Cooler Saturday then a warm up into mid-week……October 20th weather system has more support from global models now and may bring 1st good shot of snowfall to the high country prior to next weekend……More thoughts about this winter….

Although it will be a cooler day today, high pressure will build over the Eastern Sierra Sunday into Monday for a couple of very nice fall days. High temperatures will reach well into the 60s.

The big news this morning is that the European and GFS models are coming into more agreement (With timing differences) with a good October storm that has the potential to bring good moisture to the Eastern Sierra. Both the European and GFS have a decent “AR” subtropical connection that hits Central CA on the 144hr prog. PWAT (Precipitable Water) tools shows amounts over 1.5 inches moving on-shore later Thursday afternoon. The plume pushes through by 12:00PM Friday on the EC and by Friday night in the GFS model. The snow levels fall in both models as the SW fetch and plume passes from north to south Friday. With any AR, the main questions that come up are how cold it will be during the AR and thus how much snow will fall at what snow level. Best odds are that the majority falls above the Town of Mammoth Lakes Thursday and Thursday night with snowfall most likely Friday in town after most of the plume has pushed south. This is just a rough idea at this point in regards to the timing in the Towns of Mammoth and June. During the meat of the AR, higher elevations could pick up several feet.
Although it is way to early to be specific on amounts, there is much agreement with the two favored global models at this time that a potential wet storm is on its way after mid-week next week. The storm looks to be out of here by Saturday.

More winter thoughts:

1. The National climatic center came out with a report that indicated that La Nina is expected to be a weak La Nina. If true that increases the odds for more AR events this winter. Remember, the highest winter incident’s with AR’s occur when ENSO is +.5C to -.5C in the ENSO 3.4 region. Conversely, strong El Ninos and Strong La Ninas have the lowest odds for AR events, statistically.
2. Another important key to this winter or any winter is where will the blocking set up? Last winter it was over AK and west in the WPO and EPO region. Unlike last winter at this time, both of these teleconnections are showing strong positive phases through the next 10 days so much more low pressure in this region at this time. (ANTI BLOCKING)
3. Were still dealing with an easterly QBO vs a westerly QBO with last winter which tends to keep the upper jet further north. However, there is an early buildup of snowpack over Eastern Asia which favors a negative phase NAO and AO.
4. Odds are that we will have more meridional flow this winter.
5. So the winter from a long-range forecast point of view is still quite the mystery. However, no matter how this winter ends up, it should be a good one!

PS. The Dweebs will focus on the next 2 weeks and use MJO to offer a glimpse beyond……:-)

Periods of warming and cooling expected for the next two weeks….overall pattern for the Central Sierra is dry with cooler than normal temps….MJO flaring over Maritime Continent likley to bring important changes to west coast weather next week…

Wednesday AM 10/11/2017

After an exceptionally long quiet period for Tropical Storm activity over the Western Pacific, a strengthening MJO over the Maritime Continent (Phase 5 of the RIMM index) promises to bring a return of Typhoon action for the Western Pacific in the coming 2 weeks or the 2nd half of October. This is important for west coast weather during the month of October as when these Tropical Storms recurve to the north, they can become constructively or destructively phased with the westerlies. Major amplification or the Zonaling of the upper pattern downstream over the Pacific will play havoc with longer range guidance. As its accuracy deteriorates due to the timing of the aforementioned; will we bite on the guidance? It is going to get interesting…………………..:-)

Although another warm up is in store for the high country today with further warming for the Owens Valley tomorrow Wednesday, another dry cold front will approach the Eastern Sierra Wednesday causing gusty winds Wednesday and another round of cooling for late Wednesday and Thursday. High Temperatures will range between the upper 40s Thursday to the low 60s by weeks end. Night time lows in the teens and 20s the 2nd half of this week… It is a dry 5 to 7 day out look.

All weather hobbyists and professionals this time of the year pay attention to many of the various climate signals that are coming out now from various sources.
Here are a few of them:

1. The MEI “Multivariate Enso Index” is tanking showing a strong move to La Nina. This years La Nina looks to be Weak to Moderate in strength according to an average of the indexes.
2. This kind of strength of La Nina suggests equal chances of an average winter’s for precipitation for our area. It suggests a dryer than normal winter for Southern California and wetter than normal winter for Northern CA.
3 There is also a bias for a bit colder winter out west.
4. Latest forecast outlook for October is for drier than normal condition’s and cooler than normal temps
5. On the positive side, new forecasts from the CFSV2 shows wetter than normal conditions developing during the month of November from about Mammoth Lakes north.
6. Sea Surface temperature anomalies are quite a bit different than last year. Last year, there were very warm SSTA’s in the Bering Straits and a warm anomaly in the Gulf of AK. That is not the case this year. It appears to be further west across the dateline. The PDO was strongly positive last winter and it is trending cooler now. The QBO has flipped from positive to negative.
7. There are so many differences this fall over the fall of 2016 that even with other indices possibly being similar, the odds of any resemblance to a winter as far as the precip totals like last year is highly unlikely.

A word about La Nina;
1. Yes we have had a big heavy winter during La Nina here in Mammoth Lakes. However, the odds are against that from a statistical point of view.
2. La Nina’s that are weak favors more “AR” events for the central west coast than La Ninas that are either moderate or strong. Last Winter was considered ENSO neutral. So AR events are expected but not nearly the frequency of last winter.

Best early October guess from the Dweebs is for more of a normal winter as far as precipitation totals December through February with a slightly higher bias for a wetter late Winter and Spring as La Nina weakens to Neutral.
I will update later this month. (PS) that does not mean that we will not have a big precip month during any particular month…

Fair Warm Weekend ahead then NW Slider Sunday night bringing breeze…..Cooling and some cloudiness….It will be a dry 5 day period ahead…..

High pressure will build along the coast the next few days bringing a good warm up over our region. Temperatures are likely to reach near the 70 degree mark at resort levels Saturday, however night time lows will still dip into the 20s and 30s. Light winds are expected through Saturday. The pattern will change a bit Sunday into Monday as a NW slider digs down into the Northern Great Basin. The GFS model is deeper and brings more cooling than the Euro. Either way there is no precipitation expected for the east Central Sierra, but there will be an uptick in breeze Sunday with some high clouds possible into Monday. Otherwise…It is October weather at its finest for the Eastern Sierra. As a note…Fall color is coming on strong now and for those that are interested in taking advantage of the change….plan your trips to the high country now!

Winter Outlook:

I will have an update on what the Dweebs are looking for the Winter of 2017/2018 later next week!

Dr Howard and the Dweebs……….