October 2013 pattern and discussion

[DCMetroWinston]

WxSouth

22 hours ago

Models Show Blocking Galore.... If the pattern from last Spring, this Summer, and already this Fall, keeps on repeating....What a Winter this will be. And so far, no end in sight, on the contrary, as the cold season gets underway, the atmosphere is getting ready to reload where last Spring left off. That is, major blocking up north. I don't know if we keep this train running right through Winter, but October certainly looks like a wild pattern in the flow. A Greenland Block shows up on the European model during days 8, 9 and 10....we couldn't buy one of these at all last Winter, until early Spring arrived. With that particular block, this almost always ends up with a blockbuster snowstorm in the MidAtlantic and part of the South. And this is only October.

[CAD_Wedge_NC]

Slightly above average for the extended period. It will be an awesome weekend for sure.

What worries me is the chance of a powerful cold front next week. It could cause some very strong thunderstorms and is definitely something to watch. If the cold front is as powerful as modeled, it would bring the coolest air of the season.

 

Well, some might not know but we have two severe weather seasons in this part of the country. The Spring is the main one, but we have a Fall spike as well. It would not be out of the question to see a Fall tornado reported with one of the stronger cold fronts this time of year. It does indeed need to be watched.

[mackerel_sky]

It won't be long before a 84 NAM image is posted showing torching surface temps and marginal 850mb temps with a thread created for it. Also ready for Memphis, Birmingham, and Atlanta to be buried in a 20inch snowstorm shown on the DGEX.

. No matter how bad the DGEX is, it never shows snow or fantasy snow for BFW!

[fountainguy97]

I am just glad those 80s are gone, and most likely for good.  Dreary here past few days nice soaking rains today.  Ready for some big time cold fronts.

[HKY_WX]

The huge 500mb cutoff developing near new foundland on the euro LR is interesting. I haven't seen that at all the last 2 years. If that's a trend into winter, could be good news. That's a pretty classic -NAO configuration.

[Met1985]

The huge 500mb cutoff developing near new foundland on the euro LR is interesting. I haven't seen that at all the last 2 years. If that's a trend into winter, could be good news. That's a pretty classic -NAO configuration.

Good to see you post right in time for the seasons to change. Ya I noticed that the LR Euro was bringing down a load of cold air across the country towards the East. The NAO does show signs of going negative and maybe showing it's hand for the winter. To me all good signs right know as we are heading towards December into winter.

[Carvers Gap]

Bout time to bring the Tennessee portion of the wx board back to life after its long summer's nap. Looks like, according to the 6z GFS, that this late summer weather is coming to an abrupt halt. Could see some flakes fly in the higher elevations before two weeks are finished. The blocking pattern that many have referenced is about to take hold. Let's just hope some of that is left for "real" winter.

[POWERSTROKE]

Several models pointing to major changes coming. we shall see

[DCMetroWinston]

Larry Cosgrove: 

With the coming temperature flip (in place east of the Rocky Mountains by the 11 - 15 day period), I have an inkling that we may have a large-scale, critical storm threat as we end the month of October. Unlike the past two years, which targeted the Mid-Atlantic region, I draw my suspicions on the Gulf Coast, Ohio valley, Appalachia and the lower Great Lakes. The numerical model ensemble groups are very keen on keeping a full-latitude, cold 500MB trough with an axis over the eastern third of the U.S. And with that potential to latch on to the formative subtropical jet stream near Mexico as well any late-occurring tropical cyclone over the Caribbean Sea. That speculation aside, another (possibly) strong intrusion of polar air seems likely to reach the area from the High Plains to the East Coast before the month is out.

 

 

[Snowless in Carrollton]

I sure hope accuweather is right. They are forecasting mid 30s for lows in GA in about 10 days.

[Met1985]

Interesting that the Euro has pretty much fallen in line with the GFS on the significant cold front coming down for the end of the week. This will be the coldest air of the season and for sure give several areas around WNC frost chances and maybe some freezing potential. I think the GFS has the right idea especially with the NAO really tanking. Close to 2 SD in the negative which would really buckle the jet stream and I think this could be the lowest the NAO has dropped since last spring and something we really have not seen the past couple of Octobers. To me this is a good sign for the upcoming winter months but time will tell.

[Cold Rain]

Well, the models backed off of the really cold stuff in the LR, as they usually do. It still looks pretty seasonable through the period for the majority of folks. There is lots of high latitude blocking showing up. Hopefully, that won't fade as we head into winter.

[FallsLake]

Well, the models backed off of the really cold stuff in the LR, as they usually do. It still looks pretty seasonable through the period for the majority of folks. There is lots of high latitude blocking showing up. Hopefully, that won't fade as we head into winter.

It's always nice to get a cold shot anytime(for us cold type people), but this time of year it's more important for the northern hemisphere snow cover to build as fast as possible. The GFS LR still shows Canada doing very well with some snow cover build up over the next few weeks and that is getting me excited about the upcoming winter.

[Cold Rain]

It's always nice to get a cold shot anytime(for us cold type people), but this time of year it's more important for the northern hemisphere snow cover to build as fast as possible. The GFS LR still shows Canada doing very well with some snow cover build up over the next few weeks and that is getting me excited about the upcoming winter.

Yep, snowfall build-up is looking pretty good. It's going to be interesting to see if the fact that we're already a good amount ahead is a positive factor this winter.

[1300m]

Yep, snowfall build-up is looking pretty good. It's going to be interesting to see if the fact that we're already a good amount ahead is a positive factor this winter.

 

We are well ahead of last winter, or even October 2009 which had a mega-negative AO. It appears as though we may be headed for a possible top-5 snowiest October in that region, so this will be an excellent test of the theory.

 

I definitely believe that this has an effect on the dominant phase of the AO during the winter, and if the AO is negative for long enough it almost has to impact the NAO from a purely physical/scientific standpoint. I think last winter the AO just wasn't quite strong enough until late winter -- likely aided by the SSW event -- to get the NAO to respond. Hopefully this winter the AO and NAO will get their act together sans winter 2009-10.

[metalicwx366]

Last December folks were saying the same thing. The AO was negative all December and nothing happened. The SSW event happened in January and nothing happened unless you count the Arctic outbreak in March which I doubt was a direct result of that. The super negative AO last didn't do anything for out region I believe in late March. Correct me if I am wrong.

The snowcover thing is interesting though. How was snowfall at this time last year?

[1300m]

Last December folks were saying the same thing. The AO was negative all December and nothing happened. The SSW event happened in January and nothing happened unless you count the Arctic outbreak in March which I doubt was a direct result of that. The super negative AO last didn't do anything for out region I believe in late March. Correct me if I am wrong.

The snowcover thing is interesting though. How was snowfall at this time last year?

 

If you look at the AO last year, it didn't spend significant time down into major negative territory (which I would loosely consider something less than -2.0 or so) except for in March. I don't think a negative AO (or NAO or really any teleconnection indice) that is only marginally in a phase really has a large impact on the pattern. I wish we didn't even keep track of marginal phases, because I'm not sure they actually mean anything.

 

Snowfall is ahead of pace from last year, and it has been increasing at a strong rate, which is potentially what is the driving force behind the linkage between Siberian snowfall and the AO.

 

Anyways, at least it's something to give us some hope in an otherwise very uncertain winter forecast!

[FallsLake]

If you look at the AO last year, it didn't spend significant time down into major negative territory (which I would loosely consider something less than -2.0 or so) except for in March. I don't think a negative AO (or NAO or really any teleconnection indice) that is only marginally in a phase really has a large impact on the pattern. I wish we didn't even keep track of marginal phases, because I'm not sure they actually mean anything.

 

Snowfall is ahead of pace from last year, and it has been increasing at a strong rate, which is potentially what is the driving force behind the linkage between Siberian snowfall and the AO.

 

Anyways, at least it's something to give us some hope in an otherwise very uncertain winter forecast!

Thanks for the article. Interesting correlation (from graph) with AO and snow cover. The biggest difference I see with snow coverage is actually with the arctic sea ice extent. It is way better this year than last.

http://www.natice.noaa.gov/ims/

See past years

[Cold Rain]

We are well ahead of last winter, or even October 2009 which had a mega-negative AO. It appears as though we may be headed for a possible top-5 snowiest October in that region, so this will be an excellent test of the theory.

I definitely believe that this has an effect on the dominant phase of the AO during the winter, and if the AO is negative for long enough it almost has to impact the NAO from a purely physical/scientific standpoint. I think last winter the AO just wasn't quite strong enough until late winter -- likely aided by the SSW event -- to get the NAO to respond. Hopefully this winter the AO and NAO will get their act together sans winter 2009-10.

Russia and Europe have been the beneficiaries the last couple of winters. I wonder if there are any indicators that take into account, along with the Snowfall Advance Index, the regions that might most benefit from a -AO? How about the magnitude of the -AO? The SAI correlates pretty well to the state of the -AO, but I don't think it has any correlation to the state, although I may be wrong on that.

[Met1985]

There is a good thread started by Sam on the main page talking about the recurving ts that affect the pattern and particularly blocking with the NAO. Good read.

[Met1985]

I do think that the pattern after the 20th becomes more active with a trough in the East.

[Met1985]

Well this is the coldest GFS run so far this Fall. Just for fun this run would give the mountains there first upslope snowfall of the season on the 29th. Hey just for fun. It will be gone by the nect run but I do think we tape into some colder air especially with the blocking that is going to occur.

[DCMetroWinston]

So many people waiting on a cold late October. Hope the models verify.

[FallsLake]

So many people waiting on a cold late October. Hope the models verify.

It would be nice to get our first frost/freeze; kill bugs, stop grass from growing, etc. GFS LR continues to show the cool down for the last part of this month. Of course each model run flip-flops around; but it looks like we're now within 10 days of the cool down. Once we get to day 7 or so the big flip-flops should stop. 

[metalicwx366]

It would be nice to get our first frost/freeze; kill bugs, stop grass from growing, etc. GFS LR continues to show the cool down for the last part of this month. Of course each model run flip-flops around; but it looks like we're now within 10 days of the cool down. Once we get to day 7 or so the big flip-flops should stop.

I hope this cool down comes soon. Our forecast highs on TWC are ridiculous this week. (Today might be the exception with this cloud cover) They are usually more right with highs. Our NWS is usually way to low.

[Carvers Gap]

Man, the 0z GFS was cold. 6z wasn't overly warm. Looks like the GFS is sniffing out a major pattern change. Interestingly, it does seem that cold and snow in late October have not been an indicator of a subsequent cold winter here in NE TN. I am not "all in" on this going East. Strong possibility it could come down the front range of the Rockies. Either way, winter in the northern plains is here early.

[GaWx]

Man, the 0z GFS was cold. 6z wasn't overly warm. Looks like the GFS is sniffing out a major pattern change. Interestingly, it does seem that cold and snow in late October have not been an indicator of a subsequent cold winter here in NE TN. I am not "all in" on this going East. Strong possibility it could come down the front range of the Rockies. Either way, winter in the northern plains is here early.

In contrast, I have found some correlation between having at least one top three cold daily reading at KATL in the last half of Oct. and cold winters at KATL. I believe this correlation also considers Nov. days of cold. I haven't looked at the specifics in a while. So, I'm going on memory. Therefore, for KATL at least, I'd be rooting for an intense cold snap in late Oct. for increased chance at cold winter based on the partial positive correlation of cold then and overall cold in winter.

[GaWx]

Last December folks were saying the same thing. The AO was negative all December and nothing happened. The SSW event happened in January and nothing happened unless you count the Arctic outbreak in March which I doubt was a direct result of that. The super negative AO last didn't do anything for out region I believe in late March. Correct me if I am wrong.

The snowcover thing is interesting though. How was snowfall at this time last year?

I had a problem then calling it a SSW due to it not being intense enough and posted about it several times. I'm maintaining that opinion.

[DaculaWeather]

Larry, I remember at one time you posted a nice write-up here about a weak Nino and our winter weather in the southeast, but I can't find the right words to search for to find it. Do you remember the post I'm referring to?

[GaWx]

Larry, I remember at one time you posted a nice write-up here about a weak Nino and our winter weather in the southeast, but I can't find the right words to search for to find it. Do you remember the post I'm referring to?

 

Steve,

 This?

 

11 Coldest (back to 1879-80) KATL Winters’ ENSO/PDO/NAO/AO

 

    Winter……DJF Temp Anom…ENSO……..PDO………NAO….…AO

1) 1976-7……….…..-7.6…………WEN…....+1.5………..-1.7………..-1.8

2) 1977-8…………...-6.2…………WEN…….+0.7……….-1.1………..-0.5

3) 1904-5……………-5.8………...WEN…….+1.3……….+0.8……….+0.8

4) 1962-3……………-5.8…………WLN……..+0.0……….-1.6………..-0.7

5) 1935-6……………-5.7………….NP………+1.5………-2.0………..-2.4

6) 1963-4……………-5.7…………WEN…….+0.4………-1.6………..-0.7

7) 1939-40………….-5.5…………WEN……..+1.7……...-1.9………..-1.9

8) 1901-2…………...-5.4………….NN………+1.5………-0.7………..-0.5

9) 2009-10………….-4.4…………SEN……..+0.1……..-2.9…………-2.6

10) 1885-6………….-4.3…………WEN……..+0.8……..-0.6…………N/A

11) 1969-70…….…..-4.1………….WEN……..+1.2…….-1.1…………-1.8

 

Findings:

 A very impressive 7 of the 11 coldest (of the 133 winters) and 3 of the 4 coldest were weak Nino’s. Only about 1 in 8 winters is a weak Nino. So, only about 1-2 of the 11 coldest would be the “expected value” (vs. 7) if there were no bias of weak Nino’s toward either warm or cold.

 The PDO was positive for all 11 (1962-3 was barely above zero).

 The NAO was -0.6 or more negative for all but one, 1904-5.

 The AO was -0.5 or more negative for all but one, 1904-5. (I couldn’t find the AO for 1885-6.)

 Based on the above stats, I’m fully aware that one can make the argument that it was the +PDO/-NAO/-AO combo that was a big reason for the cold for all but 1904-5. However, one could make the argument that the weak Nino phase, itself, also had a major influence. I’ll now explain:

 I looked at all winters back to 1879-80 and found 26 that had the +PDO/-NAO/-AO combo, including the 9 noted above from the 11 coldest. A total of 6 of those 26 were weak Nino’s. An impressive 5 of those 6 weak Nino’s (83%) were within the 11 coldest. OTOH, 20 of those 26        +PDO/-NAO/-AO winters were NOT weak Nino’s. Only 4 of those 20 that were +PDO/-NAO/-AO and that weren’t weak Nino’s (20%) were within the 11 coldest. Furthermore, 10 of the 26 were moderate to strong Nino’s. Of those 10 mod. to strong Nino’s with +PDO/-NAO/-AO, only one of the 10 (10%) (2009-10) was within the 11 coldest.

 

  So, to summarize regarding +PDO/-NAO/-AO winters since 1879-80:

- A whopping 83% of the weak Nino’s were in the 11 coldest

- Only 10% of the mod. to strong Nino’s were in the 11 coldest

- Only 20% of all winters that weren’t weak Nino’s were in the 11 coldest

 

- 40% of weak Nino’s and 47% of moderate to strong Nino’s since 1899-1900 were +PDO/-NAO/-AO….i.e., fairly similar %’s. Yet, weak Nino’s were much colder on average than moderate to strong Nino’s as a whole.

 

(MEN’s/SEN’s that didn’t have +PDO, -NAO, and –AO:

1902-3, 1905-6, 1965-6, 1972-3, 1982-3, 1987-8, 1991-2, 1994-5, and 2006-7)

 

- Conclusion:

 

The weak Nino phase, itself, has a strong cold tendency for Atlanta independent of the cold tendency resulting from +PDO/-NAO/-AO. The moderate to strong Nino phase lacks this independent strong cold tendency.