griteater

In the paper from Zhang et al., they categorized Ninas as Central Pacific when the max cool anomaly stayed along 160W from late summer thru winter, whereas the East Pacific and Mixed Ninas started with the max cool anomaly along 110 to 120W before migrating west during the winter - https://link.springer.com/article/10.1007%2Fs00382-014-2155-z The current Nina aligns more with the East Pacific or Mixed versions

By the way, for classifying ENSO strength in terms of SSTs, I've always liked how it is done by Jan Null - https://ggweather.com/enso/oni.htm So, in order for the La Nina to be classified as Strong, 3 consecutive tri-monthly ONI readings would have to be -1.5 or lower....e.g. SON / OND / NDJ would each have to be -1.5 or lower (or OND / NDJ / DJF)

Nino 3.4 has fallen to -1.72 on this daily data. It's been a steady decline thru October

Tip - you have a lot to unpack here, haha. IMO, the QBO to La Nina/Cool ENSO relationship is one of the better winter seasonal forecast correlations that exists. In a nutshell, when the QBO is positive at 50mb, this favors a more poleward North Pac ridge. When the QBO is negative at 50mb, this favors a more suppressed North Pac ridge. This correlation has been successful in 21 of 29 cases (72%). For cases where the QBO was positive, it has been successful in 14 of 18 cases (78%). 2 years were thrown out (83-84 and 85-86) because the Jul-Oct Global AAM prior to the winter was positive, which is one indicator that the La Nina is not very well coupled with the atmosphere. It is very rare to see the Jul-Oct Global AAM positive leading into a La Nina / Cool ENSO winter...the avg AAM is solidly negative in recent months. For QBO designation I like using the Free Univ of Berlin QBO chart to eyeball the QBO progression for each winter along 50mb, during the period Nov-Feb - https://www.geo.fu-berlin.de/met/ag/strat/produkte/qbo/qbo_wind_pdf.pdf. For the cases that failed, there was no bias as to whether the QBO was rising or falling, or whether the amplitude of the QBO was high or low. The key differentiating factor was whether the QBO was positive or negative. HM previously had a detailed post on his blog about this correlation (from 2012), but his blog is no longer active / posts are no longer visible...but here is what I believe is at least part of the science behind the correlation. During the +QBO (Westerly), there are warm anomalies in the lower stratosphere along the equator with cool anomalies off equator into the subtropics. The higher tropopause height off equator allows for deeper, more robust tropical convection there (compared to normal) - this is termed the "QBO Induced Meridional Circulation" Images below contain OLR for a mix of weak to strong La Ninas. On the left are -QBO Ninas. +QBO Ninas on the right. We can see the +QBO composite showing enhanced off-equator convection in the 10N to 25N zone. Note: on these images, the color scheme is reversed from the typical OLR composites...that is, the warm colors are showing -OLR anomalies (enhanced convection), with the cool colors showing +OLR anomalies (reduced convection). It's my belief that the enhanced off-equator convection aids more poleward ridge building in the North Pacific via the typical process (image below from: https://blog.timesunion.com/weather/how-el-nino-influences-our-weather/1247/) Looking at daily Singapore sounding data, we can see that the +QBO is behaving as expected this fall as temperatures in the lower stratosphere along the equator are showing plus anomalies (far right side of image) Also, we can see in this loop of 50mb temperatures, the warm anomalies along the equator, with the cool anomalies off equator Here are composites of -QBO / "South" / Suppressed North Pacific Ridge winters VS. +QBO / "North" / Poleward North Pacific Ridge winters during La Nina / Cool ENSO (I used SON to JFM averaged ONI of -0.20 or lower for selection of the years) Here is the +QBO "North" composite with trends noted for years since 1990 Having said all of that, there are years where the correlation doesn't work. 2 reasons can be: 1) The lower stratospheric temperature profile in the tropics and subtropics doesn't match the QBO Induced Meridional Circulation pattern discussed earlier, and 2) The polar vortex / AO / NAO are overly positive/strong and zonal flow is too strong to allow development of poleward ridges in the mean pattern. Lastly, there were 2 other things you mentioned that I wanted to touch on. One was the interrupted QBO cycle. Indeed, one interruption occurred in the winter of 15-16 and the other occurred last winter. The QBO does however appear to be back to a more typical cycle (at least for now). We can see the tan colors here showing the +QBO stretched out from roughly 20mb down to 70mb on the far right You also mentioned utilizing the QBO in terms of its movement thru the QBO cycle/progression. Sam Lillo has done work in this arena. Here is one of his images showing the occurrence of strat vortex weakening events at various times in the QBO cycle. You can see at various points in the cycle where there is preference for early winter vs. late winter weakening events. My guess is that we are currently somewhere between W30 to W50 on this image.

Yeah it looks like that page was taken down. You can do a google image search on madus weather teleconnections and it will show some of those teleconnection pages scattered throughout the internet where folks have pasted them into a blog, etc., like here - https://dcstorms.com/2019/01/06/capital-weather-teleconnections-mjo-indicate-a-return-to-winter-january-2019/

40/70 - thing is, at 500mb, a composite of the last 2 winters (below) looks like La Nina instead of El Nino with NPac ridge and -PNA. So, when I composited the last 4, it came out to kind of what I had in my head for this winter in the big picture. +QBO this winter would favor a more poleward NPac ridge. That composite of mine does have a poleward ridge (no negative anomalies in Alaska), but it's biased to the NW. 4 of the last 5 mod-strong Ninas with a poleward NPac ridge were biased to the NW ('56, '71, '74, '11) . '89 is the lone exception. One thing that would support the idea of a suppressed NPac ridge would be a strong +AO. The seasonal models favor a suppressed ridge at the moment. AO/NAO are always a challenge to figure out. Anyway, those are some thoughts on it...hope I will have time to put more into it the next 2 weeks...my work has been busier than normal of late.

My first guess on winter...

raindance - is this your SOI 10 point drop storm?

Yes. It will end up being classified as east-based or hybrid/mix. If it were west-based (Central Pacific), the max cool anomalies would be centered roughly along 160W thru the fall/winter.

Monthly 500mb anomaly forecasts from the Oct release of the seasonal models via Oct Copernicus ECMWF update (via twitter @SimonLeeWx). Overall theme from the models is high latitude blocking in Dec, transitioning to -PNA / +NAO in Feb

The Met Office prides itself on its predictions of the NAO with its seasonal model. I looked at the NAO prediction from prior October seasonal model output back to Oct 2009 (this is the oldest date in the archive on the seasonal model site - https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/ens-mean). In looking at the charts, I would say that in 9 of the 11 years, the October prediction of the NAO on the model was a good one. The 2 misses were in Oct 2013 and 2015. Here was the Oct seasonal output from 2010 and 2011 - both quite good with the NAO prediction (-NAO in 2010-2011 / +NAO in 2011-2012), with both of those being La Nina winters. Finally, here is a chart from the Met Office showing hindcasts for their prediction of the NAO with the GloSea5 seasonal model for the winters of 1993 to 2012. The results are pretty good. Note: this is the NAO prediction from the Nov1 release each year - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014GL059637

^ Other somewhat similar years to these 2 model outputs are: 2011-2012, but the +EPO/+NAO was even stronger in the analog year 2007-2008, but the negative height anomaly extended much farther south (down into the southern plains) in the analog year 1999-2000, but the negative height anomaly was farther north from Alaska to northern Canada

The October release from the Euro Seasonal (ECMWF SEAS5) and Met Office / UKMet Seasonal (GloSea5) are similar for Dec-Feb with +EPO and +NAO, and lots of zonal flow. They are most similar to the winter of 1998-1999. Are they correct? Time will tell, but they paint a grim picture for cold and snow across the lower 48. Euro and UKMet Seasonals... 1998-1999 500mb, Temperature, and Snowfall Anomalies...

Opening up this thread for cross regional discussion prior to and during the winter of 20-21 One of the well-known 'problem areas' in recent winters has been the highly positive AO & NAO. Here is a map showing how the 500mb pattern from the winters of 11-12 to 19-20 (last 9 winters) has compared to the winters of 02-03 to 10-11 (12-20 minus 03-11). Getting the AO/NAO even back to neutral would be a step in the right direction. Last winter alone, the AO numbers were kind of astounding. The AO was +2.42 / +3.42 / +2.64 for Jan / Feb / Mar. That's the highest on record for Jan-Mar going back to 1950 The October release of the Euro Seasonal predicts the greatest potential for a -NAO to be in December, with higher values predicted for Jan-Mar. The purple covers the range of ensemble members on the Euro Seasonal (purple line is the median). The gray area is the model climatology. The yellow and orange is from the analysis in the 24-year hindcast period

Eurasia snow extent lowest in the last 15 years for mid-late September

5 Euro runs leading up to the storm showed the following for total precip in Charlotte: 8.3, 4.5, 7.8, 5.2, 5.0 (this was 00z run last night) As of 3pm, Charlotte has recorded 1.53

RGEM / RDPS and IBM GRAF 4km (from @MJVentrice) are 2 models that are farther south with the axis of heaviest rain.

psu - enjoyed your write-up. Regarding the orientation of the North Pac High during cool Enso winters, I wrote a bit about this in an outlook from winter 17-18. Take a look at the section titled "North Pacific Pattern" https://www.americanwx.com/bb/topic/50432-griteaters-winter-outlook-17-18/

The last time we had a weak La Nina, it snowed in Atlanta and Charleston in separate storms, and we had such a prolonged and severe cold spell that kids played ice hockey on frozen ponds in Wilmington...all of that occurring during a winter with above normal temperatures

My kids laugh (as do I) at how we can follow a storm for 2 weeks and end up getting a trace of snow

On Monday June 1, GFS MOS has highs in the 70’s with dewpoints in the 40’s across the region under sunny skies. I’d say we’ve earned such a day given the weather in recent weeks

@xhong - take a look at these links: http://lukemweather.blogspot.com/2012/04/connecting-height-changes-to-weather.html http://www.atmos.albany.edu/facstaff/rfovell/meteo_slides/Lecture15_slides.pdf

I have a cousin who lives in Estill, SC. They dodged the storm but said that “it took out some homes completely and there’s been a few casualties to their east”

Heightened potential noted here for the folks in Georgia. Cameron had some excellent analysis prior to the early March Nashville tornado.

Very strong +AO in the stratosphere here (1hPa to 100hPa) of late. Also shown is the coupled +AO in the stratosphere and troposphere since January, and forecast to continue, which suggests a mild March is in the offing. Good by me, as spring is the only season of the 4 that I want temperatures to be above normal.