Monday December 5, 2016
Posted at 12:57 pm by Howard
A Sierra Breeze came up Sunday afternoon in Mammoth, an indication that (heights) “pressures aloft” were lowering. A beautiful northwest-southeast sierra wave cloud prevailed much of Sunday afternoon, indicating that the upper jet was to our north.
Technical discussion related to current events…
Many thousand miles away a flood of moisture is being drawn northward by a strong Kona low (a quasi-stationary upper low NW of Kawaii. The pattern effecting Hawaii at the moment, can be attributed in part to the strong blocking Upper High over the Bering Sea which is also related to the warmer than normal SSTs in the Bering Sea this Fall. The Teleconnection name of this Block over or near the Bering Sea is the “negative phase of the WPO”, AKA, the Western Pacific Oscillation. Although SSTA’s in the Bering Sea are cooling, the block continues to redevelop in the foreseeable future.
Over the next several days, the PWAT Plume “Precipitable Water plume” affecting Hawaii, will find its way to “couple” with the westerlies later this week…helping to create a moderate Atmospheric River Event “AR” for Central and Northern CA. As a side note, this plume is rich with moisture with the ECMWF model showing isolated areas of 3 inches in the column affecting the big island tonight and Monday. There will be flooding in several areas of the big island of Hawaii late Sunday night and Monday.
Short term forecast and discussion;
A northwest slider will quickly spill some very cold air into the Great Basin as it move east southeast. This system is different than the last cold system in that it is not a true inside slider, its bias is more east than SSE. Additionally, it is not as cold as last week’s system. It is unlikely to dump the 5 to 6 inches like the last system. Estimates? A trace to 3 inches most.
Expect mostly sunny skies Monday with gusty winds out of the West Southwest. Expect winds 15 to 30 at times. Highs Monday will be in the 40s cooling to the low to mid 30s Tuesday with overnight lows down into the teens Tuesday night/early Wednesday AM. Expect a chance of light snow showers Tuesday and Tuesday night. Wednesday will be Sunny with increasing clouds later in the day. Highs near 30 degrees.
It is what happens after the dump of cold air that is so interesting weather-wise later this week. That rich moisture laden river of air will begin to merge with the polar jet and really spin it up! Jet-O’ geneses is what it is called which will deepen a surface low to some pretty low values. All this will advance upon the cold air in place over California by this Thursday. Precipitation will come from the warm air riding over the existing cold air dome in place for warm advection snowfall Wednesday night through Thursday and possibly into Thursday night. However, as the cold air mixes out at the surface, it is possible that snow will change to rain in many areas late Thursday and Friday. The AR event may continue into the following weekend or it may not. Details are forth coming. Snow levels are very difficult to know at this this point in time other then they will start out low and move upward later in the week and then back down. Precipitation amounts could be moderate to heavy. Time wise, we are still 3 to 5 days out. The Dweebs will update later this week. Check out mammothweather.com for an interim update Tuesday.
Dr. Howard and the Dweebs………….:-)
Progressive pattern to highlight next weeks weather with Monday-Tuesday system most likey now a strong NW Slider…..Light snowfall amounts expected…….Wetter pattern with “AR”and higher snow levels still looks good during second half of next week…..
Thursday December 1, 2016
Posted at 4:11 pm by Howard
Sunday Afternoon the 4th:
Cold wave moving in Monday night into Tuesday with light snow possible into Tuesday…..Very Significant AR event developing for the Central and Northern Sierra beginning Thursday AM as Kona Low draws up copious amounts of moisture from the ITZ then through Hawaii…as Warm front pushes into the sierra Thursday…..The Dweebs will have a complete and detailed report in the “weather letter” early Monday AM.
No sooner than the Dweebs put out a Platinum Powder Watch this AM, the upper jet with the next Monday-Tuesday system, the models showed the upper jet more along the west coast/CA with little over water trajectory. Although there is still the chance it may flip back somewhat for better snowfall opportunities, the odds are increasing against it. This is why the Dweebs put out a Watch instead of a warning last night in my weather letter which would be more likely. The watch is now cancelled….
Not only is the pattern quite progressive, but the KONA low developing NW of Hawaii is aiding to pump up quite a bit of warm air over the subtropical eastern pacific. This subtropical ridge will act as a buffer combined with the progressiveness of the pattern to keep this short wave moving rather quickly southeast, instead of digging south first. No doubt this will be another cold system. However, not as cold as it appeared Tuesday but likely colder than the one currently in our area at the moment. Snow showers are still a good bet with light accumulation’s.
Should this system decide to slow down a bit and the upper jet backing a bit more off shore Monday, that would help with snowfall prospects. Although there is still 4 days for a little adjustment, the closer to the event, the better the models are at getting a handle on it.
The longer range still holds the possibility for a light to moderate AR event about Friday the 9th, give or take a day.
More on that later>>>>>>>>>>>
Dr Howard and the Dweebs…………………….:-)
Mammoth Mountain Reports 15 to 34 inches in the wake of weekend storm…Weather pattern now turning decisively drier as upper pattern shifts to strongly progressive…
Monday November 28, 2016
Posted at 10:12 am by Howard
In accordance with my last weather letter and Dweeb update, the WX pattern by both models have turned decisively progressive. This means that the weather is moving quickly from the eastern pacific across the CONUS; (contiguous united states) and pausing from the Gulf of Ak to deepen down the west coast. As an example, the storm that was supposed to drop down over the Nevada and spin up over CA, will now move quickly and spin up somewhere between the Sea of Cortez and the desert southwest. Then shortly after, it will be whisked away by the westerlies. A pattern like this favors northwest or inside sliders. It is a mostly dry pattern for Eastern CA and one that is highlighted by occasional snow showers, colder than normal temps and periods of wind. Thus we will not get us a decent storm anytime soon… In looking at the MJO RIMM phase space, it is going into the circle of death. This means that there will be no tropical forcing for sometime to come. So the word is, enjoy the great snow that we have, and as soon as the pattern changes, well give you all a heads up in my news letter 1st.
Sea Surface temperatures:
As compared to the past several years, the key warm SSTA, is in the Bearing Sea now. As with most anomalously warm SST pools over the north pacific, this is where you will find the predominance of upper high pressure or anomalous upper heights. Underneath this warm water pool the WX is often times quiet. The subject pool becomes a key quasi thermal anchor or what ever is driving the warmth, will begin to dominate the pattern over the eastern pacific. The Dweebs expect a blocking pattern to develop over or near the Bering Sea during Week 2 or 3. Once it develops, the models will latch on to it and have better visibility of the next series of storms and their trajectory. In the meantime, expect ciaos in the models without a good bias one way or another…. (lots of phantom storms with shifting dates) As a note, it has been forecasted over the fall and summer that there will be a reemergence of the RRR “Ridicules Resilient Ridge” over the far north eastern pacific near the BC, Canadian Coast. So far, this prognostication has not developed and may not this winter. The latest CFS prediction is for the pool to remain in the current area all winter. This means that the majority of all winter forecasts by the “Experts” will be wrong! So Southern CA, you may have it your way after all with at least a normal winter or even a wet one. The position of the warm water in the Bering Sea would deliver more of the Split systems like this Fall at times, that does well for Southern CA! Also the current SST setup suggests possible AR events for the west coast later in the Winter. (Warm Wet Storms)
Dr Howard and the Dweebs…………..:-)