Today I am going to put up a little debate, arguments for why the pattern could remain a warm one for the east and arguments for why the arctic cold could get pushed to the eastern sea board, considering I have laid out my thoughts on a warm weather pattern multiple times I will spend more time on the cold argument today.
If you remember back to the winter forecast, I said this winter would consist of a battle between El Nino and a cold PDO , and the MJO would be a big player in that , when convection developed around the dateline we would see a cold and active weather pattern , when convection was lacking around the dateline we would be in a warm pattern, we saw convection around the dateline between December 20th and early January and we had a very active pattern with temperatures seasonable to below average, now there is lack of convection around the dateline and it’s clearly showing. The reason I have been thinking the pattern will remain dominantly warm is because El nino has since rapidly collapsed so there is no more battle, the cold PDO pattern has clearly been dominant with La Nina like effects and a SE ridge showing up here and there.
But if you remember, in a blog I wrote last week stated that our winter and my winter forecast would come down to one factor, a stratospheric warming event that would have to power to over come the Pacific if it came to fruition. I have been spending a lot of time showing why the pattern could end up being warm and I have been leaning that way , being there are more factors in play that could make the future pattern more warm than cold for the east , however today I am going focus more on why the weather pattern could become very cold by late January and why chances are increasing
Above is a map of stratospheric temperature anomalies, we see the warming event has CLEARLY came to verify and right over the Arctic , which is right where we needed it to occur to save our winter . I said that stratospheric warming doesn’t always work and that’s why I was extremely skeptical about the arctic cold making it to the east coast , but since I came across this last night my confidence is increasing because this stratospheric warming event is not only powerful enough to over come the unfavorable Pacific but enough to improve it
The warming event has split the polar vortex and will force the piece that has been over north central Canada southward, this is the driving force to our upcoming pattern because 1 it will push arctic air into the US, which was expected anyway but 2 will push colder air down through the Pacific , and the cold polar air mixing with the warm tropical air could cause convection to develop around the dateline, of course this is going to depend just how far south the Polar vortex gets pushed but based on the strength of the warming confidence is growing that it will push far enough south
The polar vortex coming south and convection developing around the dateline would suppress the SE ridge drastically , and force a trough to develop around the Aleutians , which would push the large east Pacific ridge responsible for dropping this cold into the Midwest, east ward which would in turn force the cold air east right into the eastern United States . With all this said I am still a bit skeptical, because I wold like to see the warm anomalies more oriented towards the US to really help push the vortex south but te warm anomalies are still oriented in a very important direction, which is towards Japan which is causing a dominant trough , there is a simple rule we go by, when there is a trough in Japan there is typically a trough in the eastern US 10 days later , that trough is what would really help the vortex come south and push the really cold air to the coast. So while the initial push of colder air comes next Wednesday into Thursday , I think the true push of arctic air would come next weekend , 7-10 days from now.
So its going to all depend on how far south the PV gets pushed and if the polar air can get pushed into the equatorial Pacific and force convection to fire around the dateline ,the stratospheric warming anomalies are there but they are not perfect and I will below still make a very compelling argument for why the east could be left out of the Arctic cold.
My thoughts in summary , warmth continues through next Wednesday before a push of seasonably cold temperatures comes next Thursday-Saturday behind a cold front then a potential push of very cold arctic air next weekend , we still have a while to watch this but just keep in mind chances are increasing for a very cold weather pattern to take hold .
A pattern like this would occur should this happen
Argument against the cold: Just in a brief summary as I have stated it several times in detail
Due to the stratospheric warming and it anomalies not being oriented towards the US and a bit displaced from the ideal positioning, the polar vortex does not get pushed as far south as expected , therefore convection does not fire around the dateline, the MJO remains stuck in phase 6 the east Pacific ridge does not get pushed east and the cold is forced down into the middle of the country but a stubborn SE ridge keeps the true cold to our west with just brief cold and wintry shots and the influence from the cold PDO win out here in the east. This is still the side I am personally leaning towards but it is going to be a VERY CLOSE CALL and latest data is making me sway away from this idea a little.
This is the pattern to expect should this occur
So as you see this is a very volatile forecast and something to watch closely over the next week