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⚠️Storm Ashley, Sunday 20 Oct 2024
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16-10-2024 6:38pm#1
A bit early but why not open a dedicated thread to the potential for a storm in the early hours of Sunday 20-10-24 and during Sunday day. Lots of uncertainty yet ( but isn't that what we like to speculate over 😁 ). Some very stormy charts starting to emerge from the main models but as ever different shape, track and timings that will align more over the coming days. Also of note this weekend are the exceptionally high tides which may cause difficulties in their own right only enhanced by the advancing very deep Low Pressure and strong onshore winds.
From Met Eireann:
Meteorologist's Commentary
The following information is valid on Wednesday 16th October 2024 and until further update.SummaryThis Friday, a brief period of heavy rain and strong winds across the country is expected,
We are monitoring another low-pressure system which could undergo rapid deepening on Saturday with the potential for strong winds and potentially a named storm; however, uncertainty still exists about this event.
Additionally, we are currently in one of the highest Spring tides of the year and this, tied in with any strong winds and high waves will increase the risk of coastal flooding.
Meteorological situationThe Jet Stream is expected to become very active across the Atlantic later this week and into this weekend which allowing it to pick up low-pressure systems and deepen them as they cross the Atlantic. The first low pressure system of interest (Figure 1 forecast time 12Z on Friday) is currently off the coast of Newfoundland, (Canada) as of Wednesday 16th October, and this system will undergo a period of deepening as it tracks towards Iceland by Friday night. Even though the low itself won’t impact us directly, an associated active frontal system will move eastwards over Ireland on Friday. All areas are likely to see a brief period of heavy rain and strong winds during the day on Friday.
We are currently in one of the highest Spring tides of the year and unusually high tides mean coastal flooding is possible. These exceptionally high Spring tides are due to the current proximity of the moon to the earth leading to an increased gravitational pull. Given the high astronomical tides any strong winds and high waves will increase the risk of coastal flooding, especially along Atlantic coasts.
Fig 1– Wind and Temperature forecasts at 300 hPa and the Geopotential at 500 hPa
However, our meteorologists’ gaze is also turning towards a different area of low pressure (see Figure 2 below, forecast time 00Z on Sunday), which will be developing in the western North Atlantic, about 500 nautical miles southwest of Nova Scotia. This low-pressure system is expected to travel quickly eastwards over the Atlantic this weekend. Current guidance suggests that this low will be on the southern side of the Jet Stream on Friday and will then cross over to the northern left exit region of the Jet Stream on Saturday. This system is then expected to undergo a period of rapid deepening, creating a storm depression as it swings up to the northwest of Ireland around Saturday night or Sunday morning.
Fig 2: Wind and Temperature forecasts at 300 hPa and the Geopotential at 500 hPa
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There is still a lot of uncertainty in the details at this time, but the potential is there for strong winds and therefore a named storm on Saturday night into Sunday” said Liz Walsh, Met Éireann Meteorologist.Updated information can be expected as the situation evolves and we analyse model data. Keep up to date with the forecast through your usual channels and for live updates, check met.ie or the Met Éireann app.
Post edited by Meteorite58 on14
Comments
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Models evolving. Latest ECM very windy to stormy early Sunday morning and through Sunday from different areas of LP spawning off the main storm which as can be seen is deepening rapid along the coast. UKMO even stronger than the ECM but ECM would be a better average atm. GFS less developed than the European models so far less windy. ICON initially very windy overnight but less windy during the day with the main body of the storm staying further out to sea.
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Tide tables for Sunday that might cause a bother in the usual areas being just a couple of days after some of the highest Spring tides of the year. That is a huge area of LP along with winds that will be pushing up the tide even more . Maybe not a good time to park on the Salthill prom on Sunday!
Fenit
Galway
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Arpege showing hurricane force mean wind speeds just off Mayo for 5am Sunday. It did this before for another system last year but didn't verify.
GFS and ECM showing the smaller lows spinning off which will chop and change loads before Saturday I'm sure. They must be very hard to model.
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Yeah some models showing less of an impact some showing very stormy, I think the ECM is probably a fair average atm and been the most consistent with very strong to stormy conditions. In general most models showing very windy frontal passage in the early hours and then the difference is where the storm will track either keeping winds offshore and glancing the coasts or overland. UKMO is very extreme at this stage and on the main probably overdoing it a bit as it is prone to. I think uncertainty but too close for comfort to ignore also.
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Looking at the fax charts, widespread yellow winds warnings on Sunday with probable orange ones merited for the NW, Going to strip the trees of their leaves for sure.
Have a weather station?, why not join the Ireland Weather Network - http://irelandweather.eu/
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Good graphics and discussion from the Met Office about the uncertainty around track, depth and strength for the expected storm on Sunday.
The main models ECM, UKMO, GFS , ACCESS-G all showing a very windy event with slight differences in strength in different locations depending on track. ICON a lot tamer in comparison keeping most of the winds off shore and less strong looking. ARPEGE starting to get into the grove , strong overnight into the early morning countrywide for a time and then strong along the W and NW coastal counties. The HI Res models still a bit out . GFS showing stronger winds now than earlier runs as it tracks closer ( perhaps stronger overnight /early morning than the ECM at this stage ) , showing very strong winds in the Northern half of the country especially in coastal counties whereas the track from the ECM is more countrywide.
Apart from the UKMO ( exceptionally strong in places , Red Level some counties in the W, but on its own at present and inclined to overdo it this far out and usually tames down closer to the event ) the other models currently not showing exceptionally high winds at this stage, probably widespread yellow and some counties in Orange warning and some coastal fringes getting high gusts. Trees of course are mainly in full leaf so that will have a bearing perhaps on warnings.
A wet day Friday for a time but a chance to dry out some bit on Saturday before some heavy falls on Sunday. No model showing huge rainfall at this stage but maybe a few areas could be within yellow warning level and some accumulations on mountainous areas, will see closer to the time.
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Marco Petagna tweets below
12Z UKMO suggesting Sunday's low pressure system to be 6hpa deeper than the earlier 00Z output..
Explosive cyclogenesis UKMO model output signalling low pressure to the SW/W of the UK to deepen by 31hpa in just 12hrs Saturday afternoon/evening
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UKV
First batch of strong winds impacting the SW
6 hours later stormy around eastern coastal areas
By 9am the second batch of stormy conditions is approaching the west coast
By midday Sunday extremely stormy for westernmost parts of Connacht. 96mph/154.5kmh gust just off Mayo.
3pm
6pm still big gusts across the NW.
If it plays out like that the longevity of the storm will be noteworthy . Exposed coastal locations gusting above 130km/h for 9 or 10 hours.
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This mornings fax has it further away to the NW, looks like a regular windy day now, would have thought only yellow warnings needed now for the NW and probably none for the rest of the country.
Have a weather station?, why not join the Ireland Weather Network - http://irelandweather.eu/
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Models aligning more but as normal some differences at this stage, ARPEGE probably an average representation atm anyway, some models that bit stronger, GFS widespread gusting to 90 Kmph and higher in places. I think with this set up we will be seeing high sustained mean wind speeds for a fair duration leading to weakening of branches and trees so a heightened risk to power outages and dangerous conditions. Still plenty of time for tweaks to warnings .
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The WRF is a great model nearer the time, conservative in its approach, can't remember it ever overdoing the windspeeds. The latest run an upgrade, possibly going through a small bit quicker by an hour or so then other models but the main point is the widespread gusts well inland of up to 100Kmh and up to 110Kmh in parts of the W and NW again well inland.
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From a weather account on twitter, metmonkey ha , seems like a decent account but it’s nothing official so bear that in mind
Damaging gusts of 65-75mph are likely across the worst affected inland areas, with the potential of violent wind gusts of 80-90mph at 50% for extreme North Western tip of N Ireland/Ireland and the Western Isles during Sunday.
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