Summer 2021 General Discussion

Xenji wrote: »

I spoke too soon, currently a torrential downpour with some hail mixed in and thunder, I cannot remember the last time I saw hail in June.

gee where is that?

Xenji wrote: »

Castlebar.

gee - crazy...


lashed rain the whole day yesterday down in West Cork.. :mad:

Xenji wrote: »

I spoke too soon, currently a torrential downpour with some hail mixed in and thunder, I cannot remember the last time I saw hail in June.

Proper hail is actually a summer phenomenon. I think in Ireland we think it's a winter thing.

Xenji wrote: »

I spoke too soon, currently a torrential downpour with some hail mixed in and thunder, I cannot remember the last time I saw hail in June.

Knocked out the internet around Tuam

compsys wrote: »

Proper hail is actually a summer phenomenon. I think in Ireland we think it's a winter thing.

I never understand why people think that.
I certainly see a lot more hail in summer and April than in the winter.
Maybe other parts of the country dont normally get hail in the summer?
Strange

You'd get far more Graupel in winter than true hail, the terms are fairly interchangable, but the stuff that falls out of a brisk shower in a strong Northwesterly is very different from the hail you'll get from a home grown slow moving thunder cell.

Certainly much more graupel here in Winter than hail in summer.

JCX BXC wrote: »

You'd get far more Graupel in winter than true hail, the terms are fairly interchangable, but the stuff that falls out of a brisk shower in a strong Northwesterly is very different from the hail you'll get from a home grown slow moving thunder cell.

Certainly much more graupel here in Winter than hail in summer.

I have to disagree, 'grapel' is common enough in winter but some of the most severe genuine hail storms I have seen have been in winter (esp December & March for some reason). Of course big hail can and does occur during warmer season convection but it is nowhere near on the same scale. As Donegal Storm alludes too, hail seems a bigger deal in the east because they don't really get to see it as often as we do on this side of the isle.

Omg it’s so bloody cold out
Longest day of the year in less than 3 weeks ?

km79 wrote: »

Omg it’s so bloody cold out
Longest day of the year in less than 3 weeks ?

Thought I was the only one. Very autumnal feel to this evening black clouds overhead windy and feeling cool at 12 degrees.

Quite windy in Dublin now but it's definitely not cold and the clouds are gone

Oneiric 3 wrote: »

Started off very dull and humid early this morning. Turned into a glorious, blazing late morning and early afternoon, then turned very dull and quite cool from about 3pm onwards. Very odd day I have to say.

I was stuck inside a stuffy office until 3
I had a blinding headache from the humidity alright
Makes sense now

Showery all afternoon and now a temperature of 10c but feels a lot colder in a stiff breeze,stove lit again

Xenji wrote: »

I think you are referring to the landslide that happened in Pollathomas among other villages in September 2003.

Wow, that long ago already?

Looked it up just now and found this nice, first hand report of that event:

"It started just after 7pm as Teresa McGrath and her partner Patrick Flannery were getting ready to go out. Rain is hardly unusual on the west coast of Co Mayo but something told McGrath this was different. From her kitchen window she watched the shower turn into a torrential downpour. It developed with such force that a neighbour of hers thought someone was spraying rooftops with a machine gun".

and it goes on...
https://www.friendsoftheirishenvironment.org/eu/27-papers-today/global-warming/2255-

And a reanalysis chart for that evening shows a very unremarkable looking pattern with a high pressure cell lying very close to Ireland.



Sort of goes to show, that while the Irish weather is 99.99% utterly predictable and 99.99999% utterly unremarkable, that every now and again, and nearly always unexpectedly, something like this will occur just to keep us on our toes.

Heading to achill island camping for a week later and Interesting variations in long term forecasts from Met eireann and MT.

Met eireann are predicting cloudier, cooler and damper conditions for the west coast for much of next week as opposed to MT who thinks all of the country will be warmer and sunnier.

Hoping MT is right!. Anyone have any thoughts as i know so many people are going west?

Goldfinch8 wrote: »

Apologies in advance if I go slightly off topic but I found it interesting to read and be reminded about this weather event again as Oneiric and Xenji discussed it.
I actually have a strong memory of that evening myself as I was out on Lough Mask with a friend. Showers were forecast but nothing out of the ordinary. I certainly try to avoid being afloat on the western loughs if thunder is imminent. The wind had been slack enough and variable but it definitely swung around to the northeast in the evening and we started drifting down towards the Lusteen islands and Maamtrasna Bay.
I will never forget the eerie darkness that descended on the lake that evening as the shower clouds rolled over the mountains and headed in a general northwards direction. The rain seemed to run along the mountains and we seemed to miss it on the lake but the sky started to grow darker and darker out to the northwest. I recall both of us saying that somewhere was in for a soaking but we had no idea what was about to unfold until we heard the news the next morning as to what happened in Pullathomas.
As much as I recall the darkness that evening, what was just as memorable was the clearance that came from the Maamtrasna direction as blue skies and golden rising mist punctured that darkest of evenings.
I just dug out of a drawer an old printed photograph that I took that evening with the 19th September, 2003 written on the back of it.
Not great quality but it is a personal reminder of that weather event that happened in the northwest of the county that evening.

Clearing skies over Maamtrasna Bay. 19/9/2003

What an amazing account Goldfinch and what an incredible photo! And nothing wrong with the quality because it looks as if it could have been taken yesterday! I don't remember the weather of 2003 that much but if I recall correctly, August that year brought a number of thunderstorms, both by day and by night, that came up on a southerly wind.

Your account is interesting also in how you observed the movement of clouds and the direction of the wind. NE wind but northward bound clouds. That tells me right there that something big must have been brewing. If you look at the map I posted above, the 500mb flow was SW to NE, but the lower level flow was NE to SE, so even between these two random levels, there was big shear going on which no doubt helped build up those big showers that evening.

This is a analysis map from the UK Met for midnight that night. One would think that nothing out of the ordinary was at play, but that shallow trough over the NW of Ireland proved to be far meaner that it looked:



And according to Met Eireann in their monthly summary for September 2003.. "A gauge at Inver, close to the site of the landslide, recorded a daily fall of 89mm, the bulk of which was associated with a thunderstorm late on the 19th (see back page).. and on the back page:

"Late on the 19th, a severe thunderstorm over the
Pollathomas area of north Mayo, twelve
kilometres east of Belmullet, caused devastating
floods and landslides within the immediate
locality. A number of bridges were washed away,
hundreds of livestock were drowned and many
families were forced to abandon their homes after
they were undermined by landslides. Although
the dry condition of the peat after relatively little
rainfall in the area during the late summer period
probably contributed to the instability of the
terrain, the major cause of the more than 20
landslides was the exceptional intensity of the
rainfall over a short period. More than 80mm of
rain fell within the space of 3 hours, a rainfall
event with an expected return period for the area
of 100 years. Large hail was also reported at the
height of the storm".

They then go on to give a short summary of the synoptic situation:
"The synoptic situation at the time, shown below left,
shows a slow-moving cold front with waves over Munster
and Leinster, while a trough off the northwest coast
brought showers during the day near Atlantic coasts.
Between 2000 and 2300UTC on the 19th, intense shower
activity developed in the area of Pollathomas, as shown
in the radar image below. Over this critical period, the
immediate area of Pollathomas was under the influence
of almost stationary cumulonimbus, or shower cloud; the
vertical windshear (northeasterly surface winds, southwesterly
mid-tropospheric winds) probably contributed to this effect.
The very localised nature of the heavy rainfall is shown
by the fact that at Inver National School, five kilmoetres
west of Pollathomas, a daily value of 89.3 mm was
measured, while the stations at Belmullet and
Bunnahowen (Muingnachree), both within ten kilometres,
recorded daily values of only 5 and 8mm respectively."

I'll attach the full PDF summary below, which also contains radar imagery from the evening as well (easier than finding the web link for it)