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Winter 2019/20 | Moans, Ramps & Chat

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1 minute ago, Ed Stone said:

Is it the usual 9-hours' long, feb?:oldlaugh:

about 23 mins - its right at the end - the last item he discusses - if you ask me the BCC has got the months the wrong war around - can't see that happening in Jan but possible for Feb.

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1 hour ago, carinthian said:

Yes and crazy positive temp anom over much of Europe for the big day. Could be some slushy ski resorts apart from Scotland and Norway.

C

2mtemp_anom_20191215_12_240.jpg

An eye opener that is! 

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1 hour ago, feb1991blizzard said:

about 23 mins - its right at the end - the last item he discusses - if you ask me the BCC has got the months the wrong war around - can't see that happening in Jan but possible for Feb.

Nice to see something positive for a change.  Question is, has it picked up on the correct trend?  I'll be happy if that comes off, be it January or February!

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9 minutes ago, nn2013 said:

It makes a change we're the coldest for once! 

Aye, but rather it was milder in a way, as many areas will see no snow in the uk, south anyway

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Just now, I remember Atlantic 252 said:

Aye, but rather it was milder in a way, as many areas will see no snow in the uk, south anyway

I'm used to it down here anyway. At least it's "normal" for December if such word can be used. 

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By mid January normally down here you would hope to see snow by otherwise panic mode sets in and the days get longer 

But saying that Feb has been good down here in the past 

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Astronomical Spring doesn't start for over 3 months yet and severe cold and snow has even occurred post then (such as 2013). There's loads of time left for a cracking snow event or more before it becomes impossible again until next Autumn. Stay positive folks 😀.

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3 hours ago, Don said:

Nice to see something positive for a change.  Question is, has it picked up on the correct trend?  I'll be happy if that comes off, be it January or February!

Talking January - here is the 79 redux chart.

image.thumb.png.6a7f3607aa5e7051f5d8db1ad0b5e3f9.png

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11 hours ago, Ed Stone said:

Is it the usual 9-hours' long, feb?:oldlaugh:

Dry and long - unlike our winters! 

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This lying snow we have looks like hanging until midweek,very lucky to of had that this month looking at the dominant SWlys all month.

Some frost next 2 nights.

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16 hours ago, hillbilly said:

Your not far from me then,i used to live and work on farms in our area between 1100 and 1200ft above Sowerby being a kid in the 70s.I remember the discussion with a farmer in the late 90s saying I couldn't believe it hadn't snowed before Xmas.Anyway am happy now as it is white on the tops here even though there is none in the valley right now.

I'm now a lowlander in the Vale of York. Hotter summers, frostier winters. No snow drifts while I've been here. I don't know how I'd go on cycling those hills now, especially with fewer good pubs these days!

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The met office have issued a level 2 alert for severe cold weather in North East England, Yorkshire and the Humber between today and Wednesday.

Current alert level: Level 2 - Alert and Readiness

Issued at: 09:04 on Mon 16 Dec 2019

There is a 60% probability of severe cold weather between 0900 on Monday 16 Dec and 1200 on Wednesday 18 Dec in parts of England. This weather could increase the health risks to vulnerable patients and disrupt the delivery of services. Please refer to the national Cold Weather Plan and your Trust's emergency plan for appropriate preventive action.

A brief cold period is likely for much of England from Monday evening through to Wednesday evening, peaking on Tuesday night into Wednesday morning. The required 48-hour duration of 2C is very marginal in this instance, hence the limited areal extent and relatively low likelihoods of the temperature criterion being met. The northeastern English regions of North East and Yorkshire are the last to see the relieving much milder conditions spreading in from the southwest into Thursday, and hence are the only regions included in the alert.

An update will be issued when the alert level changes in any region. Alerts are issued once a day by 0900 if required and are not subject to amendment in between standard issue times. Note that the details of the forecast weather are valid at the time of issue but may change over the period that an alert remains in force. These details will not be updated here unless the alert level also changes, the latest forecast details can be obtained at the following link: http://www.metoffice.gov.uk/public/weather/forecast/#?tab=map 

https://www.metoffice.gov.uk/public/weather/cold-weather-alert/?tab=coldWeatherAlert&season=normal#?tab=coldWeatherAlert

 

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5 minutes ago, Faronstream said:

That would be horrible, it usually takes 4-5 weeks before we see the effects of an SSW so the beginning of spring will be cold like last years. If we don't get one before 10th of january then so be it

No it doesn't - SSW 24th Jan 2009 - London and South Eastern transport network rasberry rippler  8 days later.

Edited by feb1991blizzard

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6 minutes ago, feb1991blizzard said:

No it doesn't - SSW 24th Jan 2009 - London and South Eastern transport network rasberry rippler  8 days later.

Looks like it was very short lived (1-2 days). The longer colder period just affected northern europe and that was from the 10th of february so 2.5 weeks after.

Edited by Faronstream

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struggling to see any improvement on the models today????ec looks at best lame 

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Looks like Sidney's 'brown' Xmas is on track

95923846-sandy-beach-tropical-fruit-and-sunblock.thumb.jpg.ab7c83e29b94c6c4d795ec4aa0d9adde.jpg

Edited by knocker

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Another brilliant in depth blog by Judah Cohen, here are some bits that may be relevant for UK.

"I spent last week in San Francisco attending the Fall AGU and one thing that I was trying to understand was the quasi-biennial oscillation (QBO). I was under the impression that the QBO was in its easterly phase this winter that favors disruptions of the stratospheric polar vortex (PV) in early winter.  The winds along the equator are indeed easterly in the mid to upper stratosphere but are still westerly in the lower stratosphere (see Figure i). Therefore, the QBO influence on the PV is more consistent with a westerly QBO that does not favor a PV disruption in the early part of the winter.  I raise this because our statistical model (which I have acknowledged suffers from too many false positives) and the dynamical weather prediction models all predicted a significant if not major disruption of the PV that failed to verify for early to mid-December.  I think categorizing the QBO this winter as westerly and not easterly helps to place those poor forecasts in context.  It reminds me of early winter 2016/17 when a weakening PV was predicted by the dynamical models to achieve major warming status (reversal of the zonal mean zonal wind from westerly or positive to easterly or negative at 60°N and 10 hPa) but never did and instead the PV quickly spun up contributing to a mild pattern across the Northern Hemisphere (NH) for an extended period.  Westerly QBO favors a strong PV as atmospheric vertical energy transfer is directed towards the tropics and away from the North Pole that favors a strong PV. Still if a major warming is to occur during a westerly QBO winter, it is preferred mid to late winter. 

The QBO phase this winter seems similar to me as in 2017/18 when a major warming occurred in February.  Whether the QBO is easterly or westerly does not change our temperature forecast as it is not currently used as a predictor, though there are studies that argue easterly QBO favors colder winters relative to westerly QBOs.  Still in our analysis on reflective PV disruptions (Kretschmer et al. 2018), it did seem that they are more common in westerly QBO winters, which does favor colder winters in central and eastern North America and has been the pattern so far this winter.  The GFS is predicting a return of blocking in the Barents-Kara Seas so I expect perturbations to the PV to continue into the New Year.

I tweeted out yesterday that the models are predicting colder temperatures to become more widespread across Siberia and wherever you live in the NH mid-latitudes this is something that you should pay attention to, if you are interested in knowing the weather.  On the simplest level cold air that builds in Siberia often discharges to the southeast towards East Asia or west towards Europe.  But even for North America, relatively cold temperatures in Siberia are favorable for more active atmospheric vertical energy transfer that disrupt the stratospheric PV.  The largest PV disruptions can unleash severe winter weather in favored locations for an extended period but especially the more minor PV disruptions that I refer to as “reflective” events that are of shorter duration - favor cold temperatures focused in central and eastern North America.  It does look like such an event is possible the end of December with the surface impacts felt in early January.  So, as I have been saying for years, “Siberia is the refrigerator for the NH” and if Siberia turns cold that increases the risk of cold air outbreaks in East Asia, Europe and even eastern North America.

But that is not the main point that I want to make.  In my mind the best support that the Arctic influences mid-latitude weather is if Siberia experiences a cold winter.  And if high Eurasian snow cover/low Arctic sea ice can contribute to a cold winter in Siberia, then high Eurasian snow cover/low Arctic sea ice can contribute to cold winters elsewhere including East Asia, Europe and the US.  This idea was the main focus of my two talks at Fall AGU.  Most of the critics of the idea that Arctic change (warmer temperatures, less sea ice and I include heavier snowfall) can contribute to colder temperatures in the mid-latitudes argue that any observed cold winters over the past two decades are due to chance (or maybe due to tropical variability) and therefore cannot be attributed to the Arctic.  The main tool to support this argument are the dynamical models that when forced with low Arctic sea ice they do not simulate cold temperatures across the continents.  Therefore, if we observe cold temperatures it is not forced but rather is attributable to randomness in the atmosphere or natural variability.

However, I believe that the warm models and colder observations are not symptomatic of randomness but rather due to systemic errors in the models.  To me the most compelling support of this position is juxtaposing the model forecasts with the observations.  In Figure ii, I show the winter (Dec-Jan-Feb) surface temperature anomaly forecasts from the North American Multi-Model Ensemble (see NMME website) from 2011/12 through 2018/19 on the left and the observed winter surface temperature anomalies on the right.  The forecast temperatures are always warmer than the observed temperatures for the NH.  But sometimes the models do predict cold temperatures across North America but never for Northern Eurasia.  I am assuming this is because in the models, tropical variability (mostly ENSO) can force cold temperatures in North America but not Eurasia.  In the models the only truly important forcing for Eurasia is increasing greenhouse gases (which may include the warming influence of Arctic sea ice loss). Yet despite the model forecasts Eurasia is always observed to be colder than the forecasts, with the one possible exception of winter 2014/15, where any observed cold was regional.

If we can predict that the model forecast will be universally warm for Siberia and that the observations will be colder, then this is less consistent with randomness and more with systemic model errors i.e., the models incorrectly simulate the influence of Arctic forcing on mid-latitude temperatures, or at least Arctic influence is incorrectly overwhelmed  by tropical influence and/or global warming.

What about this winter?  In Figure iii, I present from the C3S (the ensemble of European models – ECMWF, UK MetOffice and Meteo-France made available at Copernicus) forecast for both sea level pressure and temperature anomalies for Nov-Dec-Jan 2020.  I show these three months because we already have a fairly good idea how the forecasts are verifying.  All the models predicted a strong signal for relatively low pressure across the entire Arctic basin and the predictable universal relative warmth across the NH.  I thought the forecasts were especially notable since as I argue all the time in the blog, low sea ice and warm temperatures in the Arctic favor high pressure and not low pressure.  For example, the daily trend of geopotential heights shows increasing pressures in the Arctic troposphere throughout the winter (see Figure iv).I include in Figure iii the observations for Nov-Dec-Jan 2020 through today and so far, the Arctic is not completely dominated by low pressure and the NH continents are not universally warm.  In fact the regions of cold are downstream of the two regions that are warmest in the Arctic - in eastern North America downstream of the warm bullseye in the Chukchi Sea region (presumably aided by below normal sea ice extent) and in Siberia downstream of the warm bullseye in the Barents-Kara Seas region.  This warm Arctic cold-continent relationship was shown by Kug et al. (2015) and others.  I would argue that if the temperature variability across the NH resembles previous analysis related to Arctic warming that is not a random but supportive for a previously constructed argument.  That is why I was excited to see the cold forecasts for Siberia because in my opinion it is consistent with Arctic influence favoring colder temperatures.

Despite the stratospheric PV being displaced, strong and circular circulation exists around the PV center with relatively low heights (Figure 13).  The largest negative temperature departures in the polar stratosphere are over Central and Eastern Siberia, likely supporting the cold temperatures in that region.  Had the strong PV returned to the North Pole in this current configuration, it would likely contribute to a relatively mild pattern across the NH. For now this is not the forecast but a scenario worth considering.The forecast for the troposphere is ridging across Southwestern Europe, much of the Arctic, East Asia, Alaska and the Gulf of Alaska with troughs over the eastern Mediterranean, Central Asia, Eastern Siberia, the Dateline, and central North America (Figure 14).   This pattern favors relatively mild temperatures for Eastern Europe, Western Asia and western North America with seasonable to relatively cold temperatures for Western Europe. Siberia, Northeast Asia, Eastern Canada and the Northeastern US (Figure 15).  The CFS forecast for January has returned to predicting a circulation pattern prediction that projects on to the pattern of variability associated with a negative AO." 

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December 16, 2019 - Dr. Judah Cohen from Atmospheric and Environmental Research (AER) embarked on an experimental...

 

Edited by Kirkcaldy Weather

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