Active Weather Pattern Returning To The Eastern Sierra Beginning Tonight…..Then Moderate Snowstorm Expected Tuesday Afternoon Through Wednesday Night….Weather Turning Colder Again Second half of Next Week…
Saturday March 2, 2013
Posted at 8:53 am by Howard
Tuesday Am Update:
Latest CRFC QPF shows 1.04 for Yosemite
Freezing Level at 6000 to slightly above.
The heaviest most concentrated shot of precip will be with the front between 12z and 18Z Wednesday. (4:00am and 10:00AM) …then frequent snow showers through out the afternoon.
The 12z Tues GFS 700mb=Rh has has us in 90% with the Front mid morning then 70% Wednesday afternoon through Thursday afternoon. Then there is another RH max Friday morning into the afternoon when we might pick up significant snow again. It may be that we get as much snowfall behind the front associated with the upper low at 700mb Friday then with the front itself. Wednesday AM. The dweebs still think that this is going to be a 1+ to 2 foot storm total by early Saturday morning on Mammoth MT. There will be significant up slope Friday into the night……
Thoughts about the Winter……
Last year all the rage was that the AO was positive and the reason for the dry winter over the west was due to the +AO. Reading the studies and research….it is clear that the -AO teleconnection for the Far West means nothing!!!!!! Reason… There is a non linear relationship between the -AO and wetter then normal winters over California. Anything else said is HOG WASH!!!!
Here is something to think about though. The QBO…..
David Tollis a retired Meteorologist from the National Weather Service may be a little rough around the edges but he is a brilliant long range forecaster!
In his research, he researched the QBO signal and its affects upon high latitude blocking. QBO is (The Quasi Biennial Oscillation) From wikipedia>>>The OBO is an alternating wind regimes that develops at the top of the lower stratosphere at 30MB and propagates downwards at about 1 km (0.6 mi) per month until they are dissipated at the tropical tropopause. Downward motion of the easterlies is usually more irregular than that of the westerlies. The amplitude of the easterly phase is about twice as strong as that of the westerly phase. At the top of the vertical QBO domain, easterlies dominate, while at the bottom, westerlies are more likely to be found. The whole cycle takes about 30 months to complete negative to positive and so it can be some what predictable.
OK So what…..
When the QBO is in its westerly phase (Positive phase)…strato winds blow from west to east. When the QBO is in its Easterly Phase (negative phase) the Strato winds blow from east to west.
Strong positive QBOs correlate to Non Blocking weather patterns
Strong Negative QBO values equate to +AOs and +NAO patterns
(((However))) when the QBO is in transition……. -10 to +10, it strongly forecasts blocking patterns over North America. So when it is accompanied by a strong -AO and -NAO you get a strong +PNA pattern over the far west. (+PNA Pacific North American Cir pattern…..IE the big west coast perma-ridge in the mean)
So although when the -AO is strongly negative, the west does not benefit to high degree when the QBO is very weak!!!!! That is probably in part why the relationship of the -AO is non linear to California weather!!!
See where is the QBO signal is today: See http://www.cpc.ncep.noaa.gov/data/indices/qbo.u30.index
It is probably near 0. What do we have currently. Big high latitude blocking over the northern hemisphere, -A0, -NAO, +PNA Drier then normal California WX that past two months. Imagine that…….
Monday Morning Update:
RE: Dweebs snowfall forecast for Mammoth Mt. The CRFC is forecasting close to an inch near Yosemite for this Storm. Both Upper flow at 500mb and 700MB is SW for a good 24 hours before it shifts….eventually around to the NE for upslope conditions later Thursday. 700mb RH increases to 50% by 1500Z Tuesday AM and so it may start snowing lightly even earlier in the day. Considering the upper flow natural to the Sierra which would mean good orographics and about an inch of model QPF, the Dweebs are choosing to double the QPF for Mammoth Mountain for this storm and set the range of the snowfall storm total of between 1 and 2 feet for the Tuesday Night through Thursday AM period. Light additional amounts will add to the accumulation with up-slope snowfall Later Thursday into Friday.
There is expected to be a fair amount of shadowing with this system and so the heaviest amounts will be concentrated up over the upper elevations. Snowfall amounts in the Town of Mammoth will range from between 6 to 12 inches between 8400 and 7700 feet.
A quick Look at the longer range based upon this mornings new 12Z operational GFS shows quite breezy weather over the upper elevation next weekend with more sunshine. As we go into that following week, the upper ridge over the eastern pacific amplifies and retrogrades as well as bit. The following Tuesday shows a system dropping out of BC, Canada into the Pacific NW bringing wind and unsettled weather (Snow showers). This does not look like a significant precip producer because of its trajectory overland for the most part.
Later next week beyond the 15th the following cold short wave is expected to take a more westerly track and “May” combine with a mid latitude system, “Trying” to under cut the upper ridge over AK. If that comes together right, it could bring a bonanza of precipitation to the Sierra during the 3rd week of the month.
Dr Howard and the Dweebs……………………:-)
After a long break…an active weather pattern will return to the Eastern Sierra Sunday and continue on and off next week. The biggest system by far is expected between Tuesday and Wednesday night. That storm could dump 12 to 18 inches up on Mammoth Mtn with up to a foot in town…..
The current upper ridge over Ca will begin weakening today…but not before bringing another few degrees of warming. Highs in Mammoth will be in the 50s today.
Over the pacific…..its a progressive pattern for the westerlies. The current trof that is approaching California is weakening as it encounters the west coast ridge. It is resulting in a much weaker system that will produce at most, an inch or two of snowfall between tonight and Sunday. Following a break on Monday….the next upstream system is looking much wetter, deeper and colder.
An upper high over AK is aiding the mid week storm in its more mid latitude storm track. This is the storm we have been waiting for to really freshen up the snow pack! The way its coming in will allow a period of several hours of strong orographics, and so current snowfall estimates may even be underestimated! The storm will be followed by an unsettled weather pattern for another day or two as another impulse or two follows between Thursday and Friday. Then expect a weekend that is promising to be pretty nice under upper ridging Saturday and Sunday.
PS. As far as the Tuesday/Wednesday system….There is some possibility using Tom’s western pacific *Hovmoller bomb (a means of tracking the propagation of wave energy) that the energy may come through earlier like Monday night or Tuesday AM.
* Ernest Aabo Hovmoller was Danish Meteorologist passed away in 2008. His most notable contribution was the 5 day running mean of outgoing long wave radiation. A Hovmöller diagram is a commonly used way of plotting meteorological data to highlight the role of waves. The axes of a Hovmöller diagram are typically longitude or latitude (abscissa or x-axis) and time (ordinate or y-axis) with the value of some field represented through color or shading. Hovmöller diagrams are also used to plot the time evolution of vertical profiles of scalar quantities such as temperature, density or concentrations of constituents in the atmosphere or ocean. In that case time is plotted along the abscissa and vertical position (depth, height, pressure) along the ordinate.
Longer range…..subject to change……
The next small weather system is slated to move in on the 12th of March. It looks to be a California slider bringing mainly wind and cooling along with some snow showers… It looks to be followed by yet another windy showery slider on the 15th.
The longest range of the Dweebs guidance suggests further retrogression of the eastern pacific ridge position after mid month with stronger negative tilt short wave systems rolling into the the state. However, a lot of the effects “snowfall wise”, will be dependent upon how far west the long wave ridge sets up, as well as how stable its placement will be.
More Later Next Week…………….>
Dr Howard and the Dweebs…………………………………:-)