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Messages - aslan

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1
Arctic sea ice / Re: The 2020 melting season
« on: September 17, 2020, 09:42:24 PM »
It's not just a SST thing in the Barents, Kara and Laptev seas. The heat goes town to 30m or more. Compare the 30 m Arctic temperatures of this year with 2019 on Mercator ocean and you will see that there's much more ocean heat on the Atlantic side this year than last. On the other hand, there's less heat on the Pacific side. Over both sides, there's much more heat this year, but there is almost always a see saw effect in the Arctic between the Atlantic and Pacific.

It is too bad we don't have buoy. With melt still ongoing noth of 85°N it is looking like that the halocline has taken a hit and Atlantic layer is pushing upward. Salinity at surface is higher than in 2019 also, implying a reduced stability. The high salinity is also to be compared to the high freshwater input this year.

2
Arctic sea ice / Re: The 2020 melting season
« on: September 15, 2020, 08:39:22 AM »
As a testimony of the disruption ongoing on the Atlantic front, the extraordinary heatwave is still ongoing for the Russian islands of the Barents and Kara. For weather stations with such a long record, this is crazy. Up to the 15th of Septembrer, the mean of temperature (the mean...) is above the old monthly record of September. And it is raining, raining, raining.
For Ostrov Vize, with the exception of the 10th, every day since the 14th of August is a record, and the old monthly record of 2015 has been broken twelve days as of now... The month of September is for the moment the warmest month ever recorded, ahead of August 2020  http://www.pogodaiklimat.ru/monitor.php?id=20069
For Ostrov Golomjanjy, every day of September has been a record, and the old monthly record of 2016 has been broken eleven times. http://www.pogodaiklimat.ru/monitor.php?id=20087

3
Arctic sea ice / Re: Rain-On-Snow Events (ROS)
« on: September 11, 2020, 10:30:21 AM »
Rainfall is already on the increase by the way (and this summer can testify, with record amount of rain here and there). One point that is not discussed to my knowledge is the study of warm rain in the Arctic. This study only cover the question of snow melting before reaching surface, which obviously is the biggest factor. But given the ongoing trend toward stronger shallow convection, and soundings like this one during the rain event of the 23rd and 24th of August, the question of warm rain microphysic could be asked.

4
Arctic sea ice / Re: The 2020 melting season
« on: September 11, 2020, 06:29:47 AM »

5
Arctic sea ice / Re: The 2020 melting season
« on: September 09, 2020, 07:24:37 AM »
Final answer is 983 hPa according to environnement Canada. For Ostrov Vize, the string of records is still going on. It has been since the 14th of August that every day break its record ! Almost a month of absolutely continous record. But, on top of that, every day since the 2nd of September has registered a temperature higher than the old monthly record (5.4°C in 2015) ! Probably including the 9th of Septemeber, this day, as Tx was at least 5.3°C. For now, the mean of Tx is higher than the old monthly record of Septemebr by 0.3°C.

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=9&year=2020
http://www.pogodaiklimat.ru/monitor.php?id=20069&month=8&year=2020

6
Arctic sea ice / Re: The 2020 melting season
« on: September 07, 2020, 01:34:22 PM »
In the Arctic basin, even a 8 to 10 seconds wave period is significant.

Unusual certainly, but not necessarily "significant". See just above.


For one part, forecast is worsening. Now, waves are forecasted to reach an height of up to 3 - 4 meters and a period of up to 08 - 09 seconds. Which is no surprise.

But anyway these waves are going to occur at the edge of an already weakened ice pack, and be orthogonal to the ice edge in Beaufort sea. And up to now such strong waves had consequences, so I do not see why this will not be the case today and tomorrow. And if we really want to argue over details, it is not swell but wind waves. Perhaps it is difficult to fully appreciate the consequences of this low. I do not want to forecast exact consequences of this cyclone in terms of the size of the floes break up or of upwelling, or etc... But for one part a low level jet at 30 – 35 knots with a sea state in consequence (Beaufort 6 – 7 in a word) is unusual at this time of year. It is the Arctic, not Hawaii. And on top of that, I really don’t see how this is going to just be unusual and not be significant. The arm of sea ice in Beaufort is probably going to loss ice again.

7
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 11:36:38 PM »
I think I have never seen a wave period greater than 10 seconds in the Arctic basin proper, even in 2012 or in 2016 (not counting the Kara sea were some long swells from Atlantic can be worst, of course).

In which case you might well be interested in reading about a fairly well documented 13.5 second swell in the Beaufort Sea in 2009?

https://GreatWhiteCon.info/2015/07/is-time-running-out-for-arctic-sea-ice/

Quote
On 09 September 2009, we conducted a longitudinal helicopter EMI survey at 72.5 N, and determined the limit of the swell penetration into the pack ice at 72.526 N 134.51 W, a penetration of 350 km.

Yeah ok :D But without trying to defend myself, the point was more about model values than measured values. And in the end, the difference is not that big. Long swell is usually said for period of more than 15 seconds, and my point was mostly that this definition can only be true for the Pacific or the Atlantic. In the Arctic basin, even a 8 to 10 seconds wave period is significant, even though it is not a lot by "usual" (Pacific or Atlantic) standard. But thanks for the reference anyway  ;)

8
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 09:14:40 PM »
While the weather forecasts for storms entering the arctic have been incorrect or overly optimistic, what is impressive to me is the current weather history of strong winds blowing north from the laptev/kara shores over the ice (and the fact that these were present in the forecasts 5 days out for the last 10 days at least. That length of time for a consistent 20-30+km/hr wind over the very open arctic ocean and into the ice edge has built up significant wave height that must be propagating some distance into the ice.

The only source I know of that provides an actual indication of wave close to the ice edge indicates 5-6 ft with 5-6 second period - not long swell so not as destructive to the ice behind the edge.

The forecast continues this wind through the next 4 days.

It is the Arctic Ocean here, not Hawaii. Even though I understand what you mean, even a 6 second period is quite significant for the Arctic. I think I have never seen a wave period greater than 10 seconds in the Arctic basin proper, even in 2012 or in 2016 (not counting the Kara sea were some long swells from Atlantic can be worst, of course). On top of that, wave period is probably going to be higher. I am not sure where you draw your values, but for now the forecast is for a wave period of at least 6 to 8 seconds. The strongest winds are likely to be over ice, but even in this case the fetch will probably be quite enough for this kind of value.

P.S : For ones who like esoteric diagramm...

9
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 09:22:42 AM »
Also, new daily record for Ostrov Vize this morning, at +4.6°C at least (final value at 12Z) for the third of September. Old record, +4.0°C in 2016. This is the 21th daily record in a row, almost a month of continuous daily record...

http://www.pogodaiklimat.ru/monitor.php?id=20069

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=8&year=2020

10
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 08:38:23 AM »
August 29 - September 2.

The tail is melting quite fast!

And it is not over yet.

Again, about the GAC during the month of August 2012, the minimum pressure was quite low, but environmental pressure also. And winds are function of pressure gradient, not pressure. The IFS this morning is going down to 974 hPa. But, there is an anticyclone over the coast, with pressure up to almost 1025 hPa. In 2012, pressure along the coast were around 1010 hPa. Going from 1010 to 965 hPa is about the same (45 hPa of difference) than going from 1025 to 980 hPa (45 hPa of difference). Admittedly, total kinetic energy was greater in 2012 than what is forecasted for Monday, but overall a 980 hPa low embedded in a 1020 hPa high is able to do a lot of damages also. To illustrate, the wind in meters per second analyzed by GFS at 00Z the seventh of August 2012. Maximum winds are around 30 kts (15 m/s), which is also maximum winds forecasted by models on Monday. Again, the GAC of 2012 was probably worst with a greater total kinetic energy, but overall the absolute minimum pressure of a low is quite not the full story. This is going to be a really rough ride and it is really bad, even though we are more than 10 hPa away of the lowest pressure of the GAC 2012.

P.S. : Did not see that at first glance, but IFS 00Z is pushing above 40 kts at surface on Monday 12Z O.o ouch...

11
Arctic sea ice / Re: The 2020 melting season
« on: September 01, 2020, 04:05:19 PM »
Today's images and slow animation (slightly larger version on twitter)...

The drop in concentration in the Beaufort in the last 24 hours is somewhat concerning.

Easterlies and waves are probably hitting the Beaufort sea. Winds up to 30kt from the east, for the southern part of the arm of ice :

http://ogimet.com/cgi-bin/gsynres?ind=71948&decoded=yes&ndays=20&ano=2020&mes=09&day=01&hora=15

And models are showing waves of up to 3 meters with a period of up to 7 seconds. It is not the big washing, but way enough for some floes to go "poof".

12
I'm not sure where to post this information, but the QBO is again disrupted with an anomalous interruption of the easterly phase like in 2015 - 2016 :

https://acp.copernicus.org/preprints/acp-2020-791/acp-2020-791.pdf

https://acd-ext.gsfc.nasa.gov/Data_services/met/qbo/qbo_plot.pdf

https://www.essoar.org/doi/10.1002/essoar.10503358.1#.XvEZFtQSp8M.twitter

13
Arctic sea ice / Re: Updating the ASIG
« on: August 25, 2020, 10:57:52 AM »
You probably need to update adobe on your computer, or to allow adobe to run within your browser  ;)

http://arctic.som.ou.edu/scavallo/images/real_time/conc_trth_slp/

14
Arctic sea ice / Re: The 2020 melting season
« on: August 25, 2020, 09:48:48 AM »
And, also, there are few surface observations, which makes model initialization harder. For example, the 24th of August, Polarstern ship measured a pressure of 991.4 hPa : https://www.sailwx.info/shiptrack/shipposition.phtml?call=DBLK
This is slightly off the initialization and the first forecasted hours of the weather models by one or two hPa. It is likely that the minimum pressure of this low was in the upper 980s hPa actually, as the center missed the Polarstern. But this is not unexpected. With a gap of ~500 km between Kvitoya and Polargmo Im., and a gap of ~1000 km between this two and DBLK, it is hard to know what is going on.

15
Arctic sea ice / Re: Updating the ASIG
« on: August 25, 2020, 09:10:27 AM »
I've updated the Forecasts page, as none of the images were working. Unfortunately, there aren't any good SLP forecast maps out there, either GFS or ECMWF. Tropical Tidbits has a good one, but it's for the Northern Hemisphere, so you can't see much detail when it's in the size I'm using for the Forecasts page. So, I was forced to use to the Climate Reanalyzer MSLP/Precipitation map which lacks the geopotential height colours for a quick glance.

Oh, well...

I'm a bit late, but have you consider this site ?

http://arctic.som.ou.edu/scavallo/images/real_time/conc_trth_slp/looper.html

http://arctic.som.ou.edu/scavallo/real_time_plots.html

16
Arctic sea ice / Re: The 2020 melting season
« on: August 25, 2020, 08:54:26 AM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!
It’s funny how the big storm over Greenland Gap never gets to fully realize
It's been like that for over a month now, where big apocalyptic storms get announced on the long term forecast, but never materialize.

GFS really needs to find a way to improve their long term forecast. Or just stop making them, because this is useless...

Models don't work this way.

For Franz Josef Land, record high temperature for the last decade of August, record high daily rainfall and near record gust speed for August :
http://ogimet.com/cgi-bin/gsynres?ind=20046&decoded=yes&ndays=2&ano=2020&mes=08&day=25&hora=00

Old value : 16 mm in 24h (August 89), 5.5°C (August 2019 and August 1978)

P.S. : And there is a ~500 km gap between WMO station 01011 (Kvitoya) and WMO station 20046 (Polargmo Im. on Heis Island - Ostrov Kheysa). The worst of the storm on Sunday and Monday was in this gap.

17
Arctic sea ice / Re: The 2020 melting season
« on: August 22, 2020, 12:15:57 AM »
And, as an illustration, 63.4 millimeters of rain in 1 hour at Sandefjord Gjekstad, highest hourly rainfall rate for Norway. Old record was 54.9 mm in 1 hour at Asker. The thermal wave, consequence of Kyle and Ellen, is by no mean a joke. No matter the exact to the nearest decimal of the min pressure for the North Pole, this is going to be bad for the atlantic front.

18
Arctic sea ice / Re: The 2020 melting season
« on: August 21, 2020, 01:54:42 PM »
The storm is still in the forecast for Monday. A little weaker, but within the model run to run fluctuations we might expect.

Yep. But, not wanting to sound hysterical, but the subttle changes are not good at all. Baroclinical energy is more dilute along the thermal wave. This means that the pressure at North Pole is now forecasted to be a bit higher, but the string of low pressures is still here and there. And so the winds are still forecasted at 25 - 35 kts, and rain (and really, rain, liquid water at ~5°C) amount are still forecasted to reached 20 - 30 mm.
Also, the Arctic low in this wave is forecasted to move a bit more toward the Beaufort sea, with some waves action, which was not the case in the forecast last days. And, mantra of this year, but there is still a lot of easy ice to loss in this corner of the Arctic.

19
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 01:49:10 PM »
It is not useful to look at exact number for weather forecast. This is why there is the feeling of coin flipping. That the models go back and forth for exact min pressure at the nearest hPa or max surface wind at the nearest km/h is normal and should not be confusing the forecast. Models are still a bit unsure about the deepening of the low, but in any way and in any case, a wave in the frontal boundary from the complex low linked to ex Kyle, now storm Ellen, is going to deepen. The details of the exact minimum pressure and of which exact wave in the front and of the exact km/h of the max wind and so on are not really relevant. We can be 100% that a low is going to deepen from a wave in this complex, and that it is going to be a wild ride for the Atlantic side. And the ranges of some physical parameters are not going to evolve in the coming days. Precipitable water is forecasted to reached 25 - 30 millimeters in the warm air advection and this is not going to change, strong winds of 30 - 35 kts are also a sure thing, I am ready to bet on thunderstorms northward of the 80°N also, etc... That the low go to the 970s or stall in the bottom of the 980s hPa or that lightning strike will be here or there is asking too much, and is not really the biggest question. The difference between a 980 hPa low with 34 kts of wind and 29 mm / 24 h of rain at max, which develops from this wave, or a 975 hPa low with 36 kt of wind and 31 mm /24 h at max which develops from that wave, is not significant. Weather forecasting is not reading model outputs and going back and forth with them. This is going to be a significant event for the Atlantic side, with the injection of tropical moisture from Kyle, and with implications for planetary rossby waves train, no matter the exact unit of this or that parameter.

20
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 09:50:19 AM »
silly question .. would the weather models have any concept of how wet the ice is atm ? If they see it like piomass sees it they may be surprised by developments .  b.c.

No they don't, sea ice is parametrized in the models with fixed constants. It would be way to complex to explicitly model the sea ice for a weather model running every six hours. And yes, models can be underestimating cyclogenesis, which is no news. But this is not only a problem with sea ice. Cyclogenesis is a complex process and is hard to forecast. But in the Arctic, with all the changes ongoing, this is worst, yes. As a side note, models are again forecasting explicitly thunderstorms above the boundary layer on the Atlantic and Pacific side. I did not fully check the models from 00Z today, but IFS or ARP are going on for over 30 millimeters of rain (and rain, no sleet or snow) in 24h for Franz Joseph Land this week-end ! This is crazy. And even up to 85°N, they are going with thunderstorms and a good 20 mm per 24 hours. Sea ice on the Atlantic side is going to be wash out.

For Beaufort Sea, as already said, the warm air advection on the flank of the anticyclone is going to be bad. Even though there is no deep low, there is enough pressure gradient for some significant winds (field of 15 - 25 kts), and with the help of Coriolis, with the fetch of open waters, etc... Waves are going to be pretty significant for the Arctic, from the south east to the south (wave period up to 6  to 8 seconds). This not a big event, but again locally and given the sore state of sea ice in this corner of the Arctic, and the fact that there is a lot to loss, etc... Beaufort Sea is likely to continue its nose dive in the coming days.

21
Arctic sea ice / Re: The 2020 melting season
« on: August 10, 2020, 10:19:25 AM »
As forecasted, the low over the southern CAA and Beaufort is not an event at the scale of the whole bassin, but for Beaufort sea, it is bad. This low was accurately predicted since the end of last week, as it is for now as bad as forecasted then. I did not check all the values but the station of Aulvik reached 31 knots for example : http://ogimet.com/cgi-bin/gsynres?ind=71974&decoded=yes&ndays=2&ano=2020&mes=08&day=10&hora=06
At Sachs Harbour also it was quite an event : 992.9 hPa at minimum and 25.3 millimeters of rain in 24 hours.
http://ogimet.com/cgi-bin/gsynres?ind=71467&decoded=yes&ndays=2&ano=2020&mes=08&day=10&hora=06
One thing is sure, ice in the Beaufort sea is in the washing machine for now, while there is ~ 1 million squared kilometers of weak ice there.

And the ridge over Arctic is linked to strong convection over the western Pacific, with the MJO in phase 3 - 4. For now, there is now surprise to the trend toward higher values. This said, uncertainty increased after mid-august as a new wave packet should propagate, with higher values coming from the south by the Pacific. What will happen then is not clear. GFS is leaning toward building a new ridge, while IFS is skipping into lower values.

22
Arctic sea ice / Re: The 2020 melting season
« on: August 07, 2020, 08:39:33 AM »
The low over southern CAA is forecasted to bottom to around 990 hPa (993 for the 00Z of IFS and 991 for the 00Z of ARP). This is going to be quite an event locally. Winds up to 35 kts are likely and the ice wich is already weak in the southern Beaufort could be decimated. Not an event of the scale of the whole arctic bassin, but this low is going to hit hard a region of above average but weak ice again. Also models are forecasting a new ridge building from the Pacific for after mid august. This is worth watching.

23
Arctic sea ice / Re: The 2020 melting season
« on: August 05, 2020, 12:57:08 PM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!
Trouble about to arrive to the Beaufort in a few days with warm winds off the CAA from the east. We may also see M'Clure Strait clearing out.

Nothing new, but there is as always a strong funneling effect when isobars are parallels to the coast. The easterlies are forceast to reach 25 to 35kt along the Arctic coast and in the Parry channel. This is also going to be a significant surge event for the northern coast of Alaska.

24
Arctic sea ice / Re: The 2020 melting season
« on: August 05, 2020, 10:45:28 AM »
Are there any opinions on the value and accuracy of the various arctic 10 day forecast animations at weather-forecast.com?  I like the visuals and options but am wondering about the predictive value?
10 day right now can’t be trusted. 5 day barely ok

For now, confidence in the forecast can be high up to 5 -6 days. Models are in good agreement for a weak dipole, and the spread within the ensemble is low (this is especialy noticeable for Beaufort Sea). This pattern is linked to the propagation of two rossby waves packet from Western Pacific. This pattern should break around the 11 - 12th, but until this date, confidence in the forecast can be high?

Sorry I don't have the mean to fully exploit the dataset for MERRA reanalysis

A fellow Panoply user by the look of it  :)

Can you provide a link to the data behind that visualisation? And any other data sources you access regularly. This is my favourite:

http://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/

TIA

As this map generate some interests I have updated an old chart with data for 2020 (up to the 30th of June). Accumulated net downward shortwave flux was quite low until the 30 th of June.

P.S. : By the way hurricane Isaias is not going to have a significant impact on large scale circulation despite a strong XT transition, as can be seen on the hovmöller of meriodional wind.

25
Arctic sea ice / Re: The 2020 melting season
« on: August 03, 2020, 01:31:13 PM »
Sorry I don't have the mean to fully exploit the dataset for MERRA reanalysis

A fellow Panoply user by the look of it  :)

Can you provide a link to the data behind that visualisation? And any other data sources you access regularly. This is my favourite:

http://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/

TIA

I don't use a personal computer, and I don't have many option to plot and analyse data : excel and wathever can run without any installation, so there is only few options left  :D This is data from MERRA reanalysis, the most reliable reanalysis freely available for raditiative flux to my knowledge :

https://disc.gsfc.nasa.gov/datasets/M2TMNXRAD_5.12.4/summary

You need to register to download files, but it's all. There is also some delay, you have to wait the 20th for the most recent monthly data.
There is also data from the reanalysis from the NCEP/NCAR in near real time but it is a bit less reliable. And this year, I don't know the source of the problem, but it seems to me there is an inconsistency for radiative flux.

https://psl.noaa.gov/cgi-bin/db_search/SearchMenus.pl
https://psl.noaa.gov/cgi-bin/db_search/DBSearch.pl?Variable=Upward+Solar+Radiation+Flux&group=0&submit=Search

26
Arctic sea ice / Re: The 2020 melting season
« on: August 03, 2020, 12:21:34 PM »
Sorry I don't have the mean to fully exploit the dataset for MERRA reanalysis, but as an illustration. For June, net surface shortwave (~ solar) flux was high, but not as high as in 2019. Last year was quite extraordianry from this point of view. The first map is for 2020, the second is for 2019 and the third is the difference, 2020 minus 2019. We will see what did happened in July (MERRA data are available around the 20th for the preceding month).

27
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 30, 2020, 05:28:53 PM »
For ITP 113 and 114 there is also the question of temperature. The cold pool at the surface was definitively mixed, as temperature surged at surface.

28
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 30, 2020, 04:40:10 PM »
It can be noted also that there is a surge event ongoing for the northern coast of Alaska. I don't have knowledge of a station measuring waves height for Arctic coast of Alaska, but at least there is a surge of about 0.5 meters since the 27th of July at Prudhoe. Waves will pill up above, and as sea level is already high, tops of waves reach even higher level. As a side note, waters levels at Prudhoe are higher than in 2012. In 2019 waters levels were even higher than, now, but were not as long lasting.

https://tidesandcurrents.noaa.gov/waterlevels.html?id=9497645&units=metric&bdate=20200725&edate=20200801&timezone=GMT&datum=MLLW&interval=6&action=

29
Arctic sea ice / Re: The 2020 melting season
« on: July 30, 2020, 10:26:01 AM »
It is also worth underligning that IFS is trying to deepen again the low runs over runs, with a new minima developing within the front and warm air over canadian archipelago. As a consequence, IFS go down to 991 hPa at 90 hours (sunday evening UTC), and with a high above 1025 hPa for the siberian coast, this means a continuous wild ride for sea ice. GFS is not following, but probable answer is that GFS is lost in the wildnerss of fantasy land, as usual. Even more as others models also are trying something within this front, even tough they don't go as low as the euro guy. And again, follow the trend  :P IFS is loosing hPa by hPa run over run, and it is quite likely at this point that the trend will continue and the low will end in the 980 something hPa. And again, the difference with 2012 is the strong high over siberian coast. Even if we only bottom out to 985 hPa Sunday evening (UTC), gradient will be ~ 50 hPa beetwen Beaufort Sea and siberian coast. At the height of the GAC 2012, it was only ~ 55 hPa over about the same distance...

30
Arctic sea ice / Re: The 2020 melting season
« on: July 30, 2020, 07:42:05 AM »
About wave activity, it can be noted that Indian Ocean was a strong source until lately. Pacific convection was a bit muted, but a dipole dominated over Indian Ocean, and a stationary MJO stucked in phase 2- 3 in June and July, with propagation of a wave train over Pacific and a reinforced subtropical jet here. But what is really curious is the strong source of wave activity from Arctic. I mean, I really don't remember seeing such a source independently from the mid latitudes and tropics.

31
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 11:17:08 PM »
For wave activity flux, anomalies are really showing up over arctic independently from a tropical forcing. The strong arctic anticyclone was a source of an anomalous wave activity, which was not the case in others years with an arctic anticyclone. This patterns breaks into a succesion of waves. This is noteworthy, to my knowldge arctic was never such a strong source of wave activity comapred to the tropics.
For thunderstorms, I must said that it is also quite likely that strikes happenned northward of 80°N but I don't know if the data from the vaisala monitoring network is accesible. Without data, who knows. But data from Alaska network is not meant to register strikes near the pole for sure, it was more an illustration of the convective instability in the warm sector of the cyclone.

32
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 08:44:30 PM »
Also the ligthning map from alaska weather service is impressive, with many strikes other Chukchi sea. Since 2016 we have seen strikes more to the North than this, but still having ground strikes at 71°N over sea is no small acheviement...

There was a tropopause folding along the poleward flank of the cold front, with a strong PV anomaly along the frontal slope. Classical for this kind of front. But on the equatorward side, warmth and moisture was extraordinary. It is hard to find CAPE value as it is usually calculated from surface. Here cumulonimbus started from above the boundary layer, around 900 hPa - 800 hPa. But playing the game to make sounding on the model everywhere possible, CAPE value up to 1000 J/kg appeared on the Monday (between 06Z and 15Z). The warm sector was extraordinary for the Arctic and strong isentropic lift occured in consequence.

33
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 06:21:01 PM »
I am not sure it was said, but Ostrov Vrangel and Mys Vankarem reported thunderstorm, and with gusts up to 18 m/s (about 37 knots) for Ostrov Vrangel when the front crossed the island. As others as said, it is no surprise that the low is stronger than forecasted.

http://ogimet.com/cgi-bin/gsynres?ind=21982&decoded=yes&ndays=2&ano=2020&mes=07&day=27&hora=12
http://ogimet.com/cgi-bin/gsynres?ind=25282&decoded=yes&ndays=2&ano=2020&mes=07&day=28&hora=12

34
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 09:06:58 AM »
Ok correction, 978 hPa at 144 hours... Come on Brive ! XD Forecaster widsdom, when the IFS is stable and going stronger step by step and hPa by hPa, follow the trend. Again it is not a GAC but the cyclone is going to destroy the last stronghold of this year, the Beaufort sea. We are really going to go trough the floor.

Lol wow... yeah, tonight’s Euro would be disasterous for the Beaufort. I don’t think the previous run with  the 980mb was too terrible. Pretty transient with some rain and warmth briefly pumped in, but not persistent enough to make a huge huge impact in the Beaufort via wind and waves imo. Most of the relentless warmth would’ve been over the CAA. Certainly wasn’t trying to argue it was good though, just worth watching. And now even more so for sure!

Tonight’s run would be bad bad bad news.  Relentless wind and waves pulverizing the sea ice and rubble for days. Some are overestimating the Beaufort ice, considering it a stronghold this year. But it looks terrible on satellite and the concentration maps.  A storm like this would absolutely wreck it.

Yes ;) I agree with you, to be precise I said stronghold, but it was more exactly to say that it is where there is still lot of ice, and so huge losses possible. But yeah, Beaufort sea ice is weakening and is not looking especially "strong".

35
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 08:34:36 AM »

4. Will a strong cyclone develop on the Pacific side? Right now both the GFS/Euro are forecasting a 980mb LP on day 5. The storm doesn’t look too terrible, but if a bigger/stronger/persistent cyclone does develop in this area that would be trouble for the vast amount of vulnerable ice/rubble in the Beaufort.

I kindly disagree, the forecast is looking incredibly bad for Beaufort sea over the end of the week-end. The cyclone which was forecasted to try to bomb out from the Laptev sea fizzle out, but now the machine is running full steam ahead. Each minima is pumping warm, moist air from the continent, and in the front a new low developps and push air pressure lower and lower. We are going for a persistence of cyclones rotating over Beaufort sea. IFS 12Z is reaching 980 hPa at H+120, we will see the 00Z but this is definitively a bad setup. It is not THE big one, but action will take place over Beaufort sea and act to disper sea ice here. On top of that, we still have convective instability above the boundary layer with high rain rate, locally up to 15 - 20mm in 6 hours. The washing machine is on.

P.S. : I didn't see answer from Friv' but I agree with him. And the 00Z of the IFS is still going down to 983 hPa...

Ok correction, 978 hPa at 144 hours... Come on Brive ! XD Forecaster widsdom, when the IFS is stable and going stronger step by step and hPa by hPa, follow the trend. Again it is not a GAC but the cyclone is going to destroy the last stronghold of this year, the Beaufort sea. We are really going to go trough the floor.

36
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 08:05:06 AM »

4. Will a strong cyclone develop on the Pacific side? Right now both the GFS/Euro are forecasting a 980mb LP on day 5. The storm doesn’t look too terrible, but if a bigger/stronger/persistent cyclone does develop in this area that would be trouble for the vast amount of vulnerable ice/rubble in the Beaufort.

I kindly disagree, the forecast is looking incredibly bad for Beaufort sea over the end of the week-end. The cyclone which was forecasted to try to bomb out from the Laptev sea fizzle out, but now the machine is running full steam ahead. Each minima is pumping warm, moist air from the continent, and in the front a new low developps and push air pressure lower and lower. We are going for a persistence of cyclones rotating over Beaufort sea. IFS 12Z is reaching 980 hPa at H+120, we will see the 00Z but this is definitively a bad setup. It is not THE big one, but action will take place over Beaufort sea and act to disper sea ice here. On top of that, we still have convective instability above the boundary layer with high rain rate, locally up to 15 - 20mm in 6 hours. The washing machine is on.

P.S. : I didn't see answer from Friv' but I agree with him. And the 00Z of the IFS is still going down to 983 hPa...

37
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 09:08:29 PM »
WTF

The IFS did remember what a thunderstorm of the free atmosphere means. No surprise here. Fasten your seat belt we are going for a wild ride for weather forecast -& probably for sea ice also-. Anticyclone are so anoying, now it is time for real weather forecast and putting balls on the desk :D

38
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 01:56:44 PM »
As Friv pointed out, there is lifting occuring from the warm air coming from the siberian coast above the boundary layer. It is becoming a new normal, but still on the scale of weather craziness this easily reached the batshit crazy level... Soundings are the ones forecasted from IFS 12Z (cf. the picture from wetterzentrale) over ESS and Laptev, in the ridge of warm Theta'w. If the forecast verifies as it is, this means thunderstorms. This is also probably adding instability to the forecast.

Sorry for quoting myself, but this is really going to be an important point. There is a first low east of Taymyr and Severna Zemlya, from now to H+120, going down to ~995 hPa at 72h - 96h. This first low is going to bring a massive surge of heat from Siberia, and rough sea over Laptev bite tanks to the fetch of the now open Lapev sea. But, in this massive surge of heat, isentropic lift and thunderstorms are likely, wich is going to bring cyclogenesis. This secondary low starting from the front of the first low is the one to look. Like last year and one or other years before, isentropic lift and buoyancy is going to be an important factor, thanks to the reccord warmth ongoing. And like others years, it is way more likely that models are underestimating the deepening of this low than the other way round. This can be seen comparing precipitations from the 00Z and the 06Z of GFS. The GFS 06Z is way waty worst for sea ice than the 00Z, and one reason is probably due to stronger thunderstorms and higher max rain rate forecasted in the 96H - 120H range in the front of the first low. The 00Z is reaching "only" 10 - 15mm in 06 hours -this already qualify as bath crazy for Arctic...-, the 06Z is reaching more than 30 (30 !!!) mm in 06h under the strongest cells. Don't ask why the 06Z is total mayhem for sea ice....

39
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 08:25:53 AM »
As Friv pointed out, there is lifting occuring from the warm air coming from the siberian coast above the boundary layer. It is becoming a new normal, but still on the scale of weather craziness this easily reached the batshit crazy level... Soundings are the ones forecasted from IFS 12Z (cf. the picture from wetterzentrale) over ESS and Laptev, in the ridge of warm Theta'w. If the forecast verifies as it is, this means thunderstorms. This is also probably adding instability to the forecast.

40
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: November 02, 2019, 08:00:40 PM »
Daily gain 170 k, 46 k MORE than the 2010's average of 124 k.

Still very high, and just three seas (ESS, Laptev & Kara) gained 164 k of that total.

_______________________________________________


I think this is an important point. The biggest difference with 2016 is the Kara Sea and to a lower extent the ESS. Kara Sea has seen quite unexpectedly high sea ice gain and is ahead of the most recent years (2016 and after I mean). Big gain in ESS and Laptev is a fatality, nothing can make for shallow waters and fresh water. But now that the sea ice has hit the hard land, ESS and Laptev can't see any more gain, this two seas are already near the 100% mark. If Kara sea is not able to sustain the surge in gain, it is likely that a stall in Arctic sea ice extent will happen. As for now, the great battle of this winter for Chuckchi and Barents sea is starting, and easy ice gain are likely over. I am quite ready to bet that Kara Sea will not be able to sustain the pace, and that we are going to see stall shocking the extent growth like in 2016. The biggest hope for now I think is the Beaufort Sea, the only sea which can keep things up for now I think.

41
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 19, 2019, 12:17:23 PM »
Even for the Arctic Ocean, we will be hard press to end the winter with at least a 2m first year ice, putting the risk of a memory of this summer. The islands on the russian side are nearing or breaking record which are only a few years old, like Ostrov Vrangel :

http://www.pogodaiklimat.ru/monitor.php?id=21982&month=10&year=2019

versus 2016 :

http://www.pogodaiklimat.ru/monitor.php?id=21982&month=10&year=2016

Or Ostrov Kotelnyj :

http://www.pogodaiklimat.ru/monitor.php?id=21432&month=10&year=2019

versus 2018

http://www.pogodaiklimat.ru/monitor.php?id=21432&month=10&year=2018

Or Ostrov Vize :

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=10&year=2019

versus 2016 :

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=10&year=2016

And again, a layer of low level clouds is keeping in check the refreze, as shown for example with Ostrov Vrangel between 300 and 600 meters since the end of the Summer :

http://ogimet.com/cgi-bin/gsynres?ind=21982&decoded=yes&ndays=50&ano=2019&mes=10&day=19&hora=06

And SSTs are still extrememly warm, locally up to 7 or 8 (!) °C. And with the clouds in place, cooling is going to be slow. It is a sure bet that southern Chukchi would not freeze before December or January, and it is increasingly likely that this sea could not fully refreeze before the end of the winter.
For now, the downward IR flux at surface is a bit less averaged over Arctic comapred to record holder 2018 and 2016, meaning a bit more heat is escaping the furnace of the Arctic. But we are starting with an ocean wich is way warmer than in 2016 or 2018 and to cool down this thing this small diff is not enough...

42
Consequences / Re: Forests: An Endangered Resource
« on: September 27, 2019, 05:48:20 PM »
Yes, it is already some years that horse chestnut is screaming its sorrow and pain. It is often question of Amazon or Indonesia or California... but here in northeastern France trees are dying everywhere, it is crazy. Bark beetle are eating away forest, and relentless heatwaves are drying trees. You can't walk 5 meters in any forest without spotting dead trees after dead trees, of any species, old one or young one. Leaves are already falling here, which is really early -and while temperatures are still high and there is no frost still-.

https://www.foretpriveefrancaise.com/data/fe248_p54_60_1.pdf

In the mean, around 10% to 20% trees are dying now. With an annual harvest of 12 millions m3 it is at least 2 millions m3 of damaged wood for this year for France. But locally up to 80% to 90% (!) of trees are dry and dead. Hornbeam, beech, spruce, ash, douglas, you name it.

http://www.fncofor.fr/docs/library/secheressequestions-reponsesonf-fncoforseptembre-2019.pdf

Here it is named a "sanitary crisis", but it is no longer a crisis as it is only worst years after years. It was already very, very bad in 2018, and "only" very bad years before. It is just that mass mortality is growing more massive years after years. And in Deutshland or in Switzerland it is no better.

43
Arctic sea ice / Re: The 2019 melting season
« on: September 06, 2019, 11:44:13 AM »
Sum of forces is definitively not the same. Ice and water does not respond in the same way to winds. And there is also hydrostatic equilibrium, 100 hPa is worth one meter of sea level, but zero point zero meter of ice level. And of course in the end gravity would even out the sea level if the winds stop blowing.

44
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 09:47:01 PM »
Yes thanks longwalks ;) If there is specfic interest for the Nare Strait, the work of A. Münchow is worth citing :

"The established flow of seawater from Pacific to Atlantic Oceans through the Arctic has been attributed to higher sea level in the Pacific (Wijffels et al. 1992), associated with the lower salinity of Pacific waters. Sea level in the Atlantic may be more than 0.5 m lower than in the Pacific and 0.1–0.3 m lower than in the Arctic (Muench 1971). More accurate estimates of steric forcing have yet to be determined, but it is probably safe to conclude that much of the drop in sea level between Arctic and Atlantic Ocean occurs along the 530-km length of Nares Strait, thereby providing the impetus for the fluxes that we have measured.'

https://journals.ametsoc.org/doi/full/10.1175/JPO2962.1

https://www.researchgate.net/publication/233704692_Ocean_current_observations_from_Nares_Strait_to_the_west_of_Greenland_Interannual_to_tidal_variability_and_forcing

45
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 09:22:10 PM »
Ok, I might be stubborn,  ;D but I will rephrase more abruptly. What if the change in sea ice extent does not reflect a change from an energy point of view?

46
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 04:22:09 PM »
Without wanting to look harsh, but I think the discussion is taking a bad way. I am not a specialist of this question, but a big missing piece of data is the problem of land versus ocean distribution in Northern Hemisphere.

I think it is useful to go in several different directions. Extract what we can from trends but also consider physical reasoning.

I am not sure I agree on the importance of land restricting ice extent. It certainly does in winter but it is constrained at same places each year. So I am not convinced it has much effect on trends.


If I may insist. Considering for example an uniform retreat of 1° northward per decade, Summer as Winter.
If the ice edge is 1 000 km long, the 1° will lead to 100 time 1 000 km², i.e. 100 000 km² ice loss over a decade. Or, said otherwise, peanuts.
If the ice edge is 10 000 km long, this will lead to 10 000 time 100 km², i.e. 1 000 000 km² ice loss over a decade.
This is really what is ongoing. In winter, the "free" ice edge is not really wide, so even if the ice is marching toward the North at the same speed as in Summer, ice loss will be small. And as said, in the Pacific we are now in the bottleneck of the strait, and in the Atlantic it is not really better. So even a retreat of 2 or 3° over a few years will lead to almost no sea ice extent loss in Winter, while in Summer a retreat of 2° or 3° will be almost the end of the sea ice. This is simple but important math’s. Of course, it makes the evaluation of trends in ice extent more complex. But I really do think brain storming over breaks of the linear slope without acknowledging this fact will lead to a sterile discussion. The changes in slope are way more better explained by changing ice edge conditions than by "hard" physics.

https://tamino.wordpress.com/2010/08/22/on-ice-with-a-twist/

47
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 03:05:44 PM »
Yes, the conditions are more suitable for ice export in Winter, mostly due to variation in sea surface elevation :

Our model results based on 26-years of simulation with monthly output demonstrate that SSH gradients (calculated between two points north and south of each passage, which are denoted with asterisks shown in Figure 12) do explain the annual peak volume fluxes (around March) through both Nares Strait (Figure 14a) and Lancaster Sound (Figure 14b). The volume flux anomalies and SSH gradient anomalies are also highly correlated. Volume flux anomalies through Nares Strait (Figure 15a) and anomalies of the SSH gradient (measured from the Lincoln Sea to Smith Sound) (Figure 15b) were highly correlated (R = 0.89). Volume flux anomalies through the mouth of Lancaster Sound (Figure 15c) and anomalies of the SSH gradient (measured between the Queen Elizabeth Islands and western Baffin Bay) (Figure 15d) were also highly correlated (correlation R = 0.85).

https://pdfs.semanticscholar.org/870a/ad3242a2f319c69031342c9cedfa291df51e.pdf

48
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 02:40:21 PM »
Without wanting to look harsh, but I think the discussion is taking a bad way. I am not a specialist of this question, but a big missing piece of data is the problem of land versus ocean distribution in Northern Hemisphere. I mean, in winter, ice edge is constrained more by geography (coast of Russia and Canada) than by physics (warming / cooling atmosphere, ocean currents, and so on). Which is no longer the case in Summer, where ice edge is, but for Greenland, in open Ocean and can retreat as the thermodynamics warrants. This is probably why seasonal cycle changed dramatically after 2005. Until 2005, ice was still mostly bounded by the coast, even in Summer. Now, ice has all the possibility to expand and retreat without being imped by the coasts. One possibility is to look instead at sea ice edge latitude. Doing this, difference between Summer and Winter is lessened and the downward trend is more even.
On top of that, captain obvious helping, it should be noted that sea ice area can't go negative. But this has the implication also that the downward trend should go to zero sooner rather than later, as there is no more ice to melt in summer. Losing 2 million squared km when you have like 20 million at hand is almost nothing, losing 2 million squared km when you have like 1 million at hand is impossible... This is probably the first big answer to the question "why trend is so irregular and the seasonal cycle has gone mad ?".

It should be noted also that from this point of view, the situation is “worsening” on the Pacific side. When the edge was in the Bering Sea, there was still some width to “yielded” big loses. Now that the edge is in the bottleneck of the strait, even a retreat of 1° North –which is quite significant– would amount to almost zero ice area loss. Zero time a thousand km is still zero :p We will have to wait for ice edge in winter to reached Beaufort / Chukchi / ESS for seeing anew some significant ice loss for the Pacific side. Same on the Atlantic side, as Barents and Kara Sea are zeroing, going further North will become complicated in the short term. It will happened in the decades to come of course, but over the course of the coming years, variability of winter sea ice as seen from the metric of extent will probably still be dampened, even if the warming speed up bigly.

https://www.tandfonline.com/doi/full/10.3402/polar.v33.21249

P.S. And on top of that "simple" geographical explanation, geaography also lead to "energy yield" vastly different from Winter to Summer. Land and Ocean distribution are also responsible for bigly different thermal answer in Summer and in Winter under the same forcing. We will also probably have to wait that the Ocean becomes an "heat accumulator" in winter for seing warming speeding up in Arctic.

49
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 07:17:06 AM »
Yes, it was bad wording on my part, not reflecting what I was actually thinking. It was more like, there was a strong preconditioning earlier with the lack of blocking in Nares strait, and now winds have an easier job.

50
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 06:42:42 AM »
This topic has drowned into the abyss of this forum, but the mega crack is still here and alive. And there is still sign of melt going on. To justify, Kap Moris Jesup hit 10.3°C the last day of August, a record for this time of year. And to the the North of Ellesmere, the Nares strait export has lead to a big, big hole. Fortunately the season is ending.

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