May 1998
Warm, dry and not quite so sunny as the rest of Shetland.
While Shetland as a whole was much sunnier than usual (135% at Lerwick) Fair Isle, due to several foggy spells, was only a little sunnier than normal (106.0%). Elsewhere in Scotland values were near average. Like the rest of Scotland Fair Isle was warmer than normal, with the mean daily temperature of 8.5° C (+1.0° C) almost approaching the highest June value of 8.7° C (1992). Rainfall in the Northern Isles was well below average, with Fair Isle receiving only 49.4% of the normal total for the month (Lerwick 50.6%). Much of the rest of the country was also drier than normal, although the Edinburgh area and the eastern Borders were wetter than average (around 150%).
May commenced with high pressure and air of cold northerly origin over Scotland and, with little cloud, cold nights and sunny days. The lowest air temperature of the month, -3.8 C, occurred at Kinbrace on the 1st - though Dumfries in the milder south-west, recorded a maximum temperature of 19° C on the same day.
Low pressure replaced high during the 4th - introducing a rather unsettled westerly regime for the next week or so.
High pressure building over the North Sea saw a south-easterly flow becoming established over Scotland by the 10th. Apart from some rain over the Borders during the 11th and into the 12th, the weather then settled down to give a spell of mainly dry, fine, sunny and warm conditions - especially over the sheltered northwest. Low cloud persisted on eastern coastal fringes where, on the 13th, an overcast Leuchars recorded a maximum of only 11° C. On the same day Aviemore, with 13 hours of sunshine, reached 28° C - a considerably higher figure than its previous highest May temperature of 26.7° in 1990 (although the station only opened in 1983). Despite accumulating almost 30 hours sunshine total in the three days, Fair Isle reported the lowest daytime maximum temperatures in the UK on the 12th, 13th and 14th, with highs of around 9° to11° C.
Fair Isle then experienced its warmest spell of the month during the period from the 15th to the 18th when the maximum temperature reached 12.7° C. Elsewhere in Scotland values were considerably higher with 28.3° C - the highest temperature of the month - recorded at Kinlochewe on the 13th. This figure is not too far short of the 29.0° C recorded in Edinburgh on 14th May 1992 - the highest May temperature of this century anywhere in Scotland.
As a consequence of the high temperatures further south, sea and coastal fog proved troublesome at times in the Northern Isles, with a thundery trough across the north of Scotland on the 14th. Generally, however, fine weather was maintained across most of the country, with maxima in the low to mid-twenties until the 19th and over 14 hours of sunshine at Glasgow on the 18th. Early on the 19th the area of high pressure receded westwards, allowing a cold front to move southwards over the country and giving much of the south the first rainfall of note for around a week or so. A colder, northerly airstream was introduced and Lerwick recorded a grass minimum of -3° C on the morning of the 20th.
There were several more nights of ground frost, although daytime temperatures managed to reach around 20° C in some places, and 21° C at Leuchars on the 24th. During the last week, as areas of low pressure dominated and N to NE'ly winds persisted, daytime temperatures dropped back into the low teens. Ground frosts also occurred in the west and north-west on the 27th and 28th The Western Isles received 14-15 hours of sunshine from the 26th to the 29th while, by contrast, southern and south-eastern areas endured a wet spell to end the month.
May ended on a cold, wet note as thundery rain in the south moved northwards to affect all but the far north. Quite breezy conditions were also in place during much of the last week of May with, for example, gusts of 50 mph in the far south-west on the 29th. After the fine spell earlier in May, it almost seemed as if winter had returned by the end of the month. Heavy rain and a fresh easterly affected Edinburgh on the 31st, with the maximum temperature only 9° C.
 | Daily Data |
| Weather Diary |
1998 |
Day |
1974-97 |
1998 |
Day |
1974-97 |
|||
Mean Maximum Temperature |
10.5 |
9.4 |
Highest Max temp |
12.7 |
15 |
17.7 |
||
Mean Minimum Temperature |
6.7 |
5.8 |
Lowest Min temp |
4.0 |
3 |
-1.6 |
||
Mean Sea Temperature |
9.3 |
8.6 |
Lowest grass minimum |
1.5 |
9 |
-7.6 |
||
30 cm Earth temperature |
9.7 |
8.3 |
Days with ground frost |
0 |
3.3 |
|||
100cm Earth temperature |
8.6 |
7.3 |
Days with air frost |
0 |
0.3 |
|||
Total Rainfall (mm) |
19.8 |
40.1 |
Days with snow/sleet |
0 |
2.7 |
|||
Wettest Day (mm) |
4.4 |
7 |
10.4 |
Days with snow cover at 09hr |
0 |
0.0 |
||
Rain Days (> 0.1mm) |
12 |
13.6 |
Days with hail |
1 |
3.3 |
|||
Wet Days (> 0.9mm) |
8 |
8.7 |
Days with fog during 24hrs |
11 |
9.1 |
|||
Total sunshine, hrs |
209.0 |
197.1 |
Days with fog at 09hrs |
3 |
2.0 |
|||
Sunniest day, hrs |
13.2 |
11 |
14.7 |
Days with NIL sun |
2 |
4.8 |
||
Mean wind speed, kts |
11.4 |
13.2 |
Days with gale |
0 |
0.8 |
|||
Maximum gust, kts |
40 |
10 |
48.1 |
Days with thunder |
0 |
0.3 |
||
Mean Sea Level pressure |
1018.1 |
1015.7 |
Days with aurora |
0 |
0.1 |
|||
Wind Direction (%) North |
12.9 |
13.2 |
Wind Direction (%) S. West |
12.9 |
8.7 |
|||
at 09 hr N. East |
9.7 |
13.5 |
at 09 hr West |
32.3 |
10.6 |
|||
East |
12.9 |
13.0 |
N. West |
9.7 |
10.6 |
|||
S. East |
3.2 |
15.4 |
||||||
South |
6.5 |
13.6 |
CALM |
0.0 |
1.5 |
Weather Diary - May 1998
- To be uploaded later
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