Archive for November, 2022

Series of storms headed into California over the next two weeks…..Squirrely Models doing their best to drive forecasters Nutty!

12/1/2022

As of 4:30PM Mammoth Mt at the Main Lodge has picked up 12 inches of new snow since 6:00AM

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Normally, when you get within 72 hours ahead of an active weather pattern, the global models have a good handel on the details of the weather systems that will affect the Sierra.  Not this time!  Timing issues and Quanitative Precipitation forecasts, (Amounts of snowfall) in our case, keep changing every 6 hours! Nothing major, but a pain in the Derriere`. The differences are some 1 to 2 feet.   The models have been flipping back and forth the past two days. What’s the latest?  Were back to 3 to 5 feet on the Mammoth Mountain by Monday. The latest details suggest: Storm 1 beginning Thursday Mid Morning in Southern Mono County, then a break Friday into Early Saturday AM. Storm #2 Begins Later in the morning Saturday and ends late Monday AM.

Snowfall totals; Based on the new at this time 18Z GFS run.

Storm number one, 1 to 2 feet.

Storm number two, 18 to 36 inches. So 2 to 3 feet from 8000 feet to the Mammoth Mt Suimmit.

More details;

1st system has weak Atmospheric River coupled with Polar Jet with Mammoth under Right Rear Entry region with good upper level divergence. The polar jetlet moves through pretty quickly Thursday night for a dry day Friday.

2nd system is just as interesting or even more so as it slows down, becomes part of a quasi mid level omega blocking pattern, long enough to allow the AR to lift back north into Central CA Saturday afternoon and evening.

The slower speed of the closed low offers a more protracted precip event Saturday PM though Sunday, as the upper jet remains coupled with the subtropical jet through Monday AM. Quite the feat! Finally the Polar jet axis is south of Mammoth, during the afternoon Monday.

Just a word of interest:

Winds at 10,000 feet will be “Orthrogonal” to the Sierra Thursday afternoon into the night.  Then Orthrogonal again Saturday afternoon through Sunday night!!

It is possible that the models are under playing the Snowfall Totals here as the Bullseye for this pattern with the 2nd storm, looks to be Southern Mono County south to the Central Southern SIerra.  With the upper Jets coupled for 4 days, no telling what we may get! 😉

 

Dr Howard and the Dweebs..

 

 

Chilly Upper Low is now dropping south into the Great Basin with high cloudiness….Increasing wind and falling temperatures….Model Solutions are becoming more inline as two cold short waves out of the Eastern Gulf of Alaska, Dive south into the far Eastern Pacific…..AR’s still lurking for Southern and Central CA.

Quick 11/29/2022 900pm update

Shows 00Z Wednesday GFS run wetter scenario again like earlier this morning, for the 2nd storm.  So 4 to 5 feet over the crest again possible by Monday.

700MB winds are Orthrogonal to the sierra both Thursday afternoon and Saturday afternoon.

GFS = Global Forecast System (American Global Model)

Z Times for PDT

00Z = 4:00PM

006Z = 10:00PM

12Z = 4:00AM

18Z =  10:00PM

ECMWF = Euro Model

ENSO = El Nino Southern Oscillation

AR= (Atmospheric River)and other usefull lnks to better understand this science

https://psl.noaa.gov/arportal/

“The difference between mediocrity and genius is persistance and time” 

 

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11/29/22

Updated GFS has 2nd system not as wet as first system. Will see  how the new 18Z ECMWF later today looks.   Thinking now is to trim back a bit Snowfall estimates for Southern Mono County, but not by a lot.  Between 3 to 4 feet over the crest seems a bit more reasonable. The Dweebs will see what the Euro run says, later today.  🙂

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Today system that pushed into the Great Basin has brought a return of below normal temperatures. The winds in town have abated somewhat as the front pushed through this afternoon. Surface pressures began to rise at 1:30PM. Winds earlier were recorded up to 45MPH. Tomorrow Tuesday will be cold with sunny skies. (Low 30s)

The next pattern change involves a couple of digging short wave trofs from the Eastern Gulf of AK. What is interesting as that there is a couple of waves in a rather weak southern branch of the westerlies, north of Hawaii, that the models are coupling with the polar jet.

Scripps from UCSD shows a couple of IVT surges; (Integrated Water Vapor Transport (IVT)) that are at the least weak with one of the models showing more of a moderate plume. Today’s 18Z GFS run is very encouraging, in bringing in a good precipitable water surge, later Thursday into Friday…..The Euro is similar.

What is especially interesting between the two models, is that they are consistent in the way they handle these two short waves. The 1st one passes through early Friday, the subsequent short-wave dives south further west, and thus has more over water trajectory as well as being able to lift that AR north again, for round two. So this is a rather complex system, but quite exciting in regards to the possibilities! Another issue worth mentioning is that the freezing level in this pattern is much lower than the one that brought 6 feet of snow over the crest with that last AR. This means that it would be all snow in town and possibly on highway 395 as well. preliminary guesstimates currently are some 3 to 5 feet of snow over the upper elevations, Thursday through Monday.  Will update the QPF this Wednesday PM.

 

Dr Howard and the Dweebs…………………….:-)

Typical La Nina Pattern in Play with dumps of cold air into the Great Basin and Northern and Central Rockies….Too much over land trajectory for meaningful snowfall until later next week…Then Weak AR to visit Thursday/Ngt and Saturday/Ngt

11/27/2020

Monday AM update

It was interesting to watch a fairly significant MJO build into Phase 7 with projections into Phase 8.  This is an area in the winter noted for Atmospheric Rivers. Up until just a few days ago, non were being forecasted by the global models.   Yesterday and the day before, a moderate one showed up on the coast with its extension weakly into the Central and Southern Sierra. This mornings models runs showed a slight backing off on duration Late Thursday and Friday as the moist band pushes through rather quickly. The Integrated Water Vapor Transport from Scripts shows this as a weak AR, inland at 37.5N/120W (300) KG/ms. The duration is about 12 hours.  The fetch on this AR is not all that long.  It begins Thursday night and lasts into Friday. Preliminary snowfall amounts suggest 3 to 5 feet by next Monday. This pattern will have to be watched over the next few days to see how it all holds together.  Again this 3 to 5 feet is very preliminary and contingent upon the strength and duration of the IVT.

 

More tomorrow…….

 

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It was a beautiful Thanksgiving Day and Friday with high temps in Mammoth the mid 50s for the Friday. Plenty of high clouds swept through Southern Mono this Saturday AM associated with weak WX front. The first in a series of short waves will began their march into the west Monday into Tuesday. The first system will be mainly wind, cooling and some snow showers with no significant accumulations expected for Monday or Monday night as the upper jet sweeps NW-SE through Central Nevada.  Subsequent systems will dig a bit further west for the potential of more significant snowfall. This looks to begin next Thursday into the weekend.

Both the European and GFS global Ensemble models have enough over water trajectory to bring as much as 12 to 18 inches by Saturday Morning according to this mornings 12z run of the ECMWF ensembles…..Then additional amounts over time. Looking at the GFS ensemble’s for the same time frame. Some 6 to 12 inches is indicated at this time through Saturday AM on the Mountain. Both models show amounts 2 feet or more by the following Tuesday the 6th on the Mountain.  Remember, this is not a forecast, it is just guidance at this time. The Dweebs will keep you in the loop this upcoming week!  🙂

La Nina;

La Nina is at it peak now for the season and is expected to begin weakening after the first of the year toward ENSO neutral. This is expected by February/March with a new El Nino developing as early as this Summer. Year 3 La Nina’s are very unusual leading to the odds being very good that ENSO Neutral to El Nino conditions will develop over the Equatorial Central and Eastern Pacific during 2023.

 

Dr Howard and the Dweebs………………….:-)