"Phil Layton" wrote in message
...

"Martin Rowley" wrote in message
...
The difficulty is judging the phasing of the low-level baroclinic
disturbance (given the multiple possibilities offered by the models)
with the upper forcing (due to the jet structure - a good way south
atm),

Martin,

Time to show my ignorance of the science!

What exactly do you mean by the above. I understand the jetstream is
moving
the whole thing at 180kts. Is the phasing the 'where and by what amount'
the
low will deepen at the surface ? and please clarify 'upper forcing'

Thanks

Phil

Not that i wish to answer for Martin, but here is what i think he is
referring to :-

The low is currently moving off the eastern seaboard of the USA, it is a
realtively shallow affair, to the NE of this off the NE coast of the USA is
an increasingly powerful Jet forecast by sunday to exceed 180 Knts,
underneath this jet lies a tight low level barcloninic zone (this is a tight
divide between the cold showery polar air over Labrador and the warmer
tropical air of the atlantic. As the low moves NE it will encounter this
jet, it is the interaction of this jet and a shortwave upper trough moving
out of canada that will determine how this feature develops. If the Surface
Low, Jet and upper trough happen to engage at the right time (typically if
the surface low moves into the left exit on the cold side of the the jet)
the low could deepen very quiclkly.

The Forcing is provided on the forward side of the shortwave, and also by
the powerful upper air dynamics.

I hope that is of some help

Paul