On Wed, 26 Oct 2016 03:02:31 -0700 (PDT)
xmetman wrote:

On Wednesday, 26 October 2016 10:40:43 UTC+1, Graham P Davis wrote:
On Wed, 26 Oct 2016 00:37:16 -0700 (PDT)
xmetman wrote:

Bernard

I took photo's of the cloud edge when it first appeared that
morning at about 0830 UTC and posted shortly after on the Weather
Climate forum in an item that I called "Skies across the SW"

https://groups.google.com/d/msg/weat...o/zFJtJn3oBQAJ

I noticed the edge of what I thought was a high AC sheet as it
moved down from the NW and pinpointed the edge on the visible
satellite image for 0815 UTC.

Unfortunately I didn't see any of the fallstreak holes which
occurred further east.

Looking back at the observation from the LCBR from the Exeter
Airport AWS I can see that AC had a very high base indeed 23,000
feet!

03844 - Exeter Airport
United Kingdom 31 M AMSL [50.7 N 3.4 W]
AAXX 10154 03844 46784 /0503 10132 20047 30219 40252 57014 333
55300 20465 83/56== AAXX 10144 03844 46683 /0606 10133 20041
30225 40258 56016 333 55304 21099 87/44== AAXX 10134 03844
46683 /0306 10147 20044 30228 40261 58018 333 55310 21955 81/39==
AAXX 10124 03844 16981 /0707 10137 20057 30234 40267 58013 69921
333 55310 21894== AAXX 10114 03844 46982 /0506 10129 20062 30241
40274 58003 333 55310 21699 81/73== AAXX 10104 03844 46978 /3302
10105 20078 30246 40279 56002 333 55302 20897 88/73== AAXX 10094
03844 46736 /1901 10091 20078 30247 40281 55000 333 55309 20930
81/56 87/73== AAXX 10084 03844 46767 /3502 10056 20055 30244
40278 58001 333 55310 20305 81/56== AAXX 10074 03844 46763 /0502
10036 20035 30248 40282 53001 333 55300 20015 87/56== AAXX 10064
03844 16761 /0602 10033 20031 30248 40282 54000 60002 333 20006
3/101 55088 55300 20000 70000 88/50== AAXX 10054 03844
46763 /3202 10012 20009 30245 40280 56005 333 55300 20000 83/50==
AAXX 10044 03844 46959 /3503 10024 20021 30246 40281 56008 333
55300 20000== AAXX 10034 03844 46862 /0302 10028 20025 30248
40282 58008 333 55300 20000 81/57== AAXX 10024 03844 46860 /0402
10020 20018 30250 40284 58008 333 55300 20000 81/57== AAXX 10014
03844 46902 /0301 10025 20021 30254 40288 58004 333 55300 20000==
AAXX 10004 03844 16860 /0202 10035 20030 30255 40290 58003 60001
333 55/// 21148 83/57==

As an observer I still would have reported it as AC but with some
exotic height of 16,000 feet or so.

Bruce.


Yes, one of the first problems I saw with the standard splitting of
cloud levels into low, medium, and high was when I was on my
Scientific Assistant course in September 1963. There was a fair
amount of unstable Ac around one day which was being reported at
anywhere between 10-15,000ft. This then precipitated out as ice
crystals and the reports changed to Ci spi at 20,000ft. ;-)

There were several occasions when I should have reported Ac or As as
25,000ft but chickened out as I knew it would trigger a row with
Group or Bracknell. One time at wethersfield, I went out for the ob
and saw that the St at 200 and 400ft had gone and been replaced by
CuSc at what looked like 3,000 and 4,000ft. Checking with the CBR
and looking outside again revealed that the CuSC was at the same
height as the St had been. Can't remember what I reported but as I
was older and more bolshie by that time, I hope I stuck to CuSC and
200 and 400ft.

Since retiring, I have seen Cirrus with a base of 6,000ft (top
13,000ft) and associated halo. I bet I would have had a struggle
getting such an ob past the powers-that-be in days of yore.



Enormous rows (and crossing outs in red in the obs book) about when
ST became SC, or whether it was type 6 or type 7 stratus at
everywhere that I worked. I liked 1000-1200 feet as a demarcation
point but others had stratus bases much higher just like the Irish,
who I did hear couldn't report a shower without reporting a CB at one
time - not checked lately!


Yes, I was never too sure about that but the in the case I mentioned
there was no doubt at all. The sky had changed from 8/8 St at 200 and
400ft with vis somewhere around a couple of Km to 7/8 Sc with 3/8 Cu
below and vis over 20km. When I saw the CBR giving the same cloud base
and cover as before, I assumed there must have been a very thin layer
below the CuSc that I'd not noticed. I stared at the patches of blue
sky but could see nothing below the CuSC. Then I saw the sharp edges of
the clouds begin to blur and they suddenly lost their structure to
become St and, at the same time, the vis dropped back to a couple of
km.

On another occasion years before at Bedford, the sky had resembled the
type of St or Sc of which you speak; large rolls of ragged, black-based
cloud resembling something at no more than a thousand feet. Trouble
was, I knew it was neither type as I'd been watching it for a long
time. An aircraft then reported the base at 25,000ft with top at
34,000. Would have caused a bit of a kerfuffle if I'd reported St or Sc
at 25,000ft! ;-)


--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
Web-site: http://www.scarlet-jade.com/
There are more fools than knaves in the world, else the knaves would
not have enough to live upon. [Samuel Butler]