Archive for year 2019

Cooler Days to begin Wednesday then through Friday….Models showing some interesting changes next week…..

11:00 PM the 12th

The more I see the Euro the more I like the way it is handling short wave energy as it approaches the mean ridge position. It is with a pattern like this with the mean ridge position over California and along the coast of BC that split flows rule the pattern over the far Eastern Pacific.  I am buying into the Euro now with an upper flow pattern that will become more split over the next two weeks. In my Oct 25th discussion, I wrote about a pattern of split systems with the over-water portion breaking off and forming quasi cut off lows that would spin up off the Northern CA Coast ‘possibly’ missing the Northern Sierra with the main precip, then heading southeast down the coast and moving inland near LA. In a pattern like this, the coastal sections are favored for rainfall and Southern CA as well. Most of the precip for the Sierra from the west would fall on the west side, if the lows are close enough to the coast. However, as the systems come east, to our south, if they come east far enough north like Ventura County, Mammoth and the Southern Sierra can pick up upslope from such a pattern. At the moment, we need to get closer in time to the event.  It looks now about the middle of next week. Wed-Thur)  There are two short waves that the Euro splits.  One is expected to spin up off the coast off Northern  California, interacting with a subtropical low off the coast of Baja. However, more importantly, the split Trof that digs into the Pacific NW may dig back WSW across the Northern Sierra to phase with the cut off west of SFO.  Lots of possibilities….  If that happens, below is a possibility for the Northern Sierra;

  1. If the upper trof digs WSW across the northern part of the state, its circulation may get over-water trajectory and pick up enough moisture before it phases with the cut off low to give the southern portion of the Northern Sierra a good shot of snowfall. Or it may not. These are the fine details that have to be worked out. The Dweebs will be watching where these close or cut off lows form off the west coast.  Sometimes 50 miles can make a huge difference whether we get snow or not. Chances are good that there is going to be more than one this month.
  2. My good friend Tom C, retired WSFO RNO, reminded me a few days ago that as we get into December, the upper jet grows stronger and as a result,  there is more consolidation in the upper flow and less splitting.  Lets all hope so!

Dr Howard and the Dweebs………………………………………:-)

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Although the global models are quite a bit different from each other next week, they all suggest a further weakening of the west coast ridge to allow significant cooling into our area.  The GFS is most aggressive with the cooling with more of a Great Basin trof, while the EURO phases a short wave moving across the North Pacific with a good sized subtropical low well west of Baja. The former would bring at least 20 degrees of cooling later next week with even some light snow showers possible, while the Euro suggests a closed, cut-off type system that would benefit the coastal sections with some rain with more uncertainty further east.  It would depend upon how close to the coast the cut off forms.   In a discussion some two weeks ago, the Dweebs highlighted that this was going to be a Fall/Winter that would be more challenging for the forecaster, especially for the Sierra as there will be splits and closed, or cut off lows.  At least through the Fall, the exact placement of these features will be key to whom gets the precip and whom does not.   Either way it will get more interesting next week, the upshot is that again, this is not a wet pattern as shown by the guidance at hand for the state….although the coastal areas could get wet.  More tomorrow late AM…after a few more model runs….

 

4:38PM Tuesday

In the CPC discussion today, the forecaster made it clear that there is no direct relationship of the IOD (Indian Ocean Dipole) and the current mid latitude flow or amplitude over the Northern Hemisphere. However, he did acknowledge that it was possible that the MJO was showing up stronger than it should be, in some of the models due to the enhanced ongoing convection over the Western Indian Ocean, due to the very strong IOD. He also acknowledged that he was not sure which models were correct between the other models and the ECMWF which has been much weaker with the strength of the MJO, in Phase 8/1.      

 

The Dweeber……:-)

Another warm few days ahead then cooler weather to follow beginning mid week into Saturday AM….Warmer weather to return by Sunday…..Time for Weather Extras…..

 

2:42 PM November the 11th…Longer Range Outlook.

 

The European model’s version of the MJO  is still not expecting a strong showing in Phase 8 (Western Hemisphere and Africa) and is very weak or non existent in the ensembles in phase 1 (Africa), which is the key for Central CA in the MJO precip composites. This is in direct contrast to the GFS, GEM and JAMSTIC with a much stronger showing of convection in those areas.  At this time I am not considering the strength of the MJO in the GFS, GEM or the Jamstc unless the Euro jumps on board at some point.  I like the Euro’s solution, and thus the odds of a deep long wave trof setting up off our coast in the next 3 weeks is not likely.  However, the ECMWF in its new weeklies package today, does show the mean ridge position retrograding in the 7 day meanst, while the upper flow de-amplifies. This occurs during the later part of week two.

This will bring about a positive change to the pattern. However, not one that is considered wet.  Rather, it will turn colder and unsettled with several waves of Low Pressure coming in from a NW direction; some splitting.  This usually brings showery weather with light amounts of snowfall to our area.  The Long range QPF amounts from the “European weekly model” shows between .50 to .75 range, beginning around the 24th through the 29th of November. That’s about 5 to 8 inches of snowfall, or maybe up to a foot over the crest. This is a much colder pattern than what we have been experiencing…..Again this is for the period beginning the 24th through the 29. Stay tuned……..

Caveat Emptor…. Remember, this is beyond the week two period…..  Over the Thanksgiving HOLIDAY.

 

I will update on the progress of the Euro next Friday……

 

CPC  tomorrow PM

 

Dr Howard and the Dweebs…………………….:-)

 

 

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As well advertised, the upper west coast ridge will begin weakening mid week and allow considerable high clouds to invade our skies. Daytime Temperatures will cool some 10 degrees by Friday and the nights will cool as well but not to that extent.  There is likely to be some breeze but no winds to be concerned about at resort levels…..The extended shows 500mb heights (18000ft level) rebounding along with the freezing level by Sunday…  Highs in Mammoth are expected in the low 60s today and Tuesday with lows in the mid to upper 20s….  The extended or longer range shows further weakening of the west coast ridge the last week of the month for the best possible odds of the month for snowfall. However, it does not look like a pattern change that will bring large amounts of snowfall at this time. I will have an update on the longer range either Tomorrow or Wednesday….

 

Weather Extras;

During dry times like this, it is a good time for though’s interested in Meteorology to learn some of the important definitions of terms used in the science. The Dweebs will begin with the Jet stream as defined below.

Jet Stream;

The jet stream essentially represents a boundary between cold air to the north and warmer air to the south, which results in a horizontal pressure-gradient force that increases with altitude. The stronger the temperature gradient, the stronger the pressure gradient, and hence, the stronger the jet stream winds. Because the biggest difference in temperature between lower and higher latitudes occurs in winter, the jet stream is strongest during this season.

Of note, it is important to know that the Jet Stream does not mean precipitation for all areas. there are parts of the jet stream that mean different weather for specific areas in its proximity.

 

The Dweeber…………….:-)

 

Blocking Pattern to continues through Mid Week then weakens a bit toward next weekend…..However, East Asian Jet Stream remains retracted from the west coast……

The weather sensibly over the next 3 to 4 days remains virtually unchanged. Thereafter, expect a gradual cool down beginning Wednesday through the following Friday with considerable high clouds over head and WSW breezes. This change comes about as the current portion for the large scale pattern affecting California weakens enough, allowing short wave action from the west to either come through California greatly dampened, or stalling out off shore. The main point of the pattern change is not really a change. Rather, it is one of de-amplification, that allows over running of our west coast ridge. This will result in an increase of high clouds, cooler temperatures and a slight chance of showers later next week. I do not expect much in the way of anything significant from precipitation. The pattern over all looks drier than normal for the next two weeks at least….

Curiosities worth thinking about…..

  1. The warm water pool that was near the west coast in September has redeveloped some 1500 miles further WNW at 150W. It is in a position, should an upper height anomaly favor its location, set up a long wave trof with axis over the far west…. Not Bad..
  2. Some Models show a strong, highly amplified MJO the next few weeks.  However, this time, there appears to be little affect on the mid latitude circulation. The GFS week 2 progs show cool short wave energy approaching the west coast with slight chance of light precipitation, while the ECMWF dives the MJO toward the circle of death near the Rimm Phase 8/1 in its climate models and the outlook remains dry. The ECMWF is an air/sea coupled model. I believe that It is better than the GFS with the MJO at distance. As long as the MJO is not propagating strongly in the key phases in the ECMWF, I am not going to be a believer in buying into an extended EAJ at any time now in the near or distant future.  One thing that is becoming more apparent for this Fall/Winter. It may be quite the humbling winter for forecasters, when the storms finally start rolling toward the west coast with some storms making it and others forecasted to make, do not. So…Some will split when they are not supposed to.
  3. CPC is telling us in their discussion that the +(IOD) will create La Nina like conditions at times with a retracted EAJ. (East Asian Jet Stream)   So has indicated in my earlier discussion, the pattern will likely go from a total blocking pattern to one of west coast split flows, later in this season. The Warm Pool in its current location suggests the possibility of some very cold western Arctic outbreaks in December as well.  Should the EAJ get modulated somehow from the tropics to the west coast, were off to the races.  However, at this time, I do not see any horses…..
  4. I will have an update later Tuesday or early Wednesday after the updated CPC discussion.

The Dweeber……..