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.



Peak of warm up in process with Thursday into Friday AM with highest Freezing levels…..Upper West Coast Ridge will begin discontinuous retrogression next week with some interesting possibilities over the next few weeks…..

For the Eastern Sierra, this pattern is still dry for the remaining time of this week, however, there will still be reasons to watch the skies over the next few nights.  The Gemini meteors will be flying tonight through Friday night with the peak of the meteor shower Wednesday night into early Thursday morning.  I guess if there is any consolation about this dry spell, it will be a spectacular night time display with up to 120 meteors per hour possible. This will be the best display of the year as the Summertime Presides meteor shower was hampered by a bright moon. The weather under the mega ridge will be cloudless. Calm winds and temperatures while still cold in the upper elevations, will be seasonably mild for this time of the year. This will make for very good viewing conditions. Constellation Gemini rises during the evening hours in the NE and is high in the sky at 2:00AM Thursday. Meteors will begin flying Wednesday mid-evening from the NE and then in all direction once Gemini is high in the sky at 2:00AM in all directions.  A small crescent moon will begin rising at 3:35AM.


The upper ridge remains in control……The Forecast still includes a warm up through Thursday and possibly Friday. Highs in the upper 50s Thursday and Friday with lows in the 20s to low 30s in the village.  WInds in town will be calm at least through Friday afternoon.

Here is the latest thinking from the Dweebs today Tuesday;

I listened in on the weekly discussion from the CPC.  The discussion mainly deals with tropical forcing which in many cases can be the tail that wags the dog.  The MJO is currently active, moving from phase 6 into Phase 7 and increasing in strength.  Phases 6-7 is the western pacific phase. When the MJO is strong in this area, it is usually associated with a strong +PNA pattern in the far west which we are now experiencing. The CPC prefers the ECMWF version of the RIMM (Phase Space) showing phase 7 to be the dominant mode for the next 5 to 7 days. Thereafter, the MJO progresses to phase 8 which moves the upper divergent and convective envelope out of the western pacific to near the dateline. This is almost always associated with retrogression of the long wave pattern for the west coast in the winter. IE the backward or westward redevelopment of the west coast ridge.  However, with the MJO forecasted to fall apart quickly as it moves through phase 8 toward phase space 1, (Possibly due to the anomalous cold waters of La Nina), most likely, we will not experience what would often take place thereafter. IE, the strong undercutting of the westerlies into the west coast. (That would be a wet pattern) An MJO strong through phase 8 usually results is an extension of the East Asian jet stream to the California coast. The CPC today indicated that this tropical convection is forecasted to be suppressed near the Dateline and in effect,  weakens the MJO…..”thus no gas to put the peddled to the metal”. (the latter are my words)

More comments……..

Most likely, we will be teased the next few weeks with some undercutting possibilities. Is undercutting of the westerlies possible? sure, but not probable.  The fact that only a few of the ensemble members shows that undercutting is testament to that possibility.

So, what is the more likely pattern that may emerge? As you all know, I am just a hobbyist. I love the science and all outcomes. Because I know that every outcome works out exactly the way it was supposed to…..Not necessary they way anyone forecasts it to!  😉

Here are my thoughts this evening….

  1. We are going a bit deeper into La Nina the next four weeks…..
  2. La Nina usually is usually highlighted by a -PNA pattern (long wave trof in the west) Occasional Arctic Outbreaks spilling westward.  (So far that has not happened)
  3. As far as weather pattern change, there is going to be retrogression…..No doubt about it!  The question is, how far west will it take place and how amplified will it be.  If a highly amplified pattern with a track down the west coast develops,, I am not all that concerned about any closed low diving so far south it misses California all together. Sea Surface temperatures anomalies have increased along the west coast and especially Southern CA due to the absence of storms this season. So the subtropical High (Hadley Cell) should be stronger further north.
  4. What the ECMWF ensembles are hinting about now is a system with “Arctic Air” plunging SW off the BC coast, spinning up then picking up some moisture from a weak undercutting. The issue is, the moisture tap is pretty much over by the time the front gets south of Northern CA. However, a cold storm for California around the 23rd of December, or any storm with Arctic Air in December is going to be a memorable cold system for Mammoth.
  5. The GFS ensembles actually has a similar pattern with the same cold Arctic Trof digging out of British Colombia. However, instead of the system coupling with moisture west and under a blocking high, this storm is just out right cold with limited moisture as the long wave sets up over the far west, more in line with what one would expect from a La Nina year.
  6. Remember, this is well over a week away and so there is plenty of time to watch and learn!
  7. The screaming message here is that we are going to get a transition and it looks cold for at least part of it.


Dr Howard and the Dweebs…………………………:-)



Upper ridge to hold steady this week with some flattening of the ridge next weekend leading to some cooling aloft…. Slow discontinuous retrogression is hinted at by the models the next few weeks…..The Forecast is still dry for a week to two weeks……Anomalous warm waters in the Bering Sea hold hope that long wave ridge may gravitate to that area during weeks 3 and 4…..

The forecast and outlook are still pretty much straight forward this upcoming week with the dry weather trend holding with strong temperature inversions, due to the persistent west coast ridge. This ridge will actually strengthen Tuesday through Thursday with the freezing level topping out at about 14,000 feet by Thursday afternoon..  Thereafter, a passing short wave Friday night will flatten the ridge somewhat, bringing some breeze over the upper elevations and some cooling aloft. It may be enough to mix out the valleys by early Saturday AM…well see.  Temperatures this week in Mammoth will rise to the mid 50s with lows in the upper 20s to possibly low 30s in the upper elevations of town by Thursday morning. Some cooling is expected over the weekend. Lows at night have been running about 10 degrees cooler in town than at the Village. So 15 to 25 degrees as of late. These lows will come up a bit by Mid-Week.

There really is not anything in the models that look striking different from what has been said of late.  Those that follow the 21 day cycle of pattern change might be interested in knowing that this current pattern began on the 5th of December as indicated by reanalysis 500mb charts. 21 days would put the next pattern change or “transition” about Christmas.  This does not mean that we will not see any moisture until then, as within this pattern we could still get something that sneaks in here bringing something light. It just means that a meaningfull transition is not expected based upon this theory until about Christmas. Furthermore, with that said, it is not really known what we are going to transition to.


Let me chat about Sea Surface Temps.

What I like out over the pacific is the increasingly warm pool in the Bering Sea.  Whether it’s the Chicken or the Egg, these anomalous warm Sea Surface Temperatures often times attract large-scale high pressure systems in their vicinity during this time of the year.  This may cause  the current long wave pattern to retrograde with a good solid block developing in the WPO region either later this month or most likely in January. If/when this happens it could get quite wet in California. The warmest positive sea surface anomalies are currently in the Bering Sea and south of there. On the negative side, SSTAs along the California coast are getting pretty warm as well. This may tend to keep Southern CA drier, I do not know.   The CPC Climate models are showing 500MB Heights retrograding to this area during the Weeks 3 and 4 period. See Graphics below.

Based upon the 21 day cycle, were probably going to have to get through the next two weeks being dry, as today is only day 5 of that period. However, if the Climate Models are correct from the CPC, showing a block developing in the southern part of the Bering Sea -(WPO);  Beginning the week following Christmas and Week 4 “New years Eve through Jan 6th”.  We could get some badly needed precipitation. Week 3 looks cold temperature wise, with week four looking more moderate in temperature as there is more over water trajectory with the upper jet. . On another note, other graphics which I am not authorized to display from another model is trending wetter as well for the northern half of California in January. I hope they all verify!


Think Snow!!!!