WEATHER ALERT - Summer Storm, Wednesday 15 August 2012

ALERT for storm force winds with hurricane force gusts in exposed locations and very heavy rainfalls sweeping north tonight and lasting much of tomorrow (Wednesday, 15 August 2012), with some blustery squalls embedded. 

Potential for wind gusts to 80 mph in the most exposed coastal and upland locations, 60 mph more widely. Potential for 30-40 mms rainfall with severe flood risk where soils now saturated from previous rainfalls.

Southern Munster and eastern parts of Leinster are most at risk of experiencing flooding and wind damage. The risk for other parts of the country remains moderate and caution is advised.

Manager of the Irish Coast Guard, Declan Geoghegan said: "Do not attempt to cross at fast running river or flood water fords as they may be stronger and deeper than you think. Flooded urban areas may contain many hazards, not least of which include submerged open manholes and downed power lines. The combination of tides, forecasted gale warnings for the next day or so, high sea conditions and swollen rivers may result in very dangerous conditions.”

EUMETSAT RGB satellite image at 8PM UTC Tuesday of the storm winding up to our southwest


A very powerful summer storm appears likely to develop explosively tonight as a deep vortex in the upper atmosphere rotates from its current location in the central Atlantic towards Biscay then north towards Valentia. A deep surface low that could reach 968 mbs is likely to develop very rapidly after midnight in response to this vortex (a swirl of colder air) slamming into the warm, humid air mass now present.

The track of this low will be approximately due north across Kerry or near Valentia, up the west coast veering more to the northwest after passing Galway Bay midday Wednesday. The low will remain intense but will pull rapidly away from Ireland in the afternoon, leaving Mayo in the wake of diminishing southwest gales. Wind speeds should both rise and fall off rather swiftly during various phases of the low's brief rampage. All regions will be exposed to strong gusts although the highest wind speeds could be expected near Cork and various exposed locations.

Marine areas will see hurricane force wind gusts to force 11-12 and sailing after about 9 p.m. tonight is strongly discouraged. Persons living in hilly areas of the southwest should think back to a similar storm in January 2010 and assess possible wind damage risks from channelling of SSE winds pulled through gaps in the terrain.


Infrared satellite image of Europe at 1pm. The genesis of tomorrow's weather system can be seen NW of Portugal. Image EUMETSAT.
Current Surface Analysis(3.30pm, Tuesday). Source
GFS Model Forecast Animation. Source
Ogimet GFS model interpretation of storm path. The storm runs up the west coast before drifting away northwestwards.  The heaviest precipitation is defined by the darker colours. The strongest winds are where the isobars are most tightly packed.

According to The Meteo Times’ Peter O’Donnell:  “Periods of rain will become with 20-40 mms potential for most but 30-50 mms locally. There will be  some severe local flooding where the ground is already saturated from previous rain. Winds across the south will peak during the morning or midday from a SSE direction, reaching 40-70 mph and gusting to near hurricane force at times. There is potential for moderate structural and tree damage. Very exposed higher terrain could see gusts to near 100 mph.”

“Around the southeast and east coasts and well inland, winds will rise to about SE 30-55 mph and will veer rapidly to SW 30-50 mph. Some squally showers or storms could develop along the windshift and the risk for local tornadic wind streaks will be monitored, especially valid around Limerick and Tipperary north into the Athlone district. Connacht will see a more gradual increase in wind speeds all morning to reach SSE 40-60 mph and then a gradual turn to SSW 40-60 mph with higher gusts possible. Ulster may be somewhat protected from the strongest winds and will see wind speeds of about 30-50 mph. There could be some brighter or even sunny intervals later in the day across the southwest and the storm may rapidly subside to more of a partly cloudy, isolated showers scenario with winds SW 20-40 mph. Highest temperatures will be 16-18 C for most, 18-20 C in parts of southwest and north Donegal (Malin Head could hit 22 C).”

"This is likely to become an explosive deepening situation. The models may not be catching the full severity of the storm because it will reach a lower central pressure on almost a meso-scale basis when the vortex interacts with the warm, humid air now present. "

"As I've stressed in other situations, central pressure is important but so is rate of pressure change. That will be unusually large for a summer season low and this storm may become similar to the gale that hit the southwest in January 2010. I think this was almost concurrent with the Haiti earthquake. Very strong winds and a continuous roaring sound were reported by several of our observers with that one. But now the trees are all in full leaf and that could greatly increase the potential for wind damage. Also we now have August sea surface temperatures and humidity levels which would increase the rainfall potential as well as the wind potential in similar energy regimes."

"Although the track might make it appear that the west is most at risk, there will be impacts all around the country with the possible exception of sheltered parts of east Ulster."

Meanwhile, Met Eireann has this evening issued a severe weather alert.

"Issued at 14 August 2012 - 11:20
Weather Warning
A combination of high winds, heavy rainfall, abnormally low pressure and high tides will cause dangerous conditions in south Munster and east Leinster during Wednesday 15th August.  Gale to strong gale force easterly winds, later veering southeasterly to southerly, will occur. Frequent spells of rain will result in accumulations of 30 to 50 mm generally, with higher totals possible in mountainous areas. The will be a high risk of coastal and river flooding.

Valid 0000 15/8/12 to 0000 16/8/1"

Position of the system on Wednesday night. Image

GEFS model precipitation charts Tue-Fri. Source

Further details available on The Meteo Times Daily Forecast.