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December and a Hint of January Pattern Discussion

Bob Chill

By Bob Chill,
in Mid Atlantic

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Bob Chill

Bob Chill

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I've been keeping an eye on the ensemble teleconnection indicies. Some promising trends the last 2 days. The potential AO spike is now getting tempered, every day has more ens members showing a -nao and now a +pna has some agreement.

 

There is still a lot of spread and uncertainty but if the latest trends keeps happening we might be in for a classic type of period in the east. One we haven't seen in December for a good bit. Sure is nice going into Dec with real optimism and not weenie hope. 

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Bob Chill

Bob Chill

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hopefully we get some snow on the 5th then it torches so matt can verify in dec. :P

 

A lot of folks went warm in Dec and now fights are breaking out in the main forum with the arctic hounds descending. 

 

We will likely have a warm spell in Dec but there is a fair chance that the - departures that could potentially build the first couple weeks may prove too much to overcome. Long ways to go but I think many of the same folks that went warm would say something different had the first forecast not been made. Not poking at matt in any way. There's been a lot of universal warm talk from a lot of folks. 

 

Now glimmers of hope are showing up with blocking. If we end up with a -ao on average for the month then more fights are going to break out. 

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usedtobe

usedtobe

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A lot of folks went warm in Dec and now fights are breaking out in the main forum with the arctic hounds descending. 

 

We will likely have a warm spell in Dec but there is a fair chance that the - departures that could potentially build the first couple weeks may prove too much to overcome. Long ways to go but I think many of the same folks that went warm would say something different had the first forecast not been made. Not poking at matt in any way. There's been a lot of universal warm talk from a lot of folks. 

 

Now glimmers of hope are showing up with blocking. If we end up with a -ao on average for the month then more fights are going to break out. 

I think the winter still is likely to be warm if the AO is positive but the Pacific can make a huge difference.  My interest is doing more than 2 week forecast has waned as too many people take stuff way too serious and some like to tear any forecasts down.  PLus in terms of skill< I don't think I have any except for those years like 2009-2010 when multiple signal point one way.  This year, even the AO signals have been mixed.  Personally, I don't understand the forcing of the EPO to know exactly what drives it or how long it will stay negative. 

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Bob Chill

Bob Chill

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I think the winter still is likely to be warm if the AO is positive but the Pacific can make a huge difference.  My interest is doing more than 2 week forecast has waned as too many people take stuff way too serious and some like to tear any forecasts down.  PLus in terms of skill< I don't think I have any except for those years like 2009-2010 when multiple signal point one way.  This year, even the AO signals have been mixed.  Personally, I don't understand the forcing of the EPO to know exactly what drives it or how long it will stay negative. 

 

Seasonal forecasting is muddy. I've seen many folks be right for the wrong reasons but claim victory. I always think to myself if the most advanced computers and weather models lose skill at short range then consistently nailing a 3 month lead carries some pretty low odds. Certain ninos and ninas are much easier to set expectations though. This year has little precedence in that part of the equation. 

 

I never look past a month and even then. One, i don't have the knowledge to decipher the seemingly endless variables and two, I'm not motivated to gain the knowledge. I simply like looking for potential and when there appears to be none then I try to figure out what needs to change and look for early clues. Pretty simple approach. And it's fun. 

 

I totally agree on the AO. I've buried my head in those #'s plenty. What's been happening lately is literally stealing time imo. Unexpected results in an expected pattern. 

 

One encouraging sign is when the ao relaxes the coldest air in the NH is spinning around on our side of the globe. That's a new phenomenon compared to recent years. There's no reason to think it won't continue even if delivery isn't there. When delivery is there, cold shots can overperform even if they are transient. Zero complaints from me. 

 

I think the state of the AO is more of a harbinger in Dec than in Nov. If we end up with a near neutral AO for the month then all bets are off. I'm sure plenty of people will disagree with that statement but it's my humble opinion. 

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Fozz

Fozz

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Very cold storm too. Just about the perfect SECS.

 

Indeed, precip type was never an issue and it was the first big snow since that awful 01-02 winter and since I really started following weather. The moment I looked out the window when I woke up very early that morning was surreal, and in the end we received 8", which was amazing for early December. Even better, we had single digit temps two nights later, the snow cover lasted for a while, and we got a nice zr storm the next week.

 

I could tell we had a great winter coming.

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mitchnick

mitchnick

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welp, there it is

http://mag.ncep.noaa.gov/Image.php?fhr=300ℑ=data%2Fgfs%2F18%2Fgfs_namer_300_850_temp_mslp_precip.gif&model=gfs&area=namer&param=850_temp_mslp_precip&group=Model+Guidance&imageSize=M

 

 

and the surface is cold enough too

http://mag.ncep.noaa.gov/Image.php?fhr=300ℑ=data%2Fgfs%2F18%2Fgfs_namer_300_10m_wnd_precip.gif&model=gfs&area=namer&param=10m_wnd_precip&group=Model+Guidance&imageSize=M

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WinterWxLuvr

WinterWxLuvr

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Start a thread.

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snow.

snow.

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It almost take an ideal track for us,,,..houston to nashville to hatteras...a little further south would be ideal....

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mattie g

mattie g

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Can you explain why it's a good setup? Thanks in advance.

I should probably leave it to the folks who know better to explain it. To me, it looks like the low south of Alaska pumps up the ridge in the West, which helps usher in cold air, which is coming from a really cold source region. Plus, the flow is split (right?), which means that we can tap into more southern moisture.

As good a look as we've seen in some time.

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WinterWxLuvr

WinterWxLuvr

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I should probably leave it to the folks who know better to explain it. To me, it looks like the low south of Alaska pumps up the ridge in the West, which helps usher in cold air, which is coming from a really cold source region. Plus, the flow is split (right?), which means that we can tap into more southern moisture.

As good a look as we've seen in some time.

With the one little thorn that it's two weeks in the future.

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nj2va

nj2va

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I should probably leave it to the folks who know better to explain it. To me, it looks like the low south of Alaska pumps up the ridge in the West, which helps usher in cold air, which is coming from a really cold source region. Plus, the flow is split (right?), which means that we can tap into more southern moisture.

As good a look as we've seen in some time.

 

Thanks!  I think I can make out the split flow.  Is it where the northern stream and southern stream get broken up by that vort (?) off the coast of CA?  

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mattie g

mattie g

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Thanks! I think I can make out the split flow. Is it where the northern stream and southern stream get broken up by that vort (?) off the coast of CA?

From what I know, I think that's right. And look at how that big ridge reaches way up into the higher latitudes - that's pretty impressive. If we can get the Atlantic to cooperate a bit, then we have a real shot at something in this period.

I'm open to be corrected or expanded upon!

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Bob Chill

Bob Chill

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Thanks! I think I can make out the split flow. Is it where the northern stream and southern stream get broken up by that vort (?) off the coast of CA?

That panel I posted is just a snapshot in time so keep that in mind. If you run the full 500 vort loop it shows a much better picture of the evolution.

We've been plagued with Pac zonal flow at times recently. Especially in Dec. When the isobars are all lined up and pretty into the west coast it floods the conus with pacific air. We do terrible at our latitude with that setup. Too warm.

The 18z gfs is showing a major road block. Our source region is the arctic. And would imply an active northern stream to some extent. It's a bit extreme but definitely shows how the Pac can cooperate to deliver cold even when our classic blocking features aren't really there.

Split flow and active southern stream are 2 different things. You need to have energy slipping underneath a pacific ridge. The panel I posted is not the best example but verbatim interpretation at long leads isn't the way to go anyway.

The short version is just hoping a Pac zonal roadblock happens and then letting the details shake out at medium to short leads. If the 18z gfs verified in some fashion or another then we won't be bored. We'll at least be cold enough for snow. That's more than half the battle.

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