Archive for September, 2011

September Surprise…..Upper low developing over Great Basin/Ca this morning to spin up, moisten, then move SW to the coast the next few days…….Showers and Thunder will Begin Mainly Friday, with periods of precipitation Day and Night through the weekend

Mammoth Best Rumor today is the 1,000 the inch winter!

A comment from the Dweebs…..

Anyone that believes in this tale must be in the league of

“Americas most gullible and ignorant!”  🙂


Tricky but fun forecast challenge through the weekend…

I. Current:  9:00am

1. Current Radar showing an area for showers occurring and developing on a line “between” Tonopah, NV and Reno. The showers are moving NE.

2. There is an 80knott upper jet at 250mb NW/SE From the Bay area SE down the San Joaquin Valley.

      a. So main divergence aloft is over west central NV…hence where the showers are.

      b. Upper jet weakens later the am.

3. Later today…weak area of low pressure at 700mb slides southeast over the southern sierra.

II. Upper low at 700mb is forecasted over Pt Conception at 00z Sat by this AMs 12z gfs while 500mb low is near Monterrey.

The Dweebs still see the development of a coll but have to definitely include some short wave action into the system from the pacific. So a Hybrid of some sort….

What to expect:

Lot of possibilities depending upon where the deformation area sets up and how it will be oriented by Sunday.

For most folks…the fact that these storms will be wet over the weekend and quite possibly occur at night will impact those back packing in the back country, as most folks will believe that after the sun goes down the skis will clear.  This will most likely ((not be the case this pattern)). There is the potential that rain and dangerous lighting will occur during the night as well…..Beginning Friday afternoon and continue through Saturday night. This period has the best potential at this time….again depending on where the deformation zone sets up.

Surface convergence)

There will be areas of heavy rain in some of these storms…..



More later…………………………….:-)

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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.

Drier Air Mass over Mammoth Today……It Should Be A Warmer Day…..Then a gradual increase in thunderstorms the 2nd half of this week…

Thursday:  ENSO UPDATE


THE CPC Concedes…….La Nina Returns…….

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml


The new guidance is pretty much in agreement that the weather will warm today and tomorrow due to both additional sunshine and higher heights…temps will be back into the mid 70s…Lows in the 40s.

An interesting development in the upper level HT 500MB maps will increase chances for showers and thunder as we go through the end of this week. Strong amplification out over the pacific will build a pretty good ridge over the west. However, it is a broad ridge with two separate height anomalies…one out over eastern pacific and the other over the Northern Rockies.  Because of wave length issues….A weakness will begin to develop over the Great Basin beginning Wednesday. Then within the two positive height anomalies, (Coll) the Dweebs expect it to gradually spin-up into the weekend while at the same-time, retrograde over Ca. This upper low then taps into monsoon moisture over AZ and wraps it westward into Central and Southern Ca. It appears that we could start seeing showers anytime beginning Thursday. As moisture increases within the column and dynamics increase this weekend, chances of measurable precipitation will increase as well. Daytime highs will cool into the 60s by Saturday. Again…..The Dweebs expect, based upon the current guidance, that next weekend will be quite unsettled and cooler.



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.

Upper Low west of San Diego working in combo with continental southern Four Corners upper high…..is channeling up some monsoon moisture…..air mass less stable this afternoon and Labor Day for some isolated thunder….Weather will continue to be highlighted by above normal temps….

The weather could not be better here in the high country. Temps in the mid to upper 70s…low at night in the 40s.   The Weather today and Labor Day should produce afternoon cloudiness as well as a chance of a few thunderstorms over the Crest and Eastern Ca. Tomorrow Labor Day PWAT is forecasted to be about .5 to .6. So although there may be showers….we do not expect a lot of rain. Additionally, the Rt Rear entry region is over the Southern Sierra Labor Day, so tomorrow will have the best chance of a little rain. Either Way odds of measurable precip .01 or better is only about 10% to 20% today and Labor Day for Mammoth.

Early Next Week:

The upper low opens up and comes through Labor day and is east of the area leaving a dry southwest flow by Tuesday. GFS plots from the 12z run this morning has HT 500 Heights over Mammoth at 590DM by late Wednesday AM.  Thus Wednesday will be well into the upper 70s.

Longer range:  The second half of next week shows a weakness developing within the long wave upper high over the west. An upper low develops over the Great Basin Friday and retrogrades toward the Central Ca coast next weekend. It is possible that a more divergent upper flow pattern may occur effecting the Mammoth area, with some showers and thunder next weekend especially if the upper low is SSW of Mammoth near PASEO ROBLES or FAT.  Although the atmosphere may be dynamic for our area, so far, there is little moisture showing up in the pattern at this time……that may change…..

Beyond next weekend….the upper flow deamplifys across the pacific and a fairly strong band of westerlies develops between 40 and 50 north…The pacific northwest will begin their rany season. This is well north of the Mammoth area. Ht 500 Heights remain in excess of 582DM that following week for our area.

SSTA”S  Sunday update:

Warmer water continues to modify the persistent -SSTS of the past 12 months well off the Ca coast and up along the coast of the pacific northwest into the Gulf of AK.  The cold -SSTA’s are also warming in the Gulf of AK. Although the SSTA;s are still in negitive terratory, this modification has been rapid since the middle of August. If the trend continues we may observe +SSTA’s off and possibly along the Ca Coast northward then northwest into the Gulf of AK. If so, odds may increase for a later start to the Fall rainy season here in the Sierra. Warmer water tends to support higher heights aloft and a stronger upper high especially during the colder half of the year…..thus it tends to weaken west coast storms.  Of course there are other stronger forcing factors hemispherically.

If this is going to be a light La Nina year, then I would expect a later start to the season with a colder winter than last, with some large powerful storms during the winter.

Again typical La Nina Winters usually start later and end earlier here in the south central Sierra. I said that last year, and of course the winter was totally opposite,  because of the combination of a strong -PDO, strong La Nina and strong northern hemi blocking.

At this time last year, La Nina was already cranking. Today, the CPC is in La Nada mode with La Nina not showing up until the end of October at the earliest. So it is very weak at best and will probably take until wintertime to strengthen. 

The storms of La Nina years can be quite impressive during the Dec, Jan, Feb into early March.  Average La Nina winters usually bring somewhere between 80% to 120% of normal. (354”) is the average for the past 41 years. Last year was about 185% of normal. So pretty much off the chart!

1000 inch winter?   We may be lucky to get 400 inchs!


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.