Jump to content
Cold?
Local
Radar
Snow?

Recommended Posts

Posted
  • Location: Carmarthenshire
  • Location: Carmarthenshire

    Presumably you'd expect some cooling in the northern hemisphere at this time of year due to winter and the lag in ocean cooling compared to the surface? Or is this not the case?

    Not sure about the southern hemisphere though - if my thinking is correct you'd expect warming to show, which those charts don't.

    I also wonder if the colours are a little misleading, because the blue and yellow in the centre of the chart are visibly different but could just relate to small differences depending on whether the temperature is just below or just above the mid-point. Not disagreeing with anyone, just an observation which could explain why the second chart appears to be so much cooler.

    Link to post
    Share on other sites
    Spotted a post you think may be an issue? Please help the team by reporting it.
    • Replies 670
    • Created
    • Last Reply

    Top Posters In This Topic

    Top Posters In This Topic

    Popular Posts

    So, have you ever wondered how exactly would N Atlantic look like if you would pump out all the water? Well, its one big mountain range (MAR - Mid Atlantic Ridge). It gives you a feeling and a differe

    Yeah, I think that's quite a disingenuous chart (no reflection on yourself , of course!).   If we look at the months used in that chart, and the 9 months leading up to them, we get the following:  

    The 13 hours later this arrived..   Many thanks for your enquiry regarding North Atlantic sea surface temperatures. I have spoken to the relevant scientists within the Met Office Hadley Centre who h

    Posted Images

    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL
    1 hour ago, virtualsphere said:

    Presumably you'd expect some cooling in the northern hemisphere at this time of year due to winter and the lag in ocean cooling compared to the surface? Or is this not the case?

    Not sure about the southern hemisphere though - if my thinking is correct you'd expect warming to show, which those charts don't.

    I also wonder if the colours are a little misleading, because the blue and yellow in the centre of the chart are visibly different but could just relate to small differences depending on whether the temperature is just below or just above the mid-point. Not disagreeing with anyone, just an observation which could explain why the second chart appears to be so much cooler.

    They are anomaly charts though, so it doesn't matter. It's the temp difference relative to the long term mean at the same date.

    • Like 2
    Link to post
    Share on other sites
    Posted
  • Location: Carmarthenshire
  • Location: Carmarthenshire
    1 hour ago, Yarmy said:

    They are anomaly charts though, so it doesn't matter. It's the temp difference relative to the long term mean at the same date.

    Thanks for replying - I'd not thought about the date but that makes sense.

    Link to post
    Share on other sites
    Posted
  • Location: Carmarthenshire
  • Location: Carmarthenshire

    Out of interest, when did we last have an Autumn and Winter like this one?

    And was it followed by a particularly dire Spring and Summer (generally speaking)?

    Link to post
    Share on other sites
    Posted
  • Location: Ouse Valley, N. Bedfordshire. 48m asl.
  • Location: Ouse Valley, N. Bedfordshire. 48m asl.

    13/14 felt very like this winter, except that felt stormier as there seemed to be a period of about 5 weeks where a decent low was passing through the country every week. I also had zero snow on the ground, this winter I've had about 10 hours max of more than 50% snow cover so not much better. 

    Link to post
    Share on other sites
    Posted
  • Location: Alston, Cumbria
  • Weather Preferences: Proper Seasons,lots of frost and snow October to April, hot summers!
  • Location: Alston, Cumbria
    On 26/01/2016 at 1:15 PM, ColdFront80 said:

    The kind of set up above has been very common through this winter.

    And that being so, this sizeable chunk of the North Atlantic will be very cold by March.  This means that the seasonal amelioration of cold conditions over North America and Europe by then combined with such a cold North Atlantic is certain to shift the upper trough in the Circumpolar Vortex further East as we go into spring (indeed there are signs of this process unfolding already). This does not bode well for those wanting warm sunny weather! 

    • Like 5
    Link to post
    Share on other sites
    Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL
    On Saturday, February 06, 2016 at 2:39 PM, Buzz said:

    Out of interest, when did we last have an Autumn and Winter like this one?

    And was it followed by a particularly dire Spring and Summer (generally speaking)?

    Last Autumn and Winter was like this one and it was followed by a dire Spring and Summer.

    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: Surrey and SW France.
  • Location: Surrey and SW France.
    On ‎10‎/‎11‎/‎2015 at 10:24 AM, Blessed Weather said:

    Join the experts and respond to the RAPID Challenge 2015

    On 15th October scientists and engineers from the National Oceanography Centre (NOC) leave Southampton for a 6-week expedition on RRS Discovery (IV) to gather the most recent data from the RAPID array of moorings across the Atlantic from Florida to Morocco. The moorings, with sensors that measure temperature, salinity and currents from the sea floor to near the surface, monitor the Atlantic Meridional Overturning Circulation (AMOC) at 26°N.

    The AMOC transports heat northwards in the Atlantic, and is important for the climate of Northwest Europe.  Recent studies indicate that it is decreasing in strength, and the decline in heat transport has been implicated in the formation of a 'cold blob' in the North Atlantic.  

    If you read this and want to have a go at your own ocean prediction, you are very welcome to download the data, carry out your own analysis, and let us have your own estimate. The deadline for submission is 31st December 2015.  In early 2016 a preliminary analysis of the new data will be available. The estimates that come closest will be published on the RAPID website…..

    Joint winners ..

    The lowest RMSE was the prediction of Leon Hermanson from the UK Met Office. The only prediction to have skill in both of the first two quarters was the entry by Daniela Matei and Helmuth Haak from the Max Planck Institute. These two entries are declared to be joint winners and will each receive a Discovery mug. Congratulations!

    http://rapidchallenge2015.blogspot.co.uk/2016/01/joint-winners-of-rapid-challenge.html

     

    • Like 3
    Link to post
    Share on other sites
    • 3 weeks later...
    Posted
  • Location: Surrey and SW France.
  • Location: Surrey and SW France.
    5 hours ago, knocker said:

    The sensitivity of the Atlantic meridional overturning circulation to enhanced freshwater discharge along the entire, eastern and western coast of Greenland
    http://link.springer.com/article/10.1007%2Fs00382-015-2651-9

    A recent related paper and open access.

    http://www.nature.com/ncomms/2016/160122/ncomms10525/full/ncomms10525.html

    Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning circulation.

    The Atlantic Meridional Overturning Circulation (AMOC) is an important component of ocean thermohaline circulation. Melting of Greenland’s ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.

    • Like 2
    Link to post
    Share on other sites
    Posted
  • Location: Newcastle Upon Tyne (Spital Tongues)
  • Weather Preferences: Cold, Snow, Windstorms and Thunderstorms
  • Location: Newcastle Upon Tyne (Spital Tongues)
    2 minutes ago, knocker said:

     

     

    Klotzbach and Gray used just the SSTs from 50 to 60°N and 50-10°W, with air pressure over the rest of the southern segment of the north Atlantic for their AMO index, so it's quite different to what we generally consider the AMO. The paper describing their method is here https://www.researchgate.net/profile/Philip_Klotzbach/publication/242473734_NOTES_AND_CORRESPONDENCE_Multidecadal_Variability_in_North_Atlantic_Tropical_Cyclone_Activity/links/00b4952b4eda19fed4000000.pdf

    It's also in stark contrast to the NOAA version, which was the second high on record for January, and it usually doesn't vary much from one month to the next.

    http://www.esrl.noaa.gov/psd/data/correlation/amon.us.data

    • Like 2
    Link to post
    Share on other sites
    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

    Yes, the conventional AMO is a weighted average from 0N to 70N of the SST data:

    http://www.esrl.noaa.gov/psd/data/timeseries/AMO/

    If we compare the anomalies mid-Jan 2014 (AMO -0.046) with mid-Jan 2016 (AMO 0.247), then 2014 has the "horseshoe" shape which I believe is more indicative of a negative AMO.

    Jan 2014

    anomnight.1.15.2014.gif

     

    Jan 2016

    anomnight.1.14.2016.gif

    The much stronger positive anomalies in the tropics are also evident; presumably a consequence of the super El Nino.

    Meanwhile, the current NOAA SST anomaly:

    anomnight.3.3.2016.gif

    I have some suspicions about this chart. There was a change in methodology at the end of Jan:

    http://coralreefwatch.noaa.gov/satellite/messages/announcement20160201_b50.php

    The Antarctic anomalies in particular are starkly different from those shown in the new high-res daily global 5 km Blended Night-only SST Analysis as described in the link above:

    cur_b05kmnn_ssta_large.gif

    Obviously there is a difference in the climatology baseline against which the SSTs are being measured, but it's not clear what it is.

    Edit: Corrected year.

     

     

    Edited by Yarmy
    • Like 2
    Link to post
    Share on other sites
    On 2/5/2016 at 9:55 PM, Yarmy said:

    I doubt it because again I'm not sure what (significant) influence the SSTs could have on the longwave patterns which ultimately determines our weather. 

    There's been a pretty remarkable change in the NOAA SST anomaly chart between the 28th Jan and 4th Feb:

     anomnight.1.28.2016.gif

    anomnight.2.4.2016.gif

     

    I'm not quite sure what to make of it. Notably, the strange extreme cold anomaly over the Gulf of St Lawrence has disappeared and now agrees with the SST analyses from other sources.

    The large change in just a week from end of January to start of February is because the anomaly is calculated using monthly mean SST -

    Quote

    The SST anomaly field (degrees C) is the difference between the 50 km nighttime-only SST and the nighttime-only monthly mean SST climatology. The climatology is based on nighttime observations from 1984-1993, with SST observations from the years 1991 and 1992 omitted due to aerosol contamination from the eruption Mt. Pinatubo in June of 1991.

     

    Link to post
    Share on other sites
    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL
    37 minutes ago, Interitus said:

    The large change in just a week from end of January to start of February is because the anomaly is calculated using monthly mean SST -

     

    It doesn't matter; the calendar month boundaries are irrelevant. Why? Because the Daily SST climatology is a weighted average for both January and February. The monthly mean SST used in the anomaly is the average of the SST on the 15th of the month taken from 7 years of satellite data. The daily SST climatology used in the SST anomaly calculation at a given date is then interpolated from the two monthly means on either side of it.  

    For example, say the monthly mean SST climatology for Jan 15th is J and the monthly  mean  SST climatology for Feb 15th is F.

    For an arbitrary grid point, the SST anomaly for Jan 28th is given by:

    A = SST - ((13/31) * (F-J) + J)

    The SST anomaly for Feb 1st is given by:

    A = SST - ((17/31) * (F-J) + J)

    So the daily SST climatology is a weighted average of the 2 surrounding month means, and consequently you therefore get a smooth progression over time and no abrupt changes at calendar month boundaries. That's not happens between the 2 dates above though, so the conclusion is that the method of calculating the monthly mean SST changed in Feb and therefore we should now be cautious when comparing current NOAA SSTA charts with those in previous years.

    N.B The actual climatologies are available on the CRW website, but I can't get ncview to open the HDF files on my computer.

     

    • Like 3
    Link to post
    Share on other sites
    1 hour ago, Yarmy said:

    That's not happens between the 2 dates above though, so the conclusion is that the method of calculating the monthly mean SST changed in Feb and therefore we should now be cautious when comparing current NOAA SSTA charts with those in previous years.

     

    Ah just dived into middle of thread and didn't read previous post about methodology change, my bad.

    It was obviously something to do with the baseline climatology and it would be stupid not interpolating the monthly mean but their brief description didn't mention it so without the climatology change it seemed the only explanation.

    Edited by Interitus
    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: Slovenia, Central Europe 1050m ASL
  • Location: Slovenia, Central Europe 1050m ASL

    Yarmy explained one major problem why using monthly climatologies for daily data is not really recommended if you want good details. but if you just want a fast overview, its not that bad.

    That is why I usually use daily mean climatologies for daily mean analysis. The most common example that I use is the UKMOs own OSTIA 0.05° SST analysis, which is an L4 product.  

    Some examples I made today for twitter:

    sstanomaly-in-metoffice-.png  sstanomaly-in-metoffice-.png  

    sstanomaly-in-feb20anom.png   sstanomaly-in-metoffice-.png  

    • Like 4
    Link to post
    Share on other sites
    • 2 weeks later...
    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

    Mechanisms determining the winter atmospheric response to the Atlantic overturning circulation

    http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0326.1?af=R

    Quote

    In climate models, an intensification of the Atlantic Meridional Overturning Circulation (AMOC) precedes a warming in the North Atlantic subpolar basin by a few years. In the IPSL-CM5-LR model, this warming may explain the atmospheric response to the AMOC observed in winter, which resembles a negative phase of the North Atlantic Oscillation (NAO). To firmly establish the causality links between the ocean and the atmosphere and illustrate the underlying mechanisms in this model, ensembles of atmosphere-only simulations are conducted, prescribing the SST and sea-ice anomalies that follow an AMOC intensification. In late winter, the North Atlantic SST and sea-ice anomalies drive atmospheric circulation anomalies similar to those found in the coupled model. Simulations only driven by the SST anomalies related to the AMOC show that the largest oceanic influence is due to the warm subpolar SST anomaly, which enhances the oceanic heat release and decreases the lower-tropospheric baroclinicity in the region of maximum eddy growth, resulting in a weaker meridional eddy heat flux in the atmosphere. The transient eddy feedback leads to a negative NAO-like response. An AMOC intensification is also followed by less sea ice over the Labrador Sea and more sea ice over the Nordic Seas. The simulations with full boundary forcing suggest that such anomalies act to strengthen both the poleward momentum flux and the upward heat flux into the polar stratosphere, and lead to a stratospheric warming, which then reinforces the negative NAO signal in late winter.

     

    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: Slovenia, Central Europe 1050m ASL
  • Location: Slovenia, Central Europe 1050m ASL

    Comparing past winter with the last super nino winter of 97/98, we see ho much stronger the eastern nino regions were in 97/98. we can also see how this winter we had much cooler Atlantic, from the tropics all up to the north. 

    analysedsst-in-16.png

    And if we look at March so far, last 23 days mean, we see the Atlantic difference even more, with a very "-AMOish" signal appearing when comparing it to 1998. But it is also generally cooler north of tropics when compared to last year. 

    analysedsst-in-166.png  analysedsst-in-1d66.png

    And March so far this year. 

    sstanomaly-ixn-djf.png

    And last 7 days of March versus first 7 days. we can see SSTs have cooled off a bit north of tropics. But what stands out the most is the typical positive IOD phase signature. 

    analysedsst-in-y1d66.png

    • Like 2
    Link to post
    Share on other sites
    Posted
  • Location: Slovenia, Central Europe 1050m ASL
  • Location: Slovenia, Central Europe 1050m ASL

    Speaking of cooler Atlantic, I have done quite a few meridional cross sections across the Atlantic. it is all on my twitter since its too much to share here, but one for the feels of it. 

    ctemperaature-in-globals.png

    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    https://www.wunderground.com/blog/JeffMasters/the-north-atlantic-blob-a-marine-cold-wave-that-wont-go-away

    A nice summary of much of what has been discussed in this forum over the past year or so, including the findings of the RAPID project.

    A slowdown if the AMOC is strongly suspected, but the cause is not clear. Meltwater from Greenland seems a strong candidate. The NAO could have played a role, but having tended positive for several winters now, the theoretical link with the AMOC seems to have been jeopardised somewhat.

    Link to post
    Share on other sites
    Posted
  • Location: Ashbourne,County Meath,about 6 miles northwest of dublin airport. 74m ASL
  • Weather Preferences: Cold weather - frost or snow
  • Location: Ashbourne,County Meath,about 6 miles northwest of dublin airport. 74m ASL

    sst_anom-160410.gifDont know how accurate these charts are but the cold pool has grown a bit more in the last month. I suppose to be expected at this time of yr being still in the first half of spring.sst_anom-160313.gif

    Link to post
    Share on other sites
    • 2 weeks later...
    Posted
  • Location: Hadleigh, Suffolk
  • Weather Preferences: An Alpine climate - snowy winters and sunny summers!
  • Location: Hadleigh, Suffolk

    Here's a quick update on the Cold Pool area that I've been monitoring using NOAA NCEP Data Reanalysis.

    The SST for Jan, Feb and Mar 2016 has continued to run below the long-term 1948-2016 mean. The Cold Pool reached its coldest point of the winter in February, with a temp of 8.5C (versus the long-term mean for Feb of 9.1C). This February's figure is the second coldest Feb in the NCEP dataset that runs from 1948 to date. Only Feb 1990 was colder at 8.4C. This current Cold Pool has now been running below the long-term mean since Nov 2014, a period of 17 months.

    The area of the Cold Pool being monitored (courtesy BFTV) BFTV Cold Pool.png

    Graph showing Mthly Temp for 2015, 2016 & long-term mean N Atlantic Cold Pool Graph Mar2016.jpg

    • Like 2
    Link to post
    Share on other sites

    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now
    ×
    ×
    • Create New...