On Nov 23, 9:20*pm, "Martin Rowley"
wrote:
david.mitchell wrote

snip various

It's interesting that you mention topography, as if you follow the
angle of the coastline from Sunderland *South to Saltburn and
continue
onto the Humber, the chunk that sits East of this jutting into the
North Sea is particularly the area prone to showers. I am totally
not
a scientist, but could the uplift of the Northerly as hits the coast
with some fairly decent cliffs in the Northern part, be the trigger
for the shower activity??? The showers seem to form off the coast
here
with no sign of them running past Newcastle, so something must
trigger
it somehow. It seems that a very slight Westerly element favours us
here as well.

David Mitchell.

... I believe that it is tied to the difference between land and sea
friction action along the northerly flow: the air flow over land (to
the west) is backed, with respect to the the airflow over the sea -
this leads to convergence along the flow, which may, as you've
indicated, be enhanced by uplift as the air rides up over the hills.
However, the convergent action is observed to take place *before* the
coast is reached, so I would think that the differential friction land
vs. sea is the key element. It's probably a delicate set of factors
involved - a slight change of wind direction or overall speed may
nullify the effect - the Forecasting Reference Book only shows the
effect in the "infrequently observed" category.

... Will Hand's the man for this as I think he published some data on
shower distribution - I've probably got it here, but can't find it :-(

Martin.

--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N * Long: 01.88W
NGR: SU 082 023

Thanks Martin, I hadn't thought about convergence.