griteater

An El Niño Split Flow Miller A, what a beautiful site

Thank you, and yes on your question

It's just the MJO really, but instead of the MJO phase chart, I prefer viewing it on a VP (Velocity Potential) map or on a hovmoller chart. The chart below is the EPS VP Forecast (courtesy of a Mike Ventrice tweet). The blues and pinks are -VP anomalies indicating upper level divergence which aids in rising motion and acts to enhance tropical convection more than normal. The yellows and reds are +VP anomalies indicating upper level convergence which aids in sinking motion and acts to suppress tropical convection more than normal. The location of the enhanced / suppressed areas of tropical convection have a large influence on the 500mb pattern over the Pacific and North America. El Nino like is when you have +VP anomalies in the Maritime Continent and -VP anomalies in the central and eastern Pacific. La Nina like is the opposite, -VP anomalies in the Maritime Continent and +VP anomalies in the central and eastern Pacific. Typically, the stronger the ENSO phase (stronger El Ninos / stronger La Ninas), the more locked-in these VP anomalies become as opposed to cycling around the earth. Here in late Nov into early Dec we are going thru an El Nino like period. The building warmth on the EPS in mid-December is tied to the -VP anomalies moving east and reaching the Indian Ocean and the Maritime Continent (La Nina like). The 500mb pattern for El Nino like vs. La Nina like varies some based on the month, and even the time of the month (it can be different for early Dec vs. late Dec)...but that's a topic for another day. When I say that the MJO has been active since late Sep, you can see that on this hovmoller chart below. CHI200 on this chart = VP anomalies (at upper levels - 200mb). This chart is showing VP anomalies along the equator from 15S latitude to 15N latitude over a time period (from early Sep to late Nov, with the CFS forecast beyond into Dec). The black lines show the movement of the MJO. This shows how the MJO has been very active since late Sep (active cycling of alternating solid and dashed black lines). If you just go down the chart from Sep to Nov along 120E longitude (location of the Maritime Continent), you can see how over time the Maritime Continent has alternated between -VP anomalies (green, which is La Nina like) and +VP anomalies (brown, which is El Nino like). What we would typically want to see for an established El Nino is a low frequency signal that is El Nino like (i.e. +VP in Maritime Continent and -VP in C & E Pacific) - in other words, we would want to see that type of pattern be predominate in the hovmoller chart over time, but with some level of MJO activity mixed in to enhance / suppress the overall low frequency signal. Instead, what we have seen since late Sep is a lot of MJO variability (also referred to as inter-annual variability). So, that's why I made the comment here that I would favor pattern variability that is higher than normal for early winter - https://twitter.com/griteater/status/1064557377050025984 Lastly, Mike Ventrice has a nice product that shows the VP movement in real-time here (via loop): http://www.atmos.albany.edu/student/ventrice/real_time/maps/mjo/global_analyses.html

The tropical forcing is so active right now (has been since late Sep) that variability isn't surprising to see on the modeling, so I personally wouldn't be too concerned with getting into a stuck pattern here in early winter.

So the going theme on the GFS and Euro Ensembles is this... Possible wintry threat there in the Dec 8-9 timeframe with a split flow wave entering California - GEFS has a colder and more suppressed look compared to EPS. After Dec 10th, zonal flow breaks out with NE PAC / AK trough, and warm anomalies spread out east of the Rockies. EPS is on the aggressive side with the warming. GEFS has it too, but it's not as aggressive

There's so much warmth extended to the west, even west of the dateline, that's it's difficult for the SST base readings to not be at least somewhat in the west-based or modoki camp....but overall, I'd say it's not clearly in the west-based or east-based camp when you look at the recent SST images. Atmospherically, the VP pattern associated with the MJO has been very active since late Sep, so we don't have a clear signal on the base of the nino from that standpoint either.

Today's NOAA reading is up to +1.3 in Nino 3.4, and more warming is likely over the next 2 weeks due to enhanced westerly winds east of the dateline. However, these SSTs will rise and fall over time as part of the back and forth with ENSO. IMO, it's highly unlikely that this reaches strong El Nino status which I would define as at least 3 consecutive tri-monthlies of +1.5 or higher. Even if it were to somehow get that high, strong El Ninos have typically been on the cold and wintry side for us. It's the super ninos that have predominately been warm and less wintry (years like 97-98 and 15-16).

It looks like the anticipated Nino 3.4 spike has begun... Nino 3.4 / Modoki Index (Daily AVHRR Data): 11/25: 0.98 / 0.66 11/24: 0.69 / 0.59 11/23: 0.81 / 0.69 11/22: 0.65 / 0.48 11/21: 0.71 / 0.46

^ Raindance is dying to somehow get it warm in the east I agree with your thought though on the cycling of the tropical forcing and potential impacts. Seems like it just wants to be cold though. We’ll see

^ I’m with mister snow niner. Full blocking all the time is the way to go at our latitude

High chance these upcoming westerly wind anomalies east of the dateline will lead to a solid spike in Nino 3.4 (image from @mjventrice)

Nino 3.4 / Modoki Index (Daily AVHRR Data): 11/20: 0.72 / 0.49 11/19: 0.67 / 0.53 11/18: 0.65 / 0.51 11/17: 0.60 / 0.51 11/16: 0.59 / 0.44

850mb temps same period

Pretty split flow pattern on the aftn Euro Ensemble (days 6-13). Split flow wave 1 hits the west coast on day 9 (hr216) and wave 2 hits the west coast on day 11 (hr276), underneath west-based -NAO.

Nino 3.4 / Modoki Index (Daily AVHRR Data): 11/18: 0.65 / 0.51 11/17: 0.60 / 0.51 11/16: 0.59 / 0.44 11/15: 0.55 / 0.41 11/14: 0.57 / 0.35 We should see another round of warming in Nino 3.4 at the end of the month and into early Dec when the MJO related westerlies move out into the central Pacific

The afternoon Euro Ensemble for days 5-15

Enjoyed it Don, thanks for posting. Hope you will continue to do these. One thing - check your surface temp anomaly maps - it looks like you need to change 2009 to 2010 in your Jan and Feb composites

The warm anomalies are stretched out across a large portion of the Pacific right now. That look registers more in the camp of west based / modoki than it does east based. No, I don't think we are going to see a hard move west or east. That would be the thing to look for though in order for it to have implications on the winter...and whether there are also atmospheric changes to go along with it (e.g. changes to VP anomaly patterns).

Nino 3.4 / Modoki Index (Daily AVHRR Data): 11/14: 0.57 / 0.35 11/13: 0.71 / 0.50 11/12: 0.64 / 0.53 11/11: 0.51 / 0.51 11/10: 0.48 / 0.50 11/8: 0.69 / 0.61 11/7: 0.85 / 0.73 11/6: 0.84 / 0.65 11/5: 0.94 / 0.55 11/4: 1.13 / 0.86

Nino 3.4 / Modoki Index (Daily AVHRR Data): 11/12: 0.64 / 0.53 11/11: 0.51 / 0.51 11/10: 0.48 / 0.50 11/8: 0.69 / 0.61 11/7: 0.85 / 0.73 11/6: 0.84 / 0.65 11/5: 0.94 / 0.55 11/4: 1.13 / 0.86

The AVHRR numerical data for Nino 3.4 hasn't updated since 11/8. Tropical Tidbits has it down to 0.44. The Euro doesn't show any westerly wind anomalies over the central Pacific over the next 10 days. The next round of warming will likely have to wait until later in the month when the tropical forcing becomes more favorable for westerly anomalies

Enjoyed the write-up Iso. You continue to push the science forward, kudos. Love the NAO predictor. I spent more time in this arena with my outlook this year as well, looking for more clues. If we do in fact see a 10mb SPV that is stronger than normal along with a solid -NAO, that would be quite the call. Good luck and thanks for taking the time to post it.

There was increased Greenland Blocking on the 500mb chart, and on your precip chart, the tropical precip is farther west

Thanks for the compliments Iso, appreciate it. Ha, I forgot to post the snow map. Added it this morning. I find precip maps to be extremely difficult to predict. Sure, you can get an idea from the projected pattern, but then you have to account for convective (down south) vs. cold sector precip etc...so, it gets quite complicated IMO. I'm staying away from that for now. On the climo base, I just state that I'm predicting against the 81-10 base and go with it that way (i.e. stating that up front). Thanks again.

I realized this morning that I screwed up and forgot to include the snowfall map in the outlook....probably best that I did forget it for this subforum