Your daily forecasts from Boards.ie weather forum (NO CHAT)

Wednesday, 18 November, 2009
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Although it will be quite windy today and Thursday, we are now tracking an intense storm that refuses to die on the model runs as we get closer to Saturday. There are worrying indications of storm to hurricane force winds for many parts of Ireland and only three days to see any relief in the forecast models -- essentially, if there is no downgrade later today, this storm should be regarded as an imminent danger. See my forecast below for an estimate of how it could play out.

TODAY will become increasingly windy and quite mild with this morning's steady rain possibly easing to drizzle or even a few dry intervals before more steady rain arrives from the southwest by afternoon. Highs will reach 14-15 C and rainfalls will average 20-30 mms. Winds are already SSW 30-50 mph in many southern and western counties, and these will soon spread further north, with a general increase to 40-60 mph later on in exposed areas (more like a steady 30-50 in less exposed locations). Although some periods of better visibility may develop, fog and mist may become widespread in the second half of the day.

TONIGHT will continue windy and very mild with more rain at times, fog and mist clinging to higher ground, and lows (if we can call them that) near 10 or 11 C. Expect perhaps 10-15 mms further rainfall tonight, and winds holding steady in the SSW 30-50 mph range.

THURSDAY could become a little more windy especially near the south coast, gusts to 65 mph are possible there, and 50-55 mph more generally. Highs will edge up to 15-17 C and rain will become heavy and perhaps thundery in a few places. Sorry to report that a further 30-40 mms could fall and create some localized flooding.

FRIDAY will see a little improvement as winds swing more into the WSW at 25-45 mph, with variable skies, some passing showers, even a few heavier ones with thunder or hail at first, but also some sunny breaks, with lows near 9 C and highs near 14 C.

Now, SATURDAY will at least be windy and showery with mild temperatures; about the best one could hope for given all the guidance available would be SSW winds of 30-50 mph and 10-20 mms of rain with highs near 13 C. Some of the more extreme model output would suggest a low of 948 mbs just west of the Shannon estuary causing afternoon and evening winds rising to SSW 60-100 mph, 30-50 mms of rain from early morning to mid-day sweeping north, squally and possible violent showers, as the wind veers from SSW to W -- in this worst case scenario, the very strong winds would be particularly bad in south coast and west coast to central counties but really, the whole country would be under siege from a hurricane-like storm. Like anyone making forecasts today, I'm stuck between hoping this won't happen, and trying to warn people that it may well happen. Stay tuned and look in on the other threads especially the one entitled weekend storm, because there you'll get a wider range of opinions as to what could happen here, but essentially, we are all wondering if one particular forecast system (the GFS model) has this storm "nailed down" today, whereas some other forecast models offer hope of a less violent solution.

Whatever Saturday brings, Sunday looks likely to be windy and colder with passing squally showers of hail, and snow on higher mountain peaks as temperatures up there drop to -1 to +3 C ... down near sea level it may be more like 7-9 C, so if you live fairly high up it could be 4-6 C and rather mixed as to precipitation type. Winds on Sunday are likely to be W 40-60 mph but if the major storm hits, that will be relief by comparison to the day before.

Another mild windy system threatens to sweep away the brief insertion of colder air on Monday night and then (this is starting to read like a movie plot) the models have yet another intense storm in mind for Wednesday (Connacht would be hit harder by this one).

Final thought for this segment, the risk of the intense Saturday storm is probably rising to about 50% now ... and with rather gusty winds likely on Thursday, you might want to think about what could happen if various trees fall (towards a north to northeast direction mostly) or if there were to be structural damage to any buildings near your parked car, for instance ... and take the appropriate action or at least be prepared for Saturday.

Meanwhile, it's not exactly calm here either, we've had strong winds now for two days and we're looking at two more, not as strong as what I'm forecasting for Ireland, but 40-60 mph in gusts, and with some further rainfall, as temperatures hover in the 8-10 C range.

UPDATE _ Wednesday, 1845h
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Here comes the heavier rain and it may indeed cause some severe flooding in places as it mounts up to eventual totals of 40-70 mms through late tomorrow (including what's already fallen).

As for the Saturday storm event, there is somewhat good news -- the latest GFS run looks more like the GEM in keeping the deep low centre a little further west through Saturday and reducing wind speed potential down into the range that would be severe in places but not on the scale of a national emergency (in other words, yet another windy day with gusts possibly as high as 80 mph). Now this situation is far from clarified, the jet stream wind forecasts remain ominous and any small changes in the energy of weak systems now approaching the Atlantic trough from eastern Canada would hold the potential of returning the forecasts to the high level of concern.

I've posted some more about this on the weekend storm thread including a map showing where this weekend storm is today (it's actually quite a weak and small low in the region south of Baffin Island in northeast Canada -- you wouldn't think it could harm a fly from today's view of it).

Meanwhile, tomorrow's wind and rain can be clearly seen in the central Atlantic where there is a deep low and strong fronts already.

Over here on the west coast of Canada (and you can check that out too on the map I am attaching here as well as the storm thread), we have our own little slice of heaven with a strong low forming up for an overnight assault on the coast, and it's already quite foul outside with periods of hail-mixed showers and gusty SW winds, but worse will develop tonight here (it's only 1045 here of course).

(map of weather systems across North America and the Atlantic, you're looking at North America, western Europe is on the right side of the map and oriented sideways in case you're having trouble finding Ireland, it's under all those isobars somewhere. )

http://www.weatheroffice.gc.ca/data/analysis/935_100.gif

Thursday, 19 November, 2009
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TODAY will continue very windy and wet, with the stronger winds being felt in the southeast (SSW 45-70 mph) while the west and northwest see a little reduction in their wind speeds (SW 30-50 mph), while the axis of heaviest rain slides slowly east through central counties towards the east. A further 30-50 mms of rain is possible, and the flooding potential seems evident to all. It will be muggy with all this, as temperatures stay mainly in the range of 14 to 16 C (12-14 C close to the south and west coasts).

TONIGHT the rain should become more showery although it could end with a few rumbles of thunder in the east, and eventually skies may begin to show a few clear patches with winds veering to SW 30-50 mph and becoming less gusty by morning. Lows will fall to only about 7-9 C.

FRIDAY will see a few breaks in the extensive overcast and there will be a few lingering areas of light rain or drizzle, mostly over higher parts of the west and north. Winds will continue WSW 20-35 mph then back to southerly by evening, picking up as rain moves in from the Atlantic. Highs for the day will be near 13 C and it likely won't drop much from that by nightfall.

SATURDAY looks very windy but so far, the models seem to agree, the strongest winds will wait now for round two of the weekend storm on Sunday, however, there may still be some very strong gusts in the south and southwest from this first phase, as winds rise to SSW 45-75 mph, with some higher gusts possible. Squally showers or periods of rain will develop from early morning and spread across the country, followed by variable cloudiness and more scattered showers or thundershowers. Highs will be near 14 C.

SUNDAY will perhaps see a few hours of less blustery winds in the early morning hours (still SW 30-50 mph though), then the winds will gradually increase from the SW all day to reach peak speeds of 60-90 mph across many parts of the west and south, possibly a little less extreme in the north and east (40-70 mph would still be very blustery though), and with some potential for gusts above 100 mph in exposed locations and at higher elevations. Somewhat colder air will arrive, keeping temperatures around 8-9 C and bringing more of a mixture to the form of showers, especially in elevations above 300 metres, where hail will be frequent, and with snow falling at times on higher slopes. Hail and thunder could reach lower elevations at times too. In other words, this is not the day for a picnic.

MONDAY will be slightly improved as the westerly flow relaxes to 30-55 mph with less frequent showers and a few sunny breaks, lows near 4 C and highs near 10 C.

TUESDAY is looking like yet another very strong wind event, with potential to reach SW 50-85 mph, and more rain with that.

The longer term prognosis is for this windy, wet onslaught to continue for about another week beyond mid-week, as a very deep "parent" low is going to be trapped by the larger features just southwest of Iceland, which means that every bit of energy coming along in a strong jet stream will be directed right over Ireland. It's almost as bad as the refereeing at the WC football qualifier. :eek:

UPDATE _ Thursday, 7 p.m.
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It continues to look as though Saturday will be moderately windy in all parts of Ireland and perhaps very windy at times in the southwest (gusts to 70 mph or so), as to rain potential I would say 10-20 mms generally and locally up to 30 mms. Sunday continues to look more ominous as the deep low that was always being speculated on by all models arrives off the Mayo and Donegal coasts by mid-day, bringing whatever westerly gales and storm force winds it can muster at that point, which looks more like gusts to 80 or even 90 mph in exposed locations. By that point the flow will be considerably colder as some maritime arctic air is mixing into the strong circulation.

The seeding low for this event has now reached about 41W and has dropped down from 60 N to about 53 N, just to the northeast now of St Johns Newfoundland. The central pressure has dropped from 994 to 984 mbs in the past day, which is not extreme but shows that it's gaining while the larger parent low northwest of Ireland has been steady at about 955 mbs. Eventually this new low will just take over most of the old circulation and the current low will be pulled back into the new circulation -- this is what the GFS was having its troubles with, because it wanted to race the area of strongest winds east on Friday and explosively develop off the west coast of Ireland -- now all major models seem to agree on a more gradual development that still sends out quite a strong leading wave on Saturday, so I wouldn't urge anyone to make big plans for the outdoors at any point this weekend, it's more a case of a disastrous event turning into something that can be more or less weathered, I suppose.

Speaking of which, it continues to blow from the west here and rain lightly at times, and it's about 7 C which feels quite raw in the 30 mph wind.

I may update again if the 18z GFS has new ideas, otherwise, I hope everyone stayed dry and we'll see how things look in the early morning.

Friday, 20 November, 2009
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TODAY will provide some welcome relief from the rain and cloud, although there will be a few isolated and generally light showers mixed in with some sunny breaks and also more moderate winds WSW 15-30 mph in most places, occasionally gusting to 40 mph near the west coast. Highs today will be about 11 C.

TONIGHT will start out dry and perhaps clear in some eastern counties, but cloud will rapidly overspread around midnight with rain arriving by morning in the southwest, as winds back to southerly and begin to rise to 30-50 mph in exposed south coast and western counties. It won't get this windy until after sunrise in the east. Lows will be about 7-9 C (it could fall lower briefly in rural eastern counties).

SATURDAY will become very windy as SSW gales of 40-70 mph develop, with higher gusts mostly expected near the south and west coasts. There is still some potential for higher gusts in this phase, and periods of rain will drop another 15-30 mms of rain, followed by squally showers or thundershowers with hail as winds veer a little more to the SW by afternoon. Highs of about 11 or 12 C can be expected; it will feel colder in the wind.

SATURDAY NIGHT, any reduction in wind speed will be short-lived and then followed by stronger SW winds before daybreak, as squally showers continue to pelt most regions under very strong winds of 45-75 mph. Lowest temperatures will be about 6 C but colder at high elevations, with hail or a bit of snow possible well above 300 metres.

SUNDAY will be a cold and blustery day with temperatures staying in the range of 7 to 9 C mostly, and passing showers of rain or hail, with snow possible on higher peaks. There will be a constant strong wind in the range of 50-80 mph from the WSW but potential for gusts to as high as 100 mph in exposed locations and on higher slopes. Watch for updates as the storm develops. Much depends on the exact track and intensity of the low; the current forecast models are showing a slightly less extreme solution than a worst-case scenario but there is also room for a slight downgrade. Precip amounts may be fairly moderate (10-15 mms) but variable from place to place due to the showery nature.

MONDAY should see a bit of improvement in the wind although it will remain in the 30-50 mph range, with slightly milder air working its way east at 10-11 C, and showers or periods of light rain (10-15 mm potential).

TUESDAY into WEDNESDAY, another strong wind and rain event appears possible. Wind gusts to 70 mph from the south to southwest, and rainfall amounts of 20-30 mms, are currently indicated with this next storm, with highs of about 11-12 C.

Colder air should then arrive on more of a west to northwest wind, and while skies should brighten, a few more mixed showers could be expected as temperatures fall to around 7 C by day and 1-3 C by night.

Watch for updates ... the 06z GFS will soon be rolling out.

Here, I have about the same weather misery, constant strong winds and occasional pelting rain with temps barely holding around 7-8 C. It sounds like a strong front is coming through here now.

Saturday, 21 November, 2009
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A two-part storm will rapidly develop this morning, with the first wave likely to move through the south before noon, and then on to the central and northern counties by afternoon. There may be a brief lull in the stormy conditions this evening but winds will gradually increase overnight to reach a peak around mid-day Sunday, lasting in many places for many hours into the early hours of Monday.

This forecast is going out a bit early to catch any early risers but I will keep updating the progress of "part one" of the storm as well as updating the prospects for Sunday as later information hits the desk, so to speak.

TODAY, the south will see very rapid increases in wind and heavy rain will develop, becoming squally at times with thunder and lightning possible. Winds will start off SE 30-50 mph, rise to S 40-65 mph and end up SSW 50-70 mph briefly before settling back to SW 30-50 mph again -- the afternoon in the south may be a little more tolerable with some sunny breaks, but meanwhile, this gusty storm front will move north through the rest of the country bringing the same sequence of weather, perhaps with somewhat less wind speed further east and north. Any given place could see a heavy squally thunderstorm out of this too. Rainfalls of 20-30 mms appear likely, bringing renewed flooding risks. Highs will reach about 12-13 C mostly after the front passes. Winds will be very strong offshore too, reaching force 10-11 at times.

TONIGHT, cloudy skies with rising winds will foretell a strong windstorm arriving in the west coast counties in the early morning hours, and breaking on the rest of the country after sunrise. Winds will generally be SW 30-50 mph but will rise to 50-80 mph near the west coast before 0700h. Overnight lows will be about 7 C to near 10 C in the southwest.

SUNDAY will see persistent strong winds from the WSW, veering gradually more to the W and achieving speeds of about 55 mph with gusts to about 90 mph in exposed locations. There will be a risk of locally tornadic wind streaks with any well-developed waterspouts or hail shower cells both near the coast and inland, in all parts of Ireland.

Force 11-12 winds will develop in marine areas, there will be huge waves (8-15 m) and swells on the west coast especially but also off the south coast, and around high tides there could be overtopping of seawalls especially in places like Galway exposed to a west wind. There will also be some squally showers as well as longer periods of rain but the sun could be out briefly too. Highs will be about 10-11 C but it will feel more like 5 C which would be the temperature up on higher slopes where winds could reach 100 mph -- climbing is definitely not recommended. Hail and snow could be falling frequently on higher slopes all day.

MONDAY will see a bit of a break from the stormy weather but it will still be rather blustery and cool with passing showers and highs near 11 C, winds westerly 30-50 mph, with some afternoon sunny intervals possible.

TUESDAY, yet another strong storm approaches, and after some morning rain and high winds, there could be brief clearing followed by another period of storm force winds around evening to midnight across the country (SSW 50-80 mph veering to W 40-70). Highs will reach about 12 C.

WEDNESDAY to FRIDAY are looking rather windy still with a gradual cooling trend as winds swing around to more westerly then northwesterly, 20-40 mph on average, with daily highs falling off from about 9 C to 7 C.

Even colder air could be trying to work its way south towards Ireland next weekend, but my hunch is that it may be held back by weak waves of low pressure in advance of a resurgence of mild southwest flow into the first week of December.

Watch for updates on developments.

My weather has been rather dramatic, we had some thunder and lightning around here at 1730h local time and an offshore station reported some gusts to 110 mph indicating perhaps a weak tornado or waterspout embedded in a meso-scale squall line. This has moved across the urban area and well off to the east now, and I am waiting to hear any news of damage from localized winds, we didn't have any gusts here, just the lightning strikes. It may have been isolated to the offshore buoy but the same area was hit by a small tornado a few years ago which did considerable damage to the regional container port. This reminds me to place the same kind of risk factor in your Sunday forecast (waterspouts moving inland as weak tornadoes).

UPDATE _ Saturday, 6 p.m.
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The exact details of how bad the storm will get overnight and Sunday will depend somewhat on where squally lines of showers set up but there is no change to the basic outlook, steadily rising winds and large waves setting in especially after midnight.

The low centre is currently around 20 W and is still deepening. There is a small area near the M6 buoy with a slacker circulation but this will probably not reach land as the storm reorganizes and phases more with an area of strong winds near the M3 buoy at present.

Tomorrow will be one of those days when the weather board is very active and you'll have lots of information on the storm thread, the observations, and a few other places too; meanwhile, I suspect I may have to get a big pot of coffee going later on so I can watch the storm unfold all night here.

I'll be trying to pick out any tornadic wind gust risks from radar, hopefully these will avoid towns and may go unseen, like the one around here apparently did yesterday (no wind damage reports have come in yet, just the report of heavy hail along the inland track of the radar echoes ... it was probably a waterspout that hit the marine buoy).