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

Tom2006
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Re: First significant cold spell of the season due 18th Nov

Post by Tom2006 » Wed Nov 20, 2013 11:59 pm

Nigel with all due respect stephen is posting these warnings in good faith. They may eventually come to pass as lesser cold spells but much better to warn everyone and for it not to be as bad as feared than the other way around. He certainly isnt anything like those on the crazy weather forums. I admit to reading such forums as they do have the odd knowledgable person amongst the crazy cold loving people who most likely mess themselves at the sight of cold in the weather models at two weeks out. :roll: :lol:
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Re: First significant cold spell of the season due 18th Nov

Post by stephenprudence » Thu Nov 21, 2013 12:02 am

I think you're overreacting on something that doesn't require that response perhaps, Nigel. If you're getting down about our weather, then how can you find gardening enjoyable?.. and anyhow, is it not an exciting time when we have challenge of protecting plants against a cold spell? Gardening is like a game in my opinion, it's a challenge, you choose to do it, no one's forcing you to, and if people can't accept the potential for cold weather and the fact it happens, or have the potential to happen, how can anyone enjoy gardening at all with these ideas? Our weather might be depressing at times, but the beauty is that it's always on a knife edge so we really do have a stab at growing tender plants, but on the other hand we might lose them.

Yes I do worry for my plants when it gets cold, everyone does, but the challenge of looking after them, and being faced with cold etc, is fascinating. It is a challenge, that cannot be questioned, because we choose it to be that way.. A garden without a challenge would be a garden just like any other, but the weather dictates our style more than any other

As a community, one of things we do is help each other out, and that includes on this forum weather warnings for potential cold etc. The post I said above was my opinion, and also not a fact but potentially true, it may also eventually not come to that. But it is my opinion, the beauty of opinion is no one has to take it, they can choose to ignore it, but an opinion shouldn't really glean the response you made. It may be (and I accept this fully), I did not make it obvious that it was my opinion, in that case it was only my opinion and not fact.

Lets leave this to this because we don't need to argue over something we should actually be coming together to work out, not divided.
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USDA equivalent average temperature zone: 9a/RHS zone 3
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Last 5 winter minimums:
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Re: First significant cold spell of the season due 18th Nov

Post by Nigel » Thu Nov 21, 2013 9:26 am

Stephen its the second time you have told me I dont know what i am talking about.
You display lots of technical knowledge but dont seem to know that being on the warm side of the jetstream and under influence of the azores high is GOOD. At least it always has been as long as I have been following weather. You then give me a lecture on 3 things i can do if I dont like your posts, so there it is.
I have been saying all month in response to your warnings of impending doom that the weather is normal and getting hammered for it.
Yet, Hadley CET anomoly is 0.1C above normal for November so we are exacly 0.1C above average ,in other words the weather has been exactly normal as I have been saying all month.
To be honest i think the person with the weather problem is you, i admit long winters get me down, but I dont fly into a frenzy every time the temperature approaches zero and warn everybody the end of the world is nigh. I am able to rationalise it , something you need to do yourself before posting.
Winter has not even started yet, there has been nothing to sensationalise ,thats the worst thing about it.

Anyway, this will be my last post on weather , I am not going to spend winter being told i dont know what i am talking about by a cold ramper. I am sensible enough to know the greenblock can form any time and things can change for the worse, and that concerns me more than anything else, i have a lot more to lose than you if it does.

I have tried to write this in a friendly way, no offence is intended and I apologise in advance if you see it that way.
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Re: First significant cold spell of the season due 18th Nov

Post by pdid » Thu Nov 21, 2013 10:02 am

Jeez you two are worse than my 5 and 2 year olds!!!

My 2p, Stephen, you make a good contribution to the forum especially at this time of year but you do have a tendency to over egg it, possibly down to a touch of inexperience.

Nigel, you have the experience of watching the weather systems for many years so can make more rationalized forecast based on that experience.

I think I speak for most forum members by saying that I enjoy both of your forecasts and I take both forecasts into account when judging what protection I need to put in place. You can't get it right all the time, even the pro's at the met office don't!

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Re: First significant cold spell of the season due 18th Nov

Post by stephenprudence » Thu Nov 21, 2013 10:10 am

Well Nigel, your choice however had Nigel agreed to reconcile, he would have seen that my next post actually suggests maybe the Azores high could be a genuinely warm one by mid next week. As well as the unfavourable cold option, there is a warmer option now... This however would not be great news for our Central European counterparts. Good news for Britain if it were to verify. Actually for the first time this scenario has visual support.

So after a week of frosts in sheltered western areas, it should become mild and perhaps stay dry as well?

Lastly I'd like to clarify I am not a cold ramper.. I would not be growing exotics if I was icon_scratch
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 due 18th Nov

Post by stephenprudence » Thu Nov 21, 2013 10:55 am

Maybe if I posted charts images and explained it would be better? I wouldn't post anything unless there was potential for it.

Why the flip in the coin this morning, well here's why.. the original outputs were showing the polar Vortex (which is collection of low pressure around Greenland), splitting over Greenland and allowing High Pressure to build.. if we get this scenario it usually = northerlies, either temporarily or something more permanent if a link is made between the high over Greenland and the high over the Atlantic (hence the name block).. once this happens it can be difficult to shift due to warm air advection (thats warm air being pumped up the western side of high pressure from the eastern side of low pressure, if that makes sense. If warm air advection (warm air being pumped into the high) on one side is strong, and cold air advection on the other side is strong, it will make a very strong high..

However the outlook is better because there is low pressure to the immediate south of the Greenland High.. when the Greenland can't form properly, it is known as the anomalous plateau high (the high pressure is restricted to altitude, and cannot cause blocking as the low pressure to the immediate south is causing the Cold air advection to fail)..

So with the Greenland High unable to link, it means the Azores High can ridge. Nigel will be correct if that scenario comes off, and well spotted if it does. I personally find these situations too difficult weigh up by experience, but if Nigel can then I'd be inclined to go with his prediction rather than mine.

Next Tuesday we see this favourable pattern start to kick in.. bare in mind this is, on the models, a new evolution of the pattern, one to be fair I wasn't expecting in all honesty, but one that seemingly will occur? No guarantees, and if that low gets removed from the south of Greenland it could look much different.

Image

Here's the chart for next Tuesday.. great chart for us, High pressure but bringing NWlies off a relative warm ocean, warm airmass. At this point the Vortex is still over Greenland, it's shown by the deep blue shading in that area.. the deep blue represents the Polar Vortex.. not the temperature as such, but it depends.

Image

By Thursday, you see the PV has split and allowed the 'plateau high' to develop, but look at the small low pressure to the immediate southwest, it's preventing both warm air advection (which would be orange colours going up the west side of Greenland), and cold air advection (deep blue colours going down the east side of Greenland) Therefore High Pressure cannot act as a block, and is hemmed into Greenland.

Image

A day later and we see whilst the Greenland plateau high is still there, the lack of a link up to form blocking, has allowed more low pressure to build to the southwest of it, this will be the start of Atlantic zonality, and a mild outlook, should it occur.
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 due 18th Nov

Post by Tom2006 » Thu Nov 21, 2013 12:49 pm

Thats a sight for sore eyes. I can hear my garden singing!
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Re: First significant cold spell of the season due 18th Nov

Post by cordyman » Thu Nov 21, 2013 1:21 pm

I value both Nigel and stephens forcasts.

But I'm in the wrap it for narnia camp, so whether I get minus 12 or plus 5, doesn't change my protection methods. I won't be back in the garden protecting now unless heavy snow is forecast, and that will just be a quick sanity check, to assess the various protection.

It's now 10 c and pretty mild. I doubt this cold snap can reach any super cold levels. It's all about using common sense, rationale, and perspective. And for late November things are looking alright at the moment.


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Re: First significant cold spell of the season due 18th Nov

Post by Nigel » Thu Nov 21, 2013 3:32 pm

Stephen , there is almost always high pressure showing over Greenland , and I have learnt to ignore it for all intents and purposes as long as you have low pressure to west of Iceland.
The low pressure to west of Iceland is an almost permanent feature of our weather , and it is from this low that other lows spin off and head our way.
Now, if you look back at 2009/2010, and all the recent greenland blocking spells since , including the spring of 2013 that never happened, a common feature of all those charts is the low pressure to west of iceland goes AWOL.

In short , low pressure to west of iceland is an EXTREMELY solid indicator of mild weather and positive NAO and as long as it can be seen there, you should not have to worry about severe cold. If that low pressure goes AWOL then my alarm bells start to ring, and you can be pretty sure you will have something to worry about in the near future, because it will inevitably mean the jetstream diving south towards Spain and polar air plunging south towards us.
I do not look at any temperature charts because they are self defeating. It should be fairly easy to predict temperatures just from looking at an overrall chart and applying it to the time of year.
At times the low pressure can disappear from west of iceland and reappear in the next model. Panic time comes when it disappears 10 days out and stays disappeared for a couple of days.
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Re: First significant cold spell of the season due 18th Nov

Post by Dave Brown » Thu Nov 21, 2013 4:41 pm

I wouldn't trust a 10 day model further than I could throw Europe. They are right maybe 10% of the time, but mostly are superseded as the runs become more accurate. For me personally I take no notice until the Met Office is prepared to nail it's colours to the mast, normally the 5 day, but still don't believe it fully until confirmed in the 48 hour.

I prepare for winter by having things available and checked once in October, then I wait, and wait, and wait while the models forecast doom 50 times over, and still await the 48 hour forecast to tell me to act.

My weather glass is always half full, as I find winter so depressing I daren't have a half empty one. :roll: I get what I get and take it ok, but can't stand to dwell on the worst if it ain't gonna happen. Giving a 10 day/model outlook is fine if you temper that with your expected success rate, from 0 to 100% certain, but I find the constant references to cold on it's way quite depressing, especially when 90% of the time it doesn't materialise. There is a crying of wolfe, as if constantly warned and nothing happens, you are far less likely to react correctly when it really happens.

The US Hurricane forecast is one instance where they play down until things are almost certain, as if they kept giving evacuation orders without good reason, when that big one was about to hit, no one would take any notice. Same is true of Hawaii tsunami warning. They only get 1/2 notice as they have to be sure one is on it's way.
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Re: First significant cold spell of the season due 18th Nov

Post by madgav » Fri Nov 22, 2013 8:30 am

Stephen & Nigel, thanks for two very informative posts icon_thumleft
I always wondered about all the talk of Greenland blocks when there always seemed to be high pressure over Greenland icon_scratch
Appreciate the warnings about upcoming cold spells but I think they should be kept until the spell is within the reliable time frame (5-7 days?).
And I also find the winter depressing icon_thumbdown
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Re: First significant cold spell of the season due 18th Nov

Post by otorongo » Fri Nov 22, 2013 9:25 am

I see 10-11C highs and 6-8C lows from Wednesday next week icon_thumleft


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Re: First significant cold spell of the season due 18th Nov

Post by Dave Brown » Fri Nov 22, 2013 9:28 am

otorongo wrote:I see 10-11C highs and 6-8C lows from Wednesday next week icon_thumleft
Wish I had your crystal ball :lol:
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Re: First significant cold spell of the season due 18th Nov

Post by Nigel » Fri Nov 22, 2013 2:58 pm

otorongo wrote:I see 10-11C highs and 6-8C lows from Wednesday next week icon_thumleft
Yes the azores high wants to push in, and those are the temperatures it would be expected to bring, but the azores high is warm moist air, so whilst it keeps us warm, at night with clear skies that nice warm moist air quickly turns to dense fog , so those temperatures are likely to be spoiled by fog and cant be relied upon. Nevertheless it should be dry and above freezin and generally mild.
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Re: First significant cold spell of the season due 18th Nov

Post by Dave Brown » Fri Nov 22, 2013 3:39 pm

Dave Brown wrote:
otorongo wrote:I see 10-11C highs and 6-8C lows from Wednesday next week icon_thumleft
Wish I had your crystal ball :lol:
Having looked at my crystal ball, I can't see it happening. :roll:

I was expecting to see the high transfer from the west to the southeast, to give mild sw flow, but no, it is just to the west of Ireland next wednesday If anything the jet has strengthened from NE so is likely to be the same as today, maybe 8C with 5C min :roll:
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