packfan98
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Pattern Freezing Ferocious February
- Thread starter Snowfan
- Start date
https://weather.mdaus.com/home
By the way, MDA recently merged with another company and has just taken on the name "Radiant Solutions".
Webberweather53
Meteorologist
I know some were feeling glum about the winter the past few days but it's not over til the fat lady sings, I definitely feel much better & more confident to go about saying that we could see a turnaround in late February & March given how the pattern is evolving and the fact that HM is on board with this idea. Amy Butler here just reminds us yet again that the models can't properly simulate tropopshere-stratosphere interactions and in concert w/ tropical forcing over the Pacific which favors disruption of the PV and a -NAO (with the -NAO lagging phases 6-7 of the MJO by a few weeks), the GEFS is beginning to sniff out a potentially significant -AO crash on the horizon.
GeorgiaGirl
Member
Bruh. That time period keeps getting worse temp wise. Considering while there's been lot's of back and forth between above average and below average, it hasn't gotten real warm (not really even any 70s!), that's very disappointing. That's going to feel hot to me.
Good point, However, one also should be wary about GEFS AO predictions as they have been biased way too negative recently:
For example, here was the 1/26/18 GEFS AO prediction:
So, the 1/26/18 GEFS 14 day prediction had the AO to be in the -1 to -2 range about now. However, we're currently nearing +1 and rising in the shorter term meaning a miss by -2 to -3! Also, check out today's GEFS prediction:
Note the mean AO over the last 4 months has been 0.0081 or essentially 0/straight neutral. However, note the bottom graph (14 day prediction), which has been mainly negative and has averaged -0.7194. So, the 14 day prediction has had a negative bias of 0.7194 + 0.0081 or a -0.73 AO bias. So, I'm advising extra caution about GEFS based -AO predictions.
Webberweather53
Meteorologist
We're going to get soaked the next 1-2 weeks, especially MS, AL, & GA. What a nice treat considering we're in a La Nina
Webberweather53
Meteorologist
Similar to the GFS's MJO biases, these stereotypical tendencies in the GFS aren't always applicable and should not be immediately broad-brushed to every situation. In this case, I think that notion holds true because there's a very clear change in the stratosphere, tropical forcing & concomitant equatorward progression of -AAM that supports a substantial dip in the AO in the longer term, in mid-late January this wasn't necessarily the case because the large-scale forcing wasn't as favorable. Models usually don't properly simulate stratosphere-troposphere interactions and the EPS is also on board w/ a -AO surge in the coming weeks. Sure you can claim the GEFS might be overzealous in its depiction of the AO and it probably is to an extent but there's very legitimate support to a -AO stint later in the month. When you stick the MJO in the Pacific, the AO & NAO usually dip negative 1-2 weeks afterwards due to the impact of diabatic heating on the extratropical circulation pattern and wave fluxes and the PV split is only going to augment this. The support for this idea from HM only lends more confidence
I hope HM and you end up right as I don't want it to stay warm through the end of the month. I am assuming most of the next 2 weeks will be warm preceding what may or may not occur late month. I am keeping in mind (what MDA said) that these SSW have more often cooled Europe than N.A.
I wonder why they have more often cooled Europe than NA ?
Webberweather53
Meteorologist
Here's leads and lags of the NAO, Atlantic Ridge, and Scandinavian blocking pattern wrt each phase of the MJO from Cassou (2008).
https://www.nature.com/articles/nature07286
Notice the -NAO peaks about 2 weeks ish after a phase 6 MJO event.
Here's another piece from Shao, Song, & Li in 2016 that simplifies the arguments presented in the aforementioned study.
http://www.lasg.ac.cn/mjo-workshop/ppt/poster/Poster-sxl.pdf
Here's a nice chart from ECMWF that shows the probability of a particular phase of the NAO based on where the MJO is located and the associated leads/lags. Almost 50% of the time we observe a negative NAO after a Pacific MJO (Phase 6-7) event.
There's a multitude of studies on this topic that delve into the MJO-AO/NAO relationship, I'll just post a few here, strongly suggest reading these, they're well worth your time and not terribly technical
http://onlinelibrary.wiley.com/doi/10.1002/qj.2917/abstract
https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0502.1
https://journals.ametsoc.org/doi/pdf/10.1175/2008JCLI2515.1
Thanks, Webb. This is still a lot to take in for someone who likes things kept relatively simple so as to be able to fully wrap my head around it all. One thing from that that immediately got my attention is the EMON (Euro monthly) MJO forecast of it going into phase 8 on 2/18 and then down into low end moderate to weak phases 1 and 2 2/22-3/9. I do like seeing that as phases 1 and 2 do lean cool on average in the SE.
Brent
Member
oh hey a winter weather advisory for freezing rain 
Webb,
So, are you predicting based on what you posted that ~two weeks after this past MJO phase 6 event (1/28-2/1) that there will be a -NAO? That would be around 2/11-15, which the GEFS still has as solidly +NAO and the GEFS over the last 4 months has on average had a -0.34 NAO bias at forecast day 14. The bias at day 10/7 has been -0.27/-0.15.
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Webberweather53
Meteorologist
It's really not as simple as "ok, the MJO is here so in exactly 2 weeks we can expect the NAO or AO to do X" or that "x model has had x bias for y period of time" it's dependent on the speed & amplitude of the MJO, what time of the year it's occurring and how this registers onto the inherent synoptic-planetary scale internal variability and background forcing, etc. For example, a faster moving MJO event may limit the amount of forcing and possibly the duration of the forcing it imparts onto the planetary-scale wave train, and it can constructively or destructively interfere with it such that the forcing response is entirely different in particular situations, even if the forcing is the same (i.e. the MJO is in the same spot with the same amplitude). I know you like to simplify things, but that's the issue with atmospheric science, it really isn't that simple, there are a smorgasbord of nuances I'm only beginning to scratch the surface with here that need due consideration. In any case, I'd postulate that we are likely to see the NAO turn out less positive during the 3rd-4th week of February perhaps extending into early March as well, a significant (< 1 sigma) negative stint is entirely and legitimately possible imo which lends credence to what both the EPS & GEFS are forecast but it's highly dependent on how much interference occurs w/ the background state, the speed and amplitude of the MJO, the evolution of the polar vortex split and how much coupling occurs between the stratosphere and troposphere, etc (all of these should sound familiar). In any case, this should be fun to watch, it's been a long time since I've seen an instance like this where literally everything is going for very strong MJO activity in general in the extended range. The MJO backswing in the Indian Ocean several weeks from now will be crucial in determining the amount of damping we see w/ our downwelling Kelvin Wave in the West Pacific, if there's limited activity here, it could allow the Kelvin wave to continue amplifying unhindered, if the easterly trades are temporarily restored, it may trigger a resurgence of easterly trade winds that could aid the NINA in hanging around a little bit longer. In any case, the combination of a record breaking +PMM in the late winter and extreme WP MJO event at this time of the year of comparable magnitude to ones that preceded our 2 most recent super El Ninos is a death sentence to this La Nina
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Congrats ! Maybe another round of wintry precip for you this weekend ?oh hey a winter weather advisory for freezing rain
Not all! I'm well within the metro but there was a sharp cutoff to my south.
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Taylor C
Member
I love how the models are warmer now, and there’s no artic outbreak for us. The GFS never gets me to freezing or below over the next 14 days. Clap to the thread title being very wrong.
The GFS never gets me to freezing or below over the next 14 days. Clap to the thread title being very wrong.
Brent
Member
Euro is close to an ice storm on Sunday morning yeah
Been hints on other models hm
I love how the models are warmer now, and there’s no artic outbreak for us.
Maybe so but the first part has had some freezing and the last week is very much in doubt as per Webb and others. Plus, the reference was to SERidge's February up in Indiana, not to the SE's Feb.
Well the title of the thread was right for some areas. North GA and the Carolinas had some ice recently. Brent may have ice tonight and then again this weekend. And of course its snowy and cold here in Indiana.I love how the models are warmer now, and there’s no artic outbreak for us.