More Discussion on Dec 9 to 15

The models today are still showing the big change in the pattern coming to North America. The most impressive thing right now is probably the strong PNA + signal–this has been absent a lot last year,and even lately in this Fall. Yet despite that lack of + PNA, we’ve managed a decently cool November…..thanks mostly to negative AO, NAO.   So you can probably imagine what happens when we flip to the +PNA pattern to boot–Colder!

The animation from GFS is especially gung ho lately on days 9 through 16 in regards to a dual block signature, meaning cold lower United States.

Thats pretty impressive widespread cold across the US–which would be rare to be that cold over that much territory. I’m not sure I’d buy that extensiveness yet.  But it does have the same general building western ridge with time, after a hand off from a stout Greenland Ridge.That part makes sense (esp. since all other globals do end up making a big deal of the western ridge–classic Winter 2014 style. Albeit a little early.

The GFS is a little quicker by a day or two on the first cold front. (ensembles)

That is a stout +PNA.  I won’t speculate yet on how much energy is left behind in the Baja or northern Mexico yet, but usually , there is some (but not the degree Euro was showing yesterday, with a full fledged cutoff).  That energy will have to be watched closely as it comes east. In fact, GFS has 3 distinct Gulf Lows in this pattern from days 9 through 16.  Pretty odd for a Nina!  Remember, we had ZERO Gulf lows last Winter. And only 1 the Winter before, truth be told.  So I can see why some Winter lovers are in excitement mode right now, but I’d advise to keep hopes low just yet for actual Winter weather too far south since December snow and ice is not that common. On the other hand, this is exactly the pattern that would deliver it—-its just that we dont normally get this kind of flow in early or mid December.

Whats more interesting is that GEFS and GEPS the American and Canadian ensembles actually retrograde this ridge, a little, tipping it inland in Canada–Oh boy–that normally means Gulf tapping ensues shortly thereafter.  The entire longwave remains put or slightly works with day 14 to day 16 or so, meaning something is coming north from the Gulf or northern Mexico.  I’d say it’s way too early to really start to look for any specific storms, but we’ll watch and see what happens once the colder air is coming down. Also, there is 1040 mb highs stacked to come down, on top of the Western PNA ridge, so any storm that were to hit the southeast or eastern US would likely be followed by very cold air.  All in all, a lot going on in the distance, but for now, its only on paper.  The good news there’s good agreement on the basics, and we have solid agreement on the indices coming up……most of which are a drastic switch from the previous two Decembers (not to mention Winters)…..and if My hunch is right, we’ll relax that flow later December, only to repeat it again in January and February and possibly March. Those months are the best months to capitalize on such a flow–not December so much. So be patient and lets watch if the blocking keeps on coming back.

Euro Ensemble Day 10:

AO outlook ……going severely negative.  The North Pole is going to warm, meaning cold pushes to the mid Latitudes soon.