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uniquorn

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Re: The 2019 melting season
« Reply #500 on: April 21, 2019, 04:29:20 PM »
50 days of ascat hopefully working better for mac users
Thanks to Sleepy for the ffmpeg conversion.

oren

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Re: The 2019 melting season
« Reply #501 on: April 21, 2019, 08:11:18 PM »
It seems that in the last week or two the movement of thick old ice towards the Atlantic has stalled. Good news, especially if it continues like this.

Neven

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Re: The 2019 melting season
« Reply #502 on: April 21, 2019, 09:33:50 PM »
It seems that in the last week or two the movement of thick old ice towards the Atlantic has stalled. Good news, especially if it continues like this.

Maybe not so much towards Fram directly, but the forecast is for some ice to get shoved towards Franz Josef Land a couple of days from now. Pressure remains (very) high over the Pacific side, with a very narrow band of isobars in the coming three days, which will inevitably continue to pull the ice in the Beaufort Sea westwards, furthering disintegration in Amundsen Bay, and causing more open water that I'm not sure will re-freeze that well anymore (see animation of the region for the past 5 days, below the forecast).

I expect this weather to abate come May, as it usually does, but if it doesn't, the Pacific side is going to take a serious beating.
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Tor Bejnar

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Re: The 2019 melting season
« Reply #503 on: April 21, 2019, 10:44:04 PM »
Uniquorn's 50-day movie reminds me of the report (maybe in a publication referenced in Icy Seas years ago?) that in 2007 (a year where Nares Strait never closed) Nares Strait ice export was 10% of that of Fram Strait. 
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bbr2314

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Re: The 2019 melting season
« Reply #504 on: April 21, 2019, 10:45:22 PM »
Yikes!


Neven

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Re: The 2019 melting season
« Reply #505 on: April 21, 2019, 11:05:07 PM »
Yikes!

8 days from now. Please, try to emphasize when you post forecasts beyond 6 days, because they're unreliable, and the writing on that map is small.
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DavidR

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Re: The 2019 melting season
« Reply #506 on: April 22, 2019, 02:01:40 AM »
Yikes!
What is a Yike  ;D and how does it relate to that image? I  presume you  are expecting  something dramatic but have no idea what it is.  :o
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bbr2314

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Re: The 2019 melting season
« Reply #507 on: April 22, 2019, 03:16:10 AM »
Yikes!
What is a Yike  ;D and how does it relate to that image? I  presume you  are expecting  something dramatic but have no idea what it is.  :o
As Neven said it is 8 days out, but the map shows a major low pressure system impacting the Bering, Chukchi, and Beaufort with +0C warmth and significant wind, waves, and likely rain as well.

Rodius

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Re: The 2019 melting season
« Reply #508 on: April 22, 2019, 03:59:52 AM »
Given the unreliable nature of forecasts beyond 5 days, why use them?

bbr2314

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Re: The 2019 melting season
« Reply #509 on: April 22, 2019, 04:13:00 AM »
Given the unreliable nature of forecasts beyond 5 days, why use them?
You don't have to! It isn't like the EURO is the most reliable forecast model on the planet and usually within the ballpark from days 6-10 even if details change substantially. It is currently indicating a heightened probability for the aforementioned LP / melt event to occur, ignore it if you  please.  :)

jdallen

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Re: The 2019 melting season
« Reply #510 on: April 22, 2019, 05:06:52 AM »
The EURO has been hinting at dual 500MB blocks over the NPAC / Bering and Greenland and tonight's 00z run certainly ups the ante re: Bering...!
There really isn't anything *left* in the Bering.

I'm more concerned about the Chukchi.

(Image from the Bering 2 days ago added for emphasis)

And yes, 6-10 days out, however great the service is still outside the event horizon as far as any ability on our part to reliably make assumptions is concerned.

BBR, please be patient.  Things are evolving.  We really don't have a sense of just how bad it will be yet, and we are far from really being able to see a sensible trend in the central basin, or even in the directly adjacent seas.
« Last Edit: April 22, 2019, 05:13:36 AM by jdallen »
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sark

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Re: The 2019 melting season
« Reply #511 on: April 22, 2019, 06:12:23 AM »
Given the unreliable nature of forecasts beyond 5 days, why use them?

Why produce them?  Because they are useful
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Viggy

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Re: The 2019 melting season
« Reply #512 on: April 22, 2019, 06:51:39 AM »
Yikes!
... it is 8 days out, but the map shows a major low pressure system impacting the Bering, Chukchi, and Beaufort with +0C warmth and significant wind, waves, and likely rain as well.

'Yikes' obviously garners more sensationalist attention (whatever the purpose of that is), than a reasoned explanation of a complicated image (which bbr is also capable of providing).

Rodius

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Re: The 2019 melting season
« Reply #513 on: April 22, 2019, 06:57:24 AM »
Given the unreliable nature of forecasts beyond 5 days, why use them?

Why produce them?  Because they are useful

They can produce them and improve on them, but seeing them time and time again on here is confusing and then the prediction dont get measured against the eventual outcomes.

I am all for predictions, just not ten days out using unreliable tools.
I would rather see a thread for ten day projections that marries up the forecast then compares the forecast to what eventuates just to have a clear example of how good they are. That way it becomes clear just how good or not they are.

At worst, at least state at the top of the post that the projection is beyond 5 or 6 days so I can skip right past them.

Grip over with :)
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El Cid

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Re: The 2019 melting season
« Reply #514 on: April 22, 2019, 10:49:29 AM »
This is from the ECMWF site:

https://confluence.ecmwf.int//display/FUG/4.1+Forecast+Error+Growth

"Small baroclinic systems or fronts are currently well forecast to around Day2, cyclonic systems to around Day4 and the long planetary waves defining weather regimes to around Day8.  As models improve over time these limits are expected to advance further ahead of the data time.  Features that are coupled to the orography (e.g. lee-troughs), or to the underlying surface (e.g. heat lows), are rather less consistently well forecast."

In this sense brr is right: although the details will change, but major weather-systems - according to ecmwf - are USUALLY forecastable for 8 days.

To check the standard deviation between the ensemble members, ie. to see how reliable the forecast is, ECMWF shows this as well with colours:

https://www.ecmwf.int/en/forecasts/charts/catalogue/plot_ensm_essential?facets=Range,Medium%20(15%20days)&time=2019042112,120,2019042612&parameter=MSLP&area=Northern%20Hemisphere


El Cid

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Re: The 2019 melting season
« Reply #515 on: April 22, 2019, 11:06:49 AM »
Two more charts about the reliability of forecasts if you don't mind:

1.500hpa geopotential is quite reliable for 6-7 days:

"The plot shows for each month the range at which the month mean (blue line) or 12-month mean centred on that month (red line) of forecast anomaly correlation dropped below 80%. The score for the northern hemisphere extra-tropics is a primary headline score of the ECMWF HRES.

Anomaly correlation scores are spatial correlation between the forecast anomaly and the verifying analysis anomaly; anomalies are computed with respect to ERA-Interim-based climate. Verification follows updated WMO/CBS guidelines as specified in the Manual on the GDPFS, Volume 1, Part II, Attachment II.7, Table F, (2010 Edition - Updated in 2012)."

2. 850 hpa temps are somewhat reliable until day8/9:

"The plot shows for each month the range at which the 3-month mean (blue line) or 12-month mean (red line) centred on that month of the continuous ranked probability skill score of the 850hPa temperature ENS dropped below 25%. This is a primary headline score for the ECMWF ENS.

The continuous ranked probability score (CRPS) compares the probability distribution of the quantity forecasted by ENS to its analysed value. Both forecast and analysis are expressed by cumulative distribution functions. The CRPS skill score then compares CRPS of the verified forecast to a reference unskilled forecast. As a reference forecast the re-analysis-based climatology is used."


Neven

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Re: The 2019 melting season
« Reply #516 on: April 22, 2019, 12:30:00 PM »
The Uni Bremen SIC maps page seems to have disappeared. Does anyone know if it has been moved?
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oren

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Re: The 2019 melting season
« Reply #517 on: April 22, 2019, 12:33:33 PM »
I use this link, it's still working but the images of the last 3 days appear as broken icons for some reason.

https://seaice.uni-bremen.de/databrowser/

gerontocrat

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Re: The 2019 melting season
« Reply #518 on: April 22, 2019, 12:41:56 PM »
I also use https://seaice.uni-bremen.de/sea-ice-concentration/ and its working OK (Windows 10 and Google)
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uniquorn

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Re: The 2019 melting season
« Reply #519 on: April 22, 2019, 12:51:17 PM »
uni-bremen smos ftp stops latest data is apr17

On a positive note, ice continues to be compacted into the triangle north west of Greenland.
Worldview terra modis apr1-21. Heavy contrast to show fractures. A faster frame rate helps to look 'through' the clouds. (11days/sec)
edit: replaced gif with mp4
« Last Edit: April 22, 2019, 02:26:52 PM by uniquorn »

sark

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Re: The 2019 melting season
« Reply #520 on: April 22, 2019, 01:35:01 PM »
Given the unreliable nature of forecasts beyond 5 days, why use them?
Why produce them?  Because they are useful
[...]
I am all for predictions, just not ten days out using unreliable tools.[...]

Since we have prediction products that extend so far into the future, but at the same time are the easiest way to show current Hour 0 conditions... I agree that some sort of notice is a necessary courtesy.  Seems simple and smart.  it's a case of implied precision.  up to hour 120 is observational talk, past hour 120 you start to blend it into model behavior talk... total respect for that.

on the other hand, making up a bunch of rules about predictions ...
« Last Edit: April 22, 2019, 02:44:58 PM by sark »
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sark

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Re: The 2019 melting season
« Reply #521 on: April 22, 2019, 02:43:25 PM »
I think below is a reasonable addition to the discussion.  Euro 500mb anomaly ensemble, hours 120-216.  Days 5-9.  Gif is not too big.  Illustrates something.  I think this is useful as it alerts people who might want to watch more closely in the coming days.

It is possible to post on this forum without making a bunch of prophetic predictions like WxJesus.  Nothing about this makes it necessary to list predictions.  Then again, the whole purpose of observational meteorology is to make predictions.  Let's not make this forum any less useful.
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Neven

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Re: The 2019 melting season
« Reply #522 on: April 22, 2019, 03:11:51 PM »
I also use https://seaice.uni-bremen.de/sea-ice-concentration/ and its working OK (Windows 10 and Google)

But the daily SIC maps are all stuck at April 18. The archives are off-line as well. This will probably soon get fixed. If not, I'll shoot off a mail.
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lifeblack

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Re: The 2019 melting season
« Reply #523 on: April 22, 2019, 04:35:05 PM »
This is from the ECMWF site:

https://confluence.ecmwf.int//display/FUG/4.1+Forecast+Error+Growth

"Small baroclinic systems or fronts are currently well forecast to around Day2, cyclonic systems to around Day4 and the long planetary waves defining weather regimes to around Day8.  As models improve over time these limits are expected to advance further ahead of the data time.  Features that are coupled to the orography (e.g. lee-troughs), or to the underlying surface (e.g. heat lows), are rather less consistently well forecast."

In this sense brr is right: although the details will change, but major weather-systems - according to ecmwf - are USUALLY forecastable for 8 days.

To check the standard deviation between the ensemble members, ie. to see how reliable the forecast is, ECMWF shows this as well with colours:

https://www.ecmwf.int/en/forecasts/charts/catalogue/plot_ensm_essential?facets=Range,Medium%20(15%20days)&time=2019042112,120,2019042612&parameter=MSLP&area=Northern%20Hemisphere

El Cid, that figure is for the overall reliability of the forecasts, correct?  Is there a separate metric for accuracy over a region from, say, 60 degrees north?  The reason I ask is because I was wondering whether the weather models might have been adjusted with some assumptions that optimize performance over populated areas at the cost of less reliability in the vicinity of the pole.

Tom_Mazanec

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Re: The 2019 melting season
« Reply #524 on: April 22, 2019, 04:44:01 PM »
I like how Accuweather gives forecasts out to 90 days. Nine-tenths of this is no better than the Farmer's Almanac, but it is fun to look at anyway.
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FishOutofWater

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Re: The 2019 melting season
« Reply #525 on: April 22, 2019, 05:03:35 PM »
Blocking highs are features that the models have trouble forecasting and that's just what we're seeing now in the 120 to 240 hour forecasts. There's a major disagreement between the GFS and the ECMWF on the surface and 500mb pressure and height patterns in the Arctic. The European model is the best model, but all the models have problems with blocks.

However, I think it is helpful and useful to look at what the models are forecasting because it's information about the state of the oceans and atmosphere at any given time. I think the ECMWF forecast of developing high pressure in the Arctic is probably correct.

gerontocrat

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Re: The 2019 melting season
« Reply #526 on: April 22, 2019, 05:09:50 PM »
I also use https://seaice.uni-bremen.de/sea-ice-concentration/ and its working OK (Windows 10 and Google)

But the daily SIC maps are all stuck at April 18. The archives are off-line as well. This will probably soon get fixed. If not, I'll shoot off a mail.
It was up to date when I looked before, and now it is not, or I am going doo lally tap even faster..
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bbr2314

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Re: The 2019 melting season
« Reply #527 on: April 22, 2019, 08:18:27 PM »
Blocking highs are features that the models have trouble forecasting and that's just what we're seeing now in the 120 to 240 hour forecasts. There's a major disagreement between the GFS and the ECMWF on the surface and 500mb pressure and height patterns in the Arctic. The European model is the best model, but all the models have problems with blocks.

However, I think it is helpful and useful to look at what the models are forecasting because it's information about the state of the oceans and atmosphere at any given time. I think the ECMWF forecast of developing high pressure in the Arctic is probably correct.
The GFS stands for good-for-sh*t  ;D

The introduction of the new FV3-GFS has been a complete disaster, they just upgraded the new version again last week which hopefully addresses some of the issues, but it is worth noting that the "GFS" is now an old model and the FV3-GFS is replacing it, with both having major problems (just FYI).

Also: the 00z EURO maintained the major cyclonic event across the PAC sector of the Arctic D7-8, although the ridging that accompanies it was slightly less amplified (the Greenland ridging became much more prominent last night). Wonder what the 12z today will show, it is running now!

bbr2314

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Re: The 2019 melting season
« Reply #528 on: April 22, 2019, 09:39:04 PM »
The 12z EURO looks like it got worse with the overall picture even if the cyclone (now D7) is weaker vs. the same time yesterday (D8). It still rolls into the Arctic on a head of very warm weather relative to normal.



It looks like the polar cell completely breaks down by D10 as the Greenland and NPAC blocks merge into a single entity over the CAA. Note, this is VERY far out, however, it is the first time this season we have seen such a depiction.


uniquorn

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Re: The 2019 melting season
« Reply #529 on: April 23, 2019, 01:18:30 AM »
It also looks like the melt of the Great Slave Lake is early. Watch for an early break up of the Mackenzie
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sark

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Re: The 2019 melting season
« Reply #530 on: April 23, 2019, 01:27:32 AM »
It looks like the polar cell completely breaks down by D10 as the Greenland and NPAC blocks merge into a single entity over the CAA. Note, this is VERY far out, however, it is the first time this season we have seen such a depiction.

If this played out as forecast, has anyone seen anything like this before?  Recall the ridge over Alaska, then Scandinavia, and now back to Alaska in the forecast.  This is all new behavior, right?
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FishOutofWater

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Re: The 2019 melting season
« Reply #531 on: April 23, 2019, 03:10:28 AM »
Blocking highs are not something new, but their intensity and persistence in increasing. The record Greenland melt years of 2010 and 2012 were associated with strong high pressure over Greenland. Those were also bad years for the Arctic sea ice.

The coming together over the Arctic ocean of the Alaskan block and the Greenland block is particularly bad for sea ice because it creates a dipole that imports heat from the Pacific and exports ice through the Fram Strait.

jdallen

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Re: The 2019 melting season
« Reply #532 on: April 23, 2019, 05:59:13 AM »
Blocking highs are not something new, but their intensity and persistence in increasing. The record Greenland melt years of 2010 and 2012 were associated with strong high pressure over Greenland. Those were also bad years for the Arctic sea ice.

The coming together over the Arctic ocean of the Alaskan block and the Greenland block is particularly bad for sea ice because it creates a dipole that imports heat from the Pacific and exports ice through the Fram Strait.
A huge change in albedo is about to take place.

It appears that as part of the evolving conditions upwards of 1 million KM2 of snow cover in Siberia and Alaska are going to vanish in the next 5 days, as well as at least 2/3rds of the snow cover on the Chukchi and Beaufort.

This I think may qualify as "momentum".
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sark

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Re: The 2019 melting season
« Reply #533 on: April 23, 2019, 06:49:57 AM »
Incredible, darkest thrill watching latest long runs of forecast products.  I want to see more.  What's the best way to read out all the daily 500mb charts for the past 15 years?  Is it  esrl.noaa?
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bbr2314

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Re: The 2019 melting season
« Reply #534 on: April 23, 2019, 08:00:08 AM »
o boy



GFS has joined the EURO party





This is by D7-8. The incursion / setup is well underway by D5-6. This would result in outright melt as well as melt ponding across a "yuge" portion of the Arctic.

The Canucks are also now in agreement!


gerontocrat

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Re: The 2019 melting season
« Reply #535 on: April 23, 2019, 09:15:28 AM »
o boy

GFS has joined the EURO party

This is by D7-8. The incursion / setup is well underway by D5-6. This would result in outright melt as well as melt ponding across a "yuge" portion of the Arctic.

Does posting images from GFS mean that your previous comments about GFS are no longer true?

Quote
The GFS stands for good-for-sh*t  ;D

The introduction of the new FV3-GFS has been a complete disaster, they just upgraded the new version again last week which hopefully addresses some of the issues, but it is worth noting that the "GFS" is now an old model and the FV3-GFS is replacing it, with both having major problems (just FYI).
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bbr2314

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Re: The 2019 melting season
« Reply #536 on: April 23, 2019, 09:18:00 AM »
o boy

GFS has joined the EURO party

This is by D7-8. The incursion / setup is well underway by D5-6. This would result in outright melt as well as melt ponding across a "yuge" portion of the Arctic.

Does posting images from GFS mean that your previous comments about GFS are no longer true?

Quote
The GFS stands for good-for-sh*t  ;D

The introduction of the new FV3-GFS has been a complete disaster, they just upgraded the new version again last week which hopefully addresses some of the issues, but it is worth noting that the "GFS" is now an old model and the FV3-GFS is replacing it, with both having major problems (just FYI).
No, they are still true -- individually the GFS is fairly useless, but when GFS + CMC are in agreement with the EURO, it is a sign of consensus and usually means a higher likelihood of verification. The EURO blew up the PAC ridge bigly tonight as well, although it doesn't merge the blocks quite as impressively as the 12z run did.

pauldry600

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Re: The 2019 melting season
« Reply #537 on: April 23, 2019, 11:26:46 AM »
Uni Bremen is off for reprocessing from Apr 19 to 22

It will be back April 23

Neven

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Re: The 2019 melting season
« Reply #538 on: April 23, 2019, 11:51:23 AM »
Thanks, pauldry600!
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Pavel

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Re: The 2019 melting season
« Reply #539 on: April 23, 2019, 03:58:40 PM »
Thing are getting exciting. I can't wait to see what will happen in 5-10 days. If it will be really above 0C in the half of the Central Basin during several days that could be a catastrophic scenario if we get the gray ice pack so early

jai mitchell

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Re: The 2019 melting season
« Reply #540 on: April 23, 2019, 06:30:09 PM »
o boy


The anomaly is very strong.  however, it is also paired with a huuuuuuge inflow of atmospheric water vapor which will suppress solar heating and will also produce large snow on CAB.
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Re: The 2019 melting season
« Reply #541 on: April 23, 2019, 07:23:30 PM »
o boy


The anomaly is very strong.  however, it is also paired with a huuuuuuge inflow of atmospheric water vapor which will suppress solar heating and will also produce large snow on CAB.
Generally concur.  Biggest impact will be on the Chukchi, Beaufort and possibly the fringes of the ESS. Cloud cover will ablate effects of insulation and limit damage. The help snow will provide may be questionable and probably localized. Pacific side snowcover on the ice is forecast to drop pretty dramatically, which will lead to subsurface pooling of melt water and lowered albedo.

There will still be down-welling long wave radiation, which combined with above freezing temperatures may be problematic.
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bbr2314

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Re: The 2019 melting season
« Reply #542 on: April 23, 2019, 07:24:02 PM »
o boy


The anomaly is very strong.  however, it is also paired with a huuuuuuge inflow of atmospheric water vapor which will suppress solar heating and will also produce large snow on CAB.
That's the question, isn't it? We have been dealing with these dueling feedbacks since 2012 it seems. However, I suspect that it will not produce large snows, but rather, rain, at least over Beaufort / Chukchi / ESS (IMO, could easily be wrong).

Aluminium

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Re: The 2019 melting season
« Reply #543 on: April 23, 2019, 07:52:34 PM »
April 14-22.

Stephan

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Re: The 2019 melting season
« Reply #544 on: April 23, 2019, 08:47:10 PM »
Just have a look at Laptev and western ESS - first breakup of sea ice from the fast ice front.
And have a look along the eastern shore of Novaja Semlja - strong SW winds open the waters again. The start of a bigger decrease in Kara Sea?

bbr2314

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Re: The 2019 melting season
« Reply #545 on: April 23, 2019, 09:18:00 PM »
The EURO has one again upped the ante at 12z.

By D6 the setup is well underway, the low is a bit further S in the Okhotsk but ridging is more impressive over AK / Beaufort --



By D9 the ridging has pinched off into the high Arctic, with the merge with the Greenland block also underway.



The medium-term solution is looking increasingly likely and increasingly warm, the D8-10 output is still variable but I do not like the trends here for retaining any real cold in the Arctic.

Viggy

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Re: The 2019 melting season
« Reply #546 on: April 24, 2019, 12:58:24 AM »
Blocking highs are not something new, but their intensity and persistence in increasing. The record Greenland melt years of 2010 and 2012 were associated with strong high pressure over Greenland. Those were also bad years for the Arctic sea ice.

The coming together over the Arctic ocean of the Alaskan block and the Greenland block is particularly bad for sea ice because it creates a dipole that imports heat from the Pacific and exports ice through the Fram Strait.

Took a few hours of staring at maps before I fully grasped what you were stating. If I understand the sequence of events that are about to unfold correctly, -
  • Over the next 2-3 days, the Low near south Greenland is going to continue to pull/disperse sea ice from the Baffin and S Greenland seas. Its already been underway for ~24 hrs and the wind speed maps beautifully show this conveyor system. Meanwhile, the leads opened up over ESS/Laptev stay open as that Low lingers, winds pushing ice away from the coast.
  • Then, a massive amount of heat starts moving in late Wednesday over Greenland from its east coast, causing widespread melt and likely dipping regional sea ice over the Greenland sea to a record low for the year. This sticks around for the foreseeable future.
  • And the main event starts early on Saturday, with the system of Lows over Russia/Chukchi and the system of Highs over Alaska/Beaufort, effectively funneling all that pacific heat, moisture and salinity through the Bering strait. Like a baseball pitching machine, a clockwise and counter-clockwise rotation on either side, forcing the ball (heat) through at great speed. Okhotsk and Bering sea ice drop to near-zero before end of this month
  • Finally, this is further out but the High strengthens and expands across Alaska, N. Canada, Greenland and pretty much the entirety of Arctic over early May, pushing all that heat towards the open leads in the ESS and Laptev. The associated winds continue to push all that sea ice into the open water between Svalbard and Novaya Zemlya, to the Barents, where the encroaching Atlantic gets a snack.
« Last Edit: April 24, 2019, 01:07:57 AM by Viggy »

Juan C. García

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Re: The 2019 melting season
« Reply #547 on: April 24, 2019, 03:23:07 AM »
Not really on topic, but it has been discussed here.

No, they are still true -- individually the GFS is fairly useless, but when GFS + CMC are in agreement with the EURO, it is a sign of consensus and usually means a higher likelihood of verification. The EURO blew up the PAC ridge bigly tonight as well, although it doesn't merge the blocks quite as impressively as the 12z run did.

"Trump administration has EPIC plan to develop the world’s smartest weather forecasting model"
Quote
It was October 2012 when the European weather prediction model beat its American counterpart in forecasting Hurricane Sandy’s hard left turn into the U.S. coastline. What scientists had known for years — that the European forecast model was superior to the American — caught the attention of the U.S. public and Congress.
Since then, the National Oceanic and Atmospheric Administration, with funding support from Congress, has worked intensely to improve the American model. It has boosted its computing power, improved the way it brings in data, and enhanced how it simulates weather systems at small scales. Yet, more than six years later, it still trails the European model in overall accuracy.
...
As part of its 2020 budget request, to the tune of $15 million, NOAA has proposed the establishment of the Earth Prediction Innovation Center (EPIC), which it says “will advance U.S. weather modeling and reclaim international leadership in the area of numerical weather prediction.”
https://www.washingtonpost.com/weather/2019/04/23/trump-administration-has-epic-plan-develop-worlds-smartest-weather-forecasting-model/?utm_term=.27bc6a92c9ea
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

sark

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Re: The 2019 melting season
« Reply #548 on: April 24, 2019, 05:40:49 AM »
is this named yet?

Days 5-12 GFS 500mb Anomaly really shows the pattern I've been seeing show up episodically all winter last year, I post this run to illustrate.  I used the graphics from https://commons.wikimedia.org/wiki/File:BuysBallot_en.svg because i couldn't figure out how to draw meshing gears
I am not a scientist

ReverendMilkbone

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Re: The 2019 melting season
« Reply #549 on: April 24, 2019, 06:16:28 AM »
Blocking highs are not something new, but their intensity and persistence in increasing. The record Greenland melt years of 2010 and 2012 were associated with strong high pressure over Greenland. Those were also bad years for the Arctic sea ice.

The coming together over the Arctic ocean of the Alaskan block and the Greenland block is particularly bad for sea ice because it creates a dipole that imports heat from the Pacific and exports ice through the Fram Strait.
A huge change in albedo is about to take place.

It appears that as part of the evolving conditions upwards of 1 million KM2 of snow cover in Siberia and Alaska are going to vanish in the next 5 days, as well as at least 2/3rds of the snow cover on the Chukchi and Beaufort.

This I think may qualify as "momentum".

Where did you read this?  Is there a website that tracks albedo?