AUTUMN 2005 - PART 1:
The Atlantic switches on! October 15th-25th


BACK TO WEATHER-BLOG MENU

New! Fine Art Prints & digital images for sale-
Welsh Weather & Dyfi Valley landscapes Slide-Library - Click HERE

Rather unexciting weather has been my lot since the end of June, when I had my last decent storm to go after. This all came to an end in October, when finally the Atlantic cyclones began to make their presence felt. Since then there has been an excellent mixture of thunderstorms, squalls, hail, all the stuff that makes the weather photographer cheer up!

It's been rather busy at the moment. At the time of writing (October 28th) we have gone "round the clock" on the Tropical Storms/Hurricanes naming system, with Tropical Storm Beta (they are having to use Greek letters for the first time ever) probably to be upgraded to a hurricane soon - the first time that 13 hurricanes have formed in one tropical storm season and there's still a month to go before the end of the season. Meanwhile Hurricane Wilma was the deepest one ever recorded at an incredible 882Mb eye pressure (982Mb is a typical central pressure for one of our cyclones). It bombed to a Category 5 from a Tropical storm in little more than a day! A lot of records broken, then, in a short timespan.

So records fall everywhere and the arguing about climate change continues. Trouble is, we have only been recording tropical storms for about 150 years, and we've only had reconnaissance flights and satellite imagery/data available since the second half of the 20th Century. So what occurred prior to all of this? We only have fragmentary evidence. Interesting stuff, all the same...

Back to here, and on Saturday 15th, despite an almost windless anticyclone sat over the UK, the lows were brewing up out there in the Atlantic. The first sign of such a happening is often the ground-swell, as any coastal dweller knows. Ground-swells are generated way offshore - like far travelled ripples from the disturbance on the pond's surface, they migrate outwards from the disturbance, barely noticeable to offshore craft. Once they reach shallow water, however, they build into a series of long, slow-moving tall waves - hence their attraction to surfers.........

At Borth, they ran ashore one after another in the still and watery sunset....
These are over 2.5m in height.... a tricky job using the camera handheld in low light conditions, but luckily Borth has timber sea defences which have useful flat areas for sitting a camera for longer exposures....
...which create some weird but pleasing effects!
My first storm-intercept since late June was on the afternoon of October 19th, again at Borth as the radar indicated a group of heavy cells heading NE across the Bay. This was the best, giving a number of good C-G lightning flashes and booming thunder as it headed for the coast north of Tywyn....
...with a developing weak gust-front ahead of the advancing precipitation, here seen sideways-on...
...plus of course a large, fluffy Cumulonimbus anvil...
Great thing about Borth is the way the wet sand reflects the sky...
Especially as the sun starts to set!
Here's a quick diversion before going on to the next sequence of events. This, taken on Saturday 22nd, shows instability being released in the lower levels of the atmosphere, resulting in thin, towering cumulus clouds. However they're only going up so far before spreading out downwind (wind being R-L). This suggests two things at work- firstly a mid-level inversion (or cap) stopping them from going up any further and secondly a layer aloft in which stronger winds exist (it's pretty usual to see windspeed increase with height). Thus they're bubbling up, meeting the cap, and spreading out downwind from that.
The following week started with weather warnings issued for many areas for heavy rain and ended with the warmest October 27th since records began in the bag! Monday 24th saw a substantial low-pressure system anchored to our NW and a trailing front reaching way down towards the Tropics, with a moisture-laden warm S to SW airflow being set up over the UK (the so-called Warm Conveyor). In such setups, as the air comes in off the sea and is forced up over the mountains, often drastically enhanced rainfall results (the technical term is orographic enhancement). The result is enormous amounts of water flowing down the mountain catchments and causing flooding along the major river valleys.....
On the morning of the 24th flood warnings were out for four rivers in Wales including the Dyfi here and the Mawddach/Wnion further north. It was difficult to get a decent shot of the Dyfi (above) in flood (pouring rain didn't help!) so I headed northwards, into Coed y Brenin, where the Mawddach flows...
This is at the top of Rhaidr Mawddach - where the river drops several tens of feet over an intrusive igneous sill consisting of the hard rock, microtonalite - you couldn't safely get to the bottom of the falls as that area was underwater! For scale, the river here is 25ft+ across!
There are two waterfalls of note here, one on the Mawddach and one on its major tributory, Afon Gain, with the remains of the old Gwynfynydd gold mill in between. The rivers join below the ruined mill. Pistyll Gain is a bigger fall than Rhaidr Mawddach: in this image it is seen from the main footpath, but I decided to get a little closer....
...but this is as close as was safe. A slip into the river below would have spelled the immediate end of me, so in clouds of swirling spray I stopped here and attempted a few shots, having to dry out the lens in between. This is the best of them! The noise was literally thunderous! A great morning out in rough conditions!
The following day, Tuesday 25th, had for some time been expected to deliver some thunderstorms in the unstable post-frontal airmass. A pore over the charts the night before led rapidly to the conclusion that an early start would be essential for anyone wanting to see much in this part of Wales, so I was off to bed early that evening. I rose at 0400, drank black coffee, checked all the forecast data, checked the camera really had dried out properly, confirmed on rainfall radar/infrared satellite/lightning plotters that something was indeed heading this way, drank more black coffee and so on. The plan was to keep observing online then head down to Borth at 0700, when signs of daybreak ought to become apparent. At just after 0600 I caught a flash in the corner of my eye through a side window and moments later a boom of thunder rolled through the valley. Hastily powering down the computer whilst simultaneously yanking the modem cable from the phone socket, I sat there feeling very alone all of a sudden - minus my data-feed on the screen, my fix that could make an intercept a success or failure. But what the hell? - the surface charts, satellite and radar all showed thunderstorm cells scattered along an active surface trough coincident with an upper shortwave - why not just get out there and go and see! Leaving Machynlleth sometime before 0700 I made it a few miles down the valley before running into a deluge of Biblical proportions forcing a slowing to 10mph and peering into the rain and spray to see where I was heading. Occasional loud crackles on the radio coincided with stabbing lightning over the hills on the north side of the valley, while ahead a most unlikely thing appeared for the time of day - a traffic-jam. Glandyfi has one of the most beautiful views in Wales, looking across the Dyfi Estuary to the wooden railway bridge and the hills beyond, but also has one of the narrowest bendiest bits of any A-road in Wales. Here, large vehicles meeting often have to engage in tricky maneouveres in order to pass one another, and this was indeed the case now. We sat there as the rain turned heavier, then to hail, while odd flashes through the gloom were probably lightning but could have been anything in that level of visibility! Finally on the move, I negotiated roads awash from the downpour, to arrive on the sea-front at Borth at about 0730....
This is what you get by trying to photograph storm-clouds moving at 60mph before it has gotten light properly! This is a 20-second plus exposure. The brighter area is not due to lightning but to a small gap in the clouds i.e. a lighter area, blurred by the speed of the clouds' movement. I quite like the effect! With one huge towering storm to my east - where the sun rises - daylight would be late arriving today.....
By 0800 it was attempting to brighten a little and I could see that I was sat under a "shower-train" updraught area. By which, I mean that convection was going on overhead and was maturing (i.e. giving downpours) downwind and a little to my NE. Given that TORRO had a Tornado Watch out on parts of the western UK, it seemed worth staying put and scanning in case any spin-ups occurred in this cloud-bank, but none were forthcoming. Had they done I had travel options both N and S (storms moving SW-NE) so a sharp exit would have been easy if required. The photo above was taken at around 0830 looking out northwards to clearer skies.
The updraught base moved away NE and left a rather unexciting greyness in its wake. I was just about to decide to head home for breakfast when a small clearance in the grey stratus revealed much more to come, with towering cumulus and cumulonimbus strung along the horizon. I stayed put again. These cells duly arrived but were of little photogenic value as they approached. An evil dark grey wall of rain with occasional lightning flashes was the lot. But through a gap between cells and their rain I could see that conditions beyond were much clearer. This suggested finding a venue where the view downwind was unobscured by buildings etc - storms can look more amazing as they clear an area sometimes - so I headed off to Ynyslas sands, where there is an open view straight up the estuary, and waited...
First the clearance passed Aberdyfi, with a large anvil visible overhead....
Then the sun, still low in the East, started to back-light the flanking towers of the storm as they billowed up. I could have done with a 20mm lens here - it would have caught the whole thing nicely!
As the whole lot rolled on up the valley conditions began to brighten at ground level...
Retreating quickly away now, this is the last of the shots. Nothing that severe about these storms, I thought to myself, but it had been great to get out there on a madcap adventure - with an early start more reminiscent of an Alpine climb! Getting back to Machynlleth around 1000, I was greeted by two fire-engines heading up out of my street. The same cell had caused quite a bad flash-flood, requiring some hasty pumping-out work. Fortunately my place was unaffected. A look on the rainfall radar (below) indicates that with rainfall rates of >46mm/hour (lower red area), this was a cell more than capable of causing local problems with flooding. 2 lots of storms in a week - and lots else in between - now that makes a change! With the remains of Hurricane Wilma affecting us this weekend, I wonder what more we can expect??
BACK TO WEATHER-BLOG MENU New! Fine Art Prints & digital images for sale- Welsh Weather & Dyfi Valley landscapes Slide-Library - Click HERE