As we head into the winter season, The Meteo Times would like to set the record straight in relation to the widely reported prospects of severe wintry weather affecting western Europe, including Ireland and Britain, at the end of the month.
As we have been saying for the past few weeks, it is highly likely that
temperatures as a whole this month (November) will finish at least 0.5c
to 1.0c below the 1981-2011 average. This follows a cooler than average
September and October.
This week will be relatively mild but
unsettled. We can see a trailing off of temps during the final 10 days
of the month but little more than that. We should see winds shift from a
SW to W-NW direction during this period resulting in a dip in
temperatures. There is little potential for “significant” wintry weather
during the next two weeks. However, wintry showers are likely,
particularly in the western half of the country and on high ground,
during brief cold incursions from the northwest during the final days of
the month.
The Daily Express (Scottish edition) today
published an article stating: “SCOTLAND can expect the first big winter
freeze by the end of the month, with temperatures plunging to as low as
-15C, forecasters predicted last night. Experts warned the UK is set to
shiver with bitterly cold winds, harsh frosts and snow likely to last
into December.”
There is little or sign that such a severe
wintry blast is likely to happen. Of course it could happen, pending a
dramatic change over the coming days in relation to what computer models
are presently saying i.e. a cool SW-W jetstream influenced weather
setup interspersed with brief colder incursions from the NW.
The UK Met Office has also been setting the record straight in relation
to media reports of “two months of snowfall” and temperatures hitting
“-20c”. http://metofficenews.wordpress.com/2012/11/12/whats-in-store-this-winter-responding-to-the-headlines/
So, will Ireland experience snowfall this winter? Ultimately, it is
impossible to tell with any certainty when and where it will snow other
than to say that there are increasing signs that that our winter will be
colder than winter 2011-12. It is important to point out that a colder
than average September, October and November does not necessarily mean
that December will follow suit. It should also not be regarded as a
precursor to a severe winter. The bottom line is that there are signs
that blocking will be more of a feature in our weather during the early
part of winter. Should this trend continue to show up on the main
computer models, then our weather will turn colder with the airmass over
Ireland originating from our east or northeast. This trend is something
that we are watching very closely. Please note that the first signs of
the late November 2010 wintry outbreak did not appear until about 10-14
days in advance. We will keep you posted.
Regards,
Mark Dunphy (TMT)
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While, we wait for our first big snowfall of the winter season, here is some snow trivia to keep you entertained.
- Snow forms from ice crystals that are created within clouds that have
a temperature of below -0.0c. These delicate crystals form when water
vapour condenses directly into ice (known as ‘sublimation’) rather than
from supercooled water droplets that subsequently freeze. A single
snowflake consists of a number of these tiny crystals.
-
Because it contains a high percentage of trapped air (between 70-95%!)
falling snow or an accumulation of fresh snow absorbs sound, which may
explain the sometimes perceived quietness when snow is falling.
- The air trapped between the clusters of ice crystals in fresh snow
also helps to make it a good insulator, keeping ground temperatures
relatively warm.
- It is never too cold to snow, but it is
less likely to snow when temperatures are exceptionally low as very cold
air contains very little moisture.
- It is impossible for
rain to turn to snow. A raindrop will freeze into an ice pellet rather
than snow if falling through a very cold layer of air.
-
Generally speaking, the larger the snowflake, the warmer and more humid
the air mass. When falling through a relatively warm, moist layer of
air, snowflakes will partially melt on their outer layer making the
easier to clump together as they descend towards the surface.
- The idea that no two snowflakes are the same is based purely on theory rather than on hard evidence.
- Broadly speaking, the water equivalent of fresh snow is around 1/10.
For example, 10cm of fresh snow will have the water equivalent of around
1cm approximately.
- In Europe and North America, the biggest snowstorms tend to be associated with Occluded fronts.
SNOWFALL IN IRELAND
- Due to its geographical location and exposer to Polar air streams,
Donegal is Ireland’s snowiest county on average. In contrast, southern
and southeastern coastal counties experience the least snow.
-
One of the heaviest snowfalls ever recorded in Ireland occurred not in
winter, but in mid-Spring, when up to 2 foot of snow fell in parts of
Connacht and north Munster in the space of a few hours on the 1st April
1917.
- The winter of 1946-1947 is probably the snowiest
winter on record in Ireland and although the winter of 62-63 was
infamously cold, relatively little snow was recorded overall during that
season.
- Although January 1982 is famed for bringing heavy
snowfalls along parts of the east coast, less documented is the fact
that equally heavy and disruptive snowfalls affected many parts of
Ulster, Connacht and north Leinster during the previous month (December
1981)
- Based on Met Eireann data, the number of days with
observed falling and lying snow in Ireland has decreased by around 10%
since 1961.
Snow facts/data by Patrick Gordon (TMT)
