The yo-yo thread, for whence and whom it may concern.

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stephenprudence
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The yo-yo thread, for whence and whom it may concern.

Post by stephenprudence » Wed Nov 13, 2013 7:46 pm

and so it's started, the first wintry weather of late 2013 is on the way.

At this stage it's looking fairly cold but with a mix of frosty, and milder nights so perhaps not a consistently prolonged frost-fest, however the cold theme (below average temperatures), could well be quite persistent, right up to December. At the moment I'm thinking light frosts only, however obviously in inland, areas, sheltered areas, and frost hollows, more significant cold temperatures will occur. Snow sadly, is also going to a be a real threat over the next 2 weeks.

Not sure as yet whether the spell will be long lasting, but, there is signals for blocking mid-Atlantic, and should the block link up with the Greenland High, we're looking at a rather cold start to winter time.

Shame we have to start this thread so soon, but mid November is about the average time when most of us record our first air frost, so it's not particularly irregular.
Last edited by stephenprudence on Tue Dec 03, 2013 11:17 pm, edited 2 times in total.
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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Adam D
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Re: First significant cold spell of the season coming right

Post by Adam D » Wed Nov 13, 2013 8:04 pm

Elizabeth Sarre mentioned it going much colder next week on the BBC lunchtime weather forecast.


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billdango
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Re: First significant cold spell of the season coming right

Post by billdango » Wed Nov 13, 2013 8:13 pm

We had our first slight ground frost in Southampton last night when the air temperature dropped to +4c.

It was only noticable on some house and car roofs and on long grass but its the start to the big nip to come i think.

I may have to tie up the Phoenix canariensis_CIDP in St denys if the snow and frost thats forecast for Southampton in the next week or so happens.

As long as the sun shines now and then its no problem.

The hot water bottles are ready to start work soon.

billdango :D


Tom2006
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Re: First significant cold spell of the season coming right

Post by Tom2006 » Thu Nov 14, 2013 12:11 am

Starting to look quite worrying in the models today. Widespread support for a cold, possibly very cold, spell of weather from the 19th onwards. Best case it will be a few days of northerly winds bringing wintery shower's southwards from the pole followed by high pressure moving over us bringing frosty foggy nights. Worst case we see north east winds set up bringing prolonged frigid conditions not all that dissimilar to nov 2010. I am certainly not shouting 2010 repeat,but put it this way.....Everything that needs protection needs to be sorted before the 19th and definitely prepare for something very cold.
Most wanted list - Any Young Trachycarpus and/or fern.


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stephenprudence
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Re: First significant cold spell of the season coming right

Post by stephenprudence » Thu Nov 14, 2013 9:28 am

As well of recent, the GFS has been putting out relatively mild runs.. to be honest I would be highly sceptical of the GFS, as in my experience it just doesn't handle blocking situations well, so I do fear that the european models maybe correct, simply because of their better track record when it comes to verifying blocking situations. There have been some alarming runs on the European models.

I think there is a chance we could have another severe start to the winter, however, personally, I have taken measures to grow hardy plants now in the my open garden, so I'm not overly worried.

However those who have not protected yet, Tom's right, protect soon.. and protect with the assumption another 2010 style spell maybe on the way (even if it's not),
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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Re: First significant cold spell of the season coming right

Post by Nigel » Thu Nov 14, 2013 9:40 am

The first cold plunge of winter is almost always in the last third of November, perfectly normal weather that. This doesnt look anything as bad as we have seen in recent years , very 90,s look to it, so far greenland block seems to be keeping its nose out.
I am delighted we are having such a good start to winter with no nasty surprises so far.
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stephenprudence
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Re: First significant cold spell of the season coming right

Post by stephenprudence » Thu Nov 14, 2013 9:56 am

Nigel wrote:The first cold plunge of winter is almost always in the last third of November, perfectly normal weather that. This doesnt look anything as bad as we have seen in recent years , very 90,s look to it, so far greenland block seems to be keeping its nose out.
I am delighted we are having such a good start to winter with no nasty surprises so far.
I don;t associate a pattern shown with the 90s, mainly because the jet is very weak, and it's not a toppler. A week ago models were showing high pressure toppling, and the Atlantic coming back in, however it's change a bit now, to something where the colder airmass sticks around, rather than getting pushed away to the east. So for me this pattern is closer to the last few years than the 90s, but plenty of time for it to change. My other experience with the models is they tend to revert back to a prior scenario from which they originally forecast (despite changing after that original forecast on the way).

So, I'd suggest at current, the initial cold spell at least, is guaranteed, but should only last 3-4 days, then thereafter, a mediating of the northerly, but the introduction of quite, settled with with harsh frost and thick fog (aka inversion time)
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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Re: First significant cold spell of the season coming right

Post by fern Rob » Thu Nov 14, 2013 10:42 am

Bad news for the garden.
Rob
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Re: First significant cold spell of the season coming right

Post by otorongo » Thu Nov 14, 2013 11:20 am

Some moving / fleecing / mulching operation is in order this weekend!

Need to figure out what to do with the in-ground Brugs and Solandra; everything else should be able deal with a night of -2 (as that's what we're forecast for Tuesday night), or is in pots, or I don't care about it.

Wunderground have us for -1 tomorrow night, but all other websites show above 0 temps, so I'll go with the majority icon_thumleft


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Re: First significant cold spell of the season coming right

Post by madgav » Thu Nov 14, 2013 12:55 pm

If I get this I won't be too unhappy :wink:
A long way off still of course and the possibility of it turning out a bit colder should be considered. Doesn't currently look like a swift return to mild conditions either, better this happens now than in January perhaps.....
My winter protection is almost complete and Fri/Sat look like very decent days to finish it :)
Anything left unprotected after that should be more than capable of laughing off a normal winter low of -4/-5C without any further effort on my part.
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stephenprudence
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Re: First significant cold spell of the season coming right

Post by stephenprudence » Thu Nov 14, 2013 5:52 pm

Im starting get a good detailed picture of how this cold spell will affect different parts of the country. I will post an in depth analysis later. Main thought is that western mainland areas should prepare for a bad period
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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Re: First significant cold spell of the season coming right

Post by stephenprudence » Thu Nov 14, 2013 7:28 pm

OK well we're looking down the barrel of a relatively prolonged cold spell, although the cold in most areas will be only containing light frost, there are areas that will see significant frost and cold over the next few weeks.

The situation is that High Pressure will ridge into Greenland allowing a link up between a topologically derived Greenland High and a Blocking Atlantic High. With low pressure sliding down the eastern side, we will get a powerful northerly flow, quickly introducing pure Arctic air from the Svalbard region/Eastern Greenland. This will mean cold air will spread south around early next week, Tuesday(ish).

There will be frost in most areas away from immediate coasts in the south and easts (and exposed north facing coasts). and the possibility of sleet or wet snow in eastern parts (coastal areas), and especially Scotland. For southern and eastern areas, generally frost will be light, typically anything from -2C up to +1C can be expected at the coldest temperature during the spell, largely thanks to a strong wind. Further west however, especially near west facing coasts, it will be very cold, perhaps severe frost here. Places like Prestatyn and Crosby may well record lows in excess of -7C and many other near coastal western areas (except notably mild areas), will also typical get between -4C and -6C.

Thereafter the low pressure becomes northeast flow.. further bad news for western areas, however in the east things should get warmer and more marginal, with more in the way of rain rather than sleet or snow.

Thereafter, the western areas staying cold, and settled with severe/harsh frosts, whilst the east stays cold but windy... at this point there is significant chance of North sea surges, this is something to take particular note of I think.

So In summary, cold outlook, very cold in the west and north, with significant and severe widespread frosts, perhaps worst along western coasts. East, very windy, significant windchill, not as cold technically, but with potential for wintry showers of sleet and snow.
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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Re: First significant cold spell of the season coming right

Post by stephenprudence » Thu Nov 14, 2013 7:56 pm

A map showing potential temperature countours.
temp map..png
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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stephenprudence
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Re: First significant cold spell of the season coming right

Post by stephenprudence » Thu Nov 14, 2013 8:14 pm

temp map..png
Here's a more defined temperature for the Wales region, if anyone wants my thoughts on their region, let me know and Ill give my thoughts.
Heswall, Wirral, UK
USDA equivalent average temperature zone: 9a/RHS zone 3
AHS Heat Zone: 1
Last 5 winter minimums:
2007: -0.1C, 2008: -4.2C, 2009: -5.7C, 2010: -10.5 (record), 2011: -4.9C, 2012: -5.3, 2013: -4.5C (so far)


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Re: First significant cold spell of the season coming right

Post by Delboy » Thu Nov 14, 2013 8:30 pm

How's worcester looking Stephen? I still have plants to dig out for the move but work keeps getting in the way!!
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