Drier Medium Range…..Recap of weather past week…..New Indian Ocean MJO Event Possible in our future…..

Lucky Friday the 13th….  Mammoth Mt opens for the season….   See:   http://www.mammothmountain.com

I Just finished looking at this mornings guidence and the many weather sites around.  Lots of discuessions!   Lots of pretty maps!   What do thay all mean?  Then I remembered what an old friend of mine that used to work for the National Weather Service in Reno once said decades ago, when I enthusiastically called him on a midnight shift at 1:00AM in the morning.  It still rings home to me. Doug said,  Howard….   “Guidence is not a Forecast!” I never forgot those words!

DId have a peak at the new 12Z Euro Ensemble.  5 and 7 day means….No surprises. Mammoth flurts with 573 to 570 mean heights at 500MB.  That’s fairly high snowlevels and well south of the polar jet. So…mainly light amounts of precip here,  more orographic in nature than forced.  Tahoe will fair better to our north, but it will be pretty wet snow at 7K.   As in my discuessions below, the dynamic models are showing quite the blow up in the Convection with MJO over the Indian Ocean. The Hovemuller time series for the MJO, shows, the outgoing long wave radiation from convection forecasted to be very strong, as projected by the Climate Forecast System. The Dweebs are very encourged with this development. Timing after the 20th…..In the meantime, I am not expecting much.

 

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

 

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It was an amazing change we had in the weather last week.   We went from a Fall Scape to one of winter in a few days. The best part of the change was to put the kabash on the Creek fire so we could all breath a lot easier.

Snowfall:  The Dweebs Forecast of 10 to 15 inches worked out to the tee as Mammoth Mt reported 11 to 14 inches storm total. Its a good start, but of course we need a lot more snow!

To understand our Weather on a climate scale this year, we have to consider the base state of the Strong La Nina, now in process in tropics. The Latest CPC information put current sea surface anomalies over the NINO 3.4 region at -1.5C. This is regarded as a strong La Nina.  The ONI which is a lagging indicator was at -.9 for AUG, SEPT and OCT.   Projections show this La Nina possibly colder than -2C by Late Dec.   With a signal this strong, the stats favor a drier than normal winter for Central and Southern CA, vs the weak la Nina which can be wetter in many cases.   Nevertheless, we will have more storms this winter and the Dweebs will be reporting on their prospects, even on an interseasonal scale time frame

Getting back to the current La Nina Base state; it suggests that tropical convection will most likely remain far west of where it would normally be during a winter.  The colder waters just west of the date line eastward to the Central American coast will constructively interfere with the MJO this Winter, until it gets over the Indian Ocean!  Thus, it is very unlikely that Central or Southern CA will experience any MJO induced Pineapple Connections.

The Western pacific westward to the Maritime continent will have the most thunderstorms. Why is this important?  Because with persistent forcing in that region, that teleconnects to the positive phase of the Pacific North American circulation pattern, (-PNA; trof in the west) or (+PNA, Ridge in the west dictates either wetter or drier conditions out west. The -PNA teleconnection pattern is the one we want. And…. although it does not “Always” mean snow for Mammoth, more often than not it does in the winter.  Persistent tropical forcing in the Western Pacific and Maritime Continent usually is associated with the +PNA teleconnection. The PNA teleconnection is pretty neutral for now.

Current Forecasts:   The Short, (1 to 2 days; Medium 3 to 5 day and Long Range 6 to 10 day forecasts are not wet for Mammoth. There is some possibilities for light precipitation this Saturday with the chance of some 1 to 3 inches of snow over the crest.  Maybe just a skiff in town. This is a warm advection pattern whereby moist air is moving over the colder air currently in place, left over from last weekends storm. However of note, there is a strong NW jet punching into Northern CA tomorrow Friday. That is usually a windy pattern but a dry one at that.  The Medium Range guidance does show a rise in the freezing level this weekend so it will be warmer Sunday and Monday and with Ridging building in early next week, it will get warmer yet. Even through there are storms hitting the pacific northwest south to Northern California, they will not do much for the Mammoth area next week.  We need a change in pattern and change in the PNA teleconnection pattern that is negative in the PNA!! (PNA acronym for Pacific North American Circulation Pattern which is the most common teleconnection for the West.

 

Interseason Forecast:

Those that have been following the Dr Howard and the Dweebs page for years know that the Dweebs have stuck their necks out a long ways at times to forecast changes in patterns that can affect Mammoth Weather. There are times when the dynamic models show a signal that affects other signals that make it possible to perform outlooks some 3 to 4 weeks out in the future. This is one of those times when the Dweebs will do just that. However, it is just an outlook, and not a forecast yet and there is a difference.

MJO:   The Madden Julian Oscillation was pretty much wiped out as La Nina destructively interfered with it. Its convective envelope is still creating a favorable environment for tropical storms over the West Atlantic. The Prind point here is that the Dynamical model MJO index forecasts favors continued eastward propagation, with a potential of a “New Indian Ocean MJO event” materializing during Week-2. Should this occur, conditions would become increasingly favorable for Indian Ocean tropical cyclogenesis during the outlook period, and may promote renewed West Pacific activity beyond the two-week outlook period.  Indian Ocean MJO events also teleconnect well with a two-week lagged midlatitude pattern featuring troughing over Western North America and ridging over Eastern North America, which is consistent with model guidance for the Week 3-4 period with the Climate Forecast System. A flip in the PNA to negative is possible during the latter part of Week 2. This means that it is possible that a stormy pattern with enhanced snowfall potential will develop during the last 10 days of November into the first week of December…..

 

Stay Tuned to the Dweebs…..They will update on this next Wednesday!

 

Dr Howard and the Dweebs………………………:-)

Cold Winter Like Weather to bring snowshowers over Mammoth Mt today along with Mid Winter Temperatures…..After a break early next week another wetter storm moves in Friday……

Tuesday AM the 10th:

Beautiful morning with Mammoth snow covered.  Cold with morning lows in the single digits and teens.

Weather pattern this morning shows NW flow with short wave bringing high clouds to our area. Precip in Pacific NW with sheering trof and energy forecasted mainly east over the Northern Rockies.  A warm air advection pattern follows with gradually rising snow levels over the weekend. This next system to effect the Mammoth area is expected to bring mainly light amounts of snowfall, up to 4 tenth of an inch H20 EQ currently forecasted. So a few inches possible.  It may begin as snow in town but turn to rain later in the weekend at elevations below 8K.   Warm air advection pattern can be trickier with snowfall est.  Models do not do as well as dynamically induced precip.  Feel comfortable in the 3 to 6 inch range between Friday and Sunday at this time over the Crest.  Much less in town with rain/snow mix at the end. Next WX system Tuesday or Wednesday next week.

 

Longer Range:

Based upon NCEP’s tropical discussion today,  the MJO weakened as it moved over the colder waters of La Ninia. It will enhance upper divergence over the far Eastern Pacific and Caribbean this week, before it emerges over the Indian Ocean.   As it moves over the warm waters of the Indian Ocean, expect strengthening. With strengthening, comes a signal for the mid latitudes. This is expected to set up -PNA (Trof over the far west) and Ridge in the east, further delaying Winter for the east with a stormy period out west. This is expected later week 2, (2nd half of next week), through the following week)   (so about the 20th through the 29th).

Expect odds for moisture leaden storms to increase for the west coast later week 2 through most of the remainder of November.

More Later……

Dr Howard and the Dweebs………………..:-)

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Of note, it has been below freezing in Mammoth for the last 24 hours.  Snowfall will wind-down today with possibly a few more inches to add to the 12 inches that has accumulated at the Main Lodge the past 36 hours.  The air is clean and fresh!  Just the way we like it!   The Cold Low is currently sliding SSW and will back door us today.  Dynamically, the main focus will be the Southern Sierra south to Southern CA for precipitation today….Highs today will be in the mid 20s with a bone chilling 4 degrees expected by Monday Morning.   Currently, Snowfall amounts on Mammoth Mt are within forecast, (10 to 15) inches. A few more inches may fall mainly this AM with just some light snowshowers the remainder of the day.

The Storm, (Pattern Wise) that brought snowfall to our region is classic in a La Nina Winter.   Cold Great Basin Long Wave trof with energy entering CA from a short distance off the west coast. This pattern is cold with usually light to moderate snowfall with any individual storm (Short Wave)……

Outlook:

The next weather system appears to have an small AR connected to it….That would be next Friday.

WX Pattern:

The Pattern later next week as shown in the 5 day means, 500mb heights, shifts the current long wave now over the Great Basin and Inter mountain westward, well off shore.  The upper jet relative to CA has currently little over water trajectory, however, is strong dynamically with lots of cold air aloft.

Again…The day 5 means shows the long wave trough retrograding over the next 5 to 7 days.  There is deamplifacation in the process where-by an almost zonal upper jet develops with lots of over water trajectory from the North Pacific to the Northern and Central CA Coast.  The longwave shifts westward to around 125 to 130 west. The upper jet also lifts northward up into the Pacific NW.

There has been an atmospheric river of modest intensity shown in the models the past few days for next Friday. The storm and pattern later next week is one of mainly warm air advection, whereby moisture coming in from the pacific is being lifted over the existing cold surface, like what we have at the moment over California. There is not much in the way of any dynamics  (vertical motion)  from a pattern like this. However, the forecasted winds at 700MB along with significant moisture advection can produce a fair amount of precipitation, well south of the anticipated upper jet position.  Snow levels will undoubtedly rise….Possibly up to 8,000 or 9000 feet.

This is what we need at this time of the year, good old fashion Sierra Cement, not cold dry powder, like what we just received!

I see more storms later in the month…..November looks Marvelous and setting up December for the holidays…………….

Dr Howard and the Dweebs……………….:-)

Another 3 to 4 days of Mild Weather then Major Pattern change this weekend to one of which is much colder with…….Snowfall……30 degree drop in temperatures expected by Sunday…..

10:00AM Wednesday the 4th of November….

Not much change to the forecast other than the Sunday system may be a little colder.   System one is slowing a bit which is a good point. Most of the precip will be behind the front.  CRFC is painting between 4 and 5 tenths between Huntington Lake and Yosemite.  That’s good for at least 5 inches of snowfall over the crest from storm one. Storm 2 is more of an inside slider type and so the crest usually does better than the west side.   All in all we may end of with around 12 to 15 inches on top of the Mountain by Sunday night.   However…theres still time to adjust.  Remember, the 2nd system is colder and snow to water ratio’s will be higher Sunday and Sunday night.   It will really be cold too with highs in the 20s on Sunday!! Lows in the single digits.   More unsettled weather next week!

Dr Howard and trhe Dweebs……………………………:-)

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Although the details have yet to be ironed our as far as snowfall amounts on Mammoth Mt,  it does appear that at least light amounts of snowfall will occur this weekend and there could be more.  Light amounts (1-6) inches. Moderate  (6 to 18 inches)

  1. The Major PNA teleconnection goes negative for at least a week, meaning that a Trof in the mean is expected to set up over the inter mountain west, over the 6 to 10 day period. This pattern is highlighted by much colder than normal temperatures and light to possibly moderate snowfall. The key will be how much upper jet gets off the coast this weekend. At the moment, the first system is expected to be a fast mover and so only light amounts are expected. However, the second system is slower and colder.  It could very well end up being a good snow producer for the sierra. Again, these storms are going to be quite cold with the 2nd system capable of producing snow to water ratios of 15 to 1, over the higher elevations Sunday.

Model Differences;

  1. Where we are at the moment is that this mornings GFS jogged a bit east with its initial short wave and was quite fast on moving it through. That’s a drier scenario.  The Euro seems to be more consistent with plenty of off shore upper jet support.  As for-mentioned, the 2nd system for Sunday seems more interesting today.

Pattern Change and Teleconnection;

  1. Change in the PNA teleconnection to negative through mid month, suggests that these weekend storms are not likely to be the last and that more snowfall is possible that following week.   Again, it is too soon to take a guess at how much we may get….  Better visibility on that subject by this Wednesday.

Dr Howard and the Dweebs………..:-)