Weather Alert: November 20, 2012

EUMETSAT image at 11am.
Low level jet conditions illustrated by 12z Valentia sounding, 60 kt winds just above surface with steady rise to maximum at about 400mb or 4,000 m height, a general shift downward in profile with winds less strong than previous days at 250-300 mb levels.

Radar indicates rapid evolution into squall line type event, severe gusts are possible and tornadic wind streaks could develop from a southwesterly direction, if you live in west Munster, any part of Connacht, west or central Ulster, be alert to this risk using radar and visual (until sunset) obs to determine whether wind streak potential is heading your way, watch for narrow relatively bright echoes oriented SW-NE. These may contain much stronger winds than the general wind field of the trough moving inland.

Would say in general that stormy conditions will peak now to 5 p.m. in Clare and west Limerick, also Galway Bay, and from 4 p.m. to 6 p.m. in north Mayo inland to about Roscommon, from 5 p.m. to 7 p.m. around Donegal Bay and into west Ulster, but this is a rough guide and you should be on alert for a few hours beyond that time frame in the warned areas. This probably won't affect most of Leinster except those counties bordering on Connacht and Ulster. However there could be some outliers so watch the radar just in case.

The large blob on radar that looks like a giant hook echo is probably going to shear apart into numerous linear cells moving into central and north Clare about 3:45 to 4:00 pm. This may mean that Galway (city) is in line for severe wind gusts if one of these cells happens to move through, but the region in general should be on alert, if you're driving, expect quite variable winds in hilly terrain as these gusts work their way around obstacles and as you encounter squally showers. 

Peter O'Donnell

UPDATE _ Tues 20 Nov 2012 _ 2:45 p.m.

The worst of the strong winds (peaking at about 60-100 km/hr with local gusts to 120 km/hr) and squally showers now approaching west Galway and Mayo, expect stormy conditio
ns to peak around 3 p.m. in the Galway Bay region and 4 p.m. around Ballina, then around 5 p.m. near Donegal Bay, inland extent of the 80 km/hr wind gusts about Lough Derg to Athlone to central Ulster. 

Conditions in west Munster, other than north Clare, have probably peaked and there will be less extensive squally showers as most of the activity passes by just offshore. There may be a slight increase in wind speeds in Leinster and east Munster as this system races past but not expecting gusts much above 60 km/hr in most places there.

Thanks for the many reports, and please note, winds will tend to veer rapidly in Connacht and later in west Ulster from S to about WSW, your local conditions will depend partly on local terrain and how these winds interact with the local hills, so as they veer some observers will see rapid changes in wind speed both increasing and decreasing depending on exposure.
If you live in a more exposed or less hilly location your exposure to the winds will be more constant but gusts will depend partly on proximity to squally showers moving past. A close watch is being kept on the radar for any locally damaging wind potential. Drive with caution and expect sudden squalls of strong wind in areas outlined above.