Monday, November 26, 2018

Quick update - 11/26/18

Back on 11/12/18 in the previous post I did, I ended with:

"I would not be surprised to see something around Thanksgiving or shortly after."  

Obviously there was a pretty major blizzard across parts of the central U.S. and midwest yesterday.  That system intensified as it moved out of the Rockies and was a little farther south than what many forecasters (and computer forecast models) had predicted.  There has already been a half dozen systems or so this fall that have been stronger and farther south than what had been expected, and that just MIGHT BE the trend this winter.  

Since the previous post on the 12th, the flow aloft has changed, at least temporarily.   Back on the 12th there was a very amplified ridge aloft across the west coast and that has since broken down enough to allow flow aloft to enter the western U.S., bringing heavy snows to much of the Sierra Nevada range (and also to the central Rockies).  On the satellite image below....

The bright area across the bottom of the image circled by blue represents deep tropical moisture, most likely associated with the warmer than average sea surface temperatures (i.e., the developing El Nino).  There has been an atmospheric response/coupling from these warm waters in the form of a sub-tropical jet stream transporting energy and moisture north into the higher latitudes.   In addition, there is a pretty good upper low near Guam across the central equatorial Pacific.  That could be a player in the U.S. weather a little down the line.  There is also a deep and strong system across the Gulf Of Alaska. 

All told, the flow aloft will continue to be rather active for the next 10 to 14 days.  There should be several more impacting storms across the central U.S., but details of timing, intensity and location will be unknown until they develop and enter the continent.  The first may be as early as the end of this week and the following may occur towards the end of the weekend or first of the next week (Dec 2-5).  Brutal cold air is not showing up at the moment.  But there is a rather robust MJO developing and the impacts may be much colder air as we get into December.   More on that later.

I'll try to update again by the weekend.


Monday, November 12, 2018

Update 11/12/18

The post I did a week ago on the 5th, I discussed a developing system that was to bring some snow to the central part of the country.  There had been many shares of a viral post about 6 to 12 inches of snow expected.  As I have mentioned numerous times in this blog, often someone will post a map of computer generated snow or rain amounts (that usually changes dramatically every six hours).  If it's "exciting", the post will usually go viral as people just blindly post or share these maps without any thought to the validity.  I guess that goes for just about everything.  Shoot even this morning there is a viral post about a huge whitetail deer that was reportedly hit by a vehicle south of Dodge City over the weekend.  It was a picture of a deer that has been circulating the internet for THREE years!

Back to that first system that occurred mid-week.  As I mentioned in that post (you can read it by clicking here), I was expecting a very narrow band of heavier precipitation (snowfall) that could be from a lot to basically nothing!  There ended up being several narrow bands.  The heaviest near St. Francis in far northwest Kansas and around 5-6 inches in the flint hills of eastern Kansas.  Dodge City for instance only got 1/2 inch and areas west and southwest got nothing at all!

The weather system that occurred yesterday (Sunday) and overnight was much stronger and more capable of producing heavier snowfall than what it originally appeared.  At this time last week when I did that post, there was just a "hint" of something that looked like it would impact southeast Colorado and into eastern New Mexico and into parts of the panhandles for late in the weekend.   Since it ended up stronger and more functional, that just might be a sign of things to come for this winter and following spring. 

Looking at this mornings satellite, the system that brought the snow is the red X across eastern New Mexico....

On the satellite image, one very important feature is the blue squiggly line that stretches up into Alaska.  That represents a sharp ridge aloft.  It's in a perfect location to allow systems to amplify as they drop into the Rockies which can also bring major shots of cold air into the U.S..  This ridge won't be in that location ALL the time, but I have a hunch that it will be there at least in the background of the flow aloft, meaning there will be repeats throughout the winter. When this occurs again during the dead of the winter, I have pretty high confidence of below zero temperatures across the high plains several times this cold season.

Something else on the satellite image...there are three areas that winds aloft are moving from the deep tropics to higher latitudes (the green arrows from the bottom of the image to the top).  This will continue to be sources of forcing going into the spring.  More on that later....

For this week, temperatures will be moderated by the snow cover with highs generally below normal until mid-week.  Lows tonight should drop well into the single digits.  There is another hint of a minor system for the weekend.  Will it also be stronger than expected and produce more snow?  I'm not too confident of that, but additional cold air looks like a strong possibility.

Following that system this coming weekend, I'm not seeing much at the moment although I would not be surprised to see something around Thanksgiving or shortly after.  Regardless, much warmer weather does seem to be in the offing beginning next week. 

The overall pattern is still in a flux and not set yet as it continues to develop and get established.  At some point during the next 2 to 3 weeks there should be a southwest U.S. or southern Rockies storm.  I'll attempt to update again in about a week.

Monday, November 5, 2018

Short update - 11/5/18

The previous post I did on the 19th of October (if you haven't read it, please do so by clicking here), the satellite image I posted showed the state of the jetstream at that time.  Today, there are major differences.  Here is this afternoons look...

The biggest change is the very strong jetstream that is coming off the Gulf of Alaska and southeast towards the central plains.  Minor disturbances in this strong jet have brought a couple of small rain events to the central plains during the past 4 or 5 days.  It will also be contributing to a possible tornado outbreak across the southeast U.S. later this Monday evening.  The configuration has also allowed for a very cold airmass to build up across the higher latitudes of Canada.

The little red X across southern Alaska appears to be a signal for some amplification that will bring a swath of precipitation across the central U.S. late Wednesday into Thursday, and that would be in the form of snow.  For forecasting purposes, these type of dynamic weather producers get most of their forcing from the wind aloft.  Thus, they have very sharp gradients of nothing to potentially a lot of precipitation. In this case, you probably have already seen forecast graphics of snowfall - but everything I've seen is computer forecast generated.  The point with that is that every time the forecast output is run, the resultant precipitation is all over the board, i.e., the models can't be trusted for specific forecasts!   For the purpose of this blog, go to for the most up-to-date NWS forecast.

The configuration of the winds aloft will also contribute to much colder weather for a few days later this week.  If it continues in that configuration, there would also most likely be another very cold shot of cold air the following week.  In the blog I did on the 19th (see above link), I mentioned November being near to above normal on temperatures for the entire month (but that was with very low confidence).  These couple of cold shots (this and next week) will probably knock the average for the month down closer to normal. 

Other than the precipitation this Wed/Thu there is not a lot showing up afterwards, at least for the high plains, through mid-month.  The pattern is still evolving.  I still need time to identify the main areas of forcing of the pattern.  Another 2-3 weeks may be needed for that.