Surface Levels.

The BBC leaves a lot to be desired when it comes to making use of the
North Atlantic plots.

The reason is that they ignore most of the Atlantic and concentrate
only on the after effects of the systems portrayed on decent weather
maps.

To get the most out of a North Atlantic map, you need to consider the
coming (real time US/Canadian) mesoscales and the situation extant on
the west coast from Florida up to Greenland, as this is the deciding
factor in most coastal European synopsis.

The present dead-head regime in the BBC insists that technical stuff
be left out of all presentations. And nowadays, apart from local
regional forecasts (and not all of them too neither) it is uncommon to
see the North Atlantic map.

Well that's enough about the BBC. They can rot in hell as far as I am
concerned. I can forget the good old days now I realise how not so
good they might have been.

The weather in the USA varies according to the tenets laid down by
Weatherlawyer in work stated elsewhere. So I won't go into that yet.
Just restate the obvious that generally the weather they get is like
ours for the same reasons.

It comes in from southern climes and crosses diagonally to the
Canadian border where at Newfoundland it joins the Atlantic stream
called the North Atlantic Drift. Sometimes (and erroneously called the
Gulf Stream.) The drift is the result of tropical heating forcing
brine the same way that it forces the atmosphere. In the ocean this is
called the Thermo-Haline Column in the atmosphere it is called The
Weather.

As a mass is heated it builds up pressure. When contained -as in the
top layer of the ocean or the bottom layer of the atmosphere it
expands according to the laws of thermodynamics. And with the air this
lifts the lid called The Tropopause. And takes with it a section from
the thermo-haline column that can not escape any other way, water
being infinitely less responsive to thermodynamics than air.

Air from warm water surfaces, filling with moisture, rises to the top
of the air column -because water laden air is much lighter than dry
air. Complex, but relatively unimportant.