Upper Flow Has Now Backed to the West With Upper Flow Becoming More SW with Time……Moisture Associated with The Subtropical Jet training from the Hawaiian Islands…..Subtropical Jet to Couple with Closed Low Late in the week for the possibility of some good precipitation Over Parts of the Sierra….The Demise of the Greenland Block is at Hand……Good Riddance!
Tuesday March 26, 2013
Posted at 8:37 am by Howard
A quick look at the common teleconnections…the NAO and AO are expected to remain weakly negative the next two weeks. I think that “weakly” is the key here.
The system coming into Ca Saturday night through Monday looks wet with good diffluence and upper divergence as the nose of a 100knot jet effects the Southern Sierra with Mammoth Mt to the north near the Front left exit region, (divergence aloft). Active anti-cyclonically curved subtropical jet is pumping a lot of moisture from near the Hawaiian Islands NE into the subtropics. CIRA Blended TPW loop shows that as much as 1.25in TPW streaming from that region. So there is plenty of subtropical moisture that potentially could to be drawn into the closed low. Its slow movement will allow time for it to gather up “its cookies” by entrainment, Friday into Saturday before landfall. Although this is a very mild system with the snow level about 8000ft, it will have a convective nature to it which would allow for snowfalls within convective cells below the projected snow-level…..Thundersnow may shake up the Easter Bunny a bit Sunday. Additionally, this may also prove out to be a system that produces cold core funnels over a part of the Great Valley of Ca, especially if its timing is right during the afternoon Sunday. As mentioned before, the SPC Mesoscale Analysis Pages will be a useful tool this weekend.
Yes……Good Riddance to that awful block! Although the Weather Weenies across the Eastern US have loved every minute of it…..that Block has been a problem for most of California.
The GL Block ( Strong positive height anomaly over Greenland west to the Davis Straits…Baffin Bay) has pretty much put the kabash for storms effecting California since the 1st of the year with the PNA teleconnection fairly neutral to positive most of the time. Now the GL Block is breaking down and the east will get more Spring and the West, hopefully some Winter during early Spring!!!! Although The first system is nothing to write home about, its a start. There looks to be more behind it through the middle of April. A new but temporary block is expected to set up near AK…splitting the jet with a lower/mid Latitude storm track into California. This looks to possibly develop further the first week of April in the the following week. The Dweebs hope that there will be enough energy left in the Arctic to play catch up for California!
Otherwise what we have now is a weak subtropical connection from Hawaii with a weak subtropical jet NE into Central California this week. Some shower action mostly initiated by orographics is possible as the air mass juices up this week. By the time we get to Thursday, a short wave gets the squeeze SE into the remaining Eastern Pac blocked up pattern for a cut-off or closed low that will effect the central and northern Ca this weekend. This is a mild storm for the high country. Snow levels will respond accordingly. Saturday night through Monday appear to be the most effected time period as the upper low ejects through Central California. The EC and the GFS are now pretty similar on all this.
Longer Range…the ECMWF has another storm later next week…..That system should have an easier time getting in here as the AK block is stronger. Looks like mother nature is trying to relight the candle…….at least for a week or two.