Storm Aiden - Saturday October 31st

The key concept here is the range of possible outcomes, we have the energy from current Gulf of Mexico hurricane Zeta rapidly merging with a short wave being ejected out of an upper level low in Texas-Oklahoma (bringing them a freezing rain storm), and the combined energy races east about as fast as low pressure ever moves in the general area of this forecast scenario. That all means that tiny changes could build into significant alterations of forecasts on both timing and intensity.

Take the weekend part of this as a watch situation for now. The heavy rainfall for Thursday is pretty much locked in and a generally unsettled weekend scenario seems like a sure bet too, but these details could change. With these sorts of speeds in the jet stream, you have to think that some place is going to get nailed by the resulting frontal system.

Torrential rain in Galway now

Weather Advisory for Ireland

Very unsettled weather will occur over the Halloween weekend as a series of vigorous Atlantic weather systems pass close to Ireland.

Spells of heavy rain will lead to surface and river flooding.

Very windy/stormy at times with some severe and damaging gusts possible.

Some coastal flooding possible also due to the combination of low pressure, high tides and onshore winds.

Very high seas.

Please consult your county warnings from Met Éireann on a day by day basis https://www.met.ie/warnings/today

Valid: 21:03 Friday 30/10/2020 to 18:00 Monday 02/11/2020

Issued: 10:00 Thursday 29/10/2020

Certainly not as bad as outlier chart they showed after news at 9. It will likely be yellow with an odd chance of 115kph along coasts in South and West.

How likely is the current Met Eireann forecast for a dry night on Saturday in Dublin to stick? About the one thing I'm looking forward to about Halloween this year is my usual wander around Dun Laoghaire to watch all the back garden fireworks displays people do, the last two (I think?) years in a row have had horrendous weather on Halloween night and it seems like this year, despite the weekend in general being forecast to be a mess, the night itself might actually be dry

Our Meteorologist's Commentary regarding the scary Halloween weather on the way has been updated and is available here...

https://t.co/ktXtWjbfIg

I have one like that, lab man ... they are a rough guide at best, it can rain in some situations at higher pressures than the range where "fair" is indicated, and it can clear out at lower pressures if you get into a dry slot in a complex of low pressure. A better indicator is whether your barometer after a tap is on the rise, steady or falling. With a rise you should be seeing improved conditions, with a fall there is usually rain (or snow) on the way, and with a steady barometer whatever you've currently got is likely to remain in place.

Might want to check that your barometer is set to your local "sea level" pressure, what's your elevation above sea level and rough location? One of us could let you know what your barometer should be reading. There's usually a screw in the back somewhere that lets you adjust the reading. This would be a good time to check as pressure trend is not changing very quickly.

(will post more on the actual weather situation in a few minutes, just checking some recent updates)

lab man wrote: »

I'm living right on the shannon estuary about 50 / 100 above sea level yes a rough guide is all I want there is a skrew on the back
Thanks for your help

Okay so your barometer at present should be reading 1001 mbs or 29.55" ... and if you happen to check a bit later, it should be slowly rising to reach a peak around 29.8" tomorrow mid-day, then it should fall to around 29.3" late Friday night. If you seem to be in that range you don't need to adjust.

At your elevation your actual air pressure is just slightly lower than sea level pressure. All the weather stations and weather maps you might see anywhere are converted to sea level pressures. Somebody living high up on a hill could have as much as an inch or 30 mbs lower "actual" pressure but if their instrument is set at the actual pressure it will range lower than the design values for "fair, change and stormy" or whatever they show.

---

Meanwhile, had a look at latest guidance ... Zeta was whistling along even a bit faster than yesterday's model guidance had shown, the ragged centre just left the U.S. mainland around Ocean City MD ... model consensus seems to be that the core of Zeta's energy will remain intact for 48-60 hours and zoom past Donegal Bay late overnight Saturday into Sunday morning, probably leading to a peak in wind speeds from midnight to 0600h on the west coast. Before that, the low forming up in the middle of the Atlantic now will be bringing an interval of strong winds Saturday morning, these will veer westerly for a time, and some clearing will develop later Saturday, a brief break in the strong winds could mark the passage of a very weak ridge before Zeta's remains arrive.

The supporting upper low is trying to keep up but is falling behind and will force a secondary low to form in the same zone as Zeta runs through, that second low will never totally develop and will remain a trailing wave but we need to keep an eye on that plus the final stage of low pressure dropping southeast on Monday.

Still some potential for any of these to develop an intense band of strong winds as the jet stream is quite compressed. Will probably just be a long term disturbed period of weather with mostly level one alert conditions and the occasional localized level two (or orange alert if you prefer).

Gaoth Laidir wrote: »

Is it just me or are the two streamline animations in the Howling Hallowe'en discussion not loading?

not loading here also.

Cranium , it was at 1010. So have it changed to 1002 so looking forward to seeing how it goes
1 thing though the black hand does seem a bit loose thanks lab man

Some potential for model error even at this range because the core of Zeta has moved even faster into the Atlantic than models were suggesting over first 6-12 hours, which could give it less time to gain latitude (as the second round of strong winds). Not sure if this would impact any of the evolution of the first round earlier Saturday. Waiting to see if ECM has caught this because so far GEM, GFS and Arpege have not quite got the speed, it may be that cloud formations have accelerated past pressure patterns too.

Anyway, I think we need to underline the potential for last-minute changes in forecasts especially with the late Saturday early Sunday time frame.

There could also be late stage changes in the evolution of third wave in the series due to pass south coast Sunday night. Not sold on this one being suppressed as shown.