Biggest Storm in Two Years bears down on Southern Ca….Sierra Braces for Major Dump……

Thursday AM Update:

Not much to add this morning….  I picked up 8.5 inches at the 8200 foot level and I understand that Mammoth Mountain picked up about a foot at the main lodge with up to 15 inches over the upper elevations.  I personally estimate that with the water content and the colder temps, more like 17 inches is up there.

Storm #2 looks better for us then it did yesterday as the upper cyclonically curved jet and UVM between 17Z to 22Z will really pound the Mammoth Sierra. Additionally, looking at the 700mb heights and RH from the new 12Z Thursday WRF, there is now a fairly sustained period of quasi SW flow which will add orographic’s to the mix. The WRF has the upper flow over the Mammoth Sierra more southerly late tonight then becomes more Southwesterly about 15Z Friday.  The 700 flow continues between Southerly and southwesterly on and off through the afternoon. So Mammoth is on the boarder of the 700MB flow that is between these two directions. This is much better then the last few days guidance with southerly flow. So the models may not have a complete handle on the QPF because of the potential now for orographic’s.  IE We may get more snowfall from the Friday/Saturday storm than is predicted.

So we may get another 25 to 35 inches at 10:1 over the Mammoth Crest by Saturday night.

The longer range still shows the upper ridge building over the west coast with time……Next week will be unsettled with periods of snow showers but nothing strong at this time…..

 

Dr Howard and the Dweebs……………….

 

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WHY SO MUCH QPF IN THE MODELS FOR THIS AREA?

I have been researching the reasons why the HPC QPF has been going so hog wild on the QPF for this particular area of the Sierra.  I can understand why for LA and for parts of the Southern Sierra. However, why so far north with southerly flow and with little orographic’s in play for storm #2.

When you think about it,  the reasons are not all that complicated.  The answer I believe lies in the Upper Jet dynamics associated with Storm #1 and especially the 2nd storm.

In storm #1 the upper jet “was” expected to be pretty zonal across Southern California. Now it is coming in from the SW across Pt Conception. The Left Front Exit region is very close to Mammoth now with strong divergence aloft and a VT max just to the south of Mammoth. This in itself will give the QPF a boost later tonight, especially after midnight.

Storm #2 the upper jet is not zonal either. It is cyclonically curved, coming into Pt Conception early Friday AM and rotating up through the Owens Valley during the day. This creates strong UVM over the entire Southern Sierra chain up to Mammoth.. Thereafter, we become under the Cold Pool Saturday and Saturday Night with a lot of unstable air. Expect additional accumulations.

 

The upshot is about 4+ inches of water over the Pass…..

 

So there it is……………………!!

Enjoy..

PS…. Trying to get the Mammoth WX data logger online later tonight…

The Dweeber…………………….:-)

 

 

 

I have not seen this much open cellular CU between 30N and 40N since the winter of 2011! It’s nice to see it happen again!  All systems are go for one heck of a storm for Southern California Ca.  The recent burn areas of my hometown in Glendora should take extra precautions now by sandbagging areas around homes below canyons.

The latest QPF is up to 8.5 inches from the latest HPC output in some of the coastal ranges of Pt Conception and the foothills of both valleys. There may be more rain in “some areas” that has fallen in two years down there.

So again the big story will be the enhanced Asian Jet that is making its way through the far eastern pacific. Both the EC and GFS is painting about 3 to 4 inches of water up on the Mammoth Pass. And if it were not for the best forcing to the south of us, this would be one of the EPIC and memorable 4 to 6 foot dump. Well instead have to settle for 3 to 4 feet over the crest and a couple of feet in town by weeks end.  There is the chance that snow showers may continue for sometime after the storm is through Saturday, so that several more inches could accumulate over the upper elevations throughout the weekend and even a few into the following week.

There are two separate storms. A smaller storm Wednesday night in which the town will get 5 to 8 inches and the biggie Friday AM through Saturday 12 to 15 inches will fall.   Approximately double that for the Crest…..

OUTLOOK:

I see a small system about the middle of next week, mainly effecting Tahoe, then we ridge up for the following weekend of the 8th…..

After that well see…….

 

 

Dr Howard and the Dweebs…………………………:-)

Fair Weather, w/slightly warmer than normal temps through Tuesday with periods of high clouds and light winds….Break-through of the Westerlies looking more likely for later next week…..

Sunday Morning:

MJO has made the jump to Phase space 7…thus unleashing the power of the Extended Asian Jet toward the west coast! All models working nicely together to bring the upper jet on shore over South Central California Wednesday night. CRFC just painted .70 to .75 for storm #1 with the snow level beginning about 7500 to 8000 Wednesday; then during the major part of the event Wednesday night to Sunrise Thursday the snow level will be between 6000 and 7000 feet lowering to 5000 by the time most of the precip is over about Sunrise Thursday. Expect snow showers Thursday afternoon and evening, with little if any accumulation.

Storm #2 is still favoring the Southern Sierra and Southern California with what appears to be the best storm of the Winter for Southern CA! We here on the east side of the sierra will still get some good snowfall amounts. However in this case, snowfall amounts 1 to 3 miles east from the sierra crest will fall off faster than the first storm because the upper jet is so far south coming in over LA/San Diego. The Upper Flow at 700MB is due South Friday PM and so it is not orographically favorable. Nevertheless, the crest will get between a foot and two feet as there is more moisture in this system.

Again….What is interesting is that storm #1 has less moisture, however, it is orographically more favorable as the winds at 500mb and 700mb are SW or natural to the sierra. It is possible that we here in town may do about the same from the wetter storm Saturday as compared to the Wednesday night storm.

Where will the big amounts be?????   In the Southern Sierra, and Mountains around Southern Ca. This may be the first precipitation for parts of the desert South West like Phoenix, AZ this winter.

 

 

 

 

Friday AM:

Lots of hype developing with the coming pattern change next week. I heard someone quoting me by saying 9 feet of snow!  First of all, if I really believed that a storm capable of delivering 9 feet, was approaching Mammoth a week away, during a drought year, I would not even think of saying that publicly and most likely would not believe it myself until it was within 72 hours away.

I am going to preface what is to follow by saying that at this time, the MJO has not moved out of Phase 6 yet.  If it does not progress through phases 7 and 8, we may not get what we think we will get weather wise later next week.  Again, watch the phase space map to see if the MJO is progressive!!!!!

What I do see here are 3 short waves, the 2nd half of next week into the first few days of the following week. The first wave will weaken as it moves through the mean ridge position ridge. That upper ridge will dampen and shift eastward Wednesday/night. This storm “at the moment” looks like it could give us . 5 to possibly an inch of QPF or 6 to 10 inches of snow by Thursday AM over the upper elevations. Snow levels will likely start high at about 8000 feet before lowering during the night Wednesday. It is the following storm that is of interest Friday into Saturday. It has a double-barreled surface low that will entrain a lot of subtropical moisture with it. Additionally, it will be intensifying as it comes in, not weakening. The biggest problem with this storm in forecasting estimates at this time, is that the upper jet will pretty far south of that ideal position that’s across Paso Robles, Ca. The wave as it comes in will have a shorter period of 700MB winds natural to the sierra and thus a shorter period of orographic’s. In fact the winds will be more SSW which tends to favor the west side of the Sierra more, with less slop over to the eastern slopes.

At 300mb, the idea is for the upper jet to trend further south with time and so the main energy may favor the Southern Sierra more and Southern California.  Mono County will likely do better than the Tahoe area for the biggest storm totals with the 2nd storm because of the position of the upper jet and mid level 700mb flow.

The 3rd or last in the series, will roll in about Monday of the following week. It is not impressive at all with light to moderate amounts.  There after, we will be well into the first week of March. At this time, it appears that the upper cut off high will retrograde westward across Siberia. Thus west coast 500mb heights will rise, during most of that following week. Teleconnections from the ECMWF focused upon that positive upper height anomaly day 15 suggests a storm track that will shift north again. By Wednesday the 6th, Northern California will get the following storm after the Monday system and the pacific NW then BC, can expect the following train of short waves.

For those that are wishful of a Miracle March, it is this Dweeb’s opinion that it is highly unlikely. However, with that said,  the 2nd half of March looks potentially wet again for the central west coast according to the inter-seasonal climate models.

As a comment, these are not cold storms because of their trajectory. However, they are not warm storms either like the ones with snow levels at and above 9K.

I expect the snow levels to vary between 8K and 5.5K over all.

By Monday, the Dweebs will fine tune snow levels and QPF……

 

Dr Howard and the Dweebs……………………..:-)

Breezy in Town and Windy over the upper elevations Wednesday but Dry….Slow warm up through Monday……Models Still Beating Westerlies Breakthrough Drum, Timing is toward the following weekend…..

Thursday AM:

Not much to add from yesterdays discussion. The global models all have pretty much the same scenario with a break through of the westerlies next Wednesday night supported by the eastward progressing MJO into Phase Space 8. The EC this morning has two important waves for consideration. One Wednesday night the 26th and the other Saturday night March 1st.  This is from the 00z Thursday ECMWF deterministic run.  This is the 1st time this winter that the MJO is likely to progress through Phase space 6 to 8. SEE: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml

I think that those with a strong interest should read up on the MJO and how dynamically it supports the far extension of the EAJ to the west coast.  I will post links when I have time on that matter.

It is clear to me that there were several opportunities for this extension to happen in this current winter. IE (The break through extending to the South Central West Coast, which failed because of the lack of support of the MJO. This time appears to be different, and thus there is a higher level of confidence to me from this distance in time.   Follow the MJO here and look for any hesitation in its progress for hints of any future back peddling of the guidance.

See and watch: http://cawcr.gov.au/staff/mwheeler/maproom/RMM/phase.Last40days.html

 

The MJO:  http://www-das.uwyo.edu/~geerts/cwx/notes/chap12/mjo.html

 

The Dweeber…………………….:-)

 

Trying to make the case for a break through of the westerlies into California…. 

Although the forecast has been dry through the early part of next week. The longer range models of the ECMWF and GFS has been showing an extension of the East Asian Jet well into the Eastern Pacific. When this happens, one has to look at the Wheeler and Hendon Phase space to see what is happening with the MJO as well as discussion’s relating to that action. The fact that the models are making a transition based upon both the extension of the east Asian jet and heights building northward over the far eastern pacific and up over AK is not random. “There is a cause for effect” The latest discussion from the CPC clearly identifies the causes. The MJO is forecasted to strengthen and move eastward through phases 6, 7 then 8.  “Given a persistent and largely coherent pattern of tropical convection over the next one to two weeks, some extratropical teleconnections are anticipated to become apparent. The reemergence of upper-level divergence over the West Pacific coupled with upper-level convergence over the Indian Ocean favors a reversal of the recently observed retraction of the East Asian jet stream over the next one to two weeks. This would favor lower geopotential heights in parts of the North Pacific, with downstream ridging over northwestern North America.   Additionally…..There is a reasonable chance that tropical moisture becomes entrained in a low-level circulation near Hawaii, increasing odds of above-average rainfall in that region.

(As mentioned yesterday, watch for report of heavy rains over the Hawaiian Islands later this week. That can be a sign that precedes a wet event on the central west coast)

In the meantime, amplification out about 140west will build toward the Gulf of AK. At the same time, the upper ridge will become established again over the eastern pacific. This ridge will slowly progress into California, early next week.

Sensibly, we will note that it will be a cooler day today and breezy, as a short wave passes through Mammoth this morning.  Heights will continue to rise out over the eastern pacific and so a NW flow will insure a cooler than normal weather pattern the next few days.

As the upper ridge continues to both amp and progress eastward into California the next 6 days, slow moderating temps will follow. Expect 5 to 7 degrees of warming between today and next Monday. Nighttime temps will dip into the teens, then rise to the 20s by Sunday.

By next Monday, if the westerlies are going to break through later next week, the hype will be in the media and my discussion will be but a memory……

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