Cold Inside Slider pattern will bring snow showers and cold temperatures to the high country…Gusty Winds over the higher elevations prompts the awareness of a Wind Chill-Factor….. Temperatures to moderate over the weekend….No Major Storms in sight….

12/29/2018 10:00AM

Thoughts about the long range….

When ever I see a possible series of storms during any month of Winter in the week 2 period, IE in this case, between January 5th and the 11th, I always look to see where and how strong the MJO is. The MJO has a statistical relationship to the longer range for weeks 1 through 4. In this case the week one period falls within the MJO phase space 5 and 6 and for January, this tend to be a drier than normal period through early in the phase space 6 with heights increasing along the west coast; See: http://www.americanwx.com/raleighwx/MJO/MJO/JanuaryPhase6gt1500mb.gif

So the current Saturday 12Z run has some support for the weekend storm of the 5th of January late Phase 6). However, the ECMWF Shows a weakening MJO as it moves into this western pacific region with an increase in heights in the +PNA. It delays the storm into the week 2 period. Prind point here is that using only the GFS, the weekend storm of the 5th is a somewhat low confidence bet at this point. Going from phase 6 to phase 7 has a better relationship to storminess for CA and that comes during the week 2 period. This time of the year, the week 2 period storm track may favor Southern CA best, especially early during week 2 then further north later in week 2. SEE: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/LaggedComposites/whmjo6.djf.z200composite.web.png

12/28/2018

Mammoth Weather.com picked up 3 inches of snow over night. Skies are clearing….it is cold with highs near 20 today. There is a wind chill factor on Mammoth Mt today….ware face protection….:-)

As Forecasted…A a cold inside slider is bringing snow showers and cold temperatures to our region. Temperatures are running some 20 degrees below normal for this time of the year which should be in the low 40s. Both Thursday and Friday nights lows will likley be below zero over much of Mammoth. As the upper flow becomes more NE/SE orientated today, upslope snow showers are likley with light accumulations expected. 1-3 inches. Friday will be the coldest day with highs near 20 degrees.

The Weekend outlook shows moderating temperatures that become seasonal by Sunday. Wind protected colder valleys along highway 395 are likley to experience over night lows around -10 to -15 or colder.

The longer range….First week of January is being forced by a strengthening MJO entering the Western Pacific. With the MJO in phase 6, it is likely to suppress storms and precipitation over California through the first week of January. SEE MJO Phase 6 composites for California (jan): http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Precipitation/DJF/combined_image.png

This MJO is an area along the equator highlighted by a pulse of rain and thunderstorms. It is currently over the far Maritime Continent moving westward to the western pacific. Strong westerly wind bursts are now occurring over the Eastern Indian Ocean. See: http://www.bom.gov.au/climate/mjo/#tabs=Time-longitude In that the American GFS model and their ensembles really amplify this MJO feature to the point of +4 deviations of normal, it will be very interesting to note things like latent strong westerly wind bursts that develops in response, that possibly intensifies El Nino on a climate scale of time. However, on a shorter time scale, if the Climate Forecast system, (CFS) is correct, noting and contrary that the GFS and ECMWF appears to be much quicker and less amped, it is possible to have a strong atmospheric response on the central west coast in the form of an “AR”, sometime depending upon the speed of the MJO, during the week 3 period of January. The composites relate to warmer than normal temps for California phases 7 and 8 with a bias for precipitation in phase 7 followed by drier than normal in phase 8 then wet again phase 1. The classic MJO induced AR’s usually occur when the strong MJO crosses from Phase 8 to phase 1. The pattern can be forced by Rossby Wave Dispersion into the Pacific Basin with fast Meridional flow aloft, followed by retrogression of the long wave features over the Eastern Pacific. An extension of the East Asian Jet to the west coast is then possible. The process includes undercutting the EP ridge forcing -EPO, that transits to -WPO. it is a wait and see if the ECWMF and GFS follows suite. This of course is always a long shot, however possible…

Sensible Weather: Watch to see if: 1. we have a dry week during first week of January; followed by a possible storm during the second week of January, followed by a strong amplifying ridge in phase 8 with dryer than normal weather, followed by Pineapple express. Timing may change depending upon speed of MJO. Of course, if the current runs of the GFS and ECMWF are correct, then this post is one for the trash can.

Will Watch to see if the ECMWF and GFS falls in step with the NCFS keeping the MJO very strong and propagating it through phase spaces 7, 8 then possibly 1. The fact that the ENSO basin has not fired up convectively yet is a good sign in this respect.

Dr Howard and the Dweebs……….:-)

Forecast Models Coming in a Bit wetter today for the Christmas eve storm…..thereafter…inside slider pattern to wrap up the year with below normal temps and periods of mainly light snowfall….January will begin mostly on a dry note

Warm Frontal precip began in Mammoth around 3:30PM, however UVM related precip will start about 8:30pm tonight..

12:30pm Christmas Eve;
looks like our storm has slowed a bit. It’s beginning looks to start between 8:00pm to 9:00pm tonight. Looking for snowfall accumulations between 12 and 18 inches between Main lodge and the upper bowls by Christmas mid Morning. In town….expect some 5 to 10 inches by 7:00AM. Christmas Day looks snow showery with another 1 to 3 inches. Next weather system will bring snow showers, later Thursday into Friday. That will be followed by some very cold weather. Another COLD slider looks possible New Years Eve.

Long Range: MJO forecasted into Phase 6 and 7. (Western Pacific) GFS went bonkers…The ECMWF is not nearly as strong. The Dweebs feel that strong ridging will take place the first week of January, following by possible retrogression, then sometime beginning the 2nd week of January, an active wet pattern will develop. This is based upon climate models weeks 3 and 4.

From Sunday AM; Latest guidance this morning from the 06z and 12z runs are showing a richer PWAT push of moisture ahead of the Christmas Eve storm. This means that we can expect a bit wetter scenario Monday Night with amounts now projected to be in the 10 to 15 inch range over Mammoth Mt. The Town of Mammoth could see anywhere between 5 to 10 inches by mid morning Christmas Day. The storm should clear out to just snow showers over the higher elevations by mid morning on the 25th. Between Christmas Day and January 1st, we can expect weather systems to take on a more inside slider track. This means that weather systems (WX) will drop south along the eastern slopes of the sierra or Great Basin producing upslope snow showers. There is a significant wave coming through Thursday night and another about New years Eve.

Happy Holidays to all from the Dweebs!!

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.