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Weather Diary - September 1999
A cloudy, dry morning with a F5-6 SSW'ly wind. Some low ST overnight, otherwise AC/AS lowering to SC by 4500 ft by 0800 UTC. Drizzle from 1130 UTC, becoming moderate at times. With the onset of the drizzle low ST soon spread in and the visibility fell with fog (sky obscured) shortly after 1300 UTC as the ST base descended to station level. At the same time the SSW'ly wind eased F3-4. Becoming dry between 1500 and 1600 UTC, the fog clearing to fog patches at 1800 UTC and adjacent fog at 1900 UTC. A dry, cloudy evening with SC, 20 km visibility and F4-5 SSW'ly winds. Cloud becoming well broken overnight with 1 or 2 oktas SC/AC Cas/CI by 0600 UTC. SC increasing after 0700 UTC with patchy drizzle 0800 - 1100 UTC. Cloud clearing rapidly after 1100 UTC to small amounts of SC/CU/ST. Visibility 20 km to 25 km, falling to 2500 m in drizzle. Wind S to SSW'ly F5-6 overnight, veering F% SSW'ly during the drizzle and W'ly F4 with the late morning clearance, then easing F3 during the afternoon before backing SW'ly in the evening. A fine clear night and morning with 30 km visibility and F2 SSW'ly winds. Winds backed S'ly between 0800 - 0900 UTC. A bank of sea fog was observed forming to the SE of the isle at 0940 UTC. By 1030 UTC, by which time the wind had backed SSE to SE'ly, this had become more extensive and was within 1500 m of the S, E, and NE coast of the isle. with 6 oktas of stratus at <100 ft. jf - fp 1035 UTC - fog 1037 UTC with sky obscured (280 m visibility) 1059 UTC. During the period 1100 - 1200 UTC the sun's disk remaind visible. After 1200 UTC the fog lifted to low stratus (the sun's disk no longer visible) - fp 1255 UTC - mist 1300 UTC with 06 km and ST at 50 ft. [At 1410 UTC an aircraft reported the cloudtops at 1100 ft at Sumburgh] Mist - fp 1415 UTC - fog 1420 UTC with sky obscurred. The fog persisting for the remainder of the afternoon, cleared after 2100 UTC to 20 km by the end of the day - at which time the sound of a heavy sea crashing on the West Cliffs could be heard. A dry, mainly cloudy and hazy day - the early visibility of 20 km falling to 06 km - 12 km. F3 S'ly wind backing SSE'ly during the morning and increasing F4-5 through the afternoon with small amounts of ST forming on the Hill during the afternoon. Becoming sunny after 1530 UTC as the SC cloud-sheet became well broken - with some SC Lent during the evening with an extensive SC cloud-sheet again by the end of the day. Moderate rain overnight, becoming light and intermittent with fog (sky obscured) by 0600 UTC, the F4 S'ly wind easing F2-3. Outbreaks of patchy light drizzle becoming persistent rain and drizzle, moderate at times, after 0800 UTC - the visibility improving 3000 m as the wind veered NW'ly and increased F4 with a further improvement to 5000 m - 12 km during the morning as the wind veered N'ly. A cloudy afternoon with extensive very low ST7 and further persistent rain and drizzle - moderate or heavy at times - with a F3-4 N'ly wind. A wet evening with moderate rain and F4 NW to N'ly winds later veering NE'ly and easing F3. Overnight rain becoming intermittent by 0600 UTC, the F3 NE'ly wind veering ESE'ly. A period of moderate rain/rain and drizzle 0700 - 0830 UTC with the visibility falling from 20 km to 1200 m in the precipitation with ST cloudbase down to 50 ft. An improvement following by 0900 UTC as the wind veered SSE to SE'ly - some low ST remaining but the visibility improving to 50 km. Cloud becoming well broken later in the morning. A dry afternoon with 40 km - 50 km visibility, the wind veering SW to WSW'ly F3-4. A fine, clear evening with a slight aurora arch and glow observed at 2350 UTC. A cool day - but still slightly above normal. AS/AC cloud increasing overnight, the F4 WSW'ly wind backing SE'ly by 0600 UTC. A dry start but with rain from 0955 UTC as the AS thickened and lowered, the SE'ly wind increasing F6 by midday. [At 1305 UTC a helicopter reported the wind as 175°/48kt at 3000ft and another as 170°/52kt at 2000ft]. The rain, moderate at times, continuing through the afternoon as the AS lowered to NS/SC/ST with the visibility falling to 3000m to 5000m. SE gale F8 from 1500 - 1615 UTC and from 1650 - 1745 UTC. Wind then veering 190°/26kt at 1915 UTC followed by a further veer to 260°/16kt at 1925 UTC with a backing to SSW'ly F4 by 2100 UTC, later increasing F5. Rain ceased soon after 2100 UTC with cloud then becoming well broken and visibility improving to 25 km. 2350 UTC Strong aurora arch with short rays. A dry day with well broken cloud, 20km - 25 km visibility and a F5 SSW'ly wind increasing F6 overnight and veering WSW'ly late afternoon before easing F4 and backing SSW'ly during the evening. No aurora visible despite only 2 oktas of cloud. Continuing dry, but generally cloudy - the majority of cloud AC/AS/CI at first, but this thickening and lowering to AC/AS during the afternoon before thinning to well broken CI early evening. Visibility 20 km at first but falling to 15 km as the F4-5 S to SSW'ly wind backed S to SSE'ly during the morning. 2050 UTC Moderate aurora glow, weak arch with faint rays. Cloudy with increasing AC later. Cloudy and dry overnight, the F6 SSE'ly wind easing F5 and backing SE'ly. Light rain from 0445 UTC, becoming moderate 0620 - 0645 UTC. Visibility falling from 15 km to 1500 m in precipitatio, with fog from 0725 UTC as extensive low ST developed. Further moderate rain 0735 - 0815 UTC, rain then ceased 0835 UTC. Visibility falling to 80m during the morning with sky obscured from 0900 UTC. Some light rain early afternoon, the fog thinning to mist at 1430 UTC and visibility improving to 1500m - 2500 m as ST base lifted to just above station level. Wind SSE to SE'ly F5-6 through the morning and afternoon. Some sun visible 1600 UTC. F5 SE'ly wind increasing F6 and veering S'ly after 1600 UTC with outbreaks of rain 1700 - 1900 UTC. Wind easing and veering F4-5 W to WNW'ly after 1800 UTC with a few early evening light showers. A cloudy night with early showers and then moderate rain and F3-4 NW to N'ly winds. Becoming dry by 0800 UTC, the lower cloud breaking to CU/SC and CS7 with a moderate halo. Some showers later in the afternoon. 25km visibility falling to 15km overnight in rain, improving to 30 km later in the morning. F3-4 NW to N'ly wind easing F3-4 and veering NE'ly early evening with a SC cloud-sheet spreading in. A ST overcast by the end of the day, the visibility falling to 10 km in light rain and drizzle. A cloudy night with outbreaks of rain and drizzle becoming dry by 0600 UTC, the 10 km visibility improving to 40 km and the F3 N'ly becoming F3 SSW'ly. A cloudy day, variable amounts of SC/CU with extensive AS/AC, a F2-4 SSW wind steadily backing SE to ESE'ly by 1800 UTC. A cool day, but still above normal values. Some early dizzle with a F3 SE'ly wind. Overnight cloud clearing to a fine sunny morning after 0600 UTC, the F3 wind veering SW'ly and the 20 km visibility improving to 60 km. Wind backing S to SSE'ly late afternoon. Another dry day, clear overnight with a trace of ST and CI increasing during the morning, CI only during the afternoon. Cloudless for a time in the evening, some ST later. Visibility 60 km falling to 20 km to 25 km by dawn. Wind SE F4 easing F3-4 and backing ESE late evening. SC/ST increasing overnight with fp by 0600 UTC, the 20 km visibility falling to 700 m. fp - f 0705 UTC - F 0720 UTC with sky obscured. Visibility falling to 80 m at times during the morning. Some patchy light drizzle late morning and mid-afternoon. F - f 1535 UTC - m 1550 UTC with extensive low ST and visibility 1500 m. Some further drizzle during the evening and m - f as ST base temporarily fell to station level. F4 ESE'ly wind increasing F5 late afternoon. Rain and drizzle overnight. Dry by 0600 UTC, the F4 ESE'ly wind having veered F4 WNW'ly and the 1200 m visibility improving to 30 km. Becoming fine and sunny during the morning. An almost cloudless afternoon with 40 km to 60 km visibility, the wind - backing SW'ly during the morning - backing further to be F3 SE'ly. With the change in wind direction ST became extensive for a while. Partly cloudy during the evening. A dry, partly cloudy day - some ST, CI/CS extensive for a time during the morning producing a moderate halo. A SE'ly wind, F4 at first, gradually increasing F5 bringing small amounts of ST on to, or just above, the hill. "0 km visibility falling to 12 km by evening. Continuing dry and becoming quite mild with a F5 SE'ly wind gradually backing E to ESE'ly and increasing F6 for a time during the afternoon before easing F4 in the evening. Mostly cloudy - low ST at first but this clearing to ST/SC then SC/AC during the afternoon. Hazy with 07 km - 12 km visibility. A cloudy and mild day, mostly dry apart from a little light rain late morning. Visibility 20 km with a F5 E'ly wind gusting to 40 kt during the evening. Some rain and drizzle overnight, becoming foggy with 800m visibility by 0600 UTC. An overcast day with fog, dense at times throughout and persistent rain and drizzle form mid-morning. A continuing E'ly wind, increasing F7 0300 - 0430 UTC, F5 during the morning and easing F3 by the end of the afternoon. A mild, foggy day with drizzle at times. f - m 0450 UTC - f 0705 UTC - F 0720 UTC. A continuing F3-4 E'ly wind. Fog clearing to mist overnight as ST base lifted to just above station height. Drizzle overnight with rain and drizzle during the morning, followed by a dry afternoon and evening. m - f briefly around midday as ST base lowered. Fog then rolling in from the east at 1317 UTC - F 1420 UTC - f 1610 UTC - m early evening. F3-4 E to SE'ly wind. A dry, misty and cloudy day - apart from a little light drizzle during the evening. Visibility 10 km to 15 km falling to 3000 m to 5000 m by the end of the afternoon with very low ST becoming extensive. F3 SE'ly winds. Drizzle overnight with ST lowering to give fog by 0600 UTC, the F2-3 wind becoming W'ly. Sky obscured for much of the morning with further light drizzle. Visibility improving after 1000 UTC as ST base lifted. A cloudy afternoon with F3-4 W'ly winds and visbility improving to 20 km under ST at 500 - 900 ft. ST base lowering during the evening with further mainly light rain and drizzle. A mainly cloudy day. Some early drizzle reducing the 20 km visibility to 4000 m with variable amounts of ST at 200 ft. A general improvement afetr 0800 UTC. A F1-2 W to WNW'ly wind. Overnight mist, rain and drzzle followed by a dry day. Partly cloudy during the morning and mostly clear through the afternoon but with increasing high cloud later. F2-3 WNW'ly winds falling calm in the evening and 40 km to 50 km visibility. Dry, but with increasing cloud overnight. A few scattered showers at first but turning rather wet with heavy rain from 1040 UTC, the 50 km visibility falling to 2000 m. Wind calm at first, increasing F2 S to SSW'ly by morning, veering WSW to WNW'ly with the heavy rain. A dry, bright cloudy or partly cloudy afternoon , the wind easing F1 and backing SSW'ly. A light rain shower between 1700 - 1800 UTC and further light showers during the evening, the wind becoming a F1-2 NE'ly. Visibility 60 km, but reduced in direction of the adjacent showers. Rain and drizzle, moderate at times, overnight, the NE'N'ly wind increasing F4 with the 40 km visibility falling to 4000 m. A general improvement after 0900 UTC, the visibility improving to 40 km as the NE'ly wind increased F4. Becoming partly cloudy by afternoon. The F4 NE'ly wind backing N'ly by evening then easing and backing further to be F3 W'ly by the end of the day. A somewhat cooler day. Overnight showers dying out during the morning. A bright, mostly cloudy day with extensive AS/AC and variable amounts of CU/SC. 40 km to 50 km visibility, the F2 W'ly wind backing S to SSW'ly and increasing F4 during the afternoon. Wind veering F3 WSW'ly during the evening with moderate rain showers. Another cool day.
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