Christmas Week and the "interesting" pattern evolving by KHOU BLake » Sun Dec 10, 2017 4:01 pm Howdy, err'body. Been a long time since I've last logged on here. Been lurking from time to time but wanted to kick off a new thread here regarding the week of Christmas and the pattern that is evolving that could lead to "interesting" weather at that time.
Usually I don't like to jump on board model runs that are in the la la land range of 228 hours (10 days) and beyond but I can't help but notice a few things.
First, the Euro ensembles continue to advertise a very persistent and amplified pattern leading into the week of Christmas with deep troughiness in the eastern 2/3 CONUS. While I don't quite see a McFarland signature in the 500 mb heights near the Yukon, there is no doubt a very stout ridge that will be building into Alaska that should help funnel blistering cold air out of that region and down into Canada. Plus you don't necessarily have to have the McFarland Sig to get cold down here. Placement of the arctic high is everything (normally want to see it drop into central Montana and down the lee of the Rockies like last week).
Second, the GFS may finally be sniffing the MJO phase 7/8 by the end of the run and aligning more with the Euro. What's that mean? Phase 7/8 tends to be a very favored phase for cold outbreaks in the US. Phase 8 especially for Texas. I've noticed that beginning with the 12z GFS Saturday, it brings snow to west Texas by 384 hours. Now you say, "wow, that's a long ways out." No doubt and I'm not sold. I sort of have the idea of "the safest place to be in the cone of uncertainty is right in the middle of it 5 days out." However, the 00z Sunday GFS came in and shows an ice event for central and north Texas. Okay, that's interesting. Then the 12z GFS continues the line of thinking except brings wintry weather clear down to Brownsville and up the Texas coast. Okay, now that's really interesting. So three out of the last five runs are now sniffing, A: much colder weather for the US, as seen in the height anomalies and the expanse of the 540 thickness values and B: noise in the subtropical jet.
Anecdotally speaking, snow or ice events in southeast Texas aren't well advertised this far out. Even this past winter storm, it wasn't sniffed out by the models until 18z Wednesday (the day before). I could tell something looked funny to me as early as 06z on the 5th but nothing definitive. Now before we all get hysterical, forecast soundings indicate perhaps this will be a much shallower airmass than what came through a few days ago meaning the chance of snow might be restricted due to warm mid levels. Ice (PL), if and only if the current 12z model is correct (and it likely is not) might be the predominant precip type.
The overall pattern certainly warrants a watch and wait because the pattern that is evolving does NOT indicate another blowtorch Christmas but one that makes the 1983 analog stick out like a sore thumb. After speaking with srainhoutx, we're both in agreement that there are interesting days that lie ahead.
Could "it" really happen twice in one year? Yes! If you go back and look at 1973, there was not 1, not 2 but THREE accumulating snowfalls that winter in Houston; two of which happened back to back within one week of each other that February. Stay tuned!
Harp, I mean you get sneaux on December 8, one of, if not the biggest, earliest widespread southern deep south sneauxstorms that has ever occurred and you are asking for more, like even a white Christmas? Gosh, How can you, like I mean, come on now....................................... Well is the GFS dry? Seriously now. In order to have two sneauxs in a season, you have to have the first one. And we have had the first one. For the next 1-2 weeks towards Christmas the AO looks to rise quickly going positive and PNA drop so we will have some seasonal weather. However the longer range ensembles towards, more likely just after Christmas, before New Years, are suggesting ridging to develop again over Alaska, Asia and Greenland with some decent cold air coming south. This time with more of a sneaux pack up north. Hopefully our sneaux storm is just beginning of a remarkable winter here in the deep south including Harpland!
Kenneth, you have to understand, those of us in Harpland (the south shore of Lake Pontchartrain), only got teased. Here is our official gauge. Thanks for the update!
Would like to see more that just some flurries on the southshore! Enough to cover the ground would be nice!!! If not, cold weather can stay up north and I'll take what we had for Thanksgiving!!
Last Edit: Dec 10, 2017 15:32:18 GMT -6 by southernlady1: Didn't post my comment.