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Thread: high icing index above freezing level

  1. #11
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    Hi Peter,

    thanks for the hint to this publication and the information below.

    Good point, the last sentence :-)

    Marcel

  2. #12
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    Having read the Night Raid Report in full I can understand why the icing index was given as High, Marcel. The forecast also included cumulonimbus (CB) cloud and thunderstorms along the weakening front along 2W (see #8) and further thunderstorms over France and Germany. CB clouds are almost invariably associated with severe icing, hence the Icing Index was given as high. Your initial query referred only to the Icing Index in isolation - hence my difficulty in providing a definitive answer - had I been aware of the references to the CBs and thunderstorms in the forecast it would have immediately been clear what was intended.

    Brian
    PS Although isolated thunderstorms were reported at Spurn Point and Cranwell, I think the forecast was overly pessimistic and vague, but that is with the advantage of hindsight.

  3. #13
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    Hi Brian,

    thanks a lot for taking your time to study the report and sorry that I did not give the full details at the beginning of my thread. Now I know a bit more about the icing topic. That was very kind of you.

    And thanks to Peter, too.

    Best wishes.

    Marcel

  4. #14
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    Thanks for this timely discussion on icing. Since we have a couple of meteorologists engaged, I am interested in your views on the likelihood of icing at very low level on October 4, 1944 on the operation to Bergen by 6 and 8 Groups.

    Dad recalled “Well we flew at 100 feet because we couldn’t see the sea, it was so dark and it was raining . Golly it was pouring buckets… And all of a sudden, and it was the most amazing thing, because these were all cumulonimbus clouds that we had over us. There was as I say, rain and hail and everything else, it was a real mess…and all of a sudden the sky just opened up and it was almost like a cathedral with great big hammerheads or the tops of the clouds looked like the claw of a hammer and it just looked like a massive cathedral with the sun streaming down and there was Norway ahead.”

    In his diary, F/O J.A. Anderson (DSO, DFC) recorded “…The icing level was 250 ft and cloud from 250 yo ti 30,000 ft. Cloud dispersed completely over the target…”

    So how likely is it that icing would be present at 250 ft in early October?

    Jim

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    There are a couple of items in this account which makes me wonder about its veracity, in particular Well we flew at 100 feet because we couldn’t see the sea, it was so dark and it was raining. I would have thought it dangerous in the extreme for 140 (from the Bomber Command Diaries) 4-engined heavies to fly at 100 ft in heavy rain which prohibited the crews from seeing the sea. So before I answer could you tell me which squadron(s) these two extracts refer to, please?

    Also, is there a raid report?

    Brian

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    Hi,

    I just wanted to mention that the Forecasters’ Reference Book Met.O1023 of 1997 can be downloaded from the address below. But maybe you know already.

    https://www.google.com/url?sa=t&rct=...5H6fRzCJ1NADrU

    Marcel

  7. #17
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    Thanks Brian: F/Lt. HHM Cave (in KB762) and F/Lt. J.A. Anderson (in KB744) both with 419 Squadron.

    http://heritage.canadiana.ca/view/oo...92/861?r=0&s=3

    Anderson corroborates dad's statement about flying heights and that they were late taking off:
    "We were 1 hr. late on take-off and cut our first corner by 280 miles to E...we flew across the north sea at 200-100 ft to within 60 miles of the Norwegian coast."

    I transcribed Dad's statement from audio recordings he made circa 1986. I've put the route on Google maps and the turning points based on "62-Base Summary of Operations." The flight plan in this document notes: “Set course and fly below 2000 ft. at 175 IAS TO 0400 E and climb at 160 IAS to bombing height…” Dad also recalled cutting the corner to Bergen because everything was late. Dad's navigator (Marv Seale) is still alive and he confirmed cutting the corner on the route. Seale also noted that many crews wanted to avoid Scotland because of the weather and the possibility crashing into the hilly terrain. In fact one a/c did crash into the hills in Scotland on the return journey killing all crewmembers.

    https://drive.google.com/open?id=1Sr...8g&usp=sharing

    64 Base summary of operations:
    http://heritage.canadiana.ca/view/oo...28/199?r=0&s=3

    6-Group Summary:
    http://heritage.canadiana.ca/view/oo...20/247?r=0&s=2

    Jim

  8. #18
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    Jim,

    I think it is extremely unlikely that the freezing level was as low as 250 ft asl on this occasion. Had it been then the heavy precipitation described by the aircrew would have been of snow. At the time the aircraft left their bases at about 0530 hours, a depression of 1009 MB was centred at 54N 04E and moving south. In the NE'ly flow on the northern flank of the low temperatures along the east coast ranged from 8-10C.. When the aircraft returned at approximately 1200 hours the temperatures had risen to 10-11C; these equate to a freezing level of about 5000 ft. Had there been the cold air described by the aircrew the temperatures would have fallen as the cold air advected southwest towards the UK - there is no evidence of this.

    I don't know if there is a raid report which sheds light on the claim, but a variety of ORB reports I've seen make no reference to the en route weather, only that it was clear over the target. The crews appear to have flown through a trough marked by a line of intense convection, although this (the trough) does not appear on the simplified chart I'm using.

    Brian
    Last edited by Lyffe; 24th October 2019 at 10:09.

  9. #19
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    Brian: that you for your reply and sorry for my late response. I had thought that 250 feet would be too low for icing, which is why I thought I’d ask. Dad himself never commented on that. I have no addition information on flying heights or why both Anderson and dad remembered crossing over the ocean at that height. Dad had no further contact with Anderson after the war. They shared a room at Middleton St George in the officer’s mess, what is now the St George Hotel.

    Jim

  10. #20
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    Jim,

    The 419 Squadron ORB ((Summary of events (https://discovery.nationalarchives.g...ils/r/D8404083)) includes the following Tactics were to set course at low level and continue at low level until approaching the target which seemed consistent with your #17. The take off time was planned for 0445, but there must have been an operational delay as all actual t/o times were much later: three a/c took off between 0518 and 0522 hours, but all the others between 0545 and 0605 (Anderson's at 0558) so it was a planned delay as opposed to one aircraft starting late.

    I still have my doubts about the claim to be flying at 100-200 ft in the dark and rain - even the met reconnaissance crews only descended to that level of necessity to take observations, and in those instances the descent was very gradual and once an observation was made it was back to safety at 1800 ft.

    Brian

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