A Weakening Upper ridge will give way to some Unsetteled Weather Thursday with a fair and Partly Cloudy Weekend….Further weakening of the West Coast Ridge occurs Monday into Wednesday with Snow a good possibility Tuesday and Wednesday Next Week….
Tuesday November 11, 2014
Posted at 9:23 am by Howard
The AU Gov has come out and has forecasted the possibly of a moderate EL Nino by January. SEE: http://www.bom.gov.au/climate/enso/tracker/
We will need the enhancement by El Nino to strengthen the upper subtropical Jet or the southern branch of the polar jet enough to plow through a persistent developing west coast ridge. Especially In light of a winter-like pattern already getting established over much of the CONUS. This pattern will tend to support a deep trof over the nations mid section and a Simi permanent ridge along the west coast. This was the classic pattern of 76-77.
What the Dweebs are seeing are several storm possibilities within the westerlies that are being weakened by the west coast ridge causing the systems to weaken and split. These systems lack cold air as well.
For the up coming week I see three systems:
1. A very weak system that pretty much falls apart Thursday bringing a chance of showers
2. A back door dry cold front giving us a sample of the colder air that is currently over and east of the Rockies late this weekend
3. Another system that will weaken next Tuesday, and yet another system a few days later. Each one of these systems are coming through the west coast ridge. The upper ridge does flatten next week. So amounts will probably be in the light to moderate range. As little as 6 inches and as much as 18 inches is my best guess. Again….This is just an educated guess at this point, based more on the pattern rather than the extended guidance. The Dweebs will have a much better handle on the system by the end of the weekend.
Being optimistic, I guess the best news is that is that if the ENSO signal continues to strengthen in the El Nino mode into December next month, a stronger upper jet is likely to cause a pattern change that will make it more difficult for the Polar Vortex to remain entrenched where it is likely to set up over the coming weeks….
The concept is this. A stronger upper subtropical jet comes into the west coast over Southern CA or Baja, and as it moves east through the southern states, it then swings northeast and flushes out the cold air from the CONUS…..out over the Atlantic, thereby opening up the wavelength…..
That is what the Dweebs are hoping to see later in this or next season……………………..
The rest of the pattern is common with El Nino, during the Fall and Winter with a blocking high over the NWT and AK and the westerlies suppressed underneath. .
Tuesday Night Update:
In looking at the latest guidance…there is still a lot of questions on how much short wave energy of the westerlies will hold together as it penetrates the upper west coast ridge over the next two weeks. In that the system’s will weaken…..The big question will be how much. On an exciting note, the latest Nino region update shows that between Nino regions 3 to 4, all the SST anomaly’s are now at least +.8C or warmer. “Border line moderate”. Hope this holds through at least January.
A combination of a strong -AO/+PNA and much warmer than normal SSTA’s over the extreme Eastern Pacific up into the Gulf of AK is keeping a “very strong” upper ridge anchored along the west coast. Over the next week, there is hope that the upper jet over Eurasia and additional upper jet energy coming off Japan will combine and progress to the eastern pacific to give us a significant storm next week, Tuesday/Wednesday.
At the moment, the strong west coast upper ridge is keeping the weather warmer then normal. The Guidance indicates that a weak system will break through the upper ridge into California Wednesday Night/Thursday bringing some showers here and very light snowfall Thursday at elevations at and above 9,000 ft. The upper jet is about 100 knots and the main divergence portion of the upper jet is to our north. So we will get some showers and a dusting possibly up to an inch or so at and above 8500ft.
This weekend will be fair and a little warmer with the freezing level going back up to about 11,000ft by Sunday. It is in the extended range, next week, that holds promise for snowfall. All three global models the Dweebs looked at; IE the GEM, ECMWF, GFS and its extension the GFSX have a system that is able to break through the upper west coast ridge early next week. Over the next two days, the upper west coast ridge builds so far north that it morphs up into a closed blocking upper high that stretched from AK to the NW territories of Canada. This is in result of the weak under cutting upper jet into CA. In back of this system is more reinforcing short wave upper ridging that will provide for a fair weekend.
As the long wave Trough reloads NW of Hawaii from energy coming off Japan, upper jet energy is pushed eastward downstream through the west coast ridge again Tuesday and we get a moderate storm capable of a foot of snow or so. Now with that said , the mean ridge position will still be over us, but is in a weakened state. There will be some splitting going on, so no one at this time, including the models, have a true handle on who get the bulk of the snow. As a note, in a true El Nino year….the southern half of the state is usually favored in the split.
Now to look further out…..That energy that acts as a kicker NW of Hawaii, get squeezed toward CA later in the week as more and more short wave energy comes off Japan. In using the new Hi Res beta NCEP GFS T1534…… With the way the storm track is configured, the tempo will continue to pick up into that following weekend. Why? Not because the west coast ridge is gone. Rather, because heights have built up and formed a block from Just off the BC coast northward to the NW territories, then westward covering all of AK with the main positive upper height anomalies north of AK in the Arctic. The upper positive height anomaly then stretches westward along the Arctic circle then south over Eastern Siberia. The model suggest that upper Jet energy is forced south under this block at a latitude of about 45N when it is forced ESE into California that following weekend. More on this Later…….
Dr Howard and the Dweebs…………………….:-)