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TonyH

Summaries and statistics December 2012

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December 2012 Llanwnnen

Very wet with near normal temperatures

The wettest December since I began recording rainfall locally in 2003, and the wettest month of a soggy 2012! A cold and frosty first half was offset by a mild second half. No snow fell at all in December, and after 14th there were no air frosts even.

1st – 7th: Rather cold and unsettled rain and showers, heavy at times with hail. Sunny intervals too, but some quite sharp frosts when skies cleared overnight, as low as -5c. However the 3rd reached a mild 10c.

8th – 13th: Became very cold and mainly dry. Sunny periods with some hard frosts, lowest being -7.4c on the 11th, temperatures barely making it above freezing on the 11th and 13th.

14th - 31st: A protracted dull and really wet spell: very unsettled with showers and longer spells of rain, heavy at times, windy at times. It rained on each day from the 13th, and there were 11 days of 'heavy rain' that is having over 10mm. Not much sunshine during this period and with average to mild temperatures. Peak temperatures occurred on the 22nd and 23rd which both nudged above 12c, while the final night was the warmest with a low of just 9.2c

Total rainfall: 257.1mm

Wettest day: 27.3mm 22nd

Rain days >0.2mm: 27

Wet days >1.0mm: 24

Days of heavy rain >10mm: 11

Mean temperature: 4.5c

Mean Max: 7.6c

Mean Min: 1.5c

High Max: 12.3c 22nd

Low Max: +0.6c 13th

High Min: 9.2c 31st

Low Min: -7.4c 11th

Air frost: 15

Ground frost: 10

High RH: 100% vs

Low RH: 75% 3rd

Predominant wind directions: South

Mean wind speed: 1.8mph

Mean pressure: 1007mbar

Max pressure: 1032mbar 11th

Min pressure: 972mbar 14th

Days with:

Hail: 4

Gale: 0

Thunder: 0

Fog: 3

Fog at 0900: 1

Snow or sleet: 0

Snow lying 0900: 0

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December 2012 was the 2nd wettest month I have ever recorded, only beaten by November 2009. The mean was 1.1c lower than 2011 but that's

only due to the cold spell from the 10th-13th here the temperature stayed below 1c for 3 days.

Average max = 7.30c (Highest = 12.9c on 22nd)

Average min = 3.62c (Lowest = -4.5c on 12th)

Dry days = 7

Precip days = 24 (of which 3 wintry)

Rainfall = 172mm

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The summary

very very wet, one of the wettest months although not the wettest this year.

A month of two halves with the temperature

first 14 days the mean=2.3C and the last 14 the mean=7.3C

Mean=4.9(4.6)

Avge Max=7.0(6.9); highest day max=12.7C on 23rd and lowest day max=-0.2C on 13th

Avge Min=2.9(2.3); lowest min=-5.3 on 13th and highest min=11.7 on 29th

75.2mm with 23.2mm the most in one day=20th, 22 days with 0.2mm or more and 14 with 1.0mm or more

8 air frosts and 13 ground frosts, no snow, no thunder and 1 0900 observation of fog

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December 2012 Statistics

This month was characterised by slightly below average maxima and below average minima, continuing further the locally below average run of months. The months rainfall was way above average, and close to record breaking proportions. The first third of the month saw some notably cool weather, with the first real cold spell since February 2011. During that cold spell, 2 'ice days' were recorded, which is unprecedented on my records, even December 2010 failed to muster up 2 ice days in a row. Towards the end of the month it got milder, with the second half coming in much much milder than the first half.. a Maximum of 13.6C was recorded. The month will go down however, thanks to the cold start as a below average month. Another surprising statistic was that the highest 24 hour minimum was 6.3C in the entire month, usually we would example at least 2 minima over 10C in December here. We did record 10 or higher in the night, but often days followed that were cooler than the nights preceding it, therefore the days qualified for minima and the nights didn't

Below are the statistics for my weather station during the month of December

Mean Maximum: 7.9C

Mean Minimum: 2.5C

Overall Mean: 5.2C

Monthly Rainfall total: 141.0mm

Rainfall days: 21

Max rainfall in one day: 22.9mm (20th December)

Highest daily maximum temperature: 13.6C (22nd December)

Lowest daily maximum temperature: -0.6C (12th December)

Highest daily minimum temperature: 6.3C (31st December)

Lowest daily minimum temperature: -3.9C (13th December)

Days with Ground Frost: 11

Days with Air Frost: 8

Days of falling snow: 0

Days of lying snow: 0

Thunder days: 1

Temperature frequency breakdown

Maximum temperature:

-5.0C to -0.1C: 2 days

0.0C to 4.9C: 1 day

5.0C to 9.9C: 21 days

10.0C to 14.9C: 7 days

Minimum temperature:

-5.0C to -0.1C: 8 days

0.0C to 4.9C: 16 days

5.0C to 9.9C: 7 days

Compared to the December CET (81-10 average = 4.6), my average comes in at 0.6C above the CET average, making it a sligtly above average month when compared to the Central England mean temperature

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Mean: 3.7 °C

Mean max: 6.1°C

Mean min: 1.2°C

Max temperature: 12.8°C

Min temperature: -5.7°C

Air frosts: 10

Rainfall: 111.5 mm

Days with rain: 22

Days with rain >1 mm: 18

Most in one day: 22.8 mm

Sunshine: 60 hours

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Very much a month of two halves.

Started of notably cold with temps on the 2nd barely getting above freezing followed by light wet snow later on which gave a temporary dusting to greet the 3rd. The period 3-8th brought changeable chilly conditions with air frosts and a little bit of snow early hours of the 6th - the only morning with snow cover at 9am. The 9th brought milder conditions before we saw a very cold frosty spell between the 10th-14th with temperatures barely getting above freezing and a run of sharp frosts.

The change to much milder wetter conditions came on the 14th, with wet snow quickly turning to rain, the period up to the 21st saw average temperatures but often wet with no frost. From the 22nd - 31st, very unsettled heavy rain and strong winds at times especially christmas eve and very mild with no ground frosts.

As a snow cold lover who likes a cold second half to December, I can't help but feel cheated by how this Dec panned out, had we seen a role reversal of conditions with the first half weather occuring during the second half and vice versa, I'd be in a much more upbeat mood about how Dec as a whole panned out, hopefully next December will deliver a much colder second half.

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hobart.jpg

HOBART is Tasmania's capital city, situated at sealevel on an estuary and backed by a 1270m/4200ft mountain range

December - First month of summer

High pressure shifted south, spreading west to east across Tasmanian latitudes, resulting in a dry, mild to warm and largely settled month, high pressure effectively blocking any cold fronts with showers from crossing from the colder waters of the Southern Ocean. With weaker low pressure troughs over mainland Australia than usual barely making it into Tasmanian territory, storm activity and cut off low pressure systems to Tasmania's east, which is usually responsible for most of the rain at this time of the year, failed to materialise. The monthly average temperature exceeded the 1981-2010 average, for the 14th month in a row, and this month the positive anomoly was the highest for the year.

Average maximum: 22.5 ( +2.1 )

Average minimum: 12.2 ( +0.9 )

Rainfall: 22mm ( Average 57mm )

Extremes in December daily temperature:

Highest maximum: 32.9 ( Record 40.6 in 1897 )

Lowest maximum: 15.1 ( Record 10.2 in 1964 )

Highest minimum: 16.9 ( Record 23.9 in 1920 )

Lowest minimum: 7.0 ( Record 3.3 in 1906 )

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Hedon, East Yorkshire.

December 2012

Warmest Max: 12.1°C (on 20/12/12)

Coldest Max: 0.7°C (on 12/12/12)

Warmest Min: 7.1°C (on 31/12/12)

Coldest Min: -3.1°C (on 13/12/12)

Average Max: 6.9°C (Equal to 1981-2010 Average)

Average Min: 2.5°C (-0.3°C Below 1981-2010 Average)

Overall Average: 4.7°C (-0.1°C Below 1981-2010 Average)

Rain: 114.0mm (181% Of Normal)

Wettest Day: 20th (22.4mm)

Sunshine: 75 hours (144% Of Normal)

Air Frosts: 7

Sleet/Snow Falling: 2 days

Snow lying at 0900: 2 days

Dry Days: 6

Wet Days: 25

Days With Rain >1.0mm: 20

Days With Rain >10mm: 3

Thunder Days: 0

Days With Fog: 0

The wettest December since 1983, the 7th wettest of the last 100 years and a month of two very different halves. The first half of the month was rather cold and very sunny. The first 16 days had 64 hours of sunshine and a mean of 2.9°C, while the remaining 15 days recorded just 11 hours and had an average of 6.5°C. The coldest point of the month was an anticyclonic period between the 11-13th, with hard frosts overnight and low single-digit maxima. The maximum temperature of 0.7°C on the 12th was the equal coldest of the year.

From mid-month onwards it turned very unsettled and after the 16th just one day failed to record any rainfall. It didnt turn extremely mild until just before christmas however, with the first double-digit maxima of the month on the 22nd being the first for over 4 weeks. Christmas day was a close to average and quiet affair, before mild, wet and windy weather returned before New Year. Much like December 2011 there was little in the way of snow, with a thin 90% cover on the morning of the 5th being retained until heavy rain moved in the next afternoon.

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