part 2 - Mid-November Mayhem!
Major Atlantic storm
reveals the Fossil Forest at Borth
TO WEATHER-BLOG MENU
Fine Art Prints & digital images for sale-
& Dyfi Valley landscapes Slide-Library - Click HERE
mild but very unsettled weather had the entire UK firmly in its grip
throughout November, with a particularly stormy spell from mid-month
onwards. Record-breaking rainfall affected western areas with Cumbria's
flood disaster dominating the news - although Mid-Wales did not
entirely miss out as the images below will show. It was not until the
very end of the month that more seasonal temperatures arrived, bringing
with them the first hill-snow of the coming winter. But - justifiably -
we'll concentrate on the storms first!
A very brief settling-down in conditions allowed a fishing-trip on
November 10th. I chose the Stone Jetty at Aberystwyth Harbour for my
day out in pleasant sunshine. Here's the view from the end at dusk,
with the potting-boats coming in for the night. This is the last calm
image on this page!
middle of the month, strong jet-streaks raced one after the other out
of Newfoundland and across the Atlantic, engaging developing areas of
low pressure and winding them up into powerful, often sub-960 millibar
Atlantic storms. One storm after another passed over the UK,
alternately bringing periods of heavy rain and squally showers with
hail and thunder. The 17th brought showery conditions intense enough to
warrant a morning intercept down to the coast at Borth....
...with this squall coming
straight at me....
...gusts of wind rocking the jeep and shrill static-scream on the radio
as the hail-core lashed by, blocking out visibility....
...and clearing to this beautiful convective cloudscape!
The 18th brought severe gale-force sou-westerly winds and a huge
ground-swell from one of the biggest lows of the month. High tide at
Aberystwyth was just after 0800 so I headed down there to capture some
....messing about with the camera's ISO settings got a slowish exposure
for these images, giving some interesting motion-blur effects....
A view of the Stone Jetty, where I had been fishing when the first
photo on this page was taken!
Not a safe fishing venue in conditions such
This was taken on the main Prom....
...whilst on the way
home I stopped at Borth to check out the surf!
many, the big feature of November 18th 2009 was the flooding, on a
disastrous scale up in Cumbria. The cause of the problem was a specific
synoptic set-up that we call a Warm Conveyor - I have covered severe
ones over Wales before e.g. February 2004. In brief, warm conveyors
occur when the UK is within the warm sector of a depression with winds
coming up from the SW - importantly, from way, way down so that the air
has a tropical or subtropical origin. The excessive moisture in such an
airflow falls out as rain when the air is lifted up over the western
mountains of the UK. The rains these setups give are steady, heavy and
prolonged - in the 2004 example, Capel Curig saw 261 mm in 48 hours.
Worryingly, there are two properties of a warming system that can
influence these conveyors: these are a) that a warmer sea temperature
gives more moisture to the air via evaporation and b) warmer air can
carry a greater quantity of moisture: put together, this means that a
warming climate can produce more intense rainfall rates from conveyors.
The phenomenal and record-breaking 300 mm+ day totals in the hill
country above Borrowdale are a possible sign of the influence of
climate change - it is important to note that global warming does not
CAUSE weather events - it INFLUENCES them. Climate predictions indeed
suggest that such events are likely to become more intense in the
coming decades: although the frequency of warm conveyors is unlikely to
be affected, their intensity is likely to be influenced. So forget the
hype over the so-called "climategate" - this is a real and increasing
Down here, we were luckier in that we were closer to the edge of the
conveyor, so that the duration of the rainfall was less, but by the
time I had arrived back from Aberystwyth, the valley was flooded from
side to side:
Water levels had risen
to "half gate height" in just a couple of hours and by the afternoon,
it was impossible to get out of Machynlleth to the north or south.....
a slightly cheeky caption for the image below could be
Near Dylife, this landslip of waterlogged peat and clay swept down and
over the road, blocking it completely....
...whilst once the floods receded, the damage to fences along the A487
to Dyfi Bridge was plainly evident. Several cars were lost along this
section of road, attempting to drive through deep water and either
stalling or sustaining internal engine damage due to water getting into
air intakes - with diesels this can mean the need to replace the whole
engine, so deep floods are best avoided!
I was awoken early on the morning of the 25th by a deafening crash of
thunder, and that afternoon there was more intense convection around as
I drove over to the Midlands: this was after sunset at Caersws, with a
thunderstorm anvil sporting shallow mammatus....
Things finally calmed down by the 28th and the shower-clouds parted to
reveal the first snow of the 2009-10 season. I stopped at Glandyfi to
capture the view of the white-over Tarrenhendre ridge over the Estuary:
Intense coastal storms often rearrange the local beaches and at Borth,
the "Fossil Forest" can become well-exposed. On a cold early December
afternoon, with a low Spring tide coinciding with the last hours of
daylight, I took myself down there for a look. I was not to be
forest isn't fossilised as such and is geologically young at only
6500 years before present. At the time when the forest flourished, sea
levels were a bit lower than those of today and the storm-beach is
estimated to have been a kilometre further out seawards. The trees are
mainly pines and their stumps and fallen trunks lie in a bed of peat,
overlying a soft grey estuarine clay with bivalve shells, that
represents a period prior to the forest forming when sea levels were a
little higher. Maybe this clay was deposited in an intertidal lagoon
behind the shingle bar, a bit like that one behind Chesil Beach.
The tree-stumps were superbly revealed, the wood scoured clean by the
action of wave-borne sand particles in the high-energy storm
Here is a detail of the wood. Although beautiful, it is not
particularly hard and, taken from its environs, dries and rots quickly.
Best left where it is, in other words!
Another thing the storms have done is to throw up some big sand-bars
down by the low water mark, with lagoons on their shoreward side....
The setting sun was providing some splendid crepuscular rays:
...and there's one thing that is guaranteed at Borth on a falling tide
- the incredible reflective properties of the wet sand.....
So, what can we expect this coming winter? We have a developing El Nino
in the Pacific, which should mean milder and more stormy than usual
(the colder winter of 2008-9 was influenced by the persistent La Nina
that dominated 2008), but if the other winters of this decade are
anything to go by, we should see alternating periods of mild weather
with shorter cold spells. Apart from last winter, most snowy periods in
recent years have occurred in Northerly outbreaks and have often
occurred quite late in the season - in February or even March which is
technically Spring! But long-range weather forecasting is at present
akin to alchemy and it's not something I'm going to get into - so in
short - we'll see!
BACK TO WEATHER-BLOG MENU
Fine Art Prints & digital images for sale-
Welsh Weather & Dyfi Valley landscapes Slide-Library - Click HERE