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Countdown to Winter 2017-2018 Thread

eyewall

By eyewall,
in New England

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OSUmetstud

OSUmetstud

Posted
Posted
  On 10/18/2017 at 6:17 PM, JBinStoughton said:

I thought we have -pdo or at least getting there. Why look at +pdo? Not that I don't like the look of it but still...

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we have a slightly negative PDO for September.  2000-2001, 2005-2006, and 2016-2017 all had a negative PDO now, but ended up averaging positive from December through March for their respective seasons. 

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ORH_wxman

ORH_wxman

Posted
Posted

Yeah a +PDO is definitely a possibility...though the SST trend in the past few weeks is for things to go more negative, but it's not a strong enough trend to conclude we will have a -PDO this winter. GOA is still actually a little above average.

 

 

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OSUmetstud

OSUmetstud

Posted
Posted
  On 10/18/2017 at 6:25 PM, ORH_wxman said:

Yeah a +PDO is definitely a possibility...though the SST trend in the past few weeks is for things to go more negative, but it's not a strong enough trend to conclude we will have a -PDO this winter. GOA is still actually a little above average.

 

 

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I'm not sure if it's really a significant predictor for our area of the globe but I figured it might be relevant. 

 

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nzucker

nzucker

Posted
Posted
  On 10/18/2017 at 10:00 PM, Eduardo said:

Didn't we learn anything from last year?  And doesn't the ridging east of Hawaii and troughing on the WC suggest that something about this solution seems off?

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The wavelengths are shorter this time of year, so the expected pattern with a ridge east of Hawaii in mid-winter doesn't apply here. As you can see, there is basically an "extra" ridge there. Normally in the winter a ridge east of Hawaii would result in a -PNA and high heights in the East. Here, however, the ridge east of Hawaii results in a diffuse East Pacific trough, which raises heights in Western Canada and leads to a +PNA, with a downstream trough in the Northeast. The shorter wavelengths allow for an additional step in the pattern.

The late October blocking has been signaled on most models for the past couple of weeks. So I'm pretty sure it's going to occur. What form that storm system will take is anyone's guess...

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40/70 Benchmark

40/70 Benchmark

Posted
Posted
  On 10/19/2017 at 4:06 AM, nzucker said:

The wavelengths are shorter this time of year, so the expected pattern with a ridge east of Hawaii in mid-winter doesn't apply here. As you can see, there is basically an "extra" ridge there. Normally in the winter a ridge east of Hawaii would result in a -PNA and high heights in the East. Here, however, the ridge east of Hawaii results in a diffuse East Pacific trough, which raises heights in Western Canada and leads to a +PNA, with a downstream trough in the Northeast. The shorter wavelengths allow for an additional step in the pattern.

The late October blocking has been signaled on most models for the past couple of weeks. So I'm pretty sure it's going to occur. What form that storm system will take is anyone's guess...

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Its transient ridging, not blocking.

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nzucker

nzucker

Posted
Posted
  On 10/19/2017 at 4:10 AM, 40/70 Benchmark said:

Its transient ridging, not blocking.

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I wouldn't be surprised if this pattern evolves into an overall blockier look for November. Maybe not right away, but the combination of a recurving typhoon along with a weak Nina/-QBO should prime the atmosphere for some degree of blocking. A lot of the analogs and long-range modeling has indicated a possibility of a much colder November after near record warmth in October.

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40/70 Benchmark

40/70 Benchmark

Posted
Posted
  On 10/19/2017 at 4:12 AM, nzucker said:

I wouldn't be surprised if this pattern evolves into an overall blockier look for November. Maybe not right away, but the combination of a recurving typhoon along with a weak Nina/-QBO should prime the atmosphere for some degree of blocking. A lot of the analogs and long-range modeling has indicated a possibility of a much colder November after near record warmth in October.

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I don't disagree with that, but its a whole different issue....its initially transient...at least as of now.

We need to be careful not to drop blocking bombs with every shade of red over Greenland.

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Eduardo

Eduardo

Posted
Posted
  On 10/19/2017 at 4:42 AM, 40/70 Benchmark said:

I don't disagree with that, but its a whole different issue....its initially transient...at least as of now.

We need to be careful not to drop blocking bombs with every shade of red over Greenland.

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Yeah you put this point much more elegantly than I did.  At what point do we classify Greenland ridging as blocking?  Is it a matter of degree, duration, or both?

 

  On 10/19/2017 at 4:06 AM, nzucker said:

The wavelengths are shorter this time of year, so the expected pattern with a ridge east of Hawaii in mid-winter doesn't apply here. As you can see, there is basically an "extra" ridge there. Normally in the winter a ridge east of Hawaii would result in a -PNA and high heights in the East. Here, however, the ridge east of Hawaii results in a diffuse East Pacific trough, which raises heights in Western Canada and leads to a +PNA, with a downstream trough in the Northeast. The shorter wavelengths allow for an additional step in the pattern.

The late October blocking has been signaled on most models for the past couple of weeks. So I'm pretty sure it's going to occur. What form that storm system will take is anyone's guess...

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Thanks for explaining!  When do wavelengths tend to lengthen?

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CoastalWx

CoastalWx

Posted
Posted
  On 10/19/2017 at 5:26 AM, Eduardo said:

Yeah you put this point much more elegantly than I did.  At what point do we classify Greenland ridging as blocking?  Is it a matter of degree, duration, or both?

 

Thanks for explaining!  When do wavelengths tend to lengthen?

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Usually once you get into later December and January. That's when things finally become stratified from north to south. 

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mahk_webstah

mahk_webstah

Posted
Posted
  On 10/19/2017 at 12:04 PM, OSUmetstud said:

cold neutral, weak nina, and moderate nina

positive qbo vs. negative qbo. 

 

negative on top, positive on bottom

 

 

cold_negative qbo.png

cold_positive qbo.png

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So if I am getting this right, our projected Nina for this year, is at least consistent with New England and the Mid Atlantic being on the cold side of the gradient, and Greenland blocking that could create good storms.  The analog years seem to be pretty good from a snow perspective?

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OSUmetstud

OSUmetstud

Posted
Posted
  On 10/19/2017 at 12:14 PM, mahk_webstah said:

So if I am getting this right, our projected Nina for this year, is at least consistent with New England and the Mid Atlantic being on the cold side of the gradient, and Greenland blocking that could create good storms.  The analog years seem to be pretty good from a snow perspective?

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Generally speaking is does I think.  Something that HM noted that you have to be careful of, is that there's a tendency in the composites to produce a "false" negative NAO signal because of it comparing more modern years to a longer term anomaly in a warmed arctic. 

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mahk_webstah

mahk_webstah

Posted
Posted
  On 10/19/2017 at 12:22 PM, OSUmetstud said:

Generally speaking is does I think.  Something that HM noted that you have to be careful of, is that there's a tendency in the composites to produce a "false" negative NAO signal because of it comparing more modern years to a longer term anomaly in a warmed arctic. 

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That makes sense, but it does look classic in that the deepest colors are right near the southern tip of Greenland - very good for the Mid Atlantic.  Would suggest not a lot of Miller A storms but perhaps a lot of Miller B storms, and some that slow down and deepen, and a lot of SWFEs running from the Western Canada trough through the midwest and through the northeast.   What are the precip analogs?  That looks like a moist/wet winter, with DC north getting shots for SECS, and New England getting in on some of those as well as a parade of small and mid size storms.  A wet dream perhaps.

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CoastalWx

CoastalWx

Posted
Posted
  On 10/19/2017 at 1:49 PM, 40/70 Benchmark said:

It seems like there is always a catch when it comes to the NAO....."I know the heigher heights near the southern tip of Greenland look like a negative NAO, but an obese eskimo actually queefed".. 

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:lol:

 

Those are anomalies, so beware pretty colors. Just like when Someone posts that we have blocking over Greenland, but it's still cyclonic flow, just AN heights. It's unfortunate, but we background warm.

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