Archive for December, 2017

Cold in Wake of chilly NW slider will give way to more seasonal temperatures for the Christmas Holiday Weekend…..Forecast Models continue to tease the weatherman during the week 2 period….

Friday 11:55PM

This is one ugly transition in pattern.

Apparently, we are going from one dry pattern to the next.  Time for Dan McConnell to start doing his famous snow dance….Backwards……

 

Friday 22nd

Overall pattern is unchanged for the next week with an upper ridge just off the CA coast. Although this pattern will keep major storminess out of the Sierra, the ridge this time is much less amplified and so there will be considerable high cloudiness and mid level cloudiness at times. Some weak forcing may allow for some snow showers/light precipitation into early next week.   Highs temps will be in the low 50s with lows in the teens and 20s….  There will be periods of gusty winds over the crest from time to time….

Week 2 (between the weekend) of New Years and the following weekend still looks a bit more promising at this time for a snow producing system according to the European Model.

CLIMATE SIGNELS:

The SOI has gone negative for 12 days now; a signal that will help weaken the ongoing La Nina.  According to the CPC, SSTA’s over the Indian Ocean are forecasted to warm over the coming months and promote more convection in that area. Strong convective forcing associated with MJO between 70 east and 120E is teleconnected with a negative PNA or troughing over the far west CONUS, or Eastern Pacific. This is the MJO RIMM Phase Spaces 2 and 3.

The Dweeber…………………………

 

—————————————————-

A cold northwest slider brought light amounts of snowfall to Mammoth as forecasted. Mammoth Mt at the Main Lodge site showed a good .40 water equivalent at the Main Lodge. Although winds were strong yesterday and there was a lot of blowing and drifting, Mammoth Mt reported 3 to 4 inches storm total.  However, snow to water ratios suggest a conservative 4 to 6 inches overall, with at least 6 inches of Platinum Powder over the crest, as temperature’s within the storm were between 10 and 15 degrees at 11,000 feet. A rough estimate of snow to water ratios within this temperature range over the crest suggest snow to water ratios of at least 15:1.

Looking forward:

Models continue to struggle with the week 2 period. However they seem to have the same short wave inside-slider system proged to come through between next Wednesday and Thursday, between Christmas and New Years. This has the potential to be a similar scenario to the system we had yesterday with a light snow producing storm that ended up as a NW slider. Details in this system will no doubt be forthcoming by Christmas Day.

Beyond this system we get into the Week 2 period in which the most popular global models handle the pattern different. The idea of a meaningful storm is still possible during the week two period. However its certainty is obscured by the fact that the models are still not in agreement on a storm in a specific time frame.  As an example, last nights ECMWF deterministic 00z Thursday run showed a meaningful storm between New Years Eve through the following Wednesday while the American models do not develop a similar pattern until the following weekend of the 6th. Until we get more model consensus, within a specific time frame, we will have to stay with the same dry forecast. That is, until which time, that consensus happens.  It may happen in the next few days or it may not until much later.  The forcing mechanism’s behind the “Big Trof” in the east and the ridge out west has several teleconnecting variables. Some are Air-Sea related and some related to ENSO and others related to the QBO in its negative phase.

In the meantime, we can expect moderating temps here in Mammoth with daytime highs reaching the upper 20s today, climbing to the low 50s this weekend into Christmas Day. Nighttime lows currently in the single digits will climb into the upper teens. We can expect the upper level winds to gradually diminish over time as well. Temperature inversions will redevelop this weekend with the freezing level this morning at 3200 rising above 11,000 this weekend. Temperatures will remain inverted with cold in the valleys of Mono County through Christmas Day. Air Qual may be an issue over the holiday.

Next small system is expected about Mid-Week..

 

Dr Howard and the Dweebs…………………………..:-)

 

As pattern transition nears….Brutal Cold Still a Possibility before year end……Northwest slider to bring light snowfall Wednesday…..Dweebs watching “week two period” for Model Consensus….Still the possibility of a storm….A cold one….Or a wet one!

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……………..:-)

Temperature Inversion Peaks today into Friday AM along with warmest temps in this pattern Today and Friday…..Upper west coast ridge really flattens Friday night into Saturday for much cooler temps aloft……Major Change in location of Long Wave Trof may bring Brutal Cold to the Eastern Sierra before Christmas….

December 15th:

The general trend of the models are to weaken the west coast ridge in the coming days and bring cooling and wind to the upper elevations. Although the upper ridge does strengthen early next week. It will not be to the point where it has been as there is another shot of cooling coming Mid Week. The big changes from the past few days in the outlook deal with the Christmas weekend where an inside slider type system affects the far west along with a closed low off the coast of Baja. This continues the dry pattern for the Central Sierra now until after Christmas. Of other concern, is  another opportunity later next week for another very significant Santa Ana wind event for Southern CA.

In general, the models are not handling the transitional pattern change that is upcoming very well at all.  The global models are continuing to flip-flop on the important details. They are not in sync with each other as well. Thus at the moment, long-range confidence in any specific solution is very low. The most that can be said is that it will be cooler in the coming days, breezy or windy at the upper elevations with a few period’s of light snow showers.

 

The Dweeber……………………….:-)

 

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

The Dweebs are beginning to see a trend in the Models that may bring a very Cold, “Even for December” air mass to the Eastern Sierra. This is proposed now for the weekend prior to Christmas Day..  In an earlier Discussion’s back in November, I wrote about the possibility of a major cold wave this  December for the Eastern Sierra with “CPK”  “Continental Polar” backing up from Canada, southwestward over the Eastern Sierra.  I reasoned this because of the proposed developing Meridianial  flow in the upper jet, usually associated with La Nina in combination with the negative phase of the QBO.  Over the past few days, the ECMWF has been becoming more consistent with the retrogression of the Eastern pacific ridge,  (due to the MJO going from Phase 7 to Phase 8).  The EC has the formation of a highly amplified upper ridge, currently along the California Coast backing up to about 140 West. The location of this highly amplified ridge is critical to the short wave track and cold 500mb-1000mb thickness pool over the far west.  If the upper ridge axis is a little too east, the track become a bit more east and we miss the exceptional cold over the far west. The GFS model has this ridge axis about 137 west….Too far east at the moment.  So confidence is based upon the Ecmwf being the best model at distance.  The Dweebs will follow the trend, as the trend is our friend…:-)

The bench mark for cold here in the Eastern Sierra over the past 40 years occurred 19 years ago, over the 19th, 20th and 21st.  The Morning of the 20th was the coldest aloft and Dec, 21 and 22nd over the valleys. However, surface antecedent conditions were different then, than they are today.  In the December 20th, Scenario, there was snow cover to lower elevations over Eastern CA, east and north over much of Nevada.  So there was a feed back system or at the least, less potential modification to the on coming frigid air mass.

According to the GFS Reanalysis 500MB charts as well as 500-1000mb thickness, from December 12z 19th, 1990 event, GFS 500MB heights were 513dm along the OR/WA border. The 00z 20 GFS had 515dm at the corners of CA, NV, OR.   By 12Z on the 20th, 500MB Heights were 518mb, so you can seen, there was very little modification that occurred on upper low pressure systems track SE.  According to the 500mb-1000mb thicknesses the morning of the 20th, the thicknesses were indicated to be about 516 just on the west side of the crest near Mammoth Mt.  I recall the thicknesses of 511 near Mammoth AP on the Nested Grid model (NGM). The high temperature that day was 6 degrees and the low at my home, then on Ridgecrest Dr was -12F. I did go down to the Forest Service recording site, east of the corner of Old Mammoth Rd and Main Street later that night of the 20th. I Peered into the instrument shelter, and it showed   -23F below 0.   This is the coldest temp I have experienced in nearly 40 years, living up here. It gave me a new meaning of cold.  The days that followed, were highlighted by frozen pipes all over town as well as all over the Eastern Sierra. When the weather warmed up, flooding from broken pipes were common.  PS. Even Bishop CA got down to -8 a few mornings after and Bridgeport was colder than -30F as I recall. PPS; it was the coldest Night of Lights, then at the Main Lodge, before it was moved to Canyon Lodge. (Fireworks show)

Although it is very early in the forecast game, the forecast progs are not as cold with this system as the Dec, 1990 pattern “at this time”…  Nevertheless, any extended period of below freezing temps, day and night for 5 to 7 days can create a big problem in town.

Another possibility; It is possible that this cold upper low digs west off shore. Unless that happens off the Northern CA coast, A major storm would be likely well to the south of us.