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…