Archive for November, 2014

Comment:  Nice Fetch developing out of the ITZ this afternoon. This fetch is getting juicer by the hour……Quite the rainfall event coming for LA Tomorrow/Night.  Great news! But problems for the Foothill Burn Communities….for potential mud flows….

Monday PM Update:   Some clarification due to phone calls today….

The biggest problem by far this morning is with snow levels with this storm.   Not as much an issue after midnight Tuesday, but more so Tuesday afternoon and night.  The temperatures are pretty much isothermal through the layer, which could mean that there is the possibility of microphysical processes going on….which would create quite the problem for forecasting amounts, “In town”…not on the mountain!

Snow levels could vary between 8500 and 7000 for this storm.  The thinking this morning is that during the heaviest portion of the storm, the snow level will be around 8K.   So for a period of time, it will be pretty sloppy in town, Tuesday afternoon into the night.

In simple terms….if you have 2 inches of water possible and the snow level is at 8000 feet, you could get 2 to 4 inches of sloppy wet snow on the ground at 7500 to 8K. However, the snow level will fluctuate  between 7K and 8500…..So it will be problematic for forecasting for the Snow Pushers.

If by chance the iso layer goes down all the way down to 7K, will end up with 2 feet in town. That is not impossible, but unlikely. So 6 to 12 inches still seems reasonable. If we get more…great!  As far as the upper elevations go…..2 to 3 feet will set us up for the Christmas holidays……Remember, this is dense heavy base building snow. It is absolutely the best type of snow that we could want. It becomes more difficult to ski it out!  So…. Go ahead and book it for the holiday…you will not be disappointed…. And……The Dweebs see another series of storms about mid month. That will be the icing on the cake!

Longer Range:

A moist SW flow pattern will continue throughout much of this week until the eastern pacific ridge strengthens next week. There is some strengthening and better organization to the next short wave Friday night and Saturday that now track into the Sierra south to Southern CA. This now appears to be a better storm for the Sierra then earlier thought. So….more rain could fall for CA as well as snowfall for the high country. Thereafter we ridge up for a while next week with the next series of storms likely colder based upon the position of the MJO and its composites for December. This appears to begin as we approach mid month……

The Dweeber…….:-)

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Upper long wave cold core closed was spinning at 140 west and will end up ejecting a few short waves before coming through mid week. Today, showers and moderate rain fell over the LA basin and into the mountains of the Southern CA.   In Mammoth only a dusting has fallen so far with very light snowfall occurring this evening with mild temperatures at the 8200 foot level. 30s…

The latest guidance shows the passing of the first short wave today, and short wave ridging following on its heals for Monday and Monday night. Although there are height rises ahead of the main upper low,  the upper flow is very moist and so plenty of over running moisture will occur with little precipitation if any Monday/Night. The Freezing level Monday will be about 10,500 to 11,000 feet. Again little or no precipitation is expected Monday and Monday Night.

Height Falls begin Tuesday AM as the main upper low approaches the coast. By later Tuesday morning or afternoon, Precipitation rates will pick-up with about a 12 to 36 hour period of potentially moderate to heavy precipitation expected into Wednesday. The Snow Level looks like 7500 to 8500 feet Tuesday until it begins to come down later in the afternoon. It should be all snow Tuesday Night in town and well into Wednesday.  The snow that falls will still be wet. We still could get “between” 2 and 3 feet of heavy snow over the upper elevations. (9K and above) and 6 to 12 inches at 8000 ft. The cold core or should I say cool core is only about -18C at 500MB as it comes in. So this is going to be a wet storm for the high country with good sierra cement. This is actually just what we need for the upper mountain for base building. I will add again that there is a coupling of the Subtropical Jet and a Weak Southern branch of the westerlies Tuesday and Wednesday. Coastal sections of Southern CA potentially could get a lot of rain this coming week. IE (several inches)…in the foothill communities….

Beyond this particular storm for the upcoming week are additional short waves in this moist SW flow that may effect Southern CA more then the Central Sierra. It will be showery the second half of this week here in Mammoth. There is a tremendous amount of moisture up at 700 MB associated with the subtropical jet that is progged to flow over the state this week.  More dynamics will be focused further south later in the week for Southern CA as the upper flow splits and become difluent.   So there may be another period of significant rainfall to watch out for after mid week.

Looking down the road the MJO is moving through the pacific and will reemerge back out over the Indian Ocean toward Mid month or about there after.   After this week we may have to wait awhile for another opportunity for significant snowfall.  This is not to say we will not get more storms, but stronger west coast ridging will return eventually between now and mid month. Watch the MJO as it approaches phases 8/1. Sometimes AR events are associate with that phase for CA.  Getting caught up with the WX this week….The Dweebs will update mid week or sooner if necessary.

By for Now…..

The Dweeber………………………:-)

As a caveat:

This discussion is a forward looking out look for the 1st major storm of the season.  In that it is about a week away, a lot can change with it. Better confidence is within a 5 day period with even more certainty within 72 hours.  What can change?  TIMING AND SNOWFALL AMOUNTS….. I expect several revisions both up and down for the amount of QPF…..  With that said…..the end of the weeks storm has the potential to bring a lot of snowfall to the high country…..

Quick Update This Morning:  11:45AM

No change to the thinking of a significant storm for next weekend into early that following week. Details are still coming together……And the QPF is still getting dialed in which is normal for this distance in time.  It will evolve during this week for that period of time.

At the moment, the ECMWF is painting between 24 and 30 inches of snow Saturday through Monday Evening. That difference from Sunday AM is because of new height rises weakening the Tuesday system.

That was not there yesterday….and as in this AMs run, there does not seem to be a strong second separate storm of significance. However, there are 4 parts to this weekends and early next weeks storm, Saturday Through Tuesday. 1. The first with the RT Rear entry region of the leading Short Wave that is in the rear of the departing upper ridge. That may bring some light high Elev snowfall as early as Saturday AM.  2. Then there is the lead upper jet Saturday PM associated with the lead short wave that could bring some light to moderate precip. I think that system is pretty weak ,but moisten things up for us as it brings light to possibly moderate precip.  3. Then the Big Kahuna spins up Sunday AM with the upper jet to the north of us sliding south again. The timing is a bit uncertain Sunday with the onset of the main heavy snowfall, as the main cold short wave is still digging in the morning and possibly into the afternoon Sunday. That can delay the precip until it bottoms out and kicks east.  At this point in time…..Late Sunday night into Monday is the best odds for the heaviest snowfall period based upon the new T1534. It shows that the system has the potential to bring a lot of snow as it couples with the subtropical jet around Midnight Sunday. With a subtropical tap, there is no telling how much we will get at this distance in time by Monday Afternoon.  The current timing of the main frontal band comes through about mid day Monday.  Then another NW Jet brings us strong winds Tuesday night an a chance of light snow or snow showers. There looks to be a reprieve in storminess the second half of next week.

NOTE: If the two upper jets couple early enough and it can fetch up into the Southern Sierra, we could get a ton of snow! Remember, there is a lot of anomalous warm water off the coast of Baja up along the California Coast. That’s fuel for the tool!    Southern CA could get a lot of rain!!

COMMENT:  We are a long way away from the actual event and there is still opportunities for lots of change in timing and QPF in the models.  However, of note, if the T1534 GFS is correct, there could be heavy rain in the foothill burn areas of the Local Southern CA Mtns….   Sunday Night/Monday…..IE potential Mud slide possibilities if that verifies…..

Again we are a considerable distance out.  But the trend look good….

The Dweeber………………..:-)

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Here is what the models did over night and here is what the Dweebs are thinking about:

1. I think that the whole idea of a frigid east for much of the winter is not totally in cards. Sure from time to time but the west will certainly have its winter.
2. Mainly because I think that even as strong as the teleconnections are forcing the -AO and the Cross Polar flow….It will not be able to over come what is developing with ENSO.
3. The Central and Eastern Pacific Equatorial pacific is boiling with convection because of the current Moderate signal of about +1C throughout most of the NINO Basin.
4. The Modoki EL Nino has not developed (So Far) and that would add support to a stronger STJ and Southern Polar “southern branch” over the Eastern pacific in Time. There will be a lot of phasing of these two upper jets potentially along the southern west coast.
5. The big blocking pattern of the upper high over AK and Polar Low over the East is going to come to an end next week for quite a while!

Forecast Models:

1. ECMWF  00Z
a. The Ensemble Control EPS T636L91 (5 day Mean) is the least progressive as it almost Stalls the Long/Short Wave near 140W which in theory builds a ridge over the Rockies.
b. The 00Z Deterministic run of the same time stalls out the short wave from progressing through California as it appears to need another shot of short wave energy for the boot, along with retrogression of the AK Block back to the Kamchatka Peninsula. That in time should provide the path for plenty
of Cold air via the Bering Sea to fill the Eastern Pacific During the 2nd half of the first week of Dec.  In the beginning, it forces progression of the Lead short wave through CA, but not until Tuesday night or Wednesday that following week.
2. Then there is the GEM (Canadian) that is very progressive and waists no time in progressing the 1st Short Wave through CA next Sunday followed by another colder SW the following Monday.
3. The new 12Z GFS is in. And although we do ridge up this Monday through Thursday….it is more progressive than the ECMWF, but not nearly as progressive at the GEM.  It allows next weekends potential storm to slowly approach and may actually hold it off until Sunday. The axis of the main system does not move through until Tuesday! 

Now the latest from the new 12Z Sunday ECMWF as of 11:30AM today Sunday. The new deterministic Run shows next weekends system much more progressive now with the RT rear entry of the upper jet coming into the Mammoth area Saturday AM with the nose of the second Short Wave favoring Mammoth Saturday night with the main system through by Monday AM.  Precip should end with that system by early Tuesday. However, there is another system behind it for Mid Week with precipitation beginning again Tuesday night or Wednesday AM. That looks to be associated with a strong zonal jet and some rise in the snow level with potentially heavy snow.

The Screaming message here is that there is no significant blocking across the CONUS and even well out over the Atlantic, at least for a while….

Based upon the new QPF from the EC……. the Upshot here is that odds are really increasing for a slower moving large storm that will begin sometime Saturday next weekend and end by early Tuesday followed by another system Wednesday AM with the “POTENTIAL” of 4 feet + by mid-week the 3rd of Dec.

I will update again Monday AM.. I will also update with the QPF from the GFS next time.

Dr Howard and the Dweebs…………………….:-)