Christmas week to be quite cold throughout California with Snowfall for the Sierra….Longer range has a lot to do with what the MJO does….El Nino going to play a major role this winter!

Dec 21, 2018
Dynamic Models Showing MJO into Phase 6 Toward end of year….Pattern to shift to inside slider pattern after Christmas, then potentially Strong Upper Eastern Pacific Ridge for a period of time afterwards in early January.

12-19-2018 Wednesday 9:15AM:
Observations and thoughts:
1. MJO now moving into phase space 5
2. Both GFS and ECMWF have it stalling for awhile, supporting the cold in the far west through the end of the year. This supports the idea that the mean ridge position is going to be close enough to the west coast to shut off any meaningful subtropical fetch after Christmas through the end of the year.   WX systems will dig mostly SSE over the far west/SW with little over water trajectory. We are on the cusp of going dry….

If by chance the MJO dives into the circle of death and dissipates….that would be positive for a weaker eastern pacific ridge and better for more snowfall. However, what is likley is that the MJO progresses east into phase 6 (the western pacific), setting up mean ridge position over/near the west coast and putting an end to storms for our area for a period of time. 

So far, El Nino has not coupled with the mid latitude circulation. This is evidenced by little convection over the Nino region. That may be slowly changing as the Dweebs have noticed a flareup just north of the equator  at about 130-135west.  Although quite incipient, if the MJO continues on its easterly track after the forecasted stall, the Dweebs would expect the Nino region to “light up” going into January with strong positive phase PNA implication’s.  This is where it is going to get tricky for California. Where and how the coming upper height structure effects the jet streams. Additionally, a strato-warm event is underway. That argues for a coming cold event with the intrusion of bitter Arctic Air over the east, possibly centered as far west, between the Appalachians and the Tennessee Valley. 
So the chain of events that may take place is that the west will remain cold through the end of the year followed by milder weather thereafter.

In Summery, Small storms with fluffy snowfall will be more likley through years end. After early January, winter may cut off for awhile over the far west. Once the convective stage of El Nino fires up either later this month into January, we are going to see a lot of weather changes across the western hemisphere…..More will be known over the next 2 to 4 weeks………

12-18-2018: The Dweebs have looked over the latest runs of the European and GFS models from Tuesdays 12Z run and come to the conclusion that there will be 3 significant short waves that will carve quite the cold Trof  over the far Southwest. The prind point in the Christmas outlook, is that although the two global models at this point have timing issues and even phasing issues with a couple of the short waves, the upshot is that we have a period of snowfall, beginning as early as Sunday in the case of the Euro model and in the case of the GFS (American models) Monday, that advertise moderate snowfall on and off through the following Thursday. Preliminary amounts show up to two feet of powder.

On Monday night, modified Arctic air will plunge south over the far west giving the Sierra a period of Platinum Powder Monday night (Christmas Eve) into Early Tuesday AM.  If the Euro is correct that snowfall may not be as fluffy, but may start earlier and be more of it.  There is some suggestion that the cold temperatures may begin to modify that following weekend before New years.

MJO:  The active upper divergence portion is currently over the Maritime Continent. It is expected to stall out for a while. In this location, we would expected to continue with an active pattern into the end of 2018. However, January will be interesting, as if it progresses east to the western pacific and central pacific, that favors the positive phase of the PNA. The pacific north American pattern. This usually results in a big ridge setting up over the far west, blocking storms from California. At the same time, the Polar Vortex setting up over New England often brings bitter Arctic air to the east. It is just not known yet whether the MJO will be strong enough and progress into Phase 6-7 or die in the circle of death before hand. 

El Nino:
The tropical waters near the equator are quite warmer than normal now. However, so far the atmospheric convective response has not begun yet. As the MJO shifts west with its upper divergent portion moving into the Central and Eastern pacific, that may jack start the process with an atmospheric convective response, that feeds into the mid latitudes.  Until this happens, we will not know if California will have a wet Nino or dry Nino. However, the time for all that is getting very near….  The CFS is still showing a Modoki set up with cooler SSTA off the Central American coast this winter. 

One thing is for sure, either Dry or Wet, January is going to be a very interesting month I believe from a climate perspective.

Winds Coming up Sunday will usher in Light to Moderate Storm System with some 5 to 10 inches expected over the upper elevations….2 to 5 inches in the Town of Mammoth….Pattern transition to colder NW sliders Christmas week with a hint of Retrogression in Western Hemi Pacific Pattern toward the New Year…

Weather Update at 1:00pm Tuesday…..

Saturday 4:40PM Update:  
Just had a peak at the Euro this afternoon, and it too is on board for either northwest or inside sliders beginning Christmas Day and another later that week.  This is a chilly pattern with generally light amounts of snowfall.  Snow to Water Ratios will be high….13:1 to 15:1.  More later on timing……..:-)

From Saturday AM:
Forecast is still on track for the Sunday Night/Monday Morning Storm with moderate amounts expected over Mammoth Mt. I will mention that the Saturday 12z GFS did show a narrow filament of atmospheric river sliding southward through Central CA early Monday AM. Although this storm is still expected to split as it moves onshore, the added moisture from the small “AR” might give us an unexpected bump in accumulation early Monday AM.  The Dweebs are still looking for up to 10 inches maybe a foot of snow over the upper elevations on Mammoth Mt. But a surprise might happen due to the AR.

The remainder of next week should continue to be dry. However there is a system passing to the north Thursday night the 20th that might kick up some breeze and give us some cloudiness. After a dry but possibly breezy weekend before Christmas, a transition will begin with either inside or NW sliders or in the case of the Euro, a wetter system from the west for Christmas even/day. I am not all that bullish yet on any of the particular solutions at this time because of their large differences and the fact that the CPC feels that the MJO will be in phase 4 and 5 through the end of this year. This means that there is not a significant tropical forced signal that supports strong storms in the week 2 period.  However, both GFS and ECMWF have some colder/wetter systems that may bring light to possibly moderate storms before year end. Additionally, at this time, no significant ARs are expected to affect our area as well through years end.

I will update later in the weekend……

Dr Howard and the Dweebs…………………:-)

Unsettled weekend on Tap with Wind…Sun and Cloudiness…Seasonal Temps to continue through weeks end….MJO in Phase 3 then 4 will put the Kabash on Storms beyond this Monday for next week….

12/14/2018  6:45am

Global models coming in more consolidated and a bit wetter with the Sunday night system so that’s a good point. Still looks like no more than a foot over the crest….

MJO in Phase 4 now propagating quickly according to most models….That’s excellent!  Contrary to the 8 to 14 outlook, This is an indication that we may indeed have a storm or two between Christmas and The New Year!

From December 13th; Beginning with this Friday, we are in for an unsettled period through the following Monday. The Dweebs expect a rather breezy day on Friday with Wind Warnings expected for travelers along the highway 395 corridor. For the most part, this trof is dry with little cooling for our area. The next and final upstream system continues to show weakening with just borderline light to moderate snowfall expected, mainly beginning Sunday night into Monday. The Models have been back peddling on this storm for over a week now as they play catch-up with the MJO moving out over the Indian Ocean and over the Maritime Continent where it is just now entering. The MJO; (Madden Julian Oscillation) creates a large scale area of upper divergence ahead and Upper Convergence in its rear. There is an predictable response from this air sea coupled wave depending upon “where it is”. As it moves over the Maritime Continent, the wave often forces higher than normal heights at 500MB (18000 ft) over the Eastern Pacific and far western US, often weakening or blocking storms from California. It is likley that after the upcoming Monday storm leaves, we warm up and continue to be dry though that following weekend.  It should be mentioned that this MJO in the location it is moving through will have a tendency to weaken a storm more than the global models might otherwise prog. So do not be surprised that by the time the storm gets here it is weaker and arrives even later than forecasted.  The MJO is progressive and will either weaken or progress east over a period of time and our winter weather will resume with storminess.  

Dr Howard and the Dweebs…………:-)