OCTOBER 2011 was amonth of above average temperatures (+1.6 C) but with only slightly more than average rainfall (105%), writes David Uttley.
The average temperature was 11.2C (av. max. 14.8C; av. min. 7.5C) with a rainfall total of 146.0mms giving rain on 22 days.
October began with record breaking figures of 26.0C on the 1st, the highest on local data (going back to 1951), a continuation of the ‘heat wave’ of late September, which lasted until the 3rd (minimum temperature of 14.2C).
Cooler air by the end of the first week saw night time temperatures of 6.3C (by the 7th).
Day-time temperatures remained quite high up to mid-month (see graphs) but northerly air streams brought lower temperatures in the third week (maximum 10.0C on 18th, and minimum of -1.0 on 20th).
This was followed somewhat milder weather before a series of colder nights on the 26th to 29th and rising temperatures leading into November.
By far the wettest spell was concentrated into the seven days from the 5th to the 11th which with 90.1mms had 66% of the month’s total, the wettest day being the 10th with 20.2mms; the driest spell was from the 21st to 28th (see graph).
Humidity was generally high (average R.H. of 86.9%) and there was an average cloud cover of 76.6% as estimated at 09.00hrs G.M.T. Visibility was very good on ten days and there was no mist or fog to record. There was hail on the 6th, air frost on the 20th, and three nights with a ground frost.
Estimated amounts of sunshine were slightly down on average at 89 hours largely because of seven ‘dull’ days five of which occurred between the 8th & 12th. There were seven hours of sunshine or more on the 1st, 15th, 22nd and 28th however.
Pressure fluctuated considerably during the month.
It began with moderately high readings, fell to 999.2mbs on the 10th, rose sharply to 1031.8mbs on the 14th, was down at 1002.3mbs on the 18th, then rose to 1026.9mbs on the 20th. This was followed by five days of low pressure from the 23rd to 27th (992.0mbs on the 26th) and then an increase to 1022.1mbs on the 28th.
In summary, it was a month of depressions interspersed with ridges of high pressure, giving an average of 1014.5mbs, about 4mb above the norm.
With the exception of the 11th to 15th with north easterly winds, it was southerly and westerly flows which predominated on twenty days of the month, the highest wind speeds being on the 4th to 6th but falling short of gale force.