Is Greenland Blocking Hinting At October And Beyond?

[bluewave]

While there are only two analogs with a similar blocking pattern focused over Greenland around

this part of August, I though it would be interesting to see if it will have any significance.

I have no idea yet if this is a hint that the pattern will try to repeat in October yet. The location

of recent October blocking patterns have been a good clue to where the winter blocking would

set up. But there really aren't that many analogs with a August to October relationship. We will

probably just have to wait and see what the pattern looks like in October to make a good first

guess at what the next winter may look like. The October to winter signal is a general one

and all blocking patterns are not the same. The two August analogs of 2006 and 2010 are

a good example of this. Both those Octobers featured strong blocking at high latitudes

but the nature of the winter patterns were very different. The 2006 analog may be similar

to this year as we are heading into a general Nino looking pattern this fall. But I included

August 2010 since we had a strong blocking pattern that year around this time also.

Earlier thread discussing October to winter pattern

http://www.americanw...ctober-pattern/

I just want to stress that I don't have any skill at predicting a winter pattern this early in the game

so this is not meant to be a forecast. I will make a first guess after I see what the October pattern

looks like.

August 2006 and 2010 pattern at similar time of the month

Euro ensemble forecast

[Wannabehippie]

If the blocking for the fall/winter sets up where it is now, wouldn't that mean a lot of lake cutters and snow to rain events for the I-95 corridor?

While there are only two analogs with a similar blocking pattern focused over Greenland around

this part of August, I though it would be interesting to see if it will have any significance.

I have no idea yet if this is a hint that the pattern will try to repeat in October yet. The location

of recent October blocking patterns have been a good clue to where the winter blocking would

set up. But there really aren't that many analogs with a August to October relationship. We will

probably just have to wait and see what the pattern looks like in October to make a good first

guess at what the next winter may look like. The October to winter signal is a general one

and all blocking patterns are not the same. The two August analogs of 2006 and 2010 are

a good example of this. Both those Octobers featured strong blocking at high latitudes

but the nature of the winter patterns were very different. The 2006 analog may be similar

to this year as we are heading into a general Nino looking pattern this fall. But I included

August 2010 since we had a strong blocking pattern that year around this time also.

Earlier thread discussing October to winter pattern

http://www.americanw...ctober-pattern/

I just want to stress that I don't have any skill at predicting a winter pattern this early in the game

so this is not meant to be a forecast. I will make a first guess after I see what the October pattern

looks like.

August 2006 and 2010 pattern at similar time of the month

Euro ensemble forecast

[bluewave]

If the blocking for the fall/winter sets up where it is now, wouldn't that mean a lot of lake cutters and snow to rain events for the I-95 corridor?

The wavelengths would change between then and now so a solid Greenland block would

feature a better storm track then depending on the exact alignment in the winter.

That being said, I have no idea yet what the winter will look yet until I see what October

looks like. Even if we get blocking this coming winter there is no guarantee that we will

do well. Winter 2006-2007 was all backloaded blocking after a really warm pattern.

But I would rather take my chances with a pattern like that over last winter.

[uncle W]

last year was one of the strongest -AO Augusts on record...To bad it wasn't after that...I hope blocking is better than last year...can't get worse...I'm not talking about the Jets offensive line here...

[Isotherm]

Good post as usual Chris. I agree that October, and especially November, becomes very important in terms of its correlation to the winter DJF months. The November blocking (or lack thereof) is often a good indicator of the ensuing winter, and its helpful to see what the pattern in early December may look like (which is why I plan on waiting until the end of met autumn to issue a winter outlook this year). Obviously there are no 1 to 1 correlation in meteorology, but those that yield a .6 or .7 correlation are quite useful and tend to be the strongest signals we can get for a longer term forecast.

[Analog96]

The wavelengths would change between then and now so a solid Greenland block would

feature a better storm track then depending on the exact alignment in the winter.

That being said, I have no idea yet what the winter will look yet until I see what October

looks like. Even if we get blocking this coming winter there is no guarantee that we will

do well. Winter 2006-2007 was all backloaded blocking after a really warm pattern.

But I would rather take my chances with a pattern like that over last winter.

Very good line in this post. We should use this line for anyone who makes winter forecasts too early. October is the key. Anything earlier than mid-October is ridiculously early to make a winter forecast.

[Isotherm]

Very good line in this post. We should use this line for anyone who makes winter forecasts too early. October is the key. Anything earlier than mid-October is ridiculously early to make a winter forecast.

After the research I've done following last winter's debacle, if you want more accurate LR forecasts I'd say anything earlier than mid November is foolish.

[Analog96]

After the research I've done following last winter's debacle, if you want more accurate LR forecasts I'd say anything earlier than mid November is foolish.

The problem with this is that that is too late. You can't issue an LR forecast for the NE US when many areas have already seen snow. There weren't many analogs that had October snow. But the majority of the years that did have October snow did not have much snow the rest of the winter.

[Isotherm]

The problem with this is that that is too late. You can't issue an LR forecast for the NE US when many areas have already seen snow. There weren't many analogs that had October snow. But the majority of the years that did have October snow did not have much snow the rest of the winter.

Well I'd say as long as the forecast is issued before the season in question, it's fine. Since met winter starts Dec 1st, any date until the end of Nov should be ok.

[bluewave]

last year was one of the strongest -AO Augusts on record...To bad it wasn't after that...I hope blocking is better than last year...can't get worse...I'm not talking about the Jets offensive line here...

What's interesting about that -AO was the pattern of the strongest 500 mb blocking later in the month.

The blocking wasn't concentrated right over Greenland, but extended back to the Russian Arctic.

That ridging near the Russian Arctic turned out to be a hint of were the October and winter pattern

finally set up. The ridge amplified during September 2011 a few weeks later. You can also see the

blocking was located there to some extent in October also. Notice the lack of any blocking for

the most part last October right over Greenland and how that told the story for the following winter.