• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

Pattern October Thread

NickyBGuarantee said:
How about a 25 degree temp drop with this cold front? Also fro give me a run down on the severe weather potential here .. gotta be some straight line windsView attachment 92804
Click to expand...
It’s quite far out lol not really much to breakdown now but with that ridging in Canada that’s gonna try to get troughs to slide under and progress east, which overall could increase severe wx chances if moisture return is realized
 
RainlessSnowless & Grumpy said:
Looks like last year to me. Not surprising with the same Enso state and warm waters around the Maritime continent. Will we waste another year of good blocking? I hope not because blocks are hard to come by anymore. The start of the last decade started with 2 in a row as well. 09-10 and first half of 10-11 had blocking and we did well. Then we got nada again until last year where we crashed and burned anyway. If we're in a cycle where we go almost a decade between good blocking winters I hope we don't screw this one up. I know blocking in Oct doesn't always translate to blocking in winter but just like last year this one seems to want to hang around.
Click to expand...

Regarding -NAO, specifically, it is a shame (for those who prefer cold SE winters) that there is virtually no correlation of Oct NAO to winter NAO during La Niña because it will have a chance to be the most -NAO October on record (back to 1950) for a non-El Nino, which is currently 2012’s -2.06. For whatever reason, the monthly NAO is often close to double what the dailies average out to. At a minimum, it seems to be at least 1.67 times the daily average. Based on that, this month has a good chance of ending up sub -1.8 and could easily end up sub -2.0.

Here is the link to the monthlies back to 1950:


The following Octs were sub -1.7:
1960, 1968, 1980, 1992, 1997, 2002, 2006, and 2012

The subsequent DJF NAO:

1960: +0.3/not El Niño
1968: -1.4/El Niño
1980: +0.7/not El Niño
1992: +0.9/not El Niño
1997: -0.2/El Niño
2002: -0.2/El Niño
2006: +0.4/El Niño
2012: 0.0/not El Niño

Only one of the 8 subsequent winters had a strong -NAO (1968) and it was El Niño. Two others were slightly -NAO and they were also El Niño. The 4 non-El Niño winters were in the 0.0 to +0.9 range and averaged +0.5. Looking at all 8 winters, they averaged +0.1.

Conclusion: Despite the forecast for Oct of 2021 to have one of, if not THE, most -NAO on record for any Oct, it by no means is predictive of a -NAO this winter. Of course, that doesn’t mean it can’t end up that way. I’m just saying that history says that this month being so strongly -NAO doesn’t mean an increased chance for -NAO this winter vs climo based chances. Furthermore, this winter being La Niña, if anything, reduces the chances based on ENSO climo.

Here’s the impressive GEFS NAO forecast:

C6BEB860-E065-4DB6-BE6A-C789B4B086FC.gif
 
You must log in or register to reply here.
Back
Top