GaWx

I asked my excellent Maxar contact, Brad, about his thoughts about the colder pattern shown by the EPS for 1/6-12+. Here’s his response: “I think the model might be seeing the MJO in phases 7-8 alongside a normal strength polar vortex. The following 500mb analog map for this combination comes from: https://ifurtado.org/wp-content/uploads/Publications/GreenFurtado2019.pdf If the model has these forcings correct, then I think a colder Eastern Half makes sense. That said, I’m hesitant to go all in on this pattern, at least for now. There are a couple reasons for that. The first is the MJO itself. From the hovmoller plot below, you can see that the region around Indonesia stays convectively active. This is not common of the MJO in phases 7-8, so there may be some muddying up of the signal to bring lower confidence with its role on the pattern. A second is based on model trends for the strength of the polar vortex. I would say the most recent run is still ‘normal’ for its strength during that colder window; however, there has been a strengthening trend. If that strengthening trend continues and the polar vortex remains on the stronger side, it could limit that cold response per the analog composite below (MJO phases 7-8 with strong polar vortex): The other consideration is related to the warm end of December. There’s unlikely to be much snow cover left at the end of the month; and even if we get a +PNA resurgence or even a -EPO, it may take some time to reestablish a colder source region.”

12Z EPS and GEPS, unlike the 12Z GEFS, have a very pretty +PNA at the end.

12Z Euro ensemble has a very pretty +PNA at the end. Canadian ens does, too, but not the GFS ens.

My Maxar contact just emailed me this chart, which shows that the last few runs of GEFS are predicting US pop wted HDD to be near or at record lows today as well as on Dec 26-7 (records go back to 1950):

Thanks, Mitch. Keep in mind that the GEPS tends to show as the coldest of the 3 because it has the largest cold bias overall. Also, the warmth has been progged on model consensus to be stronger to our west overall. The middle of the US is progged to boil.

Today’s GEFS MJO forecast doesn’t back it up to the border of phase 7 and 6 like yesterday, but it does at least temporarily stall it in 7 late instead of then heading to 8:

Pop wted US HDDs per last 4 GEFS: absolute blowtorch most days through Dec 31st with only ~13/day Dec 27-9, which amazingly is a mere ~50% of normal to barely above that! The 13 is the normal for Nov 13th, a full 1.5 months earlier! So, if this prog is correct, we’ll be only at mid Nov normals for a few days late in Dec just before the expected end of month cooldown! I bet that is at least near a record low for pop wted US HDD then:

OMG, Raindance is back!! Holy Moses! Welcome back. Your expertise is always welcomed.

Nice looking redeveloping +PNA on the Euro ens late! Is it real or is it Memorex? That along with the cold 0Z 12/16 extended GEFS tells me that tomorrow’s Euro Weeklies, which run off the 0Z Euro ens, may be colder in weeks 3-4.

The 0Z 12/16 extended GEFS fwiw through Jan 17th looks cold with ~4 Canadian highs plunging down about every 4 days starting ~Jan 3rd helped along by a stout +PNA, PV lobe in N Hudson Bay, a mean Aleutian Low, and no sign of a SE ridge followed by Pacific flow trying to return. Hopefully this near 2 week long pattern of cold would verify well. It has today’s Euro Weeklies on its side as well as the current dominant strong +PNA likely projected into Jan. *Edit: Actually a 5th Canadian high was coming down at the end (Jan 19-20).

Thanks. Even Judah said this in the blog: “I have never analyzed Canadian warmings in my research” So, if he hasn’t analyzed them, who has? Without analysis, they’re meaningless to me as far as what they portend for the E US.

Actually, I haven’t been following “Canadian warming”. I mainly just follow 10 mb mean winds at 60N looking for potential for major SSWs, about which a lot of research has been done with lots of data gathered/available. What is exactly is “Canadian warming” of the strat. (which portion of Canada and how much warming is required?) and what is the significance of strat. warming over Canada as opposed to centered over the Arctic? Are there a lot of analyses of past events?

Below is today’s bc GEFS MJO forecast. What are folks’ opinions about this? Before answering that, consider these seven examples of a temporary stall/reversal of direction over just the last 6 winters: 2024: look at the circling in phase 7 back into phase 6 last Feb: 2023: circled late Feb from phase 7 to edge of phase 6: 2022: reversed in phase 7 Jan 1-5: 2021: struggled to get going in Dec near phase 6-7 border: 2021: stalled/reversed in phase 6 for 10 days late Jan and then stalled early to mid Feb in phase 7: 2020: Massive very long reversal/stall late Jan through mid Feb from phase 7 to phase 5 and then finally back to phase 6 but then back again to phase 5!! 2019: early Feb phase 7 stall/reversal into phase 6:

New Euro Weeklies: -Still not even a hint for a major SSW -Week 4 (Jan 6-12): Just about as strong of a cold signal as yesterday’s, which was coldest of the then 18 runs to date, as it continues to easily stick out from global perspective at H5 -Week 5 (Jan 13-19): It’s the coldest of all 12 runs to date for this week with a notable cold signal in the E US, especially considering it is way out at week 5: So, now the Euro Weeklies have a notable E US cold signal for two consecutive Jan weeks (1/6-19) during coldest climo means. We’ll see if they hold. But strong +PNA Dec analogs along with non-GEFS MJO projections at least suggest that this is quite believable. If so, the best of winter to date by a good margin may be starting in just 3 weeks.

The MJO is headed toward phase 6 for the days preceding Christmas. Phase 6 is the warmest on average for NDJ: I’m hoping for what the non-GFS model consensus is suggesting for early Jan, weak to moderate left side of MJO diagram. If this verifies, it would be conducive to a return to cold in the E US then. Now the latest bc GEFS has other ideas with it stalling in moderate amp 7 and turning back into 6. Hoping it is out to lunch! That would not be good. Unfortunately the GEFS sometimes comes through on its own with previously seemingly out to lunch MJO paths. So, I’m not at all counting it out, especially with the warm MC.

The MJO is headed toward phase 6 for the days preceding Christmas. Phase 6 is the warmest on average for NDJ: I’m looking forward to what the non-GFS model consensus is suggesting for early Jan, weak to moderate left side of MJO diagram. If this verifies, it would be conducive to a return to cold in the SE US then. Now the latest bc GEFS has other ideas with it stalling in moderate amp 7 and turning back into 6. Hoping it is off its rocker! That would not be good. Unfortunately the GEFS sometimes comes through on its own.

At RDU: Yesterday’s 12Z Euro had a very cold mid 30s at 1PM on 12/25. Today’s 0Z had mid 40s. Today’s 12Z Euro has low 50s (close to normal). This strong warmup is not the least bit surprising because yesterday’s Euro was a huge cold outlier/head-fake that I wasn’t buying (as per my post).

The 12Z GFS is significantly less cold than prior runs in the SE for the period centered on Dec 22.

I agree to take any of these forecast maps with a grain of salt like I usually do. I‘m not debating that at all. Absolutely! Seasonal modeling is typically not high confidence for me. They can sometimes provide good hints though. I was just debating where you’re saying the JMA H5 trough axis is located. And now I’m going to also respectfully debate you saying there’s a ridge on the E coast. This JMA’s H5 ridge axis looks well out in the Atlantic to me. Why do you say it’s on the E coast? We are definitely going by different definitions.

The following example of a (positively tilted) trough axis goes by the definition I’m using, which is where it is from W to E and which you’re not using: The JMA H5 trough axis for Jan is well E of the Plains (3rd map) (and positively tilted). In the Plains, the lines are from WNW to ESE as opposed to from W to E, meaning the trough axis is well E of there:

Chris, I respectfully disagree with you. You and I are going by a different definition of trough axis. I go by where it is from W to E, which is the official definition. It looks like you’re going by where the anomaly is most negative (darkest blue). Based on where it is W to E, it clearly goes from just E of Hudson Bay to Western Lake Erie to the Central Gulf Coast. If one looks closely and takes into account that this map is tilted by tilting the phone/screen, one can see that at Chicago it is still slightly S of due E rather than straight W to E. So, I still say the JMA H5 trough axis for Jan is well E of where you’re saying it is.

The southside of Atlanta/airport E to Augusta and into SC had a bad ZR in Feb of 2014. That one took down the Eisenhower Tree at Augusta National. In my area, where ZR events are typically few and very far between, we had a rare 1/4” of ice accretion from 1/2” of ZR in the great SE coastal winter storm of early Jan of 2018. It stopped just shy of causing widespread, major problems.

SST anomalies in Nino 3.4 continue with their big drop: OISST as of 12/14: new low CRW as of 12/15: new low CDAS as of 12/16 6Z: ~tied for its lowest though it’s cold biased The equivalent daily RONI is likely now well into moderate range.

Chris, Regarding the bolded, why are you saying the latest JMA has the mean trough axis in the Plains? The H5 map (last one) looks to me like it has it well E of that from just E of Hudson Bay SSW to Lake Erie/Ohio to the NE to central Gulf of Mexico (+ tilt). That’s 750-1,000 miles E of the Plains. I’m talking about where H5 is west to east. In the Plains it is WNW to ESE.

Predictably, the 0Z Euro isn’t as cold as the very cold 12Z run on 12/23-7 and doesn’t have that Christmas snow. The 0Z GFS cooled since 12Z but is still not as cold as the 0Z Euro.