Re: [WR] Cold Langtoft

• From: "Will Hand" <will@xxxxxxxxxxxxxxxxxxxx>
• Date: Wed, 1 Feb 2006 21:50:59 -0000

"Col" <reddwarfer@xxxxxxxxxxxxxx> wrote in message
news:drr9l5$2cu$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> "Will Hand" <will@xxxxxxxxxxxxxxxxxxxx> wrote in message
> news:drr8cm$qsm$1$830fa79d@xxxxxxxxxxxxxxxxxxx
>  >
> > Due to the low cloud top and fairly thin cloud and time of year (low sun
angle)
> > the short wave radiation from the sun could not overcome the longwave
radiation
> > from the cloud top, hence the cloud top cools. Weak convective overturning
> > within the cloud eventually cools the cloud base as heat is re-distributed
from
> > base to top and then out into space and possibly giving light drizzle or
snow
> > grains (as in Leeds). Cooling the cloud base chills the air as longwave
> > radiative fluxes from cloud base to ground decrease. (Cloud acts as less of
a
> > blanket).
> >
>
> So why was this not picked up on this mornings forecasts?
> I think Manchester was supposed to reach 4C today, it only managed
> -1C (as I did). Now 5C is a huge error, is this just a tricky thing to
> forecast?
> I see that temps for Thu/Fri have now been notably downgraded from
> what they were earlier in the week. No sign of anything milder, quite
> the contrary.
> For maxima at least, the next few days could almost be like a 'real' winter!
>

Col, difficult for a human as radiation balance is just that - a balance. All
very easy in hindsight. In theory a numerical model should be able to model the
processes and give useful guidance but the trouble is that the vertical
resolution is not high enough in present operational models to accurately pick
out the steep inversions critical for thin low cloud formation. It's one of
those things that is difficult many hours ahead, although a skilled human
analyst should be able to work out what is going on by scrutinizing current
data, but then you have presentation and dissemination issues. As you say the
outlook is still cold, even into next week when we will have a northerly on the
cards.

Will.
--

" Ah yet another day to enjoy "
-------------------------------------------------------------------------------
A COL BH site in East Dartmoor at Haytor, Devon 310m asl (1017 feet).

mailto:      will@xxxxxxxxxxxxxxxxxxxx
www:         www.lyneside.demon.co.uk/Haytor/automatic/Current_Vantage_Pro.htm

DISCLAIMER - All views and opinions expressed by myself are personal
             and do not necessarily represent those of my employer.
-------------------------------------------------------------------------------


.

• References:
  • [WR] Cold Langtoft
    • From: David Mitchell
  • Re: [WR] Cold Langtoft
    • From: Will Hand
  • Re: [WR] Cold Langtoft
    • From: Col

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