Archive for November, 2013

Upper Ridge Building in Now for a Couple of Days…Warmer Days in the Upper Elevations expected through Tuesday with cloudiness increasing Wednesday for a slight chance (20%) of some very Light Snowfall Thanksgiving…….

 

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Monday AM Update:

As indicated a few weeks ago, the Dweebs indicated that a major pattern change would begin to occur about the end of November.  However, it was also indicated that it was not known if the pattern would be a wet one.  Here is what we know.

1. Here is the main teleconnection we are dealing with.  The -WPO, which is similar to the -EPO, but displaced much farther west. This link shows the teleconnection pattern for the positive phase…… just flip the anomaly then see the negative phase pattern: http://www.esrl.noaa.gov/psd/forecasts/reforecast2/teleconn/images/wpo.composite.gif

This is what is known:

1. Both GFS and the ECMWF are going to both amplify and consolidate the eastern pacific ridge early next week a little west of 140W.  There are several short waves that will be able to tap cold arctic air from very high latitude’s, and pull it down near the coast line of BC. While an upper level Arctic low develops over the Pacific Northwest bringing some of the coldest air in quite awhile to that region, there is the possibility that subsequent short waves will continue to push the Arctic ribbon further south into the Great Basin as the week progresses. This would put Western Nevada and Eastern CA into the deep freeze for a while with below 0 temps possible at night.  There is also the possibility that in time the upper flow may buckle out over the ocean where that would be beneficial in bringing a wet pattern into the Sierra later next week. So now, the ball in motion for a major pattern change next week…there are lots of possibilities.

The most likely one’s to begin with in the longer range are for:

1. Potential for high winds

2. Potential for Major Cold beginning 1st week of December….

3. The potential for a major “Cold Snowstorm” as the upper flow buckles off shore and moves south later next week….  (PS the deterministic 12z Monday ECMWF is all over that idea)

So hang in there………its going to get nasty!

 

More later……………….

 

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

 

The pattern in general continues to involve to the redevelopment of the -WPO but displaced “More to the West”.  The WPO in the negative phase is highlighted by a high latitude block in the Gulf of AK with lower pressure aloft underneath. The trend of the -WPO will again be displaced much further west with time which is not good for the central west coast.  With it ‘s current extension into Western Canada, short waves split with the stronger branch into Southern CA.

In the meantime, we have a transitory short wave upper ridge which is building in for some fair weather. It will allow inversions to set up with some 15 degree of daytime warming expected in the upper levels by Monday/Tuesday. Very Light winds are expected early this new week.

The next short wave will again be forced under the extension of the block well west of AK that extends to Western Canada. What appears to happen is that the short wave trof comes through the upstream ridge as it heads SE toward the South Central Coast…However at the same time the upstream ridge retrogrades and amps northward essentially cutting off the life of the system and leaving it offshore to die. Thus the short wave is being effected by a chronically chaotic pacific transitory pattern. It is possibly an eastern pacific wavelength problem that needs the time scale of climate as the only cure.  Where is the MJO when we need it???

At this time, additional snowfall in general is really not in the cards for the Central Sierra over the Thanksgiving holiday. There is only a slight chance at best.

Longer Range:

The Dweebs see a very cold Arctic Air mass that will slide SSE out of the BC the first week of December. There are some Ensemble Members that take it into the Great Basin and many that take it to the Rockies. This will have to be watched as although it does not mean a lot of snow, it means the potential of major wind if the upper jet is right and very cold temps for our area. Should this system  track further west into the Great basin.  It would be (a pipe buster) sometime during the 1st week of December.  At this time, the Dweebs are not confident in knowing the track of the short wave associated with this cold so stay tuned…….

 

Dr Howard and the Dweebs………………….:-)

 

 

Storm total 12 to 14 inches……Very Light upslope today is not expected to add much the next 36 hours as upper cut off gets the Boot ENE….More Snow Possible for Thanksgiving….

Saturday AM Update:

This will be brief…

The Upper Cut-Off has kicked inland along the Baja/CA border and is moving quickly into AZ.  Cloudiness will be quicker to more out today and tonight.   Fair weather is expected Sunday through Tuesday with a slow warm up. Next system will not be anything to write home about. It will weaken rapidly as it approaches the Southern CA coast line. According to the EC most of the precip will be confined to the coastal sections of LA…..Not the MTNs. However before it approaches the south land, some light snowfall may occur over the Southern Sierra Thanksgiving.  Mammoth MT looks to receive a glancing blow from this system with a few inches possible of snow possible.

More Later….and sooner if this changes….

 

The Dweeber……………………:-)

 

The pattern is winding down and it looks like Mammoth Mtn will end up with 12 to 14 inches over all. We got a few inches in town yesterday as the upper flow veered from the SSW to SSE to East to NE.  Light up slope brought upwards to two inches the past 12 hours…..    Currently the upper low is located off the coast of San Diego. The system is quite dynamic and is entraining a lot of moisture off the coast of Baja and pulling it over the deserts of SE CA and up through Nevada and AZ then west ward over the Southern Sierra. Mammoth is pretty much on the northern edge of the moisture field. However, some may surge a bit north again when the system lifts out Saturday. So either some light snow, or flurries will continue the next 24 to 36 hours. No significant accumulations is expected through the period.

Gradient’s:

Looking at this mornings 12z NAM at the Surface, there is a double-barreled strong surface high, one that’s 1048MB, located just east of Northern Canadian Rockies with pure Arctic Air just beyond the ribbon with Thicknesses down to 498DM and another center of 1046mb over SW Montana. The surface Gradient is toward the Cut Off…off San Diego and a bit east to its Surface Low.  The tightest gradient is between Northern and Western Nevada and the Southern Owens Valley.  So expect North Winds to really increase today over Eastern CA including the upper elevations of the Sierra, Western Nevada and the Owens Valley. The good news is that Mammoth Lakes is very protected from north winds because of the topography. Rarely are they any stronger than 20 to 35 MPH.

Expect a slow decrease in the winds later tonight and with the surface highs pushing ESE in general, Saturday will be breezy over the upper elevations but not nearly as windy as they will get today. Upper Elevations are considered mainly above 9,000 and the top 11,053.

Outlook is supported by all models in spreading some dry eastern pacific air over the region late Sunday night into Tuesday. This will be followed by a small storm, late Wednesday Night into Thanksgiving. That storm looks to bring the best chances of precip to the coastal sections of Central and Southern CA….inland to the most Southern Sierra South. The main concerns with this system at the moment is that it will remain too far off shore for much of the CA. The New 12Z GFS deterministic run is more progressive than last nights 12Z ECMWF.   If the EC jumps on the wagon over the next few day taking the system a bit closer to the coast…..confidence will increase.  However…..the big message here is that this is not a big storm by the looks of things…………..

Best preliminary estimates…..and I have to admit that this is probably on the high side,  2 to 4 inches in town and 4 to 8 over the upper elevations by Thanksgiving…..This precip forecast is early in the game and will change over the next few days either way but the bias is to lessen it……… In that the Dweebs are seeing a more progressive solution in the new 12Z GFS Run being a bit more progressive solution at this time, that is why the amounts are stated as it is in the guidance.

But as Dweebs know….Guidance is not really a forecast……it is just guidance……the Art is in the hands of the Chief……

 

Dr Howard and the Dweebs……………………….:-)

 

 

Up to a foot of fresh has fallen on Old Woolly…….More on the way………

Thursday AM Update:

Storm total as of this morning as reported by Mammoth Mountain was 7 to 11 inches….pretty much in line with what the Dweebs forecasted….which was 5 to 10 inches then increased to 8 to 12 inches yesterday AM.

We still may squeeze out another 2 to 4 inches from the next system as the flow at 700mh switches and becomes NE.  This is the last in the series of short wave energy with this particular Trof.  This last bit of energy has already formed a closed circulation at 700MB over Central CA. The upper low will become cut off top to bottom today as it spins up into a cut off low.  So an upslope pattern will develop today in the cold air. The Dweebs note that the new 12z NAM shows 700RH blowing up this afternoon over the eastern slopes between mid afternoon and this evening. No doubt there will be at least a few more inches of snowfall here and there. The Dweebs are expecting another 2 to 4 inches by late tonight. The bulk for the precip from this system will be to the south of us with areas of the Owens Valley and Southern Sierra getting quite a bit of precip south of Olancha.

Looking Down the Road:

A fair weather ridge of high pressure aloft will build in Sunday into Monday keeping the weather fair Sunday through Tuesday. The next upstream system is associated with a weather pattern with blocking in the Gulf of AK and a subtropical ridge upstream east of the Hawaiian islands. The upper height anomalies are out of phase for a deep full latitude long wave. Thus with the next system for the middle of next week (The turkey system) No pun in tended,  is currently being handled with uncertainty in mind.   Last nights deterministic EC closed off the system, far enough off shore that the main area of precipitation remained off shore. This is not a progressive solution.  However, if you look at the ECMWF ensemble members, they are more progressive and the GFS has been and is still progressive. So The Dweebs for the time being are into the new 12z GFS solution giving us the possibility of more snowfall Later Wednesday into Turkey Day. This is a decent storm with the possibility of a foot or better.  Again, we are 6 days away from next Wednesday and things can change. This is an outlook not a forecast…… Will check and see what the new 12Z Thursday ECMWF has in it this afternoon when it comes out.

More later……………………..;-)

 

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