Analysis Of October 5th Storm

The front has cleared the east coast now and things have died down considerably. There are some thundery showers rolling in off the Atlantic, but as far as wind goes, that’s it for now. How do the numbers look after what was a strong wind event for the time of year? Dun Laoghaire Harbour weather station gives us a spectacular insight.

The strong wind was due to a very tight pressure gradient just ahead of the cold front of a depression just off the northwest coast. As this front crossed the country from west to east there was sudden decrease in wind and rain and a strong veering (clockwise shift) in wind direction.

This wonderful site from the guys at Dun Laoghaire Harbour shows a minute-by-minute account of this event unfolding, with the frontal passage occuring at precisely 4 am (3 am GMT, as in their graphs). I would recommend bookmarking this site for future reference.

Countrywide, the strongest winds were recorded along the south and east coasts, with both Roches Point and Dun Laoghaire Harbour showing a gust of 62 knots (115 kph). Magilligan No. 2 station in Derry was second with 61 knots (113 kph). Roches Point also reported the highest 10-minute mean windspeed of 49 knots (91 kph).

Dun Laoghaire recorded 66.6 mm of rainfall, while Johnstown Castle received 46 mm, Cork Airport 39 mm and Ballypatrick Forest 36.4 mm. Roches Point and Sherkin Island didn’t report any totals in their 7 am synops so we will have to wait for Met Éireann’s totals. Roches Point had reported 31 mm in the 6 hours up to 1 am.

Here are the graphs from http://www.dlhweather.com/ showing the abrupt rise in pressure and fall in windspeeds and temperature as the front passed through at 4 am (3 am GMT). 1 knot=1.15 mph=1.85 kph.

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Windspeed (green), gust (blue) and direction (red) at Dun Laoghaire Harbour. From http://www.dlhweather.com
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Pressure (hPa) at Dun Laoghaire Harbour. From http://www.dlhweather.com/
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Temperature (red), Dewpoint (green), Windchill (blue) and Solar Irradiation (orange) at Dun Laoghaire Harbour. From http://www.dlhweather.com/
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Accumulated rainfall (blue) and Relative Humidity (red) at Dun Laoghaire Harbour. From http://www.dlhweather.com/
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