Archive for January, 2012

Cold Windy Pattern Setting Up For Sunday-Monday As Pattern Changes Force Arctic Air Into Pacific Northwest……Wind Advisories Hoisted For Mono County……Over Running Precip Begins Thursday Into Friday Over Milder Air….

Quick Monday Am Update:

First…here is a link on a simple understanding of the NAO and AO supplied by another WX Dweeb….Doug Rowe

Thanks Doug for your input….

http://www.scientificamerican.com/article.cfm?id=whats-causing-dry-winter

Just a few added points:

1. The 0C isotherm at 700mb (10,000ft) rises up from the south to Mammoth by Wednesday afternoon. So warm advection precipitation may begin as snow in Mammoth as early as Wednesday Am. However, with the 0C reaching Mammoth that afternoon…..cooler air in place will eventually mix out with the warmer air aloft…forcing the snow level to rise above 7000 feet.

2. We may actually may experience snow level that rise and fall Wednesday through Friday between 7000 feet and 9500 feet.

3. Although the 0C line moves well north of Mammoth Friday….there are times when micro-physical processes at work that can fool the weatherman with lower snow levels when the air is saturated through the Dendritic growth zone -12 to -18c at 20,000 feet when the 0c line can actually verify lower on the OAK sounding.

4. First EST QPF  5 to 6 inches Liquid EQ.  10,000ft and above (3 to 5 feet accumulation) by Tuesday morning the 24th

Quick Sunday Am Update:

1. Modified Arctic has invaded Washington State

2. Dry Cold Front moving through Northern Ca today stalling out about Tahoe…then moving again south to between MMH and Bishop by 4:00am (The front is Dry)

3. Windy today and cooler with highs about 40 at the village at MMH

4. Highs about 27 on MLK Day. Lows in the single digits Tuesday AM

5. As Upper High Anomaly develops over Eastern Siberia…Westerlies undercut block, that morphs into Rex formation by next weekend

6. Subtropical Ridge Builds over Eastern Pac mid-week effecting mid latitudes causing warming aloft into the Sierra.

7. Long Wet Fetch develops mid-week with rich subtropical plume expected to develop north of Hawaii within main wave later in the week.

8. Main Wave of rich PWAT to reach central west coast Friday then into Sierra during the afternoon. Snow levels will still be high; possibly still above 8500 to 9000 over Southern Mono County. Colder air expected to move into wave after 00z Sat. Based upon the new 12z Sunday GFS guidance….the 700MB 0C line doesn’t push south of Mammoth until after Midnight Friday NGT, so snow levels will probably stay pretty high or above 8000 Friday night until Midnight. More fine tuning later…..

Of Note: The GFS QPF from last night went hog wild with 5+through the next 7 days to as high as 10 inches of Liquid EQ through the 31st.

The ECMWF is much less.  Lots will change over the next 5 days….however, confidence is high now that at least one to two significant precipitation events will effect the Mono County area over the next 10 days.

From Saturdays discussion:

A shift to Colder Windy weather is expected for the Eastern Sierra Sunday into early Monday as this mornings upper ridge builds into the Bering Sea (-WPO) with the return flow tapping cold Arctic air north of AK which then moves south off the AK coast then down off the BC into Washington State and Oregon. The upper ridge over Ca is being flattened today and by Sunday, its remains will be south of the Mex Border Sunday. The Surface front will bottom out about Tahoe Sunday Am then shift east. Cooling will come from lowering 700-500MB heights

As the cold storm pushes through, the upper flow will become Northwesterly. This is both a cooler and windier pattern for the Central Sierra, especially late Sunday into Monday Morning……However, it is still a dry pattern.

Next Week:

What the Dweebs see is the upper closed High Monday in the Bering Sea Retrograding into Eastern Siberia, while a good portion of the Westerlies break underneath. A very long and may I add wet fetch sets up by Tuesday. The source of the moisture is from the tropics west of Hawaii. Today’s 12Z GFS has PWAT forecasted higher then 1.50-1.75 inches within the fetch, Wednesday into Friday. The initial target is the Pacific Northwest…..then Northern Ca by Wednesday shifting south into Central Ca by Thursday/Friday.

Here is the problem…… What happens is that as the upper Anti cyclone shifts westward well west of the Dateline 160E, there is a tendency because of the teleconnection, for 500mb heights to rise about 140W with a flat subtropical ridge that extends north, then east to the Central Ca coast. 700mb temps over Mammoth increase to 0c by Thursday and with 1000-500mb thicknesses about 558DM, snow levels will likely be north of 8000ft and possiby 9000ft.  Once and “if” the air-mass gets really saturated, there could be little difference in the snow level from the freezing level. So the Dweebs expect the possibility of some very heavy wet snow at and above 9000 to 10,000ft….Especially Friday in the over running pattern. Now the EC model looks a bit cooler so still time to adjust. By Friday night, the GFS has the Freezing level coming down rapidly. However, most of the fetch has shifted south with much drier air coming in from the north.  This moist wet pattern is not the system that we are really waiting for. That is still looking like 10 days away or sooner of the ECMWF is correct.  Better Vis later in the upcoming week……

 

Climate:  AO

All this Talk about the AO and SSW.

Yes there has been a Strato Warming event and yes the AO index is becoming more neutral and yes Arctic air is shifting further south out of the northern most Latts.  However, the Forecast by pundits has been a real significant Plunge in the AO index to negative. The Dweebs do not see this in the GFS operational or Ensembles, What many now see is more of a neutral AO with some incursions to slightly negative…then returning to positive. I also see that all the hype of the big cold coming into the east as mostly hype. Patterns often repeat themselves during the Winter. So more and more of the Dweebs are shifting their opinions to the idea that the current cooling across the country will be short lived then confined to the northern tier states. That anomalous warmth will be returning to much of the CONUS soon. The climate models suggest cooler weather after the 4th of February over the western half of the CONUS.

 

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

 

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

ALTHOUGH ANOTHER DRY WEEK IS AHEAD…MORE SIGNS POINTING A RETURN TO WINTER BY 2ND HALF OF NEXT WEEK….

UPDATE COMING….SATURDAY MORNING>>>>>>

 

 

 

Thursday Update:

8000ft Temps today will be cooler with highs in the low 40s…..some moderation in temps expected through the weekend with clouds increasing Saturday NGT from the cut off low kicking through So-Cal. The kicker system is modified arctic in nature. This system will bring snow to the pacific northwest Sunday. Its track is a quasi northwest slider for the high country and will be a windy system at that. At the moment, it looks pretty dry but cannot rule out some snow showers this far south….Sunday/Night.  This system is the 1st part of the pattern change that will hopefully bring snow to the high country of the Central Sierra by the end of next week. It will be rather windy Sunday/Night, especially over the upper elevations. Monday will be quite chilly with highs in the low to mid 30s in town. As the upper High builds into the Bering Sea and becomes cut off….the supporting upper ridge progresses toward the west coast for a return to milder weather from Wednesday the 18th, through as late as possibly the 20th.  Thereafter, we will just have to wait a bit longer and see how it all unfolds. Next update Monday/Tuesday or sooner if it warrants.

From Wednesday:

It’s a beautiful Wednesday in the high country. Temperatures were in the low to mid 20s at the village this morning. Yesterdays high was 51. No significant winds either. There is a small short wave that is moving through the Great Basin this morning. It is associated with a plunge of Arctic air through Montana, much of which will slide to the east of the divide. However, some will spill west through the eastern portions of the Great Basin. It is associated for the most part with a surface high of 1040MB. The NE surface gradient will give the sierra crest some gusty winds today into Thursday and bring between 5 and 8 degree of cooling today. Temps will slowly moderate upwards through the weekend. Again…I expect today to be a cooler day with highs in the lower 40s. Additionally, The Dweebs have noticed an inverted surface trof along the south coast tomorrow and so a mild Santana is probably in order for So-Cal later tomorrow into Friday.  Warmer days for you folks (Thursday and Friday). Southern Ca probably has the bragging rights of the entire CONUS for December and January to this point for the best weather.

Outlook:

A cut off low has formed at the west end of a weather front that sheered off to the east over Northern Ca yesterday. The short wave split, leaving an upper cut off over the Central Ca coast to drift southward. That small feature will get the boot into So-Cal Sunday spreading some high clouds into our area over the weekend and possibly a few showers for So-Cal.

 

Long Range Outlook:

The upper pattern over the North Pacific according to the extended models are becoming more in line with each other….and may I add finally!

Even the Climate runs this AM have turned wet for the Northern and Central Sierra starting in the middle of the 3rd week of January and continuing through the 1st week of February. The models were notably cooler in temps the first week of February so heights are expected to come down for the Ground Hog.

In that we are getting closer to the change, confidence is swinging to a wet pattern for the Northern Sierra and a less wet pattern for the Central Sierra. The immediate pattern change will be associated with a coast to coast zonal flow pattern with the Front Left Exit region of the upper jet focused upon Northern Ca., where as the Rear Rt entry region will effect the Central and Southern Sierra. Hence the pattern will be milder for the Central and Southern sierra with higher snow levels. Noting at the beginning of the pattern, the 180hr gfs has -5c at 700mb with thicknesses at 1000mb-500mb at 558DM. Hence the snow level may begin lower initially until the air mass moistens a bit later down the Rd. Will update more on snow levels later. Well see how the 700MB temps performs within this pattern and the Dweebs will highlight that later this week and into the next. In the Winter, forecasters use a combination of 700mb temps and 1000-500mb thickness as well as the Oakland sounding in a Zonal Flow to determine snow levels for Mammoth Lakes.

The Dweebs are expecting this pattern to bring several feet of heavy wet base building snow between the 18th and the end of the month and into early February, based upon this mornings guidance.

Be sure to get up over Tioga Pass this week and snap some photos. Most likely, you will never be able to do that again in your lifetime, in the middle of January.

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

 

 

————————————————-
Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

Chilly Inside Slider Brought Welcomed Cooling For The Snow Makers…..Expect Another Mild Dry Week Ahead….

Tuesday 1/10/2012 Update:

The GFS 12z Tuesday Run came in a little wetter on the longest range sagging the southern branch of the westerlies far enough south to give the Sierra some precip beginning the 19th-23rd. The interesting thing is that the heights over Central Ca are similar to the EC. Could it be that it is coming in line with a less dryer solution?   And…..its 500-1000mb thicknesses were actually a little lower. (558 to 552DM). Snow Level 7500-8000ft. 

This is beyond the forecast period and falls within the outlook period between the 19th and the 23rd. (8 to 14day). Although the latest model run is certainly encouraging, I would like to see many more runs like this as we are still in a drought pattern and until that changes the outlook remains the same…..more on tomorrows flip-flop.

From Monday:

It appears that the Long Range Means are doing some back peddling from yesterdays encouraging signs. For whatever reason, model physics are not handling the big picture very well as the ensembles spreads are increasing again and the visibility diminishing…

The key here is the handling of the long wave upper ridge that is expected to develop near or just east of the dateline. The GFS is pretty much worthless this morning and the EC is developing the upper ridge further west. If you read the discussion from yesterday, I said that the key to a good storm will be where the upper ridge sets up. That if it sets up to far west, that we will ridge up again. That is what the GFS model is suggesting. In fact it just cuts it off north of the Bering Sea and redevelops the west coast ridge at 140W. That is a dry pattern again!! 

See: http://www.hpc.ncep.noaa.gov/cpc/cpc_NHEM_f264wbg.gif

 

The ECMWF is also west of where it was yesterday in the means.  Not good!!!!  However, the ensembles still lower the HP 500 mean heights into Central Ca to 564 DM by the 18th. That would generate some precip. 

Additionally this AM, the most recent Climate model run from CPC showing above normal 500mb heights over Central Ca through early Feb. They have totally gotten rid of the Wet week from the 20th thru 26th. THERE SURE HAS BEEN A LOT OF FLIP FLOPING!  I think that until we get some confidence into the 6 to 10 day or better yet, 3 to 7 day……all bets should remain off.

 

The Weather this coming week will be highlighted by temps for the most part in the 40s in town and lows in the 20s.  There is a very small scale closed low that forms off the Northern Ca coast that drops south this week.  Little in the way of any effects are expected here in Mammoth other then some clouds and a very slight chance of a shower Tuesday night.

 

Dan…..keep doing your snow dance….

 

The Dweeber………………….:-)

 

 

————————————————-
Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.