PITSFORD HALL WEATHER STATION
NORTHAMPTON, UNITED KINGDOM

MONTHLY WEATHER REPORT - DECEMBER 2004

Note: The annual statistical summary for 2004 is also included within this
report, following the statistical summary for last month.


REVIEW OF THE MONTH

Headline: Grey but dry for the first half, turning increasingly unsettled
later. A cold and snow-less Christmas period.

A dry start to the month. Although a front edged southwards through the
first three days, it produced little more than trace amounts of rainfall at
Pitsford. Temperatures were about average, turning colder on the 3rd and 4th
due to the presence of persistent fog. As winds backed more south-westerly
on the 4th temperatures began to recover reaching 10.5C on the 5th, although
a second weak front brought plenty of cloud and drizzly spells. In fact, the
5 days between the 4th and 8th, saw no recorded sunshine at Pitsford.

High pressure over continental Europe maintained a dry theme from 10th
through to the 13th. The wind turned east or south-easterly on the 12th
feeding in cold air off the continent. It became rather grey and misty once
again. With the exception of a few hours of sunshine on the 9th, the total
recorded sunshine for the month up until the 16th was a pitiful 13.3 hrs.

By the 14th the wind had turned westerly bringing an improvement in the
temperatures. The milder air also brought with it spells of rain. A discrete
area of low pressure tracked through the county on the 17th bringing strong
winds gusting to 48mph at Pitsford. Showers on the 18th gave way to rain in
many areas on the 19th although much of the county escaped dry.

As high pressure developed on the 20th, clear skies overnight brought a
sharp frost. The air minimum at Pitsford fell to -3.6C whilst a ground
frost of -8.1C was also recorded. Over the next few days it turned milder
with an increasingly strong westerly airflow. By the 23rd daytime
temperatures had become positively balmy for the time of year with highs of
12.7C with an exceptionally mild night to follow (8.6C).

A cold front worked south-eastwards in the run up to the festive period.
Further fronts moving southwards brought snow showers to many western areas
on Christmas Day, although the county was not to experience a white
Christmas. However, it was particularly cold with highs of just 3.5C falling
close to freezing overnight. The cold weather continued into Boxing Day
which was also bright with some 6.1hrs of recorded sunshine.

As the month came to a close a succession of Atlantic fronts and westerly
winds maintained a mild, wet and occasionally windy theme. The 27th saw
7.9mm falling over nearly 5 hrs. The highest recorded temperature came near
the end of the month with 12.7C being recorded on the 30th . Despite the
mild conditions by day, clear spells overnight still produced some frosts,
moreso early on in the period.

STATISTICAL SUMMARY - DECEMBER 2004

Air Temperatures
The Highest Maximum: 12.7C on 23rd & 30th
The Lowest Maximum: 3.0C on 20th
The Highest Minimum: 8.6C on 23rd
The Lowest Minimum: -3.6C on 20th
The Mean Maximum: 8.2C
The Mean Minimum: 2.1C
The Overall Mean: 5.2C
Difference from the Monthly Mean: -0.3C

Relative Humidity:
Highest Relative Humidity (at obs): 100.0% on 3rd, 4th, 8th & 21st
Lowest Relative Humidity (at obs): 72.2% on 19th
Mean Relative Humidity (at obs): 93.3%

Dew Point:
The Highest Dew Point (at obs): 10.3C on 31st
The Lowest Dew Point (at obs): -2.6C on 19th
The Mean Dew Point (at obs): 3.8C

Rainfall:
Total: 19.6mm
Difference from the Monthly Mean: 31.2%
Duration: 22.7hrs
Highest 24 hour fall (obs to obs): 7.9mm on 27th
Rain Days (/=0.2mm): 9
Wet Days (/=1.0mm): 6

Sunshine:
Total Duration of Bright Sunshine: 58.5hrs
Sunniest day: 6.7hrs on 28th
Days without sunshine: 11
Cloud cover (mean at obs): 5.9oktas (73.8%)

Pressure (reduced to sea level):
The Highest Pressu 1031.7mb on 8th
The Lowest Pressu 991.0mb on 17th
Mean Pressure (recorded at obs): 1018.0mb

Winds
Run of wind (mean over 24 hrs): 125.1miles
Mean daily wind speed: 6.8mph
Highest mean daily wind speed: 13.9mph on 14th
Run of wind (to date): 3877.3miles
Highest Maximum Gust: 48mph on 17th
Highest wind strength (at obs): 13.8mph on 15th
Mean wind strength (at obs): 7.0mph

Winds from the Following Directions:

N 0 NE 1 E 3 SE 1 S 14 SW 2 W 4 NW 5 Calm 1

Ground Temperatures:
Lowest Grass Minimum: -8.2C on 26th
Mean Grass Minimum: -2.0C
Lowest Concrete Minimum: -5.2C on 26th & 27th
Mean Concrete Minimum: -0.3C
Lowest Bare Earth Minimum: -2.2C on 27th
Mean Bare Earth Minimum: 1.6C

Soil/Earth Temperatures:
Surface mean: 4.6C
5cm mean: 4.6C
10cm mean: 5.0C
20cm mean: 5.5C
30cm mean: 5.7C
40cm mean: 5.7C
50cm mean: 6.3C
100cm mean: 7.4C


Days with:
Thunder: 0
Hail less than 0.5mm: 0
Hail greater than/equal to 0.5mm: 0
Snow or snow & rain: 0
Fog 4
Air Frost: 8
Duration of Air Frost: 54.0hrs
Ground Frost: 21
Gales: 0


Total Evaporation (tank) 9.71mm


ANNUAL STATISTICAL SUMMARY FOR 2004

Air Temperatures:
The Highest Maximum: 30.8C on 8th August
The Lowest Maximum: 3.0C on 20th December
The Highest Minimum: 19.4C on 9th August
The Lowest Minimum: -5.4C on 29th January
The Mean Maximum: 14.7C
The Mean Minimum: 6.7C
The Overall Mean: 10.7C

Difference from the 1971-2000 mean: +0.4C

Relative Humidity:
Highest Relative Humidity (at 0900): 100% on 14th, 29th, 30th October, 21st,
25th November, 3rd, 4th, 8th & 21st December
Lowest Relative Humidity (at 0900): 47.2C on 24th May
Mean Relative Humidity (at 0900): 85.1%

Dew Point:
The Highest Dew Point (at 0900): 19.6C on 8th August
The Lowest Dew Point (at 0900): -5.7C on 28th & 29th January
The Mean Dew Point (at 0900): 8.2C


Rainfall:
Total: 681.9mm
Duration: 487.2hrs
Highest 24 hour fall (from 0900): 29.1mm on 7th July
Rain Days (/=0.2mm): 182
Wet Days (/=1.0mm): 130

Difference from the 1971-2000 mean: 104.5%

Sunshine:
Total Duration of Bright Sunshine: 1455.3hrs
Sunniest day: 14.2hrs on 7th August
Sunless days: 72
Cloud cover (mean at 0900): 5.8 oktas (72.5%)

Pressure (reduced to sea level at 0900):
The Highest Pressu 1038.2mb on 14th November
The Lowest Pressu 976.6mb on 5th May
Mean Pressu 1014.8mb

Winds
Run of wind (mean over 24 hrs): 120.5 miles
Mean daily wind speed: 6.5 mph
Run of wind: 44032 miles
Highest Maximum Gust: 59mph on 20th March
Other Gusts /= 50mph: 50mph on 8th February & 21st March,
54mph on 31st January & 55mph on 7th February

Highest wind strength (at 0900): 34.6mph on 19th March
Mean wind strength (at 0900): 7.5mph

Winds from the Following Directions:
N 43 NE 22 E 11 SE 27 S 95 SW 25 W 36 NW 91 Calm 13



Ground Temperatures:
Lowest Grass Minimum: -9.7C on 26th February
Mean Grass Minimum: 3.6C
Lowest Concrete Minimum: -7.4C on 26th February
Mean Concrete Minimum: 5.6C
Lowest Bare Earth Minimum: -3.0C on 26th February
Mean Bare Earth Minimum: 6.6C

Soil/Earth Temperatures:
Surface mean: 10.8C
5cm mean: 10.2C
10cm mean: 10.6C
20cm mean: 11.0C
30cm mean: 11.3C
40cm mean: 11.2C
50cm mean: 11.5C
100cm mean: 11.0C


Days with:
Thunder: 10
Hail less than 0.5mm: 4
Hail greater than/equal to 0.5mm: 0
Snow or snow & rain: 12
Snow lying: 9
Fog 17
Air Frost: 39
Duration of Air Frost: 255hrs
Ground Frost: 98


--
Mike Lewis

Pitsford Hall weather station
www.northantsweather.org.uk