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F.Tnioli

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Re: The 2017 melting season
« Reply #2200 on: June 22, 2017, 01:02:14 PM »
...
Rain freezing on ice is what gives the energy...
Really?

I mean, OH REALLY? =)

Come on. Let's say 1kg of rain water just got frozen on ice. OK, so that indeed releases enough energy to melt exactly 1 kg of ice. Let's say all that energy is then spent to melt 1kg of nearby ice. OK, so it melts into water. Net total ice melt as a result of _that_ kind of energy released?

Let's do the math. We just got +1 kg of ice "made" of rain water, and we just got -1 kg of ice because it was melt by the energy you talk about. +1 -1 = 0.

ZERO change in total ice mass.

binntho

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Re: The 2017 melting season
« Reply #2201 on: June 22, 2017, 02:32:09 PM »
This is something of an old discussion, rain vs. sunshine. From experience I've seen rainstorms melt ice very fast, in spite of low temperatures and not particularly large amounts of rainfall. The strength of the wind seems to be a major factor, probably because the biggest effect comes from condensation of water vapor from the air, and the stronger the wind, the greater amount of humid air can come into contact with a given area of ice.

But this is just a guess - all I can say from experience is that rain storms with strong winds seem to be the most effective way to melt snow and ice during early spring (at around 60N).

romett1

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Re: The 2017 melting season
« Reply #2202 on: June 22, 2017, 03:44:53 PM »
Sea ice concentration forecast for Jun 28 and actual Jun 20. We can find the highest concentration near Fram Strait, Nares Strait and FJL. Not the best situation as these are export-friendly areas.
Images: https://www7320.nrlssc.navy.mil/hycomARC/arctic.html

iceman

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Re: The 2017 melting season
« Reply #2203 on: June 22, 2017, 03:53:29 PM »

Does imported warm air from Siberia and ocean mixing count for more than the significant reduction in insolation during the peak week for sunlight?

I don't think so, especially near the solstice.  But these are only two factors in a system of fascinating complexity.  Among the others: rain will strip away much of the remaining snow cover over areas of higher-than-normal albedo, and the position of the cyclone means winds will push some thicker ice closer to the Fram exit.

F.Tnioli

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Re: The 2017 melting season
« Reply #2204 on: June 22, 2017, 04:47:14 PM »
I'm sure it's not that simple "yes or no" answer georged expect it be. Imported warm air from Siberia carries lots of energy with it (relative to "normal" Arctic athmosphere), and is prime reason for a cyclone to rage. Consequences will vary dramatically depending on what kind of weather will happen over affected areas during following several weeks. If it'll be much sunshine over massively ponded or (even worse) slushed ice, - Neven termed this case "high after the low" way, - then it can be said that yes, this warm air from Siberia did more harm than "just sunshine" instead of it would do. Hence Neven's mention of good old Mike Tyson in his prime.

We just don't know the answer. Yet.

P.S. I think we should never underestimate ocean mixing. Water is most dense at ~4C iirc, which means, colder water in calm conditions form up a layer on top of any +4C water, protecting the ice from a bit-deeper warmer waters. Ice itself forms such a layer directly under it, via bottom melting a little bit to make it happen, creating equilibrium state at the solid-liquid border. And then, whereever there is just 20-meters-thick layer of +4C water not far from surface - especially if it's less than 50 meters deep for such layer to exist, - mixing the column can melt 1 meter of ice real quick. Difference in density is very small, so it doesn't take much wave action to mix it up well. Storms obviously do it best, but even strong winds acting upon some openings between ice fields mix it up significantly already. And if it's more than just 20 meters of +4C water layer, - at places there is times more, - then even MYI fields can "poof" away.
« Last Edit: June 22, 2017, 05:02:05 PM by F.Tnioli »

meddoc

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Re: The 2017 melting season
« Reply #2205 on: June 22, 2017, 05:05:34 PM »
https://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif

Looking at the dynamic- brutal melt commencing in this week; I am not sure, that the Ice is gonna hold on until Autumn Equinox.
Meanwhile multi- level shelf Clouds and Supercells are popping up on a weekly Basis. Apart from the lasting Heatwaves.

This is the Prelude to PETM or even worse, once the Methane starts really firing.

Jim Williams

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Re: The 2017 melting season
« Reply #2206 on: June 22, 2017, 05:54:29 PM »
P.S. I think we should never underestimate ocean mixing. Water is most dense at ~4C iirc, which means, colder water in calm conditions form up a layer on top of any +4C water, protecting the ice from a bit-deeper warmer waters. Ice itself forms such a layer directly under it, via bottom melting a little bit to make it happen, creating equilibrium state at the solid-liquid border. And then, whereever there is just 20-meters-thick layer of +4C water not far from surface - especially if it's less than 50 meters deep for such layer to exist, - mixing the column can melt 1 meter of ice real quick. Difference in density is very small, so it doesn't take much wave action to mix it up well. Storms obviously do it best, but even strong winds acting upon some openings between ice fields mix it up significantly already. And if it's more than just 20 meters of +4C water layer, - at places there is times more, - then even MYI fields can "poof" away.

This is exactly what I expect to happen to the entire Arctic Ocean at some point, but the interplay between wind, leads in the ice, and rising water vapor is so complex and chaotic that there is no way to tell when it will happen.  I'm just convinced that at some point the heat in the sea rises and rather suddenly melts the ice -- all of it.

magnamentis

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Re: The 2017 melting season
« Reply #2207 on: June 22, 2017, 05:56:49 PM »

Does imported warm air from Siberia and ocean mixing count for more than the significant reduction in insolation during the peak week for sunlight?

I don't think so, especially near the solstice.  But these are only two factors in a system of fascinating complexity.  Among the others: rain will strip away much of the remaining snow cover over areas of higher-than-normal albedo, and the position of the cyclone means winds will push some thicker ice closer to the Fram exit.


solstice up north is not much more insolation than a winter sun in mid-latitudes and i can assure you from experience that nothing melts ice faster than warm "MOVING" air, second only to warm water, second even by far, but hot water is not the main topic here.

about that rainfall's impact on ice compared to insolation etc. it would certainly not apply like this in mid-latitudes but since, as mentioned above, insolation is never THAT strong that far up north and in combination with the winds and the water (rain) making the ice darker, especially where is still some snow on the surface, which then adds to albedo, i'd say YES to that question, depending also on the amount and time period of rain, but in general i'd still say yes.
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rboyd

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Re: The 2017 melting season
« Reply #2208 on: June 22, 2017, 06:13:38 PM »

"solstice up north is not much more insolation than a winter sun in mid-latitudes"

As per below a "winter sun at mid latitudes" (30 to 60 degrees) provides less than half the insolation of a summer solstice sun up north



Bill Fothergill

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Re: The 2017 melting season
« Reply #2209 on: June 22, 2017, 06:24:53 PM »
... solstice up north is not much more insolation than a winter sun in mid-latitudes ...

NASA (to name but one source) would disagree

https://earthobservatory.nasa.gov/Features/EnergyBalance/page3.php


Around the time of the boreal summer solstice, average daily insolation at the NP exceeds that at the equator. (This effect is even more pronounced in Antarctica at the austral summer solstice, as that occurs only about 2 weeks before perigee. There's about 5 million kms difference in Earth's distance from the Sun between perigee and apogee.)

rboyd

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Re: The 2017 melting season
« Reply #2210 on: June 22, 2017, 06:32:38 PM »
Bill, slightly OT but that means that the loss of sea ice in the Antarctic would have a greater warming effect per square metre, albedo wise, than the loss at the same latitude (north vs. south) in the Arctic?

magnamentis

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Re: The 2017 melting season
« Reply #2211 on: June 22, 2017, 06:46:03 PM »
hi all,

i put it wrong, i MEANT the angle of the sun, the objective strenth of the sun, but said otherwise, sorry for that.

of course that amount of insolation over quasi 24 hours ( i know it depends again LOL ) is providing more energy than a winter sun at a 30 degree angel for 1 or 2 hours only

sorry again for the statement that was not thought to the end, sh... happens you're all right of course

EDIT: uppssss..... almost forgot: thanks for letting me know/ making me aware again, very much appreciated
« Last Edit: June 22, 2017, 06:53:56 PM by magnamentis »
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Flocke

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Re: The 2017 melting season
« Reply #2212 on: June 22, 2017, 07:21:11 PM »
Bill, slightly OT but that means that the loss of sea ice in the Antarctic would have a greater warming effect per square metre, albedo wise, than the loss at the same latitude (north vs. south) in the Arctic?

Insolation should be inverse proportional to the square of the distance. This gives 7% more insolation at perigee compared to apogee, i.e. this is the max difference.
When nearer to the sun, the earth has a larger angular velocity. This leads to the northern summer half of the year beeing 186 days, the winter half 179 days long. Yay, we get more sunshine! ;)
My guess is that the second effect outwheighs the first.

Jim Pettit

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Re: The 2017 melting season
« Reply #2213 on: June 22, 2017, 07:40:14 PM »
Guys, this thread is for a discussion exclusively about the current melting season, not topics such as solar insolation. If you have any further comments on that matter, please take them elsewhere. Thanks!

Clenchie

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Re: The 2017 melting season
« Reply #2214 on: June 22, 2017, 08:54:27 PM »
It must be only a matter of days before Herald Island is freed from the ice, which must surely be a sign of an early melting season in the Chukchi Sea.  8)
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Lord M Vader

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Re: The 2017 melting season
« Reply #2215 on: June 22, 2017, 09:06:16 PM »
Neven, the ECMWF 12z op run, as well as the GFS 12z op run depicts just the scenario you were talking about after the bomb cyclone with a return to more high pressure influenced weather. Might be a nightmare for the rest of the season if it is a more persistent pattern shift.

mdoliner

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Re: The 2017 melting season
« Reply #2216 on: June 22, 2017, 09:13:51 PM »
Perhaps this is obvious, but I haven't seen it mentioned that every chunk of ice exported through the Fram or elsewhere into warmer non-arctic waters is equivalent to the latent heat necessary to melt that ice imported directly to the arctic ice. According to this paper
http://www.the-cryosphere.net/11/65/2017/
export has since 1935 averaged about 880,000 km2 or roughly 10% of the yearly decline, but has been trending up by 6% per decade since 1979 (11% during summers). Given the condition of the ice I wonder  if  the cloudier stormier weather might cause a big change this year.

seaicesailor

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Re: The 2017 melting season
« Reply #2217 on: June 22, 2017, 10:37:46 PM »
The circulation around the low is going to shield the Arctic against the heat wave in Siberia.
The ECMWF ensemble forecast shows a colder Arctic indeed but with a much warmer Beaufort sea and CAA from day 5. Strong pull of airmass from the Pacific and North America.
Edit. Forgot to add the plot of 850 hPa temp anomalies in five days.
« Last Edit: June 22, 2017, 10:58:52 PM by seaicesailor »

Neven

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Re: The 2017 melting season
« Reply #2218 on: June 22, 2017, 11:13:19 PM »
Neven, the ECMWF 12z op run, as well as the GFS 12z op run depicts just the scenario you were talking about after the bomb cyclone with a return to more high pressure influenced weather. Might be a nightmare for the rest of the season if it is a more persistent pattern shift.

Interestingly, the 963 hPa on D4 from today's 00Z run has disappeared again. Now we have 968 hPa on D5 as the lowest (preceded by 970 hPa one day earlier). The high pressure only shows up on D9 and D10, so that's pretty unreliable.

I'm really starting to wonder how low this cyclone will go three-five days from now. Let's see if the low hPa keeps getting closer still.
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Tigertown

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Re: The 2017 melting season
« Reply #2219 on: June 22, 2017, 11:23:05 PM »
New wave activity today between the Chukchi and Beaufort Seas.
Pic from the 20th as it was the clearest from a recent day. Not exact coordinates, but the general area.

slow wing

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Re: The 2017 melting season
« Reply #2220 on: June 23, 2017, 12:42:35 AM »
Neven, Re your #2218, yes ECMWF has backed off on the strength of the predicted 'weather bomb' storm and also pushed it later.

  The same is true of 3 other models on tropicaltidbits.com that previously predicted it. (The exception is CMC, which still shows it at the same time and strength.)

  NAVGEM is now at 976 hPa on their 12z run - close to their 978 hPa prediction from 12 hours earlier - so they were the only model not predicting 970 hPa or lower.

The updated predictions are attached. They can be compared with the predictions from 12 hours ago shown in my post #2198.


  So it looks more likely that there won't be a 960s weather bomb after all in the next few days.


  The persistent storm does look like it will re-strengthen though over that timeframe, perhaps down to the mid- or high- 970s. That would still be a strong storm and as far as I know a record low pressure for June in the satellite era (beating 980 hPa, in 2013).

  The ice appears to be mobile this year so this persistent storm will likely, by its end, have displaced ice by up to hundreds of kilometers over much of the Arctic Basin.

  As Romett1 notes above at #2202, HYCOM predicts this as well. The main effect will likely be a lot of ice pushed over towards the Barents Sea and Fram Strait, along with gaps opening up in the interior of the pack.
« Last Edit: June 23, 2017, 12:50:36 AM by slow wing »

Bruce Steele

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Re: The 2017 melting season
« Reply #2221 on: June 23, 2017, 12:44:19 AM »
We have water temperature readings again for Red Dog Dock, Kotzebue Sound. There is still some fast ice there and water temperature at 30.2F   Nome also has water temperatures at 43F.  As soon as the fast ice breaks loose at Red Dog Dock we will have real time temperatures for the Kotzebue Sound and see what is pushing through the Bering Strait.

http://www.ndbc.noaa.gov/radial_search.php?lat1=67.575N&lon1=164.067W&uom=E&dist=250

Csnavywx

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Re: The 2017 melting season
« Reply #2222 on: June 23, 2017, 12:50:28 AM »
Neven, the ECMWF 12z op run, as well as the GFS 12z op run depicts just the scenario you were talking about after the bomb cyclone with a return to more high pressure influenced weather. Might be a nightmare for the rest of the season if it is a more persistent pattern shift.

Interestingly, the 963 hPa on D4 from today's 00Z run has disappeared again. Now we have 968 hPa on D5 as the lowest (preceded by 970 hPa one day earlier). The high pressure only shows up on D9 and D10, so that's pretty unreliable.

I'm really starting to wonder how low this cyclone will go three-five days from now. Let's see if the low hPa keeps getting closer still.

Two points. I want to preface this by saying that I use these models on a daily basis as a meteorologist and have done so for quite a few years.

1) Unless you're getting pay-site data, the EC only comes in time steps of 24hr. Since it releases runs every 12 hours, you're not getting to view the same time stamp from run to run. Thus, in this case, it very well could drop to the previous run's value in between tau times.

2) The point you make about data reliability at D9/D10 can't be stressed enough. Deterministic runs lose skill rapidly after D5. It's imperative to all who post here that the ensemble runs are posted instead. The only exception is when the deterministic run is supported by the ensemble, in which case it probably has some value. Ensemble means are specifically designed to reduce error in the medium-long range by means of averaging and dampening outlier solutions. In either case, if a deterministic run is posted past D5 (120hr) -- it should have it's accompanying ensemble posted as well OR at the very least have an agreeing deterministic run posted with it (e.g. those cases where the GFS and EC agree at those time ranges). That is -- if we're to take it seriously.

Cook

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Re: The 2017 melting season
« Reply #2223 on: June 23, 2017, 01:12:13 AM »
This is something of an old discussion, rain vs. sunshine. From experience I've seen rainstorms melt ice very fast, in spite of low temperatures and not particularly large amounts of rainfall. The strength of the wind seems to be a major factor, probably because the biggest effect comes from condensation of water vapor from the air, and the stronger the wind, the greater amount of humid air can come into contact with a given area of ice.

But this is just a guess - all I can say from experience is that rain storms with strong winds seem to be the most effective way to melt snow and ice during early spring (at around 60N).

"Rain, fog or high humidity really boosts melting because water has a much higher heat capacity than air. Thus conductive and convective heat transfer is far more efficient, than when snow is surrounded by dry air."

https://www.quora.com/What-is-the-impact-of-various-factors-temperature-rain-sunlight-which-cause-snow-to-melt-Would-snow-melt-faster-on-a-rainy-40F-day-cloudy-50F-day-or-sunny-35F-day

And this:

"In the spring, snow cover can melt rapidly if warm, humid air pushes in above the snow and lowers the temperature of this humid air to the point that fog forms. The fog droplets forming at the snow surface release the latent heat of condensation, which helps to melt the snow."

https://www.quora.com/Why-does-fog-melt-snow

Warm air at near saturation combined with rain will surely melt snow and ice fast. The influx of heat, and winds that are likely to compact the ice and mix warmer waters upward are likely to be quite destructive during the next several days.

DavidR

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Re: The 2017 melting season
« Reply #2224 on: June 23, 2017, 05:48:52 AM »
Perhaps this is obvious, but I haven't seen it mentioned that every chunk of ice exported through the Fram or elsewhere into warmer non-arctic waters is equivalent to the latent heat necessary to melt that ice imported directly to the arctic ice. According to this paper
http://www.the-cryosphere.net/11/65/2017/
export has since 1935 averaged about 880,000 km2 or roughly 10% of the yearly decline, but has been trending up by 6% per decade since 1979 (11% during summers). Given the condition of the ice I wonder  if  the cloudier stormier weather might cause a big change this year.
It's also worth noting that  export throught Nares, when the arches do not form, adds about 5% to the normal export so we can expect to see an additional 150 Km^2 going out through Nares this year.
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Tigertown

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Re: The 2017 melting season
« Reply #2225 on: June 23, 2017, 09:05:36 AM »
Throughout the day, look for massive quantities of warm air to pour into the Arctic from the Pacific side. It will pass through the Bering Strait, and over Alaska and Siberia. It is a deep mass of moist warm air, not just a surface breeze. A similar situation in other areas has thus far broken loose fast ice and diminished other sea ice. Although the exact patterns may change, the overall influx will continue into the foreseeable future.

Neven

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Re: The 2017 melting season
« Reply #2226 on: June 23, 2017, 09:56:21 AM »
Enough with the theoretical stuff about fog and rain effects on snow and ice already! This is the melting season thread!  :P
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Thawing Thunder

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Re: The 2017 melting season
« Reply #2227 on: June 23, 2017, 11:32:19 AM »
Enough with the theoretical stuff about fog and rain ...

OK, so I wonder if in this rather average melt season the subperforming melt of Greenland is the price for the elevated temperatures on the pacific side - and how both factors (strong melt versus weak melt) will play out in the season's endgame?

EDIT:

All along the next 36 hours it is predicted, that Greenland will receive above average heat. This could change the melting graph considerably.
« Last Edit: June 23, 2017, 12:50:40 PM by Thawing Thunder »

Neven

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Re: The 2017 melting season
« Reply #2228 on: June 23, 2017, 01:24:40 PM »
1) Unless you're getting pay-site data, the EC only comes in time steps of 24hr. Since it releases runs every 12 hours, you're not getting to view the same time stamp from run to run. Thus, in this case, it very well could drop to the previous run's value in between tau times.

Right, that makes sense. I remember looking at GFS temperature maps and not understanding why there were these huge fluctuations every 12 hours. It took me a while to realize that this had to do with the difference between night and day!

I don't mind feeling stupid, as that means I'm catching myself. It's worse being stupid and not noticing it. On the other hand, ignorance is bliss.  ;)

But does the same apply to SLP? Ie, the fluctuations between 12-hour runs. I thought that maybe it had to do with models struggling to forecast an intense cyclone in June.

Quote
2) The point you make about data reliability at D9/D10 can't be stressed enough. Deterministic runs lose skill rapidly after D5. It's imperative to all who post here that the ensemble runs are posted instead. The only exception is when the deterministic run is supported by the ensemble, in which case it probably has some value. Ensemble means are specifically designed to reduce error in the medium-long range by means of averaging and dampening outlier solutions. In either case, if a deterministic run is posted past D5 (120hr) -- it should have it's accompanying ensemble posted as well OR at the very least have an agreeing deterministic run posted with it (e.g. those cases where the GFS and EC agree at those time ranges). That is -- if we're to take it seriously.

I wanted to ask a couple of stupid questions about ensembles, but then decided to look it up myself and found this informative PDF from ECMWF. Thanks for putting me on this track, Csnavywx.

I will try and embed the EPS forecast (based on ECMWF ensemble) in my daily routine, but here I'll keep reporting on the D1-D6 forecast from the deterministic run, especially when it concerns cyclones, as I'm mostly interested in how low the SLP could go (and an ensemble will probably conservatively muffle the number).

But as a test and educative experience, I will make a side-by-side comparison of the D1-D6 forecasts of the ECMWF deterministic run, the EPS ensemble run, and the D0 images for the coming 6 days.

Here are both the deterministic and ensemble run for the coming 6 days. The ECMWF forecast (00Z run) now has 967 hPa for D4 (ensemble has 976 hPa):
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gerontocrat

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Re: The 2017 melting season
« Reply #2229 on: June 23, 2017, 01:47:23 PM »
I was wondering if the Jaxa sea ice thickness images over the last few days have been showing the effect of winds in the CAB, especially the almost circular striations. If so, does that also indicate the poor state of the ice in both thickness and compaction?

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Re: The 2017 melting season
« Reply #2230 on: June 23, 2017, 01:51:08 PM »
@Neven

He's referring to the fact that free ECMWF access only allows one frame at 24 hour intervals.  So the 0z runs only show what's happening at 0z each day, the 12z shows only what's happening at 12z.  Without the in between frames, comparing 0z to 12z runs from free sites is problematic, as the time stamps are 12 hours apart. 
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Neven

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Re: The 2017 melting season
« Reply #2231 on: June 23, 2017, 01:54:13 PM »
@Neven

He's referring to the fact that free ECMWF access only allows one frame at 24 hour intervals.  So the 0z runs only show what's happening at 0z each day, the 12z shows only what's happening at 12z.  Without the in between frames, comparing 0z to 12z runs from free sites is problematic, as the time stamps are 12 hours apart.

Right, and like I said, you get these big swings for temperature because of night and day. But SLP doesn't fluctuate that much because of the difference between night and day, right?
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FishOutofWater

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Re: The 2017 melting season
« Reply #2232 on: June 23, 2017, 02:21:53 PM »
The arctic does not have the kind of thermal variations of a place like the Gobi desert that would cause significant diurnal pressure changes.

F.Tnioli

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Re: The 2017 melting season
« Reply #2233 on: June 23, 2017, 02:36:19 PM »
...
Right, and like I said, you get these big swings for temperature because of night and day. But SLP doesn't fluctuate that much because of the difference between night and day, right?
Between polar night and polar day, sure there are these real big swings indeed. Please be careful comparing things from 6 months ago and things from right now, OK? :)

seaicesailor

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Re: The 2017 melting season
« Reply #2234 on: June 23, 2017, 02:41:37 PM »
I was wondering if the Jaxa sea ice thickness images over the last few days have been showing the effect of winds in the CAB, especially the almost circular striations. If so, does that also indicate the poor state of the ice in both thickness and compaction?
Well, the melt over the Beaufort sea is monumental, that map confirms. Almost not visible by clouds. Really warm along  Alaska

VeliAlbertKallio

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Re: The 2017 melting season
« Reply #2235 on: June 23, 2017, 02:54:20 PM »
There appears today numerous polynyas, circular openings on CAB sea ice, north of Chukchi and Bering Seas. A telltale sign of thin ice melting fast on sun's exposure. Expect this area to melt quickly if sunshine, heat, winds or waves occur in this weak ice: https://worldview.earthdata.nasa.gov/?p=arctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2017-06-23&z=3&v=-1443301.2837102544,914100.5384559152,-1181157.2837102544,1079220.5384559152

gerontocrat

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Re: The 2017 melting season
« Reply #2236 on: June 23, 2017, 04:10:33 PM »
NIGHT AND DAY TEMPERATURE VARIATIONS.
Since I am too dumb and not up to understanding the science in all the weather projections, I have to rely on the 5 day outlooks from cci-reanalyzer. But I thought I would see what the 5 day min and max temperature  images looked like, and assume that most of the difference in such a few days would be from night and day. The simplistic conclusion seems to be that where the minimum difference between max and min temperatures is the Arctic Ocean. Given that it is the high Arctic and close to the summer solstice, and over the moderating influence of water and ice, this seems logical.
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Crocodile23

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Re: The 2017 melting season
« Reply #2237 on: June 23, 2017, 04:39:08 PM »
@Neven

He's referring to the fact that free ECMWF access only allows one frame at 24 hour intervals.  So the 0z runs only show what's happening at 0z each day, the 12z shows only what's happening at 12z.  Without the in between frames, comparing 0z to 12z runs from free sites is problematic, as the time stamps are 12 hours apart.

There is free access to ECMWF per 3 hours in windy. The interface is complicated but it has tons of features. Here i give some variables to see.

The time/date can be changed from below. It's on 3 hour steps following 0 UTC, 3 UTC etc, and if you put something in-between then it goes on the nearest possible.

wind:
https://www.windy.com/overlays?2017-06-25-12,74.730,150.293,3

wind gust:
https://www.windy.com/overlays?gust,2017-06-25-12,74.730,150.293,3

Surface temperature:
https://www.windy.com/overlays?temp,2017-06-25-12,74.730,150.293,3

950 hPa temperature:
https://www.windy.com/overlays?950h,temp,2017-06-25-12,76.101,152.402,3

Waves:
https://www.windy.com/overlays?waves,2017-06-25-12,72.554,149.238,3

pressure:
https://www.windy.com/overlays?pressure,2017-06-25-12,76.101,152.402,3

Rain/snow:
https://www.windy.com/overlays?rain,2017-06-25-12,75.629,135.879,3

Cloudiness:
https://www.windy.com/overlays?clouds,75.629,135.879,3

« Last Edit: June 23, 2017, 04:44:38 PM by Crocodile23 »

JayW

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Re: The 2017 melting season
« Reply #2238 on: June 23, 2017, 05:48:43 PM »

Right, and like I said, you get these big swings for temperature because of night and day. But SLP doesn't fluctuate that much because of the difference between night and day, right?

It's not a day or night thing I'm referring, it's what happens weather-wise between frames. 

For instance, let's say there's a forecast for a 980mb low at hour 72, and at hour 96 it's also 980mb.  That doesn't necessarily mean our started 980 the whole time, it could have dropped into the 960s and then risen back to that 980.  Or, it may have weakened and then dropped back to 980.

There's also the nature of the storm.  It's fairly prolonged.  It's a large upper level system that's gobbling up shortwave energy to sustain itself.  These shortwaves rotate into the large scale circulation, and drive the surface low pressure, often multiple low pressures.  It looks like one prolonged low, which it is in the upper atmosphere more or less, but surface lows keep redeveloping, strengthen, fill, transfer energy and weaken, and repeat..

It's difficult to time these waves, so a difference of 12 hours can mean the pressure has risen or fallen quite substantially.

Hope that makes sense.

@Crocodile23

Thanks, I'll check that out.
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A-Team

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Re: The 2017 melting season
« Reply #2239 on: June 23, 2017, 05:51:30 PM »
Quote
I found this informative PDF from ECMWF. Thanks for putting us on this track, Csnavywx.
Right. Here the question is the ECMWF's RPSS skill level (improvement relative to climatology) specifically for the Arctic Basin's SLP ensembles past D5 rather than say for some heavily instrumented mid-latitude region where the mission-critical initial conditions are much better known. That's not so easy to determine since the final conditions necessary for that evaluation aren't that well known for the AO either. Note too the pronounced season variation in RPSS skill (2nd image below, green box).

https://www.ecmwf.int/sites/default/files/elibrary/2012/14557-ecmwf-ensemble-prediction-system.pdf nice explanation
http://journals.ametsoc.org/doi/pdf/10.1175/MWR3280.1 oft-cited article on RPSS skill

I've been looking (heuristically) at 'skill level' of the much maligned Hycom ice thickness map at D7 as explained over on the mid-June Piomas forum, #1919. This is a different situation from ECMWF meteorological prediction because we have no ensembles, no stable unskilled baseline and no idea what the real ice thickness distribution is at D0 much less D7, so changes are relative.

However, just like the example in the ECMWF pdf, a lot depends on the drama level over the time span. Here I picked June 19th as D0 fixed Hycom hindcast) because the June 26th forecast was showing a remarkable thinning of ice on the Siberian side on D7.

The prediction is holding up fairly well though less has happened than originally foreseen, or rather what was foreseen on the 19th is foreseen today as coming about on the 30th, namely very thin ice expanding poleward from Siberian half of the Arctic Ocean.

There is no current observational data on actual ice thickness in this region. However there is daily data on the ice pack boundary. Hycom there uses its current position as adjusted by ice motion and concentration forecasts (which both bring in weather prediction); forecast skill for ice edge is thus more readily vetted against observation. Even here, there is no counterpart to ECMWF vs GFS comparisons as Hycom is the only one venturing out beyond D0.
« Last Edit: June 24, 2017, 06:42:15 AM by A-Team »

seaicesailor

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Re: The 2017 melting season
« Reply #2240 on: June 23, 2017, 07:54:27 PM »
Wow thx Crocodile23 for reminding us about the tool and all the uses...
So didnt wait to check on the Beaufort winds and temps next 5 days, and yes, major melt along Alaska, if this tool is showing temps right, it looks pretty in accord with what can be inferred from the tripicaltidbits. The Beaufort sea is well in its way to ice-free again.

FishOutofWater

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Re: The 2017 melting season
« Reply #2241 on: June 23, 2017, 08:57:34 PM »
All the weather models are challenged by the formation of blocking highs. The switch from a positive to negative AO is very hard to forecast. The ECMWF forecasts for temperature are stabilized by the ice and water of the Arctic ocean but the ridges, troughs, highs and lows are not.

magnamentis

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Re: The 2017 melting season
« Reply #2242 on: June 23, 2017, 10:08:57 PM »
Guys, this thread is for a discussion exclusively about the current melting season, not topics such as solar insolation. If you have any further comments on that matter, please take them elsewhere. Thanks!

probably i gonna bang my head again but i disagree as far as how is it possible to seriously discuss melting season without from time to time talking about insolation since it's a main factor around solstice ?

<snip; it's fine to talk about insolation taking place right now, or about fog or rain, or whatever, but I'd prefer not to see endless theoretical back-and-forths about enthalpy and how much energy it takes to melt 1 kg of ice, etc, etc; N.>
« Last Edit: June 23, 2017, 10:46:21 PM by Neven »
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StopTheApocalypse

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Re: The 2017 melting season
« Reply #2243 on: June 23, 2017, 11:08:00 PM »
Latest run (12z) has low bottoming out as 975 (GFS) or 970 (ECMWF) mb. Hycom suggests this will result in large drop in concentration (and thickness) over center of basin.

Edit: err, having some trouble attaching images. Any tips? I took it straight from the hycom snapshot archive.

Edit 2: Thanks!
« Last Edit: June 23, 2017, 11:44:10 PM by StopTheApocalypse »

oren

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Re: The 2017 melting season
« Reply #2244 on: June 23, 2017, 11:39:42 PM »
Edit: err, having some trouble attaching images. Any tips? I took it straight from the hycom snapshot archive.
The image is probably too large. 700 x 700 pixels should work, width especially is a constraint, try to crop or resize.

seaicesailor

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Re: The 2017 melting season
« Reply #2245 on: June 24, 2017, 01:17:08 AM »
The latest EC forecast is warmer for the Arctic than the previous ones, including the warm spell in Beaufort sea these days but also a deep low entering from Siberia will bring very warm airmasses (but very briefly) into Laptev and ESS in day 3-4. In previous runs the Arctic seemed shielded from Siberian heat wave. All within 5 days ;)
I assume the Laptev/ESS warm temperatures will come with rain.
« Last Edit: June 24, 2017, 01:22:32 AM by seaicesailor »

slow wing

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Re: The 2017 melting season
« Reply #2246 on: June 24, 2017, 02:59:12 AM »
The weather models on tropicaltidbits.com are now all predicting the storm pressure to bottom out in about 3 days' time.

 They all predict it to beat the previous record in the satellite era for low sea level pressure in the Arctic Basin in June, of 980 hPa in 2013, and by a fair margin.

As shown below, the predictions range from 966 hPa up to 974 hPa.

Tigertown

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Re: The 2017 melting season
« Reply #2247 on: June 24, 2017, 03:13:41 AM »
The areas of wave activity in the Beaufort, Chukchi, ESS, and Laptev seas are all starting to link together now.

romett1

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Re: The 2017 melting season
« Reply #2248 on: June 24, 2017, 07:06:38 AM »
Lot of clouds, but look at this ice mobility between North Pole and Kara Sea. Image: Worldview, Jun 23.

jdallen

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Re: The 2017 melting season
« Reply #2249 on: June 24, 2017, 08:09:06 AM »
Lot of clouds, but look at this ice mobility between North Pole and Kara Sea. Image: Worldview, Jun 23.
This, is a nightmare; peak of installation, major storm disrupting the pack and simultaneously pulling heat up from depth.

We arent even into July.
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