Monthly Weather No. 305 Bulletin September 2011 An onlooker enjoys a beautiful mixture of stratocumulus and cirrus clouds during a sunrise in late September at Bettystown Beach, Co. Meath (picture courtesy Donal Black) MOST PLACES WARM AND WET; DULL EVERYWHERE Rainfall in September was above average almost recorded at Carlow (Oak Park) on this date. Mean everywhere, with the west and midland areas air temperatures for the month were above normal receiving the highest percentages above normal for almost everywhere, with most stations reporting the time of year. The highest rainfall total at a differences of nearly 1°C or more above the normal synoptic station was recorded at Valentia and most stations in the east and north of the Observatory, recording its wettest September since country reported it was the warmest September 2005, receiving 162% of its long-term average.The since 2006. The majority of the highest maximum majority of the month’s highest daily falls were air temperatures for the month were reported on recorded on the 30th, with the highest September the 28th, with Phoenix Park recording a maximum daily fall (midnight to midnight) of 46.5mm air temperature of 25.7°C on this date. This was Produced by Met Éireann, Glasnevin Hill, Dublin 9. INSIDE Diary ......................... 8 Annual subscription 80 euro Rainfall .................... 10 Hurricane Katia- Temperature ............. 12 Page 3 For more information- Sunshine .................. 14 tel: +353-1-8064260 Marine & Pressure .... 1 5 fax: +353-1-8064216 [email protected] Wind & Elements .......... 4 World Weather ...........16 www.met.ie/climate Upper Atmosphere........ 5 Notes on the tables and map Laboratory .................. 6 showing location of stations Agmet...................... 6/7 appear in January issue Edition 305.1 2 WEATHER September 2011 Above: Astronauts on the the highest maximum air temperature at the end of the period. International Space station recorded at a synoptic station so far in captured this image of Aurora 8th to 13th: A mild and cloudy start was 2011 and the highest September followed by slightly cooler weather with Australis or the southern temperature recorded at the site since outbreaks of drizzle, light to heavy rain and lights on September 17th. 1906 (105 years). Mean minimum air scattered showers. A very deep depression, Auroras are caused by the temperatures were also above average for resulting from ex-hurricane Katia moved interaction between high the time of year, with Valentia across the northeast Atlantic between Ireland energy particles from the Observatory and Casement Aerodrome and Iceland, bringing extremely strong winds solar wind and the earth’s with gales recorded in coastal areas and gale magnetic field. The colours of reporting their warmest minimum air gusts recorded in most locations. an Aurora are caused by the temperatures in September since 1955 particles colliding with (56 years) and 1964 (47 years) respectively. 14th to 25th: A weakening depression moved Sunshine values were below average in from the west, bringing drier conditions oxygen and nitrogen with cloud and showers (some with thunder), molecules in the atmosphere everywhere for September, with the followed by a series of deep depressions off (picture courtesy NASA Earth highest amounts of sunshine in the east. the northwest coast which affected the Observatory) Stations in the south and southwest were country. Associated frontal systems brought the dullest, with Valentia Observatory and bands of rain and heavy showers with some Cork Airport recording their lowest clear sunny spells to parts. Winds were light to moderate at the start of the period, September sunshine since records began becoming strong in the latter half, with gale in 1893 (118 years) and 1962 (49 years) gusts recorded in most areas. respectively. Shannon Airport also reported its dullest September since 1956 26th to 30th: A high pressure system located (55 years). Mean wind speeds for the over the continent brought warmer temperatures and dry weather to most areas month were above normal for September, at the start of the period. A cold front then with gales reported on three days. passed over Ireland, with heavy consistent Belmullet reported a mean wind speed of rain and showers. Winds were predominantly 15.2 knots (28km/h), its highest mean light to moderate, south to southwesterly in wind speed for September since 1980 direction, gale gusts along western coasts. (55 years), while Shannon Airport Wind and elements: Mean windspeeds for reported a monthly mean wind speed of the month of between 8 and 18 knots (15 and 12.2 knots (23km/h), its highest since 1970 33km/h) were above normal. Gale gusts were (41 years). recorded on most days, except from the 1st to the 3rd, 8th, 15th and 26th, with gales 1st to 7th: After a brief, warm dry start to the reported on the 10th, 12th and 21st. The month, Atlantic depressions near or over month’s highest gust of 66 knots (122km/h) Ireland and their associated frontal systems was observed at Malin Head on the 12th. resulted in mixed periods of drizzle, rain and Thunderstorms were recorded on the 4th, thundery showers, with some clear dry spells 16th, 17th, 21st and 30th, with one report of in parts. Winds varied from light to strong, hail on the 17th. Fog was reported mostly in predominantly southerly to westerly in the west and along southern coasts at the direction, with numerous gale gusts as a beginning and end of the month. deepening depression moved in over Ireland September 2011 WEATHER 3 HURRICANE KATIA and continued travelling northwest over the Atlantic Ocean, before being downgraded to a Category 1 hurricane again on the 7th. Hurricane Katia continued to move northwest, until September 8th, when its trajectory moved north then northeast towards northern Europe. On the 10th, Katia continued to move towards Ireland and the UK, however, it was gradually losing its tropical characteristics and by 1500 UTC on the 10th, Hurricane Katia was downgraded to a post-tropical storm. The deep area of low pressure which contained The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-colour image at 15:15 UTC on September 7th. Katia sports the Post-Tropical Storm Katia, reached Irish waters spiral shape and eye typical of strong storms (picture courtesy of NASA Earth Observatory) on early Monday the 12th of September and September is the peak of the Atlantic was located 300km northwest of Erris Head, Hurricane season and during September 2011, Co. Mayo. It continued to move northeastward NASA satellites were keeping tabs on a number over Northern Scotland during the day, with of tropical storm systems. Hurricane Katia, the areas in Scotland and Northern Ireland worst second major hurricane of the 2011 Atlantic hurricane season, affected Northern Europe during mid-September. Hurricane Katia, who remained over the open waters of the Atlantic throughout its life cycle, formed in late August and during the first few days of September, crossed the Atlantic, reaching Irish waters and the UK as a post-tropical storm on the 12th. Katia initially formed as a tropical depression, south of Cape Verde (an island located in the central Atlantic Ocean) on August 29th 2011. By September 2nd 2011, the storm had moved northwest across the Atlantic Ocean and Pressure analysis chart for Monday 12th of September 0600 UTC, shows the low pressure system that contained Post-Tropical Storm Katia off the northwest coast of strengthened to a Category 1 hurricane, with Ireland (chart courtesy of Met Office UK) windspeeds of 65 knots (120km/h) and even higher gusts. On September 4th, Katia had affected, causing storm to gale force winds in strengthened to a Category 2 hurricane, with parts. The highest gust recorded in the UK was reported windspeeds of 86 knots (160km/h) 85 knots (157 km/h) at Cairngorm Summit in Scotland while Malin Head, Co.Donegal recorded the highest gust in the Republic of Ireland of 66 knots (122km/h) and a mean 10- minute windspeed of 48 knots (89km/h). Damage that Katia caused reached as far as Russia, with numerous homes across Ireland and the UK being left without power. The damage is estimated to have reached over one hundred million pounds in the UK, with three deaths across the globe attributed to its effects. Potential Track area for Post-Tropical Storm Katia issued at 1500 UTC on Information supplied by September 10th. The current location of the post tropical storm was U.S National Hurricane Center (www.nhc.noaa.gov/) marked by the orange circle (picture courtesy of NOAA) NOAA National Weather Service (http://weather.gov/) 4 WIND & ELEMENTS September 2011 WIND (KNOTS) ELEMENTS County / Station Mean Max. 10-min. mean Max. Gust Days with Hours with speed dir. speed date/hour dir. speed date/time gales gale gusts gale gusts Snow Snow Lying Hail Thunder Fog CO. CARLOW Oak Park 9.9 250° 31 12/11 240° 45 12/1008 0 4 14 CO. CAVAN Ballyhaise 8.4 230° 26 12/09 220° 45 12/0901 0 3 17 CO. CLARE Shannon Airport 12.2 240° 36 12/07 240° 55 12/0631 1 8 46 0 0 0 0 0 CO. CORK Roche’s Point 13.8 220° 37 12/00 210° 47 12/0 31 1 8 42 Cork Airport 11.1 210° 32 11/24 230° 46 12/0238 0 6 30 0 0 0 0 10 CO. DONEGAL Malin Head 17.5 240° 48 12/11 240° 66 12/1105 3 15 139 0 0 0 0 0 CO. DUBLIN Dublin Airport 12.9 250° 39 12/12 250° 56 12/1009 1 8 60 0 0 0 1 0 Casement 12.6 230° 35 12/09 240° 50 12/1058 1 9 67 0 0 1 0 0 CO.