Blocking Pattern over Northwest Canada will suppress Upper Jet well South into CA this week and into the next…Expect cooler than normal temps with periods of Rain and Snow in the High County…
Tuesday May 12, 2015
Posted at 8:50 am by Howard
Wednesday AM Update:
It appears that we have 3 significant short waves (Storms) to expect weather from.
1. The 14th and 15th. Cold Spring system with subtropical tap. A foot+ possible over Mammoth Mtn (4 to 7) inches at 8K….. (2 to 4 inches above 6500)
2. The 17th through the 19th ( Not as cold as Thursdays system) Snow level above 7.5K to 8K
3. *Possibly the 21st and 22nd; then outlook into the end of the month.
Interestingly….the polar jet actually couples with the subtropical jet with these systems giving them more boost…
Observation…..look at the **16K IR Satellite. You can actually see the results of El Nino in the “Massively Strong Convection” north of the equator over the Nino Basin. This is acting to spin up the subtropical jet and depress the Hadley Cell to the south to 130W/20N as the jet curves over and past the Big Island of Hawaii. So we are already seeing the incipient results from an increasingly warm Nino Basin over the Subtropical Eastern Pacific.
*Note: The NW Canadian Block will be breaking down during the end of the 3rd week of May with the anomalous 500MB heights lowering in that area. This should allow the upper jet to lift back to the north with the majority of anomalous precipitation shifting into the Northern Great Basin, Northward. Warmer and drier weather should be the result over the central sierra, except for some isolated thunderstorms the last week of May.
The new updated PDO for the month of April is out. It shows the strong positive record-breaking teleconnection that has been grossly responsible for this years drought is weakening rapidly…..The updated AMO is still negative which is a good thing.
Dr Howard and the Dweebs…………………………….:-)
I guess if you do not get it in the Winter…sometime you get it in the Spring! Global model teleconnection’s show the positive phase of the PNA teleconnection strengthening over the next week with a notable block over the NW Territories’ of Canada. This effectively splits the upper jet and forces the majority of pacific energy southeast from the GOA where it carves out a long wave Trof along the west coast. This is expected to bring the Central Sierra above normal precipitation over the next week to ten days along with below normal temps. More snowfall is expected with the snow level lowering to 6500 to 7000 at times. It would not surprise the Dweebs if another 6 to 12 inches fell over the crest by the end of this weekend. Some 3 to 6 inches is possible in town mainly Thursday AM through Friday AM and lingering into Friday.
Because of the time of the year snowfall impacts to local roads are usually short lived. However, if you are planning travel over Tioga and Sonora passes Thursday and Friday, travelers should pay close attention for the possibility of temporary road closures.
The upper pattern over the Eastern Pacific and CA remain unchanged with a series of short waves impacting the Sierra with periods of precipitation. More snowfall is expected next week in the high country. Amounts will very with each storm as zones of deformation set up in varies areas being the main focus of occasionally moderate to at times, heavy precip. This time of the year, you not only get dynamic lift from the upper jet but additionally, strong convection from the combination of deformation and surface heating…. This can lead to larger hail and even funnel clouds in extreme cases.
EL Nino: It is already there!
SOI is now crashing as a cold wave takes over Australia the next 72 hours…. Expect the SOI to come in quite negative for the Month of May when the figures are released next June. This is another indicator that this ENSO event has Legs. Watch for more westerly wind bursts over the Central Pacific.
Read how El Nino Effects our weather on the west coast. : http://28storms.com/longrange/how-enso-impacts-the-northern-hemisphere-pattern/
“Prind Point for the Effects of El Nino to the Eastern Pacific”
During an El Nino, there is more rising air in the equatorial Pacific due to the relaxed trade winds. This increased ascent helps raise the equatorial tropopause height. In turn, there is increased divergence at the tropopause and thus the air has to “more quickly flow poleward” to balance the heat.
Since the air is moving at a greater velocity, the Coriolis effect is correspondingly greater, so the air is turned to the east at a lower latitude than normal. The result is an anomalously equatorward-displaced *Hadley Cell. This forces an unusually low tropopause height over the subtropics. Since the tropopause naturally declines in altitude closer to the poles, any change in its height will have more noticeable impact on the 500mb geopotential height. So in an El Nino , 500mb geopotential heights tend to be lower than average “over the subtropics”.