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Exceptionally high supermoon spring tides with coastal flooding possible.

Wind warnings expected Saturday night and into Sunday.

Met Éireann Meteorologist’s Commentary 

The following information is valid on Wednesday 16th October 2024 and until further update. 

Summary  

 This 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 situation 

The 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 

 “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.