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Interview with Judah Cohen

sebastiaan1973

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sebastiaan1973

sebastiaan1973

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Judah Cohen is one of the world's leading scientists in winter forecast. In 1999 he and Entekhabi demonstrated a strong statistical relationship between Eurasian snow cover extent (SCE) anomalies in the fall and the Arctic Oscillation in winter, later on he found a strong correlation between Eurasian snow cover advance and winter AO. Nowadays he is Director of Seasonal Forecasting at AER and still publishing lot's of articles. For the Dutch organisation VWK we conducted an interview with him. You can find the English written interview overhere:

http://www.vwkweb.nl/index.php?page=537&sl=1

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CAPE

CAPE

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Thanks for posting this. I hope our board mets can expand on Cohen's concern over Northwest Asian low which he states is unexpected development.

Glad to see that addressed. I have been wondering about the location of that low and how persistent it is on the model guidance. Seems as long as it stays in that location the AO would tend to hang around neutral, ranging slightly positive to slightly negative. 

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GaWx

GaWx

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 I strongly recommend that people look at the absolutely fascinating animation of the high Oct. Eurasian snowcover sfc temp.'s minus the low Oct. Eurasian snowcover sfc temp.'s. that can be found at the very bottom of the link's write up. Not only is it absolutely fascinating, but more importantly it should ease the worries (due to the expected mild first week of Dec.) of those expecting an overall cold E half of US DJF based on Cohen's work. According to that link's animation, the high Oct. Eurasian snowcover years are actually clearly biased solidly warmer in the E half of the US than low October Eurasian snowcover years during the first week of Dec!! Note the reds then. Then afterward, it gets close to a wash for the 2nd week of Dec. The relative mild returns one last time over most of the US for 12/13-19. After that, the blues (cold) dominate the E 2/3 of the US from 12/21 through 2/18 almost nonstop! Then 2/19-28 is back and forth. So, this animation suggests a solidly cold dominated 60 day period over the E 2/3 of the US during the climo coldest part of winter after a mild dominated 12/1-19. After looking at the E US, I then recommend folks focus on Greenland. Note that Greenland doesn't have reds dominating until ~12/18. Then, 12/18-2/13 is heavily dominated by relative warmth, which suggests a solid west based -NAO would be favored for the 12/18-2/13 period.

Did anyone else notice this for both the E 2/3 of the US and for Greenland? If so, any comments?

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Ottawa Blizzard

Ottawa Blizzard

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 I strongly recommend that people look at the absolutely fascinating animation of the high Oct. Eurasian snowcover sfc temp.'s minus the low Oct. Eurasian snowcover sfc temp.'s. that can be found at the very bottom of the link's write up. Not only is it absolutely fascinating, but more importantly it should ease the worries (due to the expected mild first week of Dec.) of those expecting an overall cold E half of US DJF based on Cohen's work. According to that link's animation, the high Oct. Eurasian snowcover years are actually clearly biased solidly warmer in the E half of the US than low October Eurasian snowcover years during the first week of Dec!! Note the reds then. Then afterward, it gets close to a wash for the 2nd week of Dec. The relative mild returns one last time over most of the US for 12/13-19. After that, the blues (cold) dominate the E 2/3 of the US from 12/21 through 2/18 almost nonstop! Then 2/19-28 is back and forth. So, this animation suggests a solidly cold dominated 60 day period over the E 2/3 of the US during the climo coldest part of winter after a mild dominated 12/1-19. After looking at the E US, I then recommend folks focus on Greenland. Note that Greenland doesn't have reds dominating until ~12/18. Then, 12/18-2/13 is heavily dominated by relative warmth, which suggests a solid west based -NAO would be favored for the 12/18-2/13 period.

Did anyone else notice this for both the E 2/3 of the US and for Greenland? If so, any comments?

Fascinating. It fits in with what I was describing from David Ludlum's "Early American winters" book in another thread. One of the winters described in the book is the winter of 1855-1856 which was very mild in the Midwest and northeast until the solstice only to then turn steadily cold.

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GaWx

GaWx

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Fascinating. It fits in with what I was describing from David Ludlum's "Early American winters" book in another thread. One of the winters described in the book is the winter of 1855-1856 which was very mild in the Midwest and northeast until the solstice only to then turn steadily cold.

 

According to a source whose link is now dead (so I can no longer link to the data; it was a MN website), 1855-6 was El Nino fwiw. Here is what I had copied:

 

 

 “Both the 1824-1825 and 1877-1878 winters coincided with El Nino/Southern Oscillation (ENSO) episodes [Quinn, 1978], periodic warmings of the far away Equatorial Pacific Ocean that have been linked to anomalous weather conditions in higher latitudes (e.g., heavy winter rainfall in Southern California or mild winters in the Upper Midwest.  Other Quinn identified ENSO's that encompass the 1820-1869 period of study include 1819-20, 1821-22, 1828-29, 1832-33, 1837-38, 1844-45, 1845-46, 1850-51, 1852-53, 1855-56, 1857-58, 1864-65, and 1868-69."

 

So, this list claims that 14 of the 50 winters were El Ninos. That is 28% of them, which is about right.

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michsnowfreak

michsnowfreak

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 I strongly recommend that people look at the absolutely fascinating animation of the high Oct. Eurasian snowcover sfc temp.'s minus the low Oct. Eurasian snowcover sfc temp.'s. that can be found at the very bottom of the link's write up. Not only is it absolutely fascinating, but more importantly it should ease the worries (due to the expected mild first week of Dec.) of those expecting an overall cold E half of US DJF based on Cohen's work. According to that link's animation, the high Oct. Eurasian snowcover years are actually clearly biased solidly warmer in the E half of the US than low October Eurasian snowcover years during the first week of Dec!! Note the reds then. Then afterward, it gets close to a wash for the 2nd week of Dec. The relative mild returns one last time over most of the US for 12/13-19. After that, the blues (cold) dominate the E 2/3 of the US from 12/21 through 2/18 almost nonstop! Then 2/19-28 is back and forth. So, this animation suggests a solidly cold dominated 60 day period over the E 2/3 of the US during the climo coldest part of winter after a mild dominated 12/1-19. After looking at the E US, I then recommend folks focus on Greenland. Note that Greenland doesn't have reds dominating until ~12/18. Then, 12/18-2/13 is heavily dominated by relative warmth, which suggests a solid west based -NAO would be favored for the 12/18-2/13 period.

Did anyone else notice this for both the E 2/3 of the US and for Greenland? If so, any comments?

Sounds awesome!

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