Monday PM:

Just a quick comment or two;

The new 12Z GFS run is still keeping the short, medium and long-range dry.  However, the ECMWF continues to develop a pattern involving a block in the WPO and EPO region that is remarkable. So, I will begin to write about it and explain somewhat, the pattern that is evolving in the ECMWF.

All Global Model simulations show over the western hemisphere, a highly amplified long wave pattern with a ridge along 125west that is importing Arctic air into the nations mid-section. However for week 2, the Euro and now the Canadian Ensemble controls are latching on to something very interesting. On Christmas day, the Euro is developing a cold polar vortex near 75N/150E.  It is feeding Arctic Air into another Trof that it is phased along 50 North and between 120E and 140E. That Western Pacific cold trough builds a ridge along 165E that will bubble up over the Bering Sea and couples with another Blocking High over the EPO region (AK) on the 27th. From the Western Pacific east to the Eastern Pacific, the westerly’s have nowhere to go but underneath the block that forms to the north.  Todays ECMWF model simulations show short wave trajectories down through Western Canada tapping (CPK) Continental Polar Air with Cyclogenesis off the Northern CA coast next Wednesday night the 27th. There is a series of these lows that spin-up into the new year.   This would be a cold snowy pattern with Powdery type snow.

For those that are up here over the New Year weekend prior to New Years day, you plan ahead by asking your boss if you could stay a few more days in Mammoth…..Just in case we have one of those “Platinum Powder” events….:-)

 

Remember this is in the outlook period, and subject to change.  But the notion of issuing a platinum powder watch Christmas Day for later next week is exciting!

 

Monday AM:

We have about two weeks left in the year and this is what I see in the models and teleconnections as well as in ENSO and tropical Forcing:

I.

  1. The EURO and GFS are miles apart in their week two outlooks.   The Euro came in wet last night with a good sized storm the end of the year.  There is support for this in their ensembles. This is a good point to consider.
  2. The GFS is dry as a bone in their week two outlook. For you hobbyist’s, if you relying on week two GFS guidance, you have missed the boat. It may be worth it to you to pony up the bucks and buy a subscription to the ECMWF.

II.

Our La Nina has most likely peaked. Watching the SOI, (Southern Oscillation Index), the Index has been moderately to strongly negative the past 8 days and so a strong weakening of positive surface pressure difference between Tahiti and Darwin is occurring. This means that La Nina has possibly peaked and that SST waters are going to moderate warmer, or at the least the negative SSTAs over the ENSO region would be trending neutral in the coming months. Note;  “This may allow the MJO to become stronger further east” and force an extension of the East Asian Jet into the west coast under an Alaskan block at some point.  MJO’s eastward extension is easier when the SSTA’s are not so cold from the dateline east. At the moment, it is the LA Nina’s “base state” that is “inhibiting” the MJO to hold together longer further east. Never the Less, the Negative values of the SOI is saying that the forces of La Nina are on the wane.  I would imagine that there is an air-sea Coupled Kelvin Wave that is involved with all this.

 

Short Term:

The long stretch of very warm air aloft to the degree it has been, is over for the foreseeable future. We have enough retrogression in the west coast ridge to allow shots of cold to periodically bring cooling to our region. Of significance, is a short wave in the form of a NW slider coming south Tuesday night and Wednesday. Although this is still a relatively dry pattern, we could get 3 to 6 inches of cold dry powder from it by Thursday AM.  Beyond that time frame, both EC and GFS has the Arctic opening up for the Midwest and East with very cold Arctic Air invading the CONUS.

The narrow but highly amped upper ridge is forecasted to be at 130W which keeps us cool but dry.

If we believe the ECMWF, serious retrogression develops week two as we head through the Yule Season as a serious cold and wet storm is at hand for year end…… Looking at the MJO RIMM phase space with some incursions by some of the models to phase space 8 and then 1, I’d give it a 60% chance at this time, considering that the GFS has nothing but ridge at 500MB week two forecast outlook.

 

More Later:>>>>>>>>>>>>>>>>>>>>>:-)

 

 

 

 

 

 

Just a short update:

the eastern Sierra will have moderating temperatures early next week before a Northwest slider brings Wind, Cold and Light snowfall.  Snow to water ratios could be higher than normal. For the time being the Dweebs are looking at about 3 to 6 inches Wednesday.  Will fine tune in a day or two. Pattern transition still having it difficulty with GFS showing cold scenario for Christmas eve and the Euro’s cold outbreak more toward the end of the year.  We are talking about modified Arctic air in late December so it will be cold.   However, some ensemble members in both the GFS and EURO are showing undercutting of the westerlies and a wetter system. Another week is need to iron out the differences…I would prefer the wet scenario over the cold one….

 

Stay tuned…..

 

Dr Howard and the Dweebs……………..:-)