This posting contains some of the same information as my previous one about the snow drought in the West. I wanted to keep this story alive through the weekend on AccuWeather.com while also adding some new information.
I have been asked if I thought La Nina was fading and that this would mean a change, even a drastic change, in the weather pattern for the West. So I want to take a brief bit of time to answer that. No, I do not see La Nina weakening. There is nothing in the new data that is showing this. From the weekly update from the Climate Prediction Center I will show you two graphics.
The first is the upper ocean heat anomalies.
The negative anomalies continue and are as strong right now as they were back in October.
Second, here is model predictions of ENSO. The vast majority of the models, including the ensemble means, show very little weakening into early Spring then a gradual trend to neutral conditions toward late Spring and Summer.
So the overall La Nina continues and will remain about where is at into the Spring.
Does this mean it will remain as bone dry as it has been for the past 5-7 weeks? Of course not. There are bound to be storms that bring some precipitation even into places like California, Arizona and Utah. But I think what it does mean is that there is a low chance of precipitation in that region being above normal and an extremely low chance of the season ending up even close to normal. We have just dug too deep of a hole. Strange things can happen. Take for instance last year when a similar La Nina season brought over 200% of normal precipitation to the Sierra. But lets face it, the odds are not in our favor.
FROM EARLIER IN THE WEEK:
My last blog of 2011 showed how warm and dry much of the West was in December. The calendar may have been changed, but the weather pattern certainly hasn't. If the long-range models are right, we may see no appreciable change over the next two weeks.
Let's look at some interesting graphics. The first two are actual snow depth as of Jan. 4. The first graphic is the current map for 2012.
The second graphic is from one year ago today.
The difference is striking especially from Oregon south through California and east to Nevada and Utah.
The next two graphics show the departure from normal of the snow depth. The first again is from today.
The second map is what the departure from normal was from last year on the same date.
Again what a change. All the orange and deep reds on this year's map, which are far below normal snow depth, is in sharp contrast to the deep blues of last year that depicted much higher-than-normal depth.
The weather pattern we have seen for over the last month really does not change noticeably over the next couple of weeks. In general, a ridge will continue to dominate the West with a storm track very far north.
Graphics again are the best way to depict what may be coming over the next two weeks. The first graphic shows total precipitation that falls from this morning, Wednesday, Jan. 4, through Thursday morning Jan. 12.
First, notice that there is basically no rain expected during this eight-day period for California, Nevada, Arizona and for the most part Utah as well. The precipitation in the Northwest is not overly impressive and in actuality that most of that precipitation comes over the next two days with very little falling after that.
The next graphic is total precipitation from Thursday morning, Jan. 12, through Tuesday morning, Jan. 17.
Wow, most all of the West has no precipitation during this long stretch.
I will remind you that there can be errors, and sometime huge errors, in computer models that go out this far. However, given that pattern we have been in for the last five to six weeks, it is certainly conceivable.
According to just released snowpack study of the Sierra, the snowpack is only 19 percent of normal for the date and 7 percent of April 1 normal. Right now, officials are not overly concerned about these exceptionally low numbers. Quoting DWR Director Mark Cowin, he says, "fortunately, we have more of winter ahead of us, and our reservoir storage is good." I think the second part of his statement may be more valid than the first. I see no reason why there is much to be optimistic about seeing a major recovery in the snow deficit the rest of the winter as we remain in a La Nina that has been quite dominant. However, I will say that he has a point about the reservoirs. After last year's huge increases in the reservoirs, one year of drought may not bring massive changes in water allocations. I say MAY NOT because this seems tied to politics as much as reality. We will see how his statement holds as we go longer into the rest of this winter and coming spring.
The big impact in the short term is on the ski industry. The lack of nature's snowfall has to be having an effect on the turn out on the slopes. Even though resorts have been able to make snow (that costs lots of money), people that live in the lowlands that visit the resorts are just not as motivated to ski or board when they look up into the mountains and see a lack of snowfall except on the slopes. Of course, this snow drought not only affects the ski resorts but also the resort towns who rely on people to flock to the mountains for their livelihood.
The importance of this story will mean I will leave this posted for at least an extra day, so more people can read it. This is the number one weather story in the West so far this season. And it very well may be the weather story of the entire winter.
A rather extended period of unsettled weather will be occurring over parts of California and the Southwest
The remainder of the week a large building ridge of high pressure takes over
There will be more showers and thunderstorms are likely that can produce very heavy downpours in Arizona.
This rain caused problems with flash flooding producing some damage and there were a few swift water rescues.
Computer models are insistent that a rather strong piece of energy will move through California Tuesday, bringing more widespread rainfall.