West Coast Ridging building in with strong height rises and off shore flow…..Fair mild weather to rule through the weekend……Retrogression to begin Sunday with cooler weather along with gusty winds over the crest later in the weekend…..
Wednesday February 11, 2015
Posted at 12:34 pm by Howard
The Dweebs been watching the Ensembles Control of both the ECMWF and GFS that last few days. Both now seem to have discontinuous retrogression in play over the next 10 days. I guess that you can say that with the upper ridge adjusting slightly west Sunday and with some cooling next week that it has begun. However, it really does not go anywhere of significance until about the 24th or 25th. This is within that last week of the month that the CFS has been touting change for the end of the month. And…although there are timing differences, there is significant retrogression that last 4 to 5 days prior to the end of the month. That is a good thing!!
The main suggestion is that there will be a cold inside slider 1st, then a full latitude trof near the west coast afterword’s. Would that not be nice. Not taking it seriously until it gets within at least the next 6 to 10 day period.
Anomalous weather continues across the CONUS as a very strong ridge remains anchored over the west coast, building northward to the Arctic, providing both extremely warm dry conditions over the west as well as creating a direct path for polar air to sweep SE through the Western Great Lakes. It then spins up into a northwestern Atlantic Nor’easter dumping more snow across New England and strong blizzard conditions as well. So as strong as the anomalies for warmth and dry conditions are across the far west, it is just as anomalous for parts of the east with the persistence of Snow, Wind and Cold for New England. The deviation’s for warmth of 850mb temps for this time of the year are very high over the central eastern sierra. High temperatures ran 24 degree above normal Friday at 8000 feet. Mammoth Weather had a high of 65 Friday at 1:30pm. Normal high is 41 for this date.
This is all part of the same western hemispheric system and wave length that the Dweebs believe is tied into by natural forces, due in part to the natural variability of ocean currents and tropical convection. Specific teleconnections have lined up like bars on a slot machine in a row 777777 with the odds well against it for this short period climate variation. It happened in the 1930s and that sequence may be happening now with the +AMO/+PDO connection. Unfortunately, the teleconnecting AMO is not as forecastable as the PDO. So we may not know how long this drought will last in the west. I have posted more information on the AMO-PDO teleconnection below….
As it stands, we are still in our winter mode and it may be that we will need to get closer to Spring until the system creating this drought producing weather….weakens due to the seasonal differences and its effects with the same teleconnections.
For what it is worth, there are still signs of a change during the last week of February. (Via CFC) Especially near the end of the month where there are still suggestions of another AR event. This has already been touted earlier this month in the Dweebs outlook.
PS Here is another climatic study on drought.
A robust but short-lived upper height anomaly is developing over the west coast at the moment. A moderate off short flow is expected for the Southern CA later today into Friday. Santana winds will be moderate to strong is some areas with low 80 to near 90 in the LA basin by Thursday then into Friday.
For Mammoth Lakes, our warmest day will be Friday with highs in the low 60s. Lows in the 20s and 30s. light winds are expected in town and some breezes will occur over the Crest out of the ENE. Later in the weekend the west coast ridge will retrograde west. This will allow systems to drop south into the Rockies and possibly great basin next week for cooler weather. Winds will come up over the crest by Sunday out of the NW.
At the moment, the pattern through Tuesday looks dry, however any further retrogression my allow trofing to develop over the far west and eventually the far Eastern Pacific. Some under cutting is also possible as both the EPO and WPO become quite negative again creating high latitude blocking. We may have some weather to talk about for the following weekend by early next week…… At the moment, the MJO is not cooperating with a weak signal….
The Dweebs have been doing some research lately on the connection between the AMO, PDO and droughts in the West. What I have come up with is a fairly strong signal when the AMO is in its positive mode. See the following links.
See two examples of research:
What is notable is that for the Number 1 example, the research was done during the negative phase of the PDO a year or two ago in which the AMO was positive. We had very dry conditions for most of CA during that phase. This year the PDO is strongly positive and the AMO Positive as well. This led to even worse conditions for CA. Although we did get a few AR events which I understand are more common during this phase.
The graph shows that the incidence of drier conditions over the southern part of CA is less with the +PDO and +AMO combo as there tends to be a higher incidence of a low/mid latitude storm track. IE pseudo warm ENSO “like” conditions. That is why there is less bias under the current teleconnecting scenario for Southern CA. Otherwise, another example of the +PDO/+AMO combo was the big drought of the 1930s. IE the Dust Bowl years.
There is some indication that the AMO may go negative by next winter but not guaranteed. That would better for the northern half of our state for a wetter winter including Mammoth. With that said, the research also shows that the “predictability” of the sign of the AMO is poor at best.
Want to track the PDO and the AMO? The links to the induces are on the my favorite links page.
What is the perfect scenario for cool/wet in the west?
It is the -PDO combined with the -AMO. Up to 80% chance for CA to be Wet.