MJO Falls Into the Circle of Death….Weakness over the Desert SW to Keep Southern Branch Of Upper Jet Active thru So-Cal and AZ…..Strato-Warming Beginning…..
Monday December 12, 2011
Posted at 9:21 am by Howard
Thursday Am update:
Current Slider is once again a coastal slider which will mean less wind than earlier thought.
No changes in dry pattern noted through Christmas Day w/ series of pinched off short waves that dive south…either down the west coast or as Great Basin sliders….keeping Mammoth cooler then normal. Pattern will then modify slightly between Christmas and New Years with the potential for more consolidation of the upper flow. The Dweebs will follow this idea as it is a change, that although would initially spell milder weather for California…it “may be” the beginning of a transition in the pattern.
Quick Update this Tuesday AM to indicate that both EC and new 12z GFS has a more favorable track to give the Sierra a Little Snow Thursday and Friday Am. The GFS has the system pretty much a western side Sierra Slider. Best guess at the moment…..2 to 4 inches on the MTN. Update in the AM.
From Monday AM:
This mornings WX showed the well advertised Trof off the Southern Ca coast with a forecast of cooler temps for the Sierra over the coming days and some light snow shower activity. Mammoth Mt continues to spray lots of Man Made snow up on the hill with Canyon Lodge opening this weekend. However with that all said, the pattern still remains dry, dry with only the possibility of light snowfalls for the foreseeable future and that includes Christmas. Light snowfalls EQ (1-6) inches.
It is really an unusual pattern with the bulk of the cold air bottled up over the northern most Lat’s…fast flow across 50 north, and none of the type of blocking that would transport cold air south over the mid latitudes for arctic born storms over the CONUS. The Culprit? Possibly the strong positive phase of the AO. The Arctic oscillation which keeps the cold trapped well to the north with anomalously low pressure over the Pole.
Changes on the way….. There has been some interesting blogs lately about a moderate strato-warming event that is beginning to take place. Strato-warming is a phenomena that occurs during the winter with temperatures in the stratosphere growing warmer, which translates to cooling in the troposphere. IE. The level of the atmosphere that directly effects us folks at the surface. See the following link which is a good explanation of strato-warming. http://keeneweather.blogspot.com/2009/01/stratospheric-warming.html
The point is it is occurring…and that is a good thing. The bad thing is that this is a very slow process, that can take 3 to 4 weeks to have an effect. The effect is upon the hemispheric pattern which can translate to storminess in the mid latitude by reversing the +AO to the negative phase. This has the effect of releasing or forcing the cold up over the poles to the south as higher pressure builds in that region. The other important thing to remember is that no one knows where the cold is going to go.
Lets hope where ever it goes it favors long wave trofing in the Eastern Pacific. Again, please read the link above for a good explanation. What is currently happening is Strato Warming and not a Sudden Strato Event. IE “SSW”.
The upshot is that our pattern “may not” change to wet until sometime in 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.