Global forecast models have back peddeled on precipitation prospects for the month of January…..Occasional fast moving systems likely to bring only light amounts for Mono County

Tuesday Jan 5th;

Central and Eastern Sierra to remain dry another 2 weeks…..

Although there are a few more fast moving short waves that will pass through mainly Northern CA the next 7 days, none are expected to bring any signifacant precipitation to the Eastern Sierra. Last nights wind storm brought 3 to 4 inches of snow to Mammoth Mt and only an inch or so to the town, while areas east were for the most part dry.   The next upstream system will follow a storm track familuar to us this Winter, as a weakening weather front drags through Southern Mono County Friday AM. The final in the series of fronts will move through Monday with little more than clouds and breeze to contend with.

If you think that this winter and fall are drier than normal, you are 100% correct.  However, there have been several dry stretches here in the Eastern Sierra histrorically. Back in the Fall, I touted that there would be a dry bias to this years winter.  This years Cold ENSO, “a moderate La Nina” is proving to be exceptionally dry one in the record books.  We can only hope for a wet February and March to help us out…

Pattern;  looking at the ECMWF ENS 7 day 500MB Height Anomalies, there is blocking from Hudson Bay east to just south of Iceland. The westerlies are strong through this countrys deep south and south east, giving many areas like the Carolinas rain and snow. The main governing anomaly for the west coast is a ridge in the mean. This is why we are not getting signifacant storms this far south. What transpires by the 10th of January is a block setting up near Greenland. This eventually will Dam Up the cold air over East Central Canada which enhances the -NAO teleconnection. Unfourtunetly, the upstream effect is a strengthing +PNA and that’s what get us into trouble. Strong height rises are expected to take place during the 2nd half of next week that will block most if not all storms from the west coast, including Washington State.

The big question is, where will the Mega Ridge set up?  If it sets up along the west coast, “high temperature records” may be in jepordy in parts of CA..  If it sets up a bit more to the west, we may get some inslide sliders.   That’s a “chilly pattern” for Eastern CA. No matter what, it is a bone dry pattern for the Eastern Sierra next week…..  La Nina is still preventing MJO from remaining strong enough through the Central Pacific to modulate the westerlies in a positive way.

 

Highs in Mammoth are expected in the 40s with lows in the teens and Twenties.  The remainder of this week looks pretty uneventful with the exception of Friday which will be breezy with some snowshowers…

 

Dr Howard and the Dweebs………………:-)

 

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Although the Strat warming now in process has created strong high pressure in many areas of the Arctic, the over riding effects of a cold ENSO are proving to be more than enough to keep our weather drier than normal here in Southern Mono County.   Checking the key teleconnections from the GFS ENS and ECMWF ENS, although they both tout the -AO with a positive height anomaly over parts of the Arctic, the over riding factor is the +PNA, the pacific north american cir for the Eastern Pacific and far west is in its positive phase.  This keeps the upper jet for the most part, far enough north for just modest amounts of moisture from storms the next few weeks. Another factor is that the -NAO which highlights the Greenland High and Hudson Bay Low, will tend to strengthen the west coast high pressure system even further, during the second week of January into the 3rd.   (LA may experience 80s in Mid January).

All in all, the hopes of the Dweebs for some good snow producing storms have been dampened greatly by the effects of the on going dry La Nina.  The dry La Nina appears to be the over riding factor, giving all extended forecasters quite the head fake from what looked quite promissing, just a week to ten days ago. What I see now are fast moving storms that bring mainly wind, and light amounts of snowfall this week.

Currently, our sierra snowpack is running about as dry as its been historically at this time. The driest year was 2014-15. Our snow pack is running less than 30% of normal for this time of the year.

 

Forecast:

Expect two fast moving systems this week.  One today Monday and another Friday. Both will bring mainly light amounts of snowfall, (1-6 inches) with a bit more possibly, just today over the highest elevations. Any snowfall for next week will have to occur during the first half, as strong height rises next week is likley to shunt everything to our north by mid week, next week.  High temps in Mammoth will range in the upper 30s to low 40s. Lows at night in the teens and twenties.  Strong gusty winds are expected today Monday and again Friday.

 

Dr Howard and the Dweebs………………….:-)

Will SSW be the Trigger that Saves California from drought this year?

A “Major” Sudden Stratospheric warming event is underway over the Arctic at the moment. One that may change the course of one the driest beginnings of Winter to the Central and Southern Sierra in years…..  The SSW, (Sudden Strato Warming Event) is a process that can rapidly warm the stratosphere of over 100F at times, caused by planetary wave breaking (Rossby Waves) that propagate up into the Stratosphere. The sudden heating of the Stratophere creates high pressure over the polar region that can dislodge the polar vortex or even breaking it up into smaller vorticies sending them south “toward” the mid latitudes. All in all, the main effect is a southward adjustment to the Polar Jet, which is in the end, what we want to get winter going!   Thus far this winter, the polar jet has been over the Pacific Northwest, south to Northern CA.,   This is a reason why Mammoth has not received much in the way of precipitation. La Nina has effectivly blocked and/or weakend the MJO from periodically forcing the usual wet patterns that develop along the southern and central west coast, The SSW may be our savior that adds a northern latitude variable to the equation of getting the upper jet well south into CA.   Here is a link to more information on the SSW; https://www.severe-weather.eu/global-weather/stratosphere-major-winter-warming-watch-january-2021-fa/   

COMMENT:    By the looks of what is going on over the Arctic with its strong height rises in the global models and a massive PV headed south over East Asia, this is going to be a big deal for the Central West Coast this January, as the Extension of the East Asian Jet progresses to the west coast with some very signifacant “Atmospheric Rivers”.

The Screaming message here is that Winter is coming!!

 

Dr Howard and the Dweebs……………….:-)

A transitory Ridge to bring a Sunny Day Wednesday…Followed by increasingly cloudy sky’s Thursday….Active pattern to Resume Friday night into early next week….Snowfall amounts in the light to moderate amounts……..

12-25-2020

Models have come in drier with system tonight and Saturday..   1 to 6 inches over the Sierra at elevations above 6500 feet.

next system is colder for  Sunday night and Monday..  However, it too will be a light precip producer for the east side. Two to 6 inches……

it will be colder than normal the next week….

 

Outlook shows a series of fast moving storms affecting mammoth through mid January.  All in the light to moderate range for snowfall….

Dr Howard and the Dweebs….

 

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I. As we approach the end of the year….There appears to be 3 more weather systems that will bring snowfall to the high country;

  1. The Christmas Day Eve system
  2. The Sunday/Monday system
  3. The New Years Eve system

II. Currently off shore we have a mid latitude upper high that will make its way onshore today. So a beautiful day it will be with highs in the 40s.  Winds over the crest will diminish as well. To the south of this ridge is a weak subtropical low that is getting the boot from an upstream upper jet.

Currently our airmass is very dry, This weak subtropical low will serve to juice up our airmass for the next two systems arriving over the weekend.

The Friday Night system into Saturday will bring mainly light to moderate amounts of snowfall.   The Freezing level; in town will begin at about 8K, but will lower over night.  So early in the system it will be very wet snow.  The Structure of the the upper jet shows two branches. One the polar and other subtropical. The southern branch favors Mammoth with most of the dynamics remaining to our north, La Nina style.  CRFC QPF is showing .79 inches for Yosemite and about the same for Huntington Lake. That suggests 4 to 8 inches on the mountain with some 2 to 4 in town by Saturday afternoon.

There will be a break between short waves, with the next system splitting and diving south during the day Sunday. This 2nd system is problematic due to the nature of the split. It will favor the Southern Sierra. So more time is needed to provide better accuracy in the QPF. I will update for the Sunday night/Monday system on Christmas Day….

The last system for 2020 is expected “about” New Years Eve. Potentially it could be a major storm as a pattern change involving retrogression of the eastern pacific (long wave) ridge to the dateline is being suggested in the longer range guidance.

 

Tropical Forcing:

Although the MJO has not been a positive force because of La Nina’s destructive interference of the tropical mode, there is evidence that other modes of tropical variability are in play, These may be  affecting the extra tropics. There has been atmospheric wave breaking (Equatorial Rossby Wave Breaking) over the Indian ocean as touted by the CPC. These Tiny Dancers may be influencing the mid latitude circulation to some extent.