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Messages - Greenbelt

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Arctic sea ice / Re: The 2019 melting season
« on: August 22, 2019, 12:06:38 AM »
Yes good job ^^ joke aside, GFS has been really behind the curve lately.
What's a GFS?
It's the U.S. Global Forecast System, the computer weather model that drives the nullschool illustrations.
If you look at the nullschool menu bar you see this:  Source | GFS / NCEP / US National Weather Service

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Arctic sea ice / Re: The 2019 melting season
« on: August 13, 2019, 10:34:09 PM »
I've been somewhat hesitant to post about the weather forecast, but this week's forecast is too interesting to ignore. For about a week now, the models have been predicting a big surface high over the East Siberian sea, with surface low pressure around the Atlantic ice front/Barents and moderately low pressure as well around the eastern Alaskan coast toward the Beaufort sea. For example compare today's ECMWF initialization shown below with that of seven days ago, and you can see that last week's forecast for today verified quite closely: https://tropicaltidbits.com/analysis/models/?model=ecmwf&region=nhem&pkg=z500_mslp&runtime=2019080612&fh=168

What is interesting to me is that the op EC model keeps today's pattern roughly in place for the next week. The GFS and Canadian also support that idea, with the ESS high arcing gradually toward the Alaskan coast and the Atlantic side low drifting over the central ice.  Regardless of the nuances, the Siberian coast heat wave and the consistent southerly winds from the Laptev sea area should test Friv's hypothesis.  Friv had suggested up thread that the ESS didn't melt out early enough this year to allow the open water to warm enough that it could really attack the CAB ice late in the season.  That seemed reasonable at the time, but this extended warm period along Siberia, and the extended periods of southerly winds from Asia toward the pole makes it interesting. I wonder if there is still enough sun power to really heat that newly open water along the ESS and Laptev, and if the fetch of southerly wind would be enough to transport some of that warmth toward the central ice over the next week or two?

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Arctic sea ice / Re: The 2019 melting season
« on: July 16, 2019, 08:22:26 PM »
The near-term outlook looks to me to be rather poor for ice volume on the Atlantic side.  Winds around the big surface high pressure may push rather weak ice back into the Laptev Sea area, where it may melt in relatively warm seas perhaps.  Although Fram export would seem to stay stopped under this pattern, the Atlantic front may shrink back toward the pole a little maybe. There are some areas on the Atlantic side of the pole where the ice looks to me on Worldview to be a bit more contiguous and less rubble strewn than some prior years, so the weather this week may help melt an area that was looking a little bit more resilient this year? Despite the cooler air temp forecast in the ESS and Beaufort, I think much of the ice in those areas is doomed over the next two months due to warm water. Now the Atlantic may take a hit from still-strong sun for a few days at least?

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Arctic sea ice / Re: The 2019 melting season
« on: July 02, 2019, 08:13:21 PM »
Yay more long-term forecasts that'll never be referenced again.
Hmmm. I try to check the weekly forecast each weekend. So far this season I think the 5-7 day forecasts have been remarkably accurate. We had advance notice of the large ESS high that torched the Laptev and ESS, advance of the low that traversed the arctic, advance of the recent Greenland-toward-ESS ridge, advance of the current rapid Fram export, and so on. For this week we can use the forecasts to watch out for a wind and heat event in the Barentz, a heat wave with jet stream to nearly the arctic in Alaska, and lower pressure in Siberia coasts mostly. The ensembles are still showing a classic dipole with high on the Canadian side and low pressure along Russia. Below is was the operational GFS for today from 7 days ago -- to my eyes the models have been predicting the main patterns quite accurately for many weeks now. After 5-7 days the operational models can generate some fanciful results to be disregarded, of course.  Nevertheless, I find tracking the forecasts a week ahead very useful for trying to learn what sorts of weather leads to better or worse melting conditions, which is a challenging question even for our experts I think. If Neven thinks the weather forecast discussion is clogging this main thread I think we could create a different thread for the looking ahead perhaps.

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Arctic sea ice / Re: The 2019 melting season
« on: June 26, 2019, 04:01:38 PM »
Area and extent are imperfect indicators, but at least can be directly and fairly reliably measured, unlike, say, volume. Area and extent numbers and maps from the various outfits that produce them (NOAA, uni Bremen, Jaxa ...) stay in general agreement while what volume maps exist are much more idiosyncratic.

My main idea is that we stop referring to changes in area and extent as "melting" or "freezing."  Volume measures, however imperfect, indicate melt or freeze.  Although long-term trends in area and extent measures are certainly correlated with melt/freeze, short term changes in the extent and area measures do not necessarily indicate overall melting or freezing situation. Extent can increase due to dispersion etc., even where there is overall melting. I think using the shorthand of "melt" or "freeze" with area and extent measures may be a source of confusion sometimes.

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Arctic sea ice / Re: The 2019 melting season
« on: June 24, 2019, 09:08:35 PM »
How did the D8-D10 forecasts that were posted here 5/10/15/20/25/30 days ago pan out?
Was just looking. Tropicaltidbits.com makes it super easy to compare forecasts from 7 days ago with the current initialization.  A week ago (top pic), ECMWF predicted a 1033mb ridge off the ESS; today they're initializing at 1028 in the same place (bottom pic).  A pretty good forecast!  However, the huge 1040+ high that the 8-10 day forecasts had put over the central Arctic has been lowered dramatically in the new forecast runs.  Both EC and GFS have it more elongated from ESS toward Greenland and about about 1032mb, with small lows in the CAA and deeper low in the Barentz. So thankfully not the basin dominating super-high that was predicted, but still should have lots sun and still quite a bit of export to the Atlantic I think.


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Arctic sea ice / Re: The 2019 melting season
« on: June 18, 2019, 08:51:07 PM »
Two things of interest looking at today's model guidance for the next week. First, that new low that enters the Arctic from central Asia is projected to scoot very quickly across to the Canadian archipelago. Second, the persistence of the high pressure over the East Siberian sea -- GFS has it lasting into July (!) and ECMWF 12z operational shows the high continuing to build out well over a week. (Usual caveats that 5-10 day predictions not necessarily reliable etc. etc.)

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Arctic sea ice / Re: The 2019 melting season
« on: May 26, 2019, 03:17:09 AM »
Subsidence is a pretty useful precise term in meteorology. Would you also complain about a pilot using precise jargon like "elevator" or "horizontal stabilizer" or "trim" to explain an aviation concept? If you want explanation using layman's terms, feel free to ask, preferably in a different thread. This thread watches the ice and the weather etc. Mackenzie delta.

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Arctic sea ice / Re: The 2019 melting season
« on: May 01, 2019, 03:04:37 AM »
This was ECMWF's forecast for tomorrow from 7 days ago.  Pretty similar to the setup we're actually expecting tomorrow, with strong high pressure from the Beaufort coast to Greenland, and low pressure in the Kara Sea area. I know the models are often wrong, but they are also often right, at least out 7 days.

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Arctic sea ice / Re: The 2018 melting season
« on: August 13, 2018, 10:44:43 PM »
On the Pacific side, it will be fun to watch the Healy, now at 71.6n and headed north. Water temp 6.8C
http://icefloe.net/uscgc-healy-track-map
http://icefloe.net/Aloftcon_Photos/

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Arctic sea ice / Re: The 2018 melting season
« on: August 09, 2018, 11:50:55 PM »
As the high pressure slides east along the Siberian coast, low pressure builds in, mostly following along the coast from the Atlantic side. That should bring lots of southerly winds, first in the Laptev area, eventually in the East Siberian sea. If we believe ECMWF, winds could be quite strong, pushing scattered ice mostly toward the central main pack I think. After a few days, the EC model deepens the low down below 980mb for a couple days, which could really stir things up. We'll see!


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Arctic sea ice / Re: The 2018 melting season
« on: June 16, 2018, 02:39:01 AM »
A nice Worldview pic from the recent small dry cyclone between the Laptev and East Siberian seas, showing some ice moving southbound toward the Lena delta on northerly winds. Also a spectacular image of the inbound Atlantic moisture-bringing cyclone between Norway and Iceland/Greenland.


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Arctic sea ice / Re: The 2018 melting season
« on: June 10, 2018, 09:21:03 PM »
My next area to watch on worldview is the East Siberian Sea, which seems a bit behind in melt preconditioning compared with some recent years. ECMWF and GFS initialize a 1030mb high over far eastern Siberia, which should continue the clear skies and bring in southerly winds and probably finish off the land-based snow. I'm interested to see how fragile this area is.


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Arctic sea ice / Re: The 2018 melting season
« on: June 07, 2018, 06:44:42 PM »

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Arctic sea ice / Re: The 2018 melting season
« on: June 07, 2018, 01:55:34 PM »
Yep latest GFS initializes at 959!

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Arctic sea ice / Re: The 2018 melting season
« on: June 04, 2018, 08:38:04 PM »
Worldview shows the developing cyclone

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