Archive for October, 2013

October to Turn Colder Next Week as Western Canadian Short Wave Digs into Western Great Basin bringing a few inches of snow over the upper elevations of the Central Sierra…..Between today and the rest of the week enjoy Mammoth’s Excellent Indian Summer Weather!

8:30am Saturday….

Models have come around to the thinking of the ECMWF (European model) that the system will take a more westerly trek with the upper jet off shore and allowing the Front Rt exit region to do its magic by providing lift and vorticity over and near the coastal waters of the far eastern pacific. This bodes well for more significant accumulations now for the Sierra with a good 3 to 6 inches possible beginning Monday morning through Tuesday night. The new 12z NAM shows a slowing of the system over California, which if correct would keep the showers going possibly into Wednesday AM over the Southern Sierra. So the Dweebs are predicting 3 to 6 inches over the upper elevations beginning Monday AM through Tuesday night.  The snow level will begin about 8500 but lower rapidly Monday to 5000ft.

 

It is likely that Tioga and Senora passes will close early Monday AM…so visitors in the eastern sierra plan accordingly….

 

Dr Howard and the Dweebs……………………..:-)

 

More later

 

 

 

6:30pm Update,

ECMWF has been the most consistent the past 3 runs showing the upper center of the 500mb geopotential heights centered near Susanville 5:00am Monday with the upper jet off the west coast. The GFS is now trending in that direction with the upper jet axis forecasted last night to be along the NV/CA border Monday and with this afternoons run, it is displaced west over the Sacramento valley.  This is the compromise that the dweebs believed would happen. However…what may happen if it digs even further west like the ECMWF…..??? The 12z ECMWF puts the bull’s-eye back over Mammoth Lakes….

 

Update in the AM….

 

Stay Tuned…….Were almost 48 hours away>>>>>>

 

8:40AM

Latest guidance once again has gone there separate ways with the 00z run of the GFS centered near the NE Nevada Border and Southern Idaho Tuesday afternoon, while on the ECMWF, the Center swings SE from North of Tahoe Tuesday AM and is near Bishop, Ca by Tuesday at 5:00pm. This is the main reason why the big differences in precipitation for the Central Sierra Eastern Slopes, whereby the GFS model has a few snow showers and the ECMWF has a Solid 6 inches in some areas. In fact in the Tahoe area, it forecasts about an inch of Water EQ on the west side over the crest.  That’s about 10 to 12 inches of snow. So here we are Friday morning with still……A low confidence forecast for snowfall for the Monday night/Tuesday period.

What do the Dweebs think? I think that there are enough short term ECMWF ENSEMBLE Runs to argue against the greater odds of the GFS for it being totally Dry.

Thus a compromise between the two……1 to 3 inches for that time frame. If there is much more…the EC was correct. If little or nothing accumulates, the GFS was correct. In that the 12z Friday GFS was not available at the time of this discussion, I will update if necessary.

As another point not mentioned above, I took a quick look at the 200 MB Potential Heights for 00z Tuesday from last nights run of the ECMWF. The Front Right Exit region is clearly off shore. The nose of the upper jet “is off the Central Ca coast”. This is the reason why the EC is so much wetter then the GFS.

Dweebs will update later today.

 

Remember……………Forecast models are not perfect……Just forgiven……………;-)

 

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

 

 

500:PM Update

Both EC and GFS are much closer this afternoon with a closed low over the Great Basin Monday night and Tuesday. So Snow Showers and light accumulation is expected.  The EC is still in my estimation over done with well over 6 inches of snow for Mammoth Mt by Tuesday night.  The GFS is still skimpy with maybe an inch.

More in the morning………………

Dr Howard and the Dweebs………………..:-)

8:30AM Update

The Dweebs had a look at the precip forecast from the deterministic 00z Thursday ECMWF for the area around Mammoth. It showed a total of .8 to .9 of an inch of QPF. This is very likely over done. It accomplishes this by a further west set up of the upper low between Mammoth and SFO Monday night.  The GFS has only a trace (.01) within the same period of time. Its set up has the upper center over Central Idaho with the upper flow over land. Clearly, with the further westerly track of the deterministic ECMWF,  there is more opportunity of the upper flow to get over water Tuesday and this is why it is wetter. However the ECMWF Ensembles is more like the GFS this mornings. So….Chances are that there will be a compromise with the upper center closer to the Sierra but to the east of it….still limiting the QPF. The GFS track is being favored by NWS as they only have a slight chance of snow showers at this time.   Lets take a look out over the western pacific to see what is causing the Amplification up-stream…..

There are two tropical storms. One is a super typhoon. Both will become extra tropical and phase with the westerlies. This is what amplifies the down stream trof/ridge combo and drives the downstream short wave out of western Canada Sunday Night into Washington state. To the Dweebs…..The phasing of the TS’s looks constructive;  IE ahead of the next upstream short wave coming off Asia. That would argue for more amplification and thus a track more toward the EC. Will Update in the AM.

The Dweeber……

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Although little change in the weather under a ridge of high pressure is expected through weeks end…..Amplification of the eastern pacific ridge near 140West will bring a classic inside slider to the high country Monday through Tuesday night.

Temperatures will drop a good 20 degrees from current temps and along with the cold will come wind as well. Confidence in some light snowfall is increasing as the ECMWF model from last night run is now more or less in line with both the GEM and GFS.  Therefore, expect snow showers to develop anytime after Monday afternoon.  High temperatures will continue in the low 60s through Sunday then fall to the low 40s by Tuesday, Night time’s lows in the 30s will fall into the teens by Tuesday and into Wednesday AM.  Thereafter, upper ridging will build back in for All Hallows Eve and continue into the first few days of November.  So a return of fair weather with warmer temps expected for the end of October into early November.

 

 

Dr Howard and the Dweebs…………………………:-)

Fair Warm Weather to Continue in the High Country for Another Week then Colder unsettled Weather a good bet by Early Next Week…..Although No Major Storms on the Horizon…..It will be cold enough to begin Making Snow by Next Monday

 

Wednesday AM Update:

Concerning the cold short wave digging into the intermountain west next Monday/Tuesday….

The 12z GFS has it again and so odds are increasing that at least some snow showers are possible the first part of next week.

The ECMWF and GFS have reversed roles with the GFS digging the upper trof furthest west now. It appears to be responding to energy from phasing western pacific typhoons. Although the ensemble spread is too great for a confidence forecast to bring measurable precipitation to Mammoth Lakes Monday or Tuesday at this time, one can not rule out snow showers.

By Friday which is 72 Hours out from the event there should be enough runs to make that call.  In the meantime, both the GFS and GEM have the further west solution with the GEM showing a closed low over the Central California coast Tuesday night next week. Should the models sync tomorrow….the Dweebs will be all over it….

The 00z Wednesday ECMWF which is usually the best global model is further east over the Rockies

Either way it will cool off to make snow…the big question this morning is how cold will it get??

Enjoy the rest of this week…..its a beauty!

 

Longer Range:

CFS has done a 180 and is now indicating normal to above normal for precipitation in November.  THIS IS BRAND NEW!!

The trend is always my friend and so I will be watching this carefully….

Incidentally….the new 12z Wednesday has a full latitude trof off the west coast for the 6th/7th of November….

This is fantasyland but will be fun to watch in the coming days….

 

Dr Howard and the  Dweebs……………….:-)

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Currently, a strong Omega Blocking pattern is in effect and will persist this week.  Apparently there is not enough energy in an incipient southern branch to push a cut off low to the Sierra later this week. Instead, the short wave cuts off to a upper low which leaves a REX block to contain it off shore, until about All Hallows Eve when it may get the boot!  In the meantime some high clouds get generated over California but nothing else.  High temperature anomalies will remain on the plus side this week with highs in the low to mid 60s in Mammoth Lakes and lows in the 20s and low 30s. 700mb temps will be about +5C so snow making opportunities remain remote this week until next Monday. By next Monday a strong cold short wave will dive either to the Rockies or to the western Great Basin depending which model you believe at this time. The latter brings more cold with the chance of snow showers here to Mammoth between Monday and Tuesday next week. That is the ECMWF’S solution which is more amplified at this time.

The MJO is in a weakened state using the EMON, IE the seasonal prediction ensemble model of the EC.  This is in contrast to the NCEP – Global Ensemble Forecast System which shows a strong intrusion into Phase space I.   Interseasonal forecasters are poo- pooing that solution and following the ECMM which shows very weak MJO action for the next two weeks.

So expect a continuation of the recurring typhoon pattern over the West Pacific which will contribute to the current persistent, amplified pattern across the North Pacific and North America, through at least the end of October.  Mammoth will experience either cooling from inside sliders or ridging with high clouds from the west.  IE No Snow of significance the next two weeks.

The Climate forecast system has a weakening of the above normal bias it has had to temperatures for the Mammoth Lakes area next week.  An inside slider should put the chill on Mammoth early next week. However beyond that time frame, weeks 3 and 4 show a return to the above normal bias of some +.06 for Mammoth which is not all that significant. The bias continues to be less significant through the 17th of November, however the trend suggests that an increase of storminess may occur the 2nd half of November.

Significant changes in the ENSO forecast from the CFS shows that it has been trending more toward neutral for the Winter, contrary to earlier predictions of a Weak to Moderate period of WARM CONDITIONS IN THE 3.4 REGION. This makes the Winter Outlook more uncertain now. So far most of the blocking has been up over Alaska this Fall. Should that continue into the Winter that would certainly be more favorable for Sierra Snowfall.

The Westerly phase in the QBO usually does not support much blocking or any sustained blocking over Greenland and so this is less likely now for the eastern half of the country this Winter.  So odds are it will not be nearly as cold in the east and not nearly as dry in the west as last year.

It may be that high latitude blocking may be able to develop more over Western Canada or even Alaska during this winter which would be better for southern stream energy to be stronger for latitudes further south along the west coast.

The solar cycle continues to be anemic supporting a continuation of the -PDO.  Over all, the bias so far supports a colder winter out west and because of ENSO will most likely remain between 0 and +.05 this winter, it may end up that our biggest weeks of precipitation occurs with short period MJO induced extensions of the Asian Jet later this winter.  Thus once again, as I have reported during several Fall years, the incidence of MJO initiated pineapple connection’s are at there highest when ENSO SSTA’s in the 3.4 region are between 0C and +.05,  which is where it will most likely be this winter after the 1st of the year.

So this winter may be highlighted by long periods of dryness followed by periods of very wet weather of high intensity precipitation later in the Winter. Although I will have once more look at everything the end of this month, I am of the opinion today that that the MJO will be the biggest and most significant driver of precipitation this winter for Central and Northern Ca now that ENSO will not be factor.

 

The Dweeber……………………….:-)

Postive Phase PNA Pattern Likely to Persist into Months End with Cold East and Warm Dry West Although Cut Off Low May Bring Some Showers By The End of Next Week….

Thursday AM:

Although not a strong +PNA set up…it is positive phased nevertheless. The blocking pattern off shore will move inland early next week leading to warmer temperatures over the upper elevation’s with pretty much calm winds. High temps this weekend will be 55 to 60 at 8000 feet and by Tuesday or Wednesday could be in the low 60s or warmer while nights in the 20s will rise to the mid 30s by Wednesday. The pattern will deliver arctic air to the Northern Plains states with some areas getting snow.

The only hope for any precipitation is from a little cut off low that may it underneath the block by the end of next week. I guess It all depends upon how much energy there is in the Southern Stream. In that were getting to a time in the Fall that may signal some kind of Fall Pattern, the only pattern the Dweebs see is the +PNA for sometime out. If there is an advance eastward in the Asian jet later in the month there is always the possibly of undercutting of the westerly’s. But that is not in the cards yet!

Temperatures at 700mb look above freezing this weekend well through Thursday between +2C and +5C much of next week……So not much help in the snow making department.

Cliff you will have to wait a while longer to get those snow guns spraying the white stuff!

In that the Government shut down is over, the Dweebs should be able to give a better look out beyond Week 1 and even 2 when it all comes back online next week.

HAVE A GREAT WEEKEND!

NEXT UPDATE TUESDAY THE 22ND

 

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