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Pattern December to Remember

Webberweather53 said:
Can kind of make out 2 quasi-distinct MJO waves in the Western Pacific in both the analysis + forecast fields through Dec 10 on the CFSv2. The first wave is north of the equator in the NW Pacific, having already developed a few days ago, whereas the second wave forms out of the South Pacific Convergence Zone (SPCZ) in a more classic manner for this time of the year, which is a big reason why you see models like the EPS showing the MJO completing a loop-de-loop in phase 6 through mid-month.

The GFS & CFS try to push the wave out into the Central pacific by the 3rd week of the month, but these models have a habit of progressing MJO waves far too quickly across the Maritime Continent & Western Pacific and I think they're a bit fast once again (& thus too fast w/ the pattern change away from the SE US ridge thereafter). Furthermore, the La Nina will help decelerate this MJO wave as the advection by the background flow (i.e. westerly jet stream) is weaker than usual, and enhanced convection underneath the ENSO standing wave over the Maritime continent will favor increasing amplitude of the MJO (again favoring even more warmth in the east-central US mid-month), which augments the downstream planetary wave pattern, also helping to slow the wave down (as those waves obtain higher amplitudes and tend to retrogress westward in the means). All of this points to an extended warm-up that could last through the 3rd week of the month (dec 14-21) and while we're talking pretty far out, confidence is higher than usual in the outlook during week 2 & may grow more w/ time for later week 2 outlooks once the models initialize a more amplified MJO wave. (which is supported by literature)

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What are the odds this warmup extends past Christmas
 
Cary_Snow95 said:
What are the odds this warmup extends past Christmas
Click to expand...
I definitely am getting the impression that this will try to flip sometime during the last several days of December or early January, I'd personally lean towards the latter tho (early Jan), because the MJO tends to be slower in a La Nina (esp in the West Pacific) (for reasons mentioned earlier). The sub seasonal pattern looks ugly through at least the Winter Solstice (or ~ Dec 21), even on the often overly progressive CFSv2, so it's a very real possibility we're still warm right on into Christmas :/

cfs-avg_z500aMean_us_3.png


The first signs of any pattern change will show up most likely in the northern Plains and northern Rockies, not only because they are more favored for cold during a NINA/-PDO, but MJO phase 7 (which we should reach no later than the 3rd week of December) shows this as well w/ cold over Canada bleeding into the northern US & no real signal either way most elsewhere. So, if you're trying to get a sense for the first inkling of pattern change on forecast fields, look for cold sinking into the northern Rockies & upper midwest.

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Are y’all trying to weaponize the SER in the weather forum .. we get it it’s going to be warm we all thought December would be warm .. we got faked out here and there for a time but aside from some wudges we going to be warm for December .. this ain’t peak climo anyway so it’s not a huge loss as we are used to the warm and slow start to winter as most every winter aside from the December 8 storm a while back has been the same. Let’s talk potential for rain and severe weather and not oh look at this slap in the FACE!, winter canceled, golf course at Christmas?, next , looks like it’ll never end!, is this may?, 2011, we all knew this was coming kick can!
 
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