West Coast Ridge is favored to remain in control this week…..MJO moving back over Indian Ocean has good chance of initiating Pattern Change to -PNA for the far west……

12-28-17 8:40AM

 

Quick update this morning shows upper west coast ridge holding strong through New Years Day. However confidence is high for the retrogression of the ridge during the 2nd week of January. A strong interseasonal signal points toward an increase in convection off the coast of Africa and east into the Indian Ocean as the MJO is currently redeveloping in that area as per IR Sat maps. SEE: http://tropic.ssec.wisc.edu/real-time/imagemain.php?&basin=indian&prod=irbbm&sat=m5

Here is another update on the MJO and its forecasted intensity:  This is the RIMM (Phase space) from the European 00z Thursday forecast run from last night. It clearly shows an intensification of the signal and a progression from where it is currently emerging, just over the western Indian Ocean.  http://www.cpc.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmf.shtml

MJO’S convective envelope is just moving into the 40E area. Based upon the RIMM forecasts, intensification of tropical convection is expected in the coming days as the MJO either stalls out over the Indian Ocean or is progressive into the Maritime Continent.  This interseasonal signal often times affects the western Northern American PNA teleconnection which in its current phase is positive, to one that may become negative. -(PNA)  The hope is that the west coast ridge associated with the +(PNA) flips negative and a long wave trof sets up.

Note: There is usually a delay in the flip in the PNA signal until the MJO reaches the Maritime Continent or even the western pacific.

(Note the chart below)

The long-range guidance (Week 2) is responding, however, the timing and how the pattern change all unfolds is uncertain at this point. Timing is between the weekend of the 6th and Mid Month.  Although this mornings runs of the global models suggests that the pattern change will be slower, it could be quicker as well.  That is just an unknown.

 

Other climate signal’s and other thoughts:

For two weeks straight now the SOI has flipped on a daily basis to become negative, meaning that the trades have weakened significantly. This maybe due to an air-sea coupled Kelvin Wave or ??   Its affects are tearing the La Nina apart and will weaken it rapidly as we go into the spring. Once the ENSO signal crosses into LA Nada, if it happens early enough this Winter/Spring, we may begin to see “Atmospheric Rivers” return to the west coast again.

It is interesting or possibly coincidental that the MJO is moving through the Indian ocean and intensifying, while the SOI has become negative for an extended period of time……

Will this MJO or another following this Winter/Spring, be the catalyst for the Next El Nino?…..

 

The Dweeber………………….:-)

 

 

 

 

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10:45AM:

The new  12/27/17 12Z GFS is now singing the same tune of a pattern change the end of week 2.  (The Weekend of January 6th into Mid Month)

This is the best MJO signal I have seen this year.

 

Keep your fingers crossed….:-)

 

 

The Dweebs have been watchin and waiting for confirmation of a pattern change forecasted by the European Model for sometime in early to mid January…..The GFS American Models has not been in agreement. So the questions arises, which model is correct?  Although at this point there is no certainty, if the Dweebs use other climate forecasting tools such as the MJO in conjunction with the other global models, such as the Canadian and Japanese models, there appears to be more censuses that a strengthening signal will develop over the Indian Ocean over the RIMM phases 2 and 3:

SEE: * http://www.cpc.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml     One can derive a bit of bias because of global models such as the CMET, JMAN as well as the EMOM. All are pointing toward a strengthening signal over the Indian Ocean.   A strengthening signal in that area foretells a flip in the PNA teleconnection from the current positive mode to negative. A negatives sign PNA is associated with troughing instead of the current ridging we currently have over the far west.

*Dynamical model MJO index forecasts quite consistently show a re-amplification of the MJO signal as it enters the Indian Ocean, moving away from peak destructive interference with the La Nina signal. Should this occur, Indian Ocean MJO events teleconnect well with the North American mid-latitude circulation, and the MJO may therefore help effect a pattern change in the late Week-2 or Week-3/4 period.

 

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…………………………

 

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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……………..:-)