So what’s up with our weather?
This Winter, and several Past Winters, we have been in a Drought situation for all of SoCal. Rainfall, and Snowfall, (where appropriate) has been dismal to say the least. I am asked frequently, when will we get Rain/Snow, and what has happened to our Winters? Well, this is what is going on.
The last several Seasons, Spring, Summer, Fall and now Winter have all been from 5-15* above average in temperatures for the region West of the Rockies to the Pacific Ocean. In fact, the current record setting warm temperatures we are having may be of the warmest ever recorded. Not only has this last four years been warmer than normal, we have also been in a severe Drought for most of that same time frame. Last year as we all remember, one of the strongest El Nino conditions were seen in ENSO Region 3.4 (This is the area that most affects the West Coast Winter). However, SoCal was wetter than the previous years, but was not a Drought buster like we had expected. To the North in Northern California, and Oregon, they did have a “Drought Buster” Winter, however, as it now appears, that will be short lived. The Sierras, are again in poor shape as far as snow/water content this Winter, due to the lack of cold, and or wet systems. Of course, SoCal, has yet to have a normal Winter rainy season in years. Locally, we have been in a snow drought since the early 90’s. The NWS posted that in Los Angeles, the biggest rainfall amount since February 18 of 2017, was .33″. Pretty meager.
So what is the reason for all of this? The exact cause as to why the stationary blocking Ridge of High pressure sets up in the Western Pacific for weeks at a time is the subject of much research. For unknown reasons, this Ridge has set up to our West during what should be our Winter over the past few years forcing the Jet Stream, or Storm Track, North, and East, of California. This is when we would normally get the bulk of our rain/snow in SoCal. Yet we sit under a dome of High pressure. SoCal usually gets most of it’s rain from December through March. Currently, SoCal is in a severe Drought and looks like this will continue through the current rainfall year. Northern California did get a break last year from the Drought, but now is also having above normal temperatures that are contributing to snow melt below the 7500-8000′ level. As well as below normal rain/snowfall for this time of year.
The effects of the current Drought are having far reaching effects across the State besides the obvious water shortages. The Forests are seeing high Tree mortality rates due to Bark Beetle infestations on weak, and drought stricken trees locally, as can be seen around Lake Gregory as well as other local mountain communities. At the lower elevations, grass is beginning to grow, however, this is not a sign that we have had sufficient rainfall, it just shows that we are warmer than normal causing the low level light fuels to grow. I noticed that some areas have Daffodils beginning to sprout. Again a sign of warmer that normal temperatures.
During the late Summer, the El Nino, La Nina, or Winter, long range forecast is published. This years Forecast was for a La Nina to be the influential trend. So far, this has been correct. But with one additional feature, a blocking West Coast Ridge. Below are some examples of how the blocking ridge of high pressure affects the jet stream flow.