December met office Ensemble-mean maps continues to suggest northern blocking over winter

Am surprised that the met office 3 month outlook didn't receive a very enthusiastic  response.

We have got used to a procession of NAO + winters.

The Meto  outlook is not saying that we are in for a severe winter but it opts for an overall NAO -.

It suggests the highest chances of impacts from cold weather will be later in the winter presumably February.

Looking at the indicators that suggest NAO - we have

1.Moderate ENSO increasing the likelihood of NAO -in late winter.

2.Polar vortex weaker than normal in late winter

3.Stratospheric events increasing  chance of colder conditions later on.

4.Solar minimum which increases likelihood of a weak stratospheric circulation and cold weather weather alter in winter

Indicators that suggest NAO+ we have

1.QBO in westerly phase ,ncreasing likelihood of NAO +Ve

2.Pattern of SST anomalies increases the chance of NAO + conditions in early winter.

Overall it seems a to me there are enough NAO - signals to deliver at least  a couple of cold spells of cold and snow.

If the SSW propagate downward, we could see something after 10/15th of january, thus they are not all very impactful on sensible weather but if the troposphere and stratosphere will be primed for proficient "communication", or "coupled" this season, we could see this happening and a cold 2nd half of January could be on the charts, and even through out February...

Source?

https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-jfm-v1.pdf

Am surprised that this encouraging METO forecast for Jan-March has not recieved more attention.

As expected it looks like my winter forecast has gone bust! At least it stayed on track for most of December.

Bang goes the theory - or maybe the deep cold will eventually arrive, just not as soon - time will tell.

Anyway Happy New Year to everyone on here - here’s to another year of reading some great and interesting posts.

Yes, it is quite a strong signal for cold, but more particularly Feb-March. January the probabilities look quite balanced actually.

Source of what? the SSW or the monitoring charts or analyses?

SSW  occouring

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/ 

Monitoring 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_MEAN_ALL_NH_2018.png

Analyses

 this winter teleconnection and sometimes when the QBO is switching phase for a westerly one (positive) a possible SSW occours and the Polar Vortex weakens and divide propagating to the troposphere with consquences such has a PV split. At this moment it could well be a major SSW event taht could lead to a rising prussure between the North Greenland or Scandy in 15-20 days time.

The gph 10mb profile could not look any better for the UK once it propagates down. The 30 mb profile looks better with every run. Middle of last Feb 10 days prior to beast I said I would not be surprised to see synoptics showing -15c -16c 850 temps showing up and 12 days later they did. 

This time around  the strat profile looks even better and longer lasting. Patience is the key here. There still does not appear to be much evidence in the h500 charts of any ssw downwelling and it may be another 7 to 10 days before we see a consistent trop response to the ssw with a very -AO and abundant high latitude blocking.

Thought Id bring this back to the top 

Always a conundrum with these sorts of things when we all know it’s impossible to forecast the weather with any certainty beyond about 5 days. This of course could mean wintery weather is just around the corner but the models have yet to pick up on it....

Then again.... it might not.

The UK and Ireland is one of the warmest parts of Europe this morning

I'm not moaning (else I'd have used that thread!) but after temps dipped to -3c one night last week, I expected there to be further frosty nights/mornings. But it's not developed that way, and I don't think it's got lower than +2c since. We even had drizzle this morning.

Manchester Winter Index 

Formula:  10 x[(number of days with falling sleet/snow) +(number of days with lying snow at 9am) + (number of days with a minima at or below 0C)]  divided by the mean maximum 

2013-14: 7

2018-19: 11 (up to 12th Jan)

1988-89: 20

2006-07: 21

1997-98: 25

1974-75: 26

1989-90: 26

2015-16: 28

1973-74: 30

1987-88: 37

2007-08: 37

2016-17: 37

1991-92: 40

1975-76: 41

1999-00: 42

1992-93: 43

2002-03: 44

1994-95: 45

1998-99: 47

2004-05: 47

2001-02: 50

2003-04: 50

2005-06: 59

1979-80: 66

1996-97: 72

2000-01: 77

1993-94: 78

1983-84: 82

2014-15: 82

1982-83: 85

1977-78: 90

1980-81: 90

2017-18: 93

1986-87: 100

2012-13: 102

2008-09: 105

2010-11: 119

1990-91: 126

1995-96: 135

1984-85: 140

1976-77: 141

1981-82: 149

1985-86: 159

2009-10: 197

1978-79: 262

Using the same formula as above with an amendment so that I am dealing with the number of official air frosts instead of the number of days where the minimum temperature is at or below 0°C, the Edinburgh Index for the winter of 2018/19 as at midnight going into Sunday 13 January 2019 was 15.4 at Edinburgh Gogarbank and 14.9 at the botanic gardens in Edinburgh.

The met office have issued a level 2 cold weather alert

Current alert level: Level 2 - Alert and Readiness

Issued at: 08:20 on Tue 15 Jan 2019

There is an 80% probability of severe cold weather between 0600 on Friday 18 Jan and 0600 on Monday 21 Jan 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.

 Colder conditions becoming established across the country from Wednesday as a cold front clears southeast, with strong northwesterly winds following. Wintry showers spreading south overnight Wednesday and into Thursday giving a slight snow cover in places, mainly across northern hills, with some icy patches also likely. Winds then fall light overnight Thursday into Friday, with clear spells allowing a widespread frost to develop across the country. Atlantic fronts then try to push in from the west during Friday and Saturday with outbreaks of rain, preceded by some sleet and hill snow, likely to affect SW England and perhaps parts of central southern England, the West Midlands, and northwest England. However, further east remaining cold and dry.

Sunday should see largely dry but cold conditions across most areas, but a further band of rain, sleet or snow may edge into the far northwest later. There is currently significant uncertainty regarding the eastward extent of the precipitation on Friday and Saturday, but any snowfall accumulations look to be small and mostly confined to hills at the present time. There is higher confidence that many northern, central and eastern areas will remain largely dry but cold through the weekend. Trigger criteria are expected to be met for temperatures for northern, central, and eastern regions, with southern areas likely to remain above Alert thresholds for this period. This Alert may be updated later in the week when more certainty emerges in the precipitation detail for the weekend.

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

Amber level 3 cold weather alert issued for North East & North West England.

Current alert level: Level 3 - Cold Weather Action

Issued at: 08:54 on Fri 18 Jan 2019

There is a 90% probability of severe cold weather between 0600 on Friday 18 Jan and 0900 on Wednesday 23 Jan 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.

Cold for many, and remaining sufficiently cold across the northeast and northwest for a level 3 alert, with overnight frosts expected. There is also the potential for some hill snow, mainly Friday and Sunday, and perhaps briefly to lower levels in the north. However temperatures expected to be slightly less cold than recent days in the south, reducing chances of thresholds being reached here. Despite this, further cold weather is expected to return to these parts during the coming week. There is also the potential for a band of heavy rain and snow to move southeastwards across the country overnight Monday and early Tuesday. However confidence in the timing, and the extent of any snowfall remains very low. This alert is likely to be updated Monday morning.

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

London, South East & South West England remain Green which means no cold weather alert is in operation here

Updated cold weather alert

Current alert level: Level 3 - Cold Weather Action

Issued at: 08:41 on Mon 21 Jan 2019

There is a 90% probability of severe cold weather, icy conditions and mostly hill snow between 0900 on Monday 21 Jan and 0900 on Friday 25 Jan 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.

This alert extends the duration of the active alert, issued on Friday 18 January and supersedes it. All regional alert levels remain unchanged, with the exception of Southeast England which is now upgraded from Level 1 (No Alert) to Level 2 (Yellow). The main hazards in this alert period are likely to be widespread ice on Monday night into Tuesday morning, as well as the ongoing low temperatures. While some snow is expected - including sporadic slight falls to low levels - amounts are only likely to be appreciable on high ground, mainly in the northwest. There is some uncertainty in the timing of relieving less cold conditions from the west late this working week.

The present most likely scenario is for a less cold blip of one or two days' duration from Friday. This should come before a resumption of widespread cold to end the coming weekend and probably beyond.

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

SNOW ALERT! No white stuff yet this winter? The wait may soon be over! A significant snowfall is now looking increasingly likely TUESDAY OR EARLY WEDNESDAY. Extent and amount uncertain, but many SOUTHERN & CENTRAL PARTS OF THE UK are at risk. Disruption likely #uksnow #ukwinter pic.twitter.com/8Qcw49AJJa

— weathertrending (@weathertrending) January 27, 2019

Warning for snow has been issued for Tuesday night.

This is a tricky situation and there is still much uncertainty.

It’s currently classed as low likelihood.

So why is there a warning?

Because IF it happens it’d have a BIG impact

So stay up to date#WeatherReady

❄️⚠️👇⚠️❄️ https://t.co/hdjiGkAf0L

— Alex Deakin ⚡️☀️❄️🌧 (@alexdeakin) January 27, 2019

Manchester Winter Index 

Formula:  10 x[(number of days with falling sleet/snow) +(number of days with lying snow at 9am) + (number of days with a minima at or below 0C)]  divided by the mean maximum 

2013-14: 7

1988-89: 20

2006-07: 21

2018-19: 22 (up to 27th Jan)

1997-98: 25

1974-75: 26

1989-90: 26

2015-16: 28

1973-74: 30

1987-88: 37

2007-08: 37

2016-17: 37

1991-92: 40

1975-76: 41

1999-00: 42

1992-93: 43

2002-03: 44

1994-95: 45

1998-99: 47

2004-05: 47

2001-02: 50

2003-04: 50

2005-06: 59

1979-80: 66

1996-97: 72

2000-01: 77

1993-94: 78

1983-84: 82

2014-15: 82

1982-83: 85

1977-78: 90

1980-81: 90

2017-18: 93

1986-87: 100

2012-13: 102

2008-09: 105

2010-11: 119

1990-91: 126

1995-96: 135

1984-85: 140

1976-77: 141

1981-82: 149

1985-86: 159

2009-10: 197

1978-79: 262

Level 3 cold weather alert issued for north-east & north-west England + Yorkshire and the Humber

Current alert level: Level 3 - Cold Weather Action

Issued at: 08:54 on Mon 28 Jan 2019

There is a 90% probability of severe cold weather/icy conditions/heavy snow between 0900 on Monday 28 Jan and 0900 on Friday 01 Feb 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.

Cold weather is expected to continue to affect the country through the coming week with generally northwesterly winds, with the risk highest across the north of the country. Monday and much of Tuesday will be dry and cold for much of the country away from coasts where some showers are likely which could turn wintry and where icy patches are most likely.

A band of rain crossing eastwards across the country later Tuesday and into Wednesday will turn to snow at times to all levels with the some of the greatest amounts across the higher ground of the south and southeast of the UK. The cold conditions are expected to continue through the rest of the week, with bands of rain turning to snow through Thursday and into Friday, although confidence in timing and amounts beyond Wednesday is low at this stage.

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