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CreweCold

Crewecold's Winter Lrf

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Ok, I'm throwing myself to the lions here, but this is a bit of a read so I thought I would distinguish it from the other threads i.e the main winter thread. Mods feel free to lock if it's necessary. It is not anywhere as anticipated as Roger and Fred's effort but I have put a bit of work into this so here goes.

Here are my thoughts on the upcoming winter as I promised last month. Factors affecting weather forecast from the period 01.12.2010- 28.02.2011 are as follows:

  • State of the NAO
  • The current La Nina
  • QBO
  • Continued low solar activity
  • Current North Atlantic Sea Surface Temperatures
  • Potential SSW events
Looking at the current long range model output for the period in question sheds little certainty on what the likely winter patterns will be; however at present there is a consistent signal for the winter to open on a below average note in terms of temperatures. This can be misleading however as the below average temperatures could quite easily be as a result of the models picking up on an inversion 'faux cold' scenario a la December 2008, with high pressure sat across the country.
http://www.cpc.ncep..../glbz700Mon.gif
This link shows the likely pressure distributions over the coming months, though I must stress this is just one model. December and January show blocking centred around or just south and east of Greenland which is a good sign if you are looking for snow and cold weather to dominate. However, given the lack of detail this far out it is impossible to say whether a block over Greenland would result in a west based or east based -NAO. By February, the block has slipped to lie across the UK which pretty much backs up the thoughts of Stuart (Glacier Point) If that pressure distribution was to unfold for Feb as seen there, a rex block of some description would probably prevail with settled, dry and cold weather in the south and milder Atlantic weather dominating further north into Scotland and Northern Ireland.
http://weather.unisy...e/sst_anom.html
The link above illustrates the current state of the La Nina fairly well. It has been mooted that a strong La Nina can prohibit the chances of a cold winter; however, the way I am seeing things at the moment is that things are a little bit different this time round. As BFTP (Fred) has stated, we appear have entered the dominant La Nina juncture of the perturbation cycle which hasn't showed its hand for around half a century until recently.
  • Southward Shift of the Jetstream

Since the woeful summer of 2007, the jetstream has been behaving strangely and has presented us with its tendency to migrate further south than has been the case pre 2007. Also showing a tendency to amplify and 'buckle' in places bringing unusual synoptics to some areas (European winter 2009/2010, Russian heatwave, Pakistani floods as obvious examples). This southward shift enables to PF to push further south than might usually be the case and increasing the risk of cold to affect more areas.

The Forecast for Winter 2010/2011

December 2010

(Preliminary Views, made earlier in the autumn and published in the old winter thread)

Characterised by frequency of North to Northeasterly air masses. Strong jet stream forcing depressions to undercut blocking around the Greenland area. Northern Ireland and Scotland often dry but cold- lowest average temperatures for the month. England and Wales are likely to be cold and wet, especially the further southwest you are situated- repeated milder interludes may proceed bands of sleet and snow with the middle part of the country experiencing the greatest instances of snow falling.

CET estimate: 3.5-4.5c = BELOW AVERAGE

Current View

No change in the fundamentals of the forecast. Negative NAO to dominate the month. Characterised by north and northeasterly airmasses (polar and polar continental with some maritime attacks likely at times towards the west and southwest) Stron jet stream will force depressions to undercut blocking around the Greenland area and at times blocking will be forced to the east and west of this area (though likely to remain between 60 and 70 degrees latitude. Scotland looks likely to experience the lowest temperatures as a mean figure throughout the month. England and Wales likely to be unsettled at times (cold and wet) especially the further southwest you are situated; milder interludes will proceed bands of sleet and snow pushing up from a southwesterly direction with the north Midlands and northern England experiencing the greatest instances of frontal snowfall.

CET Estimate: 3-4C = Below Average

January 2011

(Preliminary View)

A month of two halves. A disturbed and cold first half of the month beckons I feel, High pressure centred to the northwest maintains a cold feed but low pressure encroaches from the south at the same time. In between, often frosty and ocassionally very wintry with snow showers and some longer outbreaks of snow towards north east facing coasts especially.

Second half of the month sees things warm up a bit as a tropical maritime airmass encroaches to bring spells of rain and only hill snow to most areas.

CET estimate: 3.2-4.2c = AVERAGE TO JUST BELOW AVERAGE

Current View

I have the least confidence in the weather for January, although I am going to stick to my thoughts that I made originally. See above.

February 2011

(Preliminary View)

After a spell of unsettled weather to finish off January, February is an uncertain month. At the moment I am going for a settling down of the weather, high pressure centred across south east Britain and the Low Countries ensures cold and frosty weather at night but pleasant by day. For Northern Ireland and Scotland, a mild, cloudy Atlantic feed is likely to bring a dull month but also milder temperatures.

CET estimate: AVERAGE

Current View

High pressure is likely to be prevelent over or just to the south east of the country. It is looking like a dry month with fog and frost being the main issues, especially towards central and eastern Britain. It should feel pleasant by day with sunshine levels probably above average and the below average rainfall figures. Northern Ireland and Scotland will see sunshine levels depressed by cloud spilling around the high from the southwest; the Atlantic feed will ensure a dull month here but there will be less of an issue with fog and frost. Towards the end of the month, the high may retreat into the continent allowing slightly more unsettled and milder weather to push down through the country.

CET Estimate: AVERAGE/SLIGHTLY ABOVE AVERAGE

In a nutshell, I believe that the winter will start off on a cold note with strong northern blocking being a hallmark throughout December and parts of January. The northern arm of the jet will really power up later in January and into February, inhibiting the blocking and sending the high further south

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Well thought out and presented forecast CC....alot more along the lines of what I was thinking but still not exactly it. :clap:

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Just a point- the predicted January CET could end up a little bit higher than I have plumped for, though this depends on the extent of the forecast milder spell during the second half of the month- though I do expect some very cold spells within the mix too, so the CET might end up balancing out as suggested in the LRF.

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I'd say the overall forecasts of average/just below average are probably some of the more realistic predictions I've seen thus far in an LRF, hope it goes well for you!

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Good work, we should all get something of our interest, just hope the dull cloudy days are not many but thats what is likely at times. anyway from all the lrf's its likely a cold and at times snowy winter to come with less rain.

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Good Work CC - Looks like you put a lot of effort into your forecast.

Think you could be on the money with this one! :pardon:

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well explained and a lot of work gone into it-result known 1 March!

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I like it CC and I think well thought out and feasible on basis of information available as you have shown. I 100% agree with the jetstream shift and the timing this happened. A lot of us seem to agree early on and indeed we seem very similar for Jan too. Feb is the divergence and is now for me a focal point.

BFTP

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Guest Quantumsnow

Nice work Crewecold, best of luck re verification :good:

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well explained and a lot of work gone into it-result known 1 March!

Yep, come March 1st I think we'll all have a clear idea on how the winter will pan out :lol:

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Well thought out forecast CC, like has been said a bit of something for everyone really :)

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Well explained and laid out, even I understood most of the reasonings behind it. :wacko:

Another forecast I personally would like to occur but you can keep the raw drizzly cloudy, nothing happening type days to yourself. :nonono:

So many forecasts to choose from now, any more to come before winter begins (next week hopefully) :cold:

Wintry Cheers

gottolovethisweather

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Well thought out and presented forecast Crewecold :drinks: .Good luck with it,only time will tell for the detail.

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Interesting read, does make a change from reading cold-colder and snowier still.

Well balanced and understandable.

Well done. May the force be with you :aggressive:

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Thank you CC for an informative and easy to understand weather forecast. Concise, clear and with valid reasons. Iagree with what SP said about any forecast going for cold early and average later is about right IMHO. I do hope March is above average , because after a long hard winter that has already arrived early I will need it.

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thank u cc i wish you luck on a sucessfull forecast.

excellent well thought out lrf and very informative.:drinks:

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Interesting read, does make a change from reading cold-colder and snowier still.

Well balanced and understandable.

Well done. May the force be with you :aggressive:

Yes, well done indeed Crewecold, but no mention of the horrendous snowfalls that Dorset will be getting this year. (well they are overdue, we got 'nuffink' last year!) That's the nearest to a forecast you will get from myself!

Dorsetbred - time to buy your snowchains?dry.gif

More seriously these forecasts do help us novices get a handle on the weight you each apply to the different indicators/factors. Keep up the great work.

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Good effort CC.

I agree generally that I think this will be a front loaded winter.

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