Archive for November, 2013

It’s all about Blocking!!…….Chilly Weekend better for round the clock snow-making today into Saturday…..Milder Weather the end of the Weekend to be Followed by a Weak System Mid Week…..

Yes it’s all about blocking! Where the blocking sets up and how you relate geographically…..Simplistic but true….

It’s mid November and it is getting to be that time of year when forecast model accuracy takes a significant jump to the better. Over the past few weeks, medium and long-range guidance has been awful. It’s not the weathers fault,  it’s the time of the year and the transition, to the ocean’s taking over as the thermal heat source with most gradient’s off shore now instead of over land. Over the next few weeks, forecasters will be able to tell what kind of animal we’ll be dealing with this winter. At least from a longer range perspective I think.

Getting back to blocking, for the past week high latitude blocking has been too far west at or beyond the dateline, conducive to storm energy reaching the central west coast. The flow has been split with that persistent Rex Block NNW of Hawaii and the upper cut off trapped underneath.  However, mother Nature is going to be putting her peddle to the metal this weekend by blowing out the block and pushing the weakened cut off to the west coast Wednesday. This might bring us some light snowfall. More importantly…..This should open up the wavelength and allow western pacific to reach to the Eastern Pacific and be more consolidated. What happens afterwards is what is most important……

There has been a few ensemble members of late that are redeveloping the block in the long-range “further east” which has wet possibilities for the central west coast. The Dweebs were counting on this over a week ago when it looked like a wet period for at least Northern Ca and heavy wet snow for the Central Sierra. Thus the Comments about the “AR” in many discussions. I think that because of what I have been seeing out over the pacific the past month that she may take another run at this pattern at the end of this month.

If Mother Nature takes another run at that pattern by the end of this month into Early December and if it sets up say another 1000 miles further east…..It would only take a short 3 day AR event to pile up so much snow on the mountain to last months….. I am including the AR type pattern in this sentence because I see the possibility of another REX Block developing again when the pattern resets in a couple of weeks.  However, this time hopefully much further east.

Note:  If we go back to the ridge and block further west again…. we will just go from one dry pattern to another.

The Dweebs will be watching to see what develops after the Central Pacific “Blow-Out” that will occur this weekend that will push the remains of the mid pacific cut off, though the west coast Wednesday, followed by a major transition in the pattern the end of this month. Chances are good, we will 1st experience the effects of the old Cut-Off low Wednesday followed by a subtropical-ridge that builds strongly the weekend of the 23rd. …….followed by a different WX Pattern the following week. IE. (End of the month)

Keep the faith as Winter is still well over a month away!

 

Dr Howard and the Dweebs………………………:-)

One More Quiet Day Today then Cold Slider Pattern to Develop Thursday Night with one-two punch…..Coldest slider to flush through Saturday Night…….Outlook still dry with milder temps returning later next week….

Thursday AM Update:

No sensible changes in the short term forecast, just cold on the way. Little change in the medium and long-range charts.

Odds are strongly against any meaningful precipitation before Thanksgiving.

Short term is most positive for snow making as a couple of dry cold fronts sweep through our area this weekend.

Oddly enough the first has the coldest air with it as the second is now taking a further eastward track.

There will be wind, cooling and a few snow showers Saturday.   700MB temps to drop to -5C by Friday morning but not as cold

Saturday AM.

There is some indication according to the CPC that the MJO may affect the weather over the CONUS week two. Not sure what that will mean for us.

One thing is for sure…..the Long Range maps are pretty ugly!

Stay Tuned…………………….

 

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

 

 

12:00 PM UPDATE

New CFS has weeks 3 and 4 wet….. Especially Week 3 which includes Thanksgiving Day through the 3rd of Dec.

SEE 500Hpa 7 day means show blocking in the Red and Below normal heights in Green.

http://www.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk3.wk4_20131112.z500.gif

 

It appears that one more nice day today will be followed by a couple of inside sliders. The First flushes through early Friday morning. This one is not a true slider as the subtropical jet plays more a role on the pattern with cloudiness and cooling.  It is interesting to note that both small, weak Jet-lets of both subtropical jet and polar jet become coupled over Central CA Thursday evening. Although there is limited moisture, there is an approaching VT Max on this mornings 12z NAM worth watching. IE. We may have a snow shower Thursday night….

It will be growing colder through the weekend as the next….. and may I add more robust short wave within the polar jet approaches. Again there is limited moisture showing up with this system, however the upper jet suggests that it may get pretty windy in the deserts and mountains as well. A westward Jog of a hundred miles or so would make quite the difference on precip too. However…the new 12Z GFS is not buying into that as it is keeping the upper jet well inland over the Nevada/CA border.  So the period to watch for the most dynamic portion of the pattern will be Saturday afternoon through Sunday AM.  The Dweebs are not expecting more than a few snow showers at this time, in that the new 12Z guidance is slightly east of last nights run….I have little hope that anything meaningful will fall in the high country. So…..Cold it will be with highs over the weekend in upper 30/40s by Sunday.

 

OUTLOOK:

The latest 12z GFS run shows the upper jet translating east quickly. So upper ridging will take over CA Monday with temp inversions setting up. Looking at the longer term….a long wave trof deepens west of the Hawaiian islands…..that pumps a ridge up just off the west coast in the longer range.  We just can not get a break!!

In the meantime, snow making conditions are going to be very good on Mammoth Mountain this weekend and I am sure that the snow guns will be going both day and night Saturday and Sunday….So more runs will open for the following week……

Think Snow and remember…….According to Dan McConnell, “When you do your snow dance, do it from right to left otherwise it will not work”…..;-)

 

Toms Corner….for our esoteric readers….

Update: latest 12z GFS runs including ensembles trending toward ECMWF solution keeping jet and cold air further east over Great Basin this weekend.  Wave off Japan was not as deep as forecast and was not deepening or bombing out so amplification was weaker (although Hovmoller timing was the same).Series of weaker sfc lows or wave coming off Asia are keeping pattern progressive and flat 5 wave or greater wave number..  Still uncertainty next week with troughing or undercutting off Pac NW coast could led to moist wly flow into Nrn California by mid week (See Canadian model and some GFS ensembles.) Moist confluent jets forecast to develop by next Tuesday between developing Gulf of Alaska trough and Quasi stationary upper low north of Hawaii setting up good warm advection overrunning pattern with good upper level difluence. Stay tuned for further updates and remember October/November are worst months for model verification as continents are cooling and becoming snow covered (diabatic affects) while tropical convection  and typhoons injecting lots of unaccountable energy (latent heat) into global circulation pattern.

 

The Dweeber……………………………:-)

 

 

Very Quiet Week Ahead with it being Very Mild the first half….Then a few inside sliders during the 2nd half to chill it down some…..Long Range Models looking Pretty Dry for much of November……

Quick Update Tuesday Afternoon:

The new 18Z GFS is trending back to an inside slider while the 12z run of the EC is most consistent as a Great Basin slider.

So for the time being this is a cold dry system with some snow showers at best for the weekend. It will definitely be cold!

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Tuesday AM UPDATE

12Z Tuesday GFS just finished its run. It shows the strong subtropical ridge centered west of Cabo San Lucas amped north to the front range of the Rockies. This upper ridge will retrograde in the coming days and redevelop out about 140west. The results are a sharp cold short wave that digs out of western Canada and brings some of the coldest air of the season….and possibly some light snowfall.  Once again like the system in October, the Precip will depend upon if the upper jet gets out over the Water as it digs south. So Yes…there is now a chance of snowfall, at least according to the new 12Z GFS run. However, the earlier runs did not show this system this far west and the EC either.  So well have to wait until we see more model runs to see if this change sticks.  The New 12z GFS paints about .5 to .6 inches of QPF over our area for several inches of snow Saturday/NGT.

For now, try not to get too excited…..as again this is only one run of an ensemble of dry runs. What is positive, is that Saturday is only 4 days away and so this change that is occurring in this model, time frame wise, is more significant.

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

Tom’s Corner:

Long wave pattern becoming a little more receptive to energy reaching the west coast by this weekend as mid pacific closed low north of Hawaii weakens thus allowing less destructive phasing or deflection of cold air advection (ie digging) into western US via back door cold front or slider. Also cold trough over eastern US ejects ewd into north Atlantic creating an excessive wavelength to allow more troughing over Western US as an adjustment wave.  An incipient wave forms off Japan on 00Z 13th with energy reaching west coast using Hovmoller timing of 10 deg long/day or 4 days later on 00Z 17th late Saturday into Pacific Northwest and early Sunday into Great Basin.

Interesting to watch this energy propagate via tightening gradients and cold air advection over western Canada and off BC coast. Latest 12Z GFS latches onto this energy and carves a deeper trough further west over California than previous runs. Will be interested to see if ECMWF and ensembles begin to trend toward this deeper and colder system digging over the area this weekend. While the effects on sensible weather may be in question… what is certain is much colder temps by Sunday with a chance of snow showers or more depending on how far west the upper jet and cold air pool aloft moves over water along the west coast.  another low develops off Japan near 150E on 00Z 17th with energy forecast to come across west coast longitude 00Z 21st. This next slug of energy may be deflected well to north if long wave pattern reverts back to normal PNA (west coast ridge/east coast trough). Keep an eye on the long range ensembles for a consistent trend or converging solutions.

Tom…

Thanks Tom for your contribution….

The Dweeber….

 

 

 

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Monday Afternoon Outlook:

New CFS finally updated.  If you want to believe this stuff…this is for you!   Actually, in its defense, it accurately forecasted the big snowy December last year, back in early November.

The Climate Forecast System is calling for a wet last week of November and a wet first week of December……
The temps are Seasonal which mean snow not rain.
What is the most interesting is how the models do it.  In looking at the 500mb for weeks 3 and 4 you will note a continuation of the block central Pacific block. However it appears to be both stronger and further north. -(EPO) The AO and NAO appear to be in positive mode which works for the Pacific Block better…..and so that would bode well for us.  Additionally, for week 3, the minor block is over Scandinavia. (Not too exciting) but week four looks especially interesting as it is both stronger and just east of Iceland. (Nice excessive wavelength!)
We’ll see if this forecast holds as we get closer to that time frame.

I will post it here for all of you.

SEE:

Precip     http://www.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk3.wk4_20131110.NA.gif

Temps   http://www.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk3.wk4_20131110.NAsfcT.gif

500MB  http://www.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk3.wk4_20131110.z500.gif

(Negative Phase of the Eastern Pacific Oscillation)

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A bit over a week ago there was lots of promise for a major change to a wet pattern for Northern and Central Ca. However, the models for whatever reason got it wrong.  What weather enthusiasts’  have to remember, is that philosophically, weather is perfect. What happens today or next week is exactly what is supposed to happen. It is man’s inability at this time to not have all the information for the models to get it right all the time!  The good news is that (The Models) are getting better every year with more and more improvements. As examples, Today’s 3 to 5 day models are nearly as good as days one and two 15 years ago. Today’s 6 to 10 day outlooks are probably as good as todays 3 to 5 day forecasts, 15 years ago.

So it is all moving in the right direction. Additionally, during the Spring and Fall, models have to deal with the change in the differential heating of the oceans and the continents. The models use different equation’s to base there calculus on in the Winter as compared to the Summer. That is why model verification is so much better in say January and February and again in the Summer than October/early Nov or March. Additionally, in the Fall you have a big factor going on as we have all heard recently…….Typhoons in the Western Pacific. They can totally change a long-range outlook with in a day, if they change direction and re-curve to the north or phase different because of upstream short wave timing.  Lots of variables.

Obviously there were too many and the best forecast long-range models blew it big time……It happens…..but much less frequently then 10 years ago.

As long as folks want to know what the weather is going to do a week or two away, there will be outlooks for them to find out. However, remember, an outlook is different then a forecast! The ability to get it right is much better 5 to 7 days out today then in the 6 to 10 day period.

Forecast Discussion:

The Upper ridge at the dateline has found a home for a while. The wavelength of 60 degrees from ridge to ridge has set up some fine weather for most of California. There is a stalled out storm off shore that will spread some subtropical moisture through the ridge over us. Lots of high clouds are expected the next day or two. Temperatures will remain much warmer than normal for the next few days. Low 60s and 30s.

The second half of the week will be dry as well. However, the upper height anomaly that is currently anchored out at the dateline will weaken as an eastern pacific ridge re developed far enough west to allow a weak inside slider pattern. This pattern will bring enough cooling for better snow making conditions and possibly a few snow showers later in the week. By Sunday, highs will be back in the low 40s.

The Western Hemispheric pattern is not showing any significant high latitude blocking. Teleconnections are pretty weak on each side of zero. So a polar recharge is going to occur for a while.

The 21 day cycle I used before the long-range CFS was available would suggest not much change in our weather until toward the very end of the month. That is contrary to some California forecasters that painted about 6 feet of snow on Mammoth Mountain for the Month of November.  Maybe well get it all the end of the month?    Will check with CPC and report tomorrow……

 

PS Some nice Satellite picts showing long wave trof off shore and short waves rotating to the NE bumping into west coast ridge…

 

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