Sunny and Warm in Arctic Maritime Air

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Sunny and Warm in Arctic Maritime Air

Postby Nick Gardner » 2014 Aug 17, 19:04

In contrast to the text book weather type usually experienced under Arctic Maritime air in the summer, today was predominantely sunny after the cold (rainless) front moved over just before midday.

Beautiful crystal clear, deep blue sky and dazzling, piercing sunshine. UV still high with a maximum today of 7.4 to top up the slightly faded suntan with.

Minimum = 13.4C
Maximum = 20.3C
Rain = 0.0 mm
Sunshine = +6.5 hours

A tad breezy at times but down on the beach (south-facing) and a big cliff behind you there was hardly a breeze and it was very warm in the sunshine.

A cool/cold night ahead for the time of year.
Near Newton Poppleford, Sidmouth - Devon
50:41N 3:17 W; 20 metres AMSL; Station Grade B-BAAA37
http://www.ottervalley.co.uk
Nick Gardner
 
Posts: 429
Joined: 2012 Jan 27, 17:25
Location: Rural riverside valley location near the village of Newton Poppleford and 2 km from the sea.

Re: Sunny and Warm in Arctic Maritime Air

Postby Graham Easterling » 2014 Aug 17, 20:48

Beautiful crystal clear, deep blue sky and dazzling, piercing sunshine. UV still high with a maximum today of 7.4 to top up the slightly faded suntan with.


That UV report got me looking, and on Scilly it reached 7.9! http://www.weatherlink.com/user/taperki ... &headers=1 , quite a surprise.

UPDATE:- The surprise was down to the fact that UV normally drops significantly behind a cold front. However, on closer examination, this high reading was ahead of it.

In west Cornwall/Scilly, there was some drizzly rain mid morning, the misty low cloud breaking to give sunny spells around 12:00-13:00, when this high UV was recorded. The cold front was accompanied by cloud (no rain) 13:30-14:30, then the sun returned. So the high UV here occurred in the humid, modified warm sector air ahead of the front, more the normal situation.


Still a below normal 18.4C maximum here (17th), pleasant out of the breeze. The lower temperatures have had little impact on the crowded beaches. This was Sennen beach on Friday 15th Aug, the coolest day (just 17.3C) since 5th June http://www.sennen-cove.com/15aug14.htm !

Just too many people around at the moment. It'll suddenly go quiet the 1st week in September and the surfing beaches will be useable again.

Graham
Penzance
Graham

Penzance Weather Station
Grid Ref:
SW464231 - Post Code: TR18 4TP
19m AMSL - Aspect SSE
In a SE - NW orientated valley

23 Years of Penzance Weather Records : http://penzanceweather.atspace.com/weather.html
Graham Easterling
 
Posts: 316
Joined: 2011 Nov 30, 20:29
Location: Penzance, Cornwall

Re: Sunny and Warm in Arctic Maritime Air

Postby Nick Gardner » 2014 Aug 18, 18:35

UPDATE:- The surprise was down to the fact that UV normally drops significantly behind a cold front. However, on closer examination, this high reading was ahead of it.

In west Cornwall/Scilly, there was some drizzly rain mid morning, the misty low cloud breaking to give sunny spells around 12:00-13:00, when this high UV was recorded. The cold front was accompanied by cloud (no rain) 13:30-14:30, then the sun returned. So the high UV here occurred in the humid, modified warm sector air ahead of the front, more the normal situation.


Graham

I've had a look at time of maximum UV for Sunday 17th and it occurred well after the cold front had moved through, i.e., in arctic maritime air. The cold front moved through at around 11:50 but the highest UV occurred at 13:00. Below are the data from my Davis AWS for the 17th:

Time UV Temp DP
11:00 2.2 16.3 13.8 SW
11:15 3.5 16.6 14.6 SW
11:30 5.7 17.1 14.7 SW
11:45 4.5 17.8 14.7 WSW
12:00 2.9 17.8 14.0 NW
12:15 6.3 17.2 14.5 NW
12:30 6.7 17.8 14.3 NW
12:45 5.5 17.9 13.9 NW
13:00 7.4 18.3 13.5 NW
13:15 7.2 18.2 12.9 NW
13:30 7.3 18.6 12.8 NW
13:45 7.2 19.3 12.8 NW
14:00 6.7 19.9 13.1 NW
14:15 6.7 20.1 13.8 NW
14:30 6.9 20.2 13.5 NW
14:45 6.4 20.1 13.0 NW
15:00 6.1 19.6 12.6 WNW
15:15 5.9 19.4 12.9 WNW
15:30 5.4 19.8 11.8 NW
15:45 5.1 20.3 12.3 NW
16:00 4.8 20.3 12.2 NW

I would have expected a UV maximum of 5.5 to 6.0 at this time of year but Am air is rare in August so that I can only assume it would give similar UV levels to Pm air. The main difference between the two is that the Pm is warmer, slightly more humid and has a much longer crossing over the ocean. Would that make any difference to UV levels?

The UV peaked at 6.8 at 13:04 today which is still on the high(ish) side. The UV peaked at 7.0 at 12:28 today on St Martins, Isles of Scilly.
Near Newton Poppleford, Sidmouth - Devon
50:41N 3:17 W; 20 metres AMSL; Station Grade B-BAAA37
http://www.ottervalley.co.uk
Nick Gardner
 
Posts: 429
Joined: 2012 Jan 27, 17:25
Location: Rural riverside valley location near the village of Newton Poppleford and 2 km from the sea.


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