Figuring out the short term patterns and the day-to-day weather can be a real challenge, but forecasts are getting better all the time.
Day-to-day weather changes eventually becomes a pattern, and often in California, we end up being very dry or very wet. California is a true boom-or-bust state, with most wet seasons drifting into either column. Take most of the last decade for example: the 2010-11 season was very wet and cold, resulting in record snow and lots of rain. The Sierra was loaded with snow, and the reservoirs were full. Everybody was happy and nobody was talking about a drought.
Then, the next year was dry, and the next year and so on. Four years later, most of the state was in top level drought, with no end in sight. The 2015-16 season was mixed with lots of rain for far Northern California and still dry for Southern California, which equaled another year of drought.
The 2016-17 season was full of statewide storms and flooding issues were common, along with washed out roads and bridges.
California has truly seen extreme years lately. and now many researchers want to know why.
Much of the emphasis in the last few decades has been on the influence of El Nino and La Nina. Every so often, the central Pacific will be warmer or colder than normal and they have seen wet and dry trends.
It doesn't link up all the time, but there is at least some connection. This year, we have a classic La Nina underway and can more or less indicate at least one reason why the Southwest has been dry, and the Pacific Northwest has been wet.
There is one new emphasis of research that deserves much more attention. Since the late 1970s, we have been monitoring floating sea ice at the poles. We have also noticed a rapid decline in sea ice coverage, with a few exceptions. Now in tandem, the North and South Poles have seen a massive shift to declining ice coverage and age of sea ice. The more surface covered by ocean, the more ice will melt in a cascading phenomena called positive feedback. Think of a snowball rolling downhill...it only gets bigger.
This year we have seen the lowest sea ice on record in the Arctic and second lowest for the Antarctic.
Scientists at the Lawrence Livermore National Laboratory are looking into the connection of Arctic Sea Ice loss and more extreme patterns. They are finding, at least initially, that there may be a connection with more ridges blocking storms from entering California along with levels of lower sea ice. Other research indicates that if the poles are warmer, there is less of a heat transfer from the equator and the jet stream may be more likely to get stuck as it slows down, meaning more wet and dry patterns emerge.
This is all very early, but it adds one more area of the planet to look for changes that could explain our extreme patterns lately.