SEPTEMBER 1997
With the mean daily temperature of 11.2° Celsius - 0.7° Celsius above the normal for September - it was a mild month in the Northern Isles. Despite winds frequently from a westerly direction it was also dry with only 59.6% of the normal figure - somewhat higher than further north where Lerwick was only some 27% drier than average. Unlike Fair Isle, where the hours of sunshine were just above average with 105.8%, Lerwick recorded sunshine some 20% above average.
The month began with a complex area of low pressure over the North Atlantic. A small low, moving north to the west of Shetland on the 1st, gave a wet night on Fair Isle. However, as the 14.5mm occurred before 09:00 UTC, this total was 'thrown back' to August. So September began with two dry - though at times foggy - days. The start of the month was also quite sunny in the Northern Isles, with Kirkwall reporting 7.2 hours sunshine on the 3rd - the sunniest place in the UK on that day. The 4th, with 10.7 hours, was the sunniest day of the month on Fair Isle.
Low pressure to the west and north-west of the British Isles kept the Northern Isles in a moist S to SE'ly airflow for the first few days. During the 5th, as the low centre moved away northwards, a mobile W'ly airflow then became established over northern Scotland.
The 7th was a wet and cold day in the Northern Isles - the temperature only reaching 8.8° Celsius at Baltasound.
On the 8th, as the low moved away into the Norwegian Sea, NW'ly winds increased strong to gale force before easing and backing W'ly on the 9th as a developing Atlantic high ridged east across the UK.
The high then drifted east across the UK on the 10th, with troughs - moving east as a low tracked east to the south of Iceland - bringing patch rain and drizzle to Shetland. By the 12th this low had become slow-moving to the north of Shetland giving a wet day in the Northern Isles - Lerwick receiving 22.2 mm in the day, making it the wettest place in the UK.
As an anticyclone built in mid-Atlantic, and the low moved away north-eastwards, a strong to gale force NW'ly airstream developed again across Shetland - giving a cold day with frequent and heavy showers on the 13th.
The 14th saw a ridge of high pressure transferring quickly east across the Northern Isles, with an Atlantic low moving NE towards Faeroe. The associated fronts moving into northern Scotland- brought strong SW'ly winds and a wet end to the day for Fair Isle.
During the 15th, with a deep low tracking NE to the S of Iceland, gale to severe gale force SW'ly winds - gusting to 61 kt on Fair Isle and 68 kt at Lerwisk - veered W then NW. The winds eased later and backed as a weak ridge of high pressure moved east across the area. The cold front, becoming slow-moving over England and Wales, gave a wet day in parts of the south - Blaenau Ffestiniog reporting 106mm of rain in the 24 hours. Kinloss - on the sheltered Moray Firth - was the sunniest place in the UK with 9.7 hours of bright sunshine.
A wave low, running NE across mainland Scotland, brought a wet day to many places on the 16th - Greenock reporting a rainfall total of 54mm.
As low pressure then became centred over Scandinavia on the 17th winds swung into the NW over Scotland. Across southern areas of the UK - under the influence of a slow-moving depression to the west of Biscay (the remains of Hurricane Erika) and high pressure over Europe - winds remained a light S'ly. While it was a cold day in the north, with the temperature at Lerwick only reaching 9.1° Celsius, on Jersey - under the influence of the mild S'lies - the temperature reached a warm 23.8° Celsius.
With a high developing to the south of Iceland on the 18th the strong NW'lies were maintained over Scotland with another cold day in the north - a maximum of 10.3° at Lerwick and Foula, but 27.5° at Jersey where winds were a light SE'ly.
On the 19th, as the high drifted south-east across Scotland, Jersey reported a maximum of 28.9° Celsius - and Lerwick only 9.2° Celsius! In the south the remains of Erika produced 42.5mm at Tenby (Pembrokshire) while further north, under the influence of SE'ly winds, the Western Isles had a sunny day with 11.5 hours sunshine recorded at Stornoway.
From the 20th to the 27th the high became slow-moving close to eastern Scotland. Continuing to benefit from the E'ly winds and the shelter of the Scottish mainland, Stornoway again recorded 11.5 hours on 20th. By the 21st, as the high slipped a little further south and winds across Scotland became S to SW'ly, it was the east side of Britain that benefited from the shelter - Sunderland having 11.0 hours sunshine. With light S to SW'ly winds it was Scotland that now saw the highest temps - with 23.4° at Glenlivet on the 24th. It was also a warm day in the Northern Isles with Fair Isle seeing the warmest day of the month (15.1° Celsius). Tynemouth, now with an onshore E'ly wind only managed 12.6° Celsius. Under clear skies nights were cold with temperatures falling to near freezing, and with many places reporting a ground frost. The 23rd, 24th, and 25th saw no sign of rainfall anywhere in the UK. On the 26th Fair Isle was the wettest place in the British Isles with only 0.6mm while on the 27th it was Foula's turn with 0.5mm!
The 28th saw the high - though hanging on in the SE - drifting away east from northern areas as a vigorous low moved NE into the N Atlantic. By the end of the day - as frontal systems swung east across northern areas - the low was 950mb to the south of Iceland.
The low moved away north-eastward on the 29th as high pressure developed across
southern areas - building across much of the UK on the 30th - although northern Scotland
was affected by fronts as a low moved east across Iceland.
ht falls increased the month's total by a further 28.6 mm (50% of the month's rainfall) -
resulting in near average rainfall for the month.
 | Daily Data |
| Weather Diary |
1997 Day 1974-96 1997 Day 1974-96 Mean Max Temperature 12.9 12.1 Highest Max temp 15.2 1 15.9 Mean Min Temperature 9.7 9.0 Lowest Min temp 5.6 26 1.4 Mean Sea Temperature 12.7 11.7 Lowest grass minimum -0.7 26 -2.6 30 cm Earth temperature 12.2 11.1 Days with ground frost 1 1.1 100cm Earth temperature 12.1 10.9 Days with air frost 0 0.0 Total Rainfall (mm) 55.0 92.4 Days with snow/sleet 0 0.3 Wettest Day (mm) 9.6 14 16.4 Days snow cover at 09hr 0 0.0 Rain Days ( 0.1mm +) 18 21.7 Days with hail 0 2.0 Wet Days (0.9mm +) 14 16.6 Days fog during 24hrs 4 6.1 Total sunshine, hrs 124.9 118.1 Days with fog at 09hrs 2 1.2 Sunniest day, hrs 10.7 4 10.4 Days with NIL sun 4 5.7 Mean wind speed, kts 15.0 15.4 Days with gale 3 3.5 Maximum gust, kts 61 15 56.1 Days with thunder 0 0.3 Mean Sea Level pressure 1014.1 1010.1 Days with aurora 1 3.3 Wind Direction% North 3.3 11.3 S. West 23.3 14.6 N. East 0.0 6.5 West 33.3 19.5 East 0.0 9.2 N. West 13.3 10.3 S. East 16.7 13.0 South 10.0 14.3 CALM 0.0 1.4
Weather Diary - September 1997
- To be uploaded later
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