Weather Warning 25th/26th April - Heavy Rain and strong winds

[Snowbie]

This is an early weather watch for the potential of heavy rain affecting the south, south east and east of the country along with strong to gale force east to north east winds.

A low pressure currently developing in the mid Atlantic tracks to the east. The center of the low pressure at this stage looks like travelling through the Celtic sea and stalling as it comes up against high pressure over southern Europe. The low pressure is then deflected into Wales and up through the UK keeping the fronts close to or over the eastern side of Ireland. With the current synoptics being output, the chance of high rainfall totals is a possibility in the south east and east but changes in the track of the system could determine the final rainfall totals.

Updates will appear here when new information is released.

These are the current high and low tides for the east coast here

Fax below shows the high over Italy stalling and deflecting the low up through the UK

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[Snowbie]

Update at 2340 23rd April

The latest High Resolution model shows the band of rain with strengthening winds moving onto the south and east coast by 6am Wednesday morning. How far north and west it moves back will show up on the next few output.



The low resolution model shows a pivoting of the front close to the east coast bringing persistent rain with the low pressure center itself stalling.



Next update in the morning.

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[Snowbie]

Update at 1000 April 24th

The low pressure center is likely to stall over Wales and keep the weather front close to the east coast during Wednesday bring heavy rain to the south and south east coast later moving north along the east coast. The rain heavy at first is set to become persistent for daytime Wednesday in places and often lighter and intermittent but with heavy bursts here and there. The rain is set to continue in the east and north east, persistent and continuous with further rainfall accumulations during Thursday before clearing away later in the late evening.

At this moment, there could be in excess of 30mm at sea level (50mm over the mountains) over the period covering 25th/26th but this will fall over 36hrs to midnight on Thursday. These totals could be upgraded as new information is released. With strong east to north east winds and high tide expected during this spell, some coastal flooding is possible along the east. Orographic lift from the Wicklow mountains may increase totals significantly locally in east Wicklow and parts of south Dublin.

Next update after 12noon.





Predicted rainfall accumulations covering to Wednesday evening

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[Snowbie]

Update at 1230

Weather warning for heavy and persistent rain with gale force east to north east winds in the south, south east and east of the country for Wednesday and into Thursday.

Rain will move onto the south and south east coast on Wednesday morning moving steadily northwards during the morning and afternoon to affect much of the eastern seaboard and into the north east by late afternoon. The rain will be heavy at times but it's persistence is of concern. The occluded front will stall over the eastern half of the country to affect much of Leinster and east Ulster and may hang around  for some time. Strong to gale force east to north east winds and persistent rain with high tides with a risk of some coastal flooding later Wednesday and into Thursday with rivers swelling. Not expecting the deluges in the short space of time to hit the Dublin region like last October but the persistent rain which could fall over eastern counties could last 36 to 40hrs. Rain will be intermittent at times but with heavy pulses during the spell leading to localised flooding.

Rainfall totals are predicted to be highest over high ground in the east with 50mm expected while at sea level 25mm to 40mm accumulating in places is a possibility during the spell.

Chart below shows the predicted rainfall accumulations to 6pm on Wednesday evening. Highest totals will always be over the higher ground.

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[Snowbie]

Update at 0000 25th April

The warning is to continue with a risk of flooding to northeast (East Ulster included), eastern and southern areas. High tides in Dublin at 2pm Wed and 2am Thursday and in Cobh at 0730am Wed, with gale force east to north east winds may bring some coastal flooding to these areas with rivers swelling. Heavy rain at first tapering off but returning again overnight into Thursday morning to east coast. With the persistent nature of the rainfall, totals accumulating to 35mm to 45mm possible on lower levels in the east while up to 60mm possible over higher ground over a 40hr period. The northeast and south accumulations of 30mm possible again higher over elevation.

Rainfall will become widespread elsewhere but only slowly reaching the northwest with much smaller accumulations here. Chart below shows the predicted accumulations.

Next update in the morning where we will update the predicted rainfall totals and nowcast the event from our stations.

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[BUTTERFLY]

These map showing predicted amounts of rainfall look good, but has anyone ever analysed the actual amounts which fell and compared them with the predicted amounts? A similar map showing the percentage accuracy would be interesting!

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[Snowbie]

Update 1000 April 25th

Rainfall accumulation totals have decreased across parts of the south while they remain similar to the previous run in the east and northeast which includes eastern Ulster for the duration of the event. Several hours of moderate to heavy rain at first in the eastern side of the country while the rain continues to move away from the south but another band will drift onshore here later. Rain becomes lighter in the east during the evening and become intermittent here. Rain may return overnight to the eastern side of the country but the intensity decreases but remains persistent. The flood risk continues with a lot of standing water and rivers swelling with high tides due today in the east and overnight tonight but should subside slightly if rain remains light for a length of time.

Over higher ground of the east, the rainfall totals remain high with up to 60mm a possibility during this event which will lead to the river Liffey remaining high along with the Dodder and all rivers in the Wicklow mtns.

Next update at lunchtime today when more information is made available.

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[Snowbie]

Update at 1400

The first band of rain is continuing to move slowly west and north west across Ireland pivoting around the area of low pressure which will come to a halt over Wales. Rain mainly affecting the northern and eastern half of Leinster with gale force east to northeast winds but soon moving into the northeast.
The front will stay close to the eastern side of the country with rain on and off for most of the day becoming light and intermittent at times but with the odd heavy bursts too. The front is predicted to pep up again through Thursday morning bringing another spell of wet weather to east Ulster and Leinster. The strong easterly winds will back to the NE during the evening and later back more to the north overnight. Winds will now reach gale force in the north, northwest and western half of the country through Thursday while decreasing over the east and south. The flooding risk will continue with a lot of surface water but any drier spells should allow for this to subside somewhat. Rivers sourced in the Wicklow mtns will continue to rise as rainfall will always be highest here.

First chart shows the predicted rainfall accumulations to midnight tonight



The next chart shows the front regenerating over the Irish sea and heading onshore during Thursday morning.



This chart shows the predicted rainfall accumulations for the entire event late Thursday evening.

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[Snowbie]

Final update at 0000

Persistent light rain will continue overnight with surface water allowing to subside but heavy bursts of rain are likely from time to time over Leinster quickly pooling surface water once again leading to some localised flooding temporarily. Winds are continuing to back to a more northerly direction becoming strong on northern and western coasts on Thursday. River levels will remain high on Thursday in East Leinster with levels dropping towards evening as the fragmenting front moves back towards the Irish sea and dies away.

@Ian, We will have rainfall totals in by tomorrow evening and we can compare with the predicted charts above.

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