shears associated
with it. This high energy gives the conditions for the formation of
this type of cyclone.
It’s a bit beyond the scope of the conference
to go into the whys and wherefores of formation but, if you are interested
I’m sure Frank would be only too happy to do so. Basically divergence
along a frontal line at the upper levels causes convergence at the surface,
then an upward movement of the air parcel, which offsets gravity acting
on the air column, the surface pressure drops further and so increases
in turn the intensity of the cyclone. So,voila, an extra tropical cyclone
is born.
If the upper level forces are strong enough the surface pressure can
fall very quickly, and these ETCs are sometimes called bombs. The low
core pressures can create a very active system.
The lowest reported in the Atlantic was off eastern
Canada in 1989 where pressure was reported as 928 millibars, the tropical
equivalent of a category 4 hurricane. Continued Donald
Burfitt-Dons explains how the GWA monitors hurricane activity
the
planet's way of recycling heat energy/
the first Brazilian hurricane/cyclones
outside the tropics/how
the GWA monitors hurricane activity/the
rising tropopause/ETC activity
since the 50s/l ETC activity
since 1990/ the effect of an ETC
on London /how superwinds form/
the impact of ETCs on aircraft/data
from 21 recent storms/ UK as a breeding
ground for tornadoes/
the impact on the insurance industry/
future implications /threat
of ETCs to Europe and UK
