Thursday, February 14, 2019

There's a Giant Atmospheric River Storm Pummeling California...So of course I'm Headed to Death Valley to Experience it...


So we here in California are experiencing one of those very intense atmospheric river storms generated when a highly active jet stream dips far to the south and starts to draw up very moist tropical air from the Pacific Ocean. The storms pound the state like a fire hose, dipping to the north and then to the south, and back again. In once sense, such storms are a godsend because they provide the bulk of our water resources.
On the other hand, the timing is...great. We can't reschedule our president's holiday weekend field studies class, so we are headed out to experience the storm firsthand, out in the elements, facing down our fears and all that other character-building stuff. We are headed to Death Valley National Park. Our best hopes lie with the Sierra Nevada's rain-shadow effect on the nation's driest valley.
It's not the first time this has happened of course. In thirty years of field studies trips we've encountered fierce storms a number of times, and it's always...memorable. Such trips give us the best memories and the best stories to tell our children and grandchildren. And all kidding aside, it's awesome to see intense weather events take place in the desert environment.

So it's probably radio silence for the next few days unless you want to follow our travels on Twitter (@geotripper). If I get a phone signal, I will try to post a few pictures. In the meantime, stay dry!

Monday, February 11, 2019

It Was That Kind of Day: Half Dome from the Central Valley



Update: I've added an extra image at the end that shows the satellite imagery in the view from Keyes Road. 

It doesn't happen often. I usually pass the right intersection once or maybe twice a week, but the most important factor is the air quality. It's almost always poor. Dust and smoke in the summer, fog and clouds in winter. There is a spot on the floor of the Great Valley (some call it merely the Central Valley) where one can see Half Dome and the other peaks around Yosemite Valley in the Sierra Nevada.
Today was one of those days. I was going to take my customary walk on the Tuolumne River, but I could see that the air was extraordinarily clear, so I headed south to the intersection of Keyes Road and S. Hickman Road. I wasn't disappointed. I could be wrong, but I think these are the clearest views I've ever caught with a camera.
The visibility of Half Dome from the valley floor has been kind of a contentious subject. There are plenty of people who think that it isn't possible, and there are some peaks that are mistaken for Half Dome off to the north. I was actually accused of photoshopping the pictures once, which if you know me is laughable (I don't do that kind of thing very well). The trick to seeing it is to know where to look (NNE from the Keyes/Hickman Road intersection), and to realize that while Half Dome is so prominent from the floor of Yosemite Valley, it is not even 9,000 feet above sea level. The peaks behind and around Half Dome are 12,000 to 13,000 feet high. Half Dome is most definitely not on the skyline. It's in the middle foreground.
The other thing to realize is that my pictures are highly zoomed images. The image below approximates what the scene looks like from just north of the intersection. Can you pick out Half Dome in the picture below? And if you know your Sierra Nevada geography, can you name the other peaks that are visible? See how you did below!

Here, courtesy of CalTopo.com is a guide to the peaks in the picture above.

POSTSCRIPT: Thank you for all the comments. Since there is still some controversy about whether this is Half Dome, it turns out that CalTopo also offers an image overlay on the viewfinder, so I have added it below. For those who feel the mountains in back are not "tall" enough, one needs to consider the curvature of the Earth over the 40-50 mile distance of the highest peaks in the view.


Sunday, February 10, 2019

It's a River Again! Winter on the Tuolumne


All the pictures in this post are from the Tuolumne River Parkway Trail in Waterford.

All in all, it's been a good year (so far). One can judge the quality of a year on the basis of many things, and in this instance I'm talking about water. So much of the time, my part of California is at an extreme in one direction or another. Last year it was a drought up until some late storms in March that salvaged the water year. The year previous was one of floods and threatened floods, unlike anything seen in twenty years, but at least it filled the state's reservoirs after an astounding five-year drought. This year finds us in the sweet spot, kind of in-between, but a bit above average.

The rainy season started a bit slowly, just enough to make one worry a little bit about drought. No storms in September. A single small storm in October. But then in late November the pace picked up with just over 3 inches in my rain gauge, and December added more than 2 inches. The same with January, nearly 3 inches, and now February has already produced 2.5 inches with more storms coming this week. Of course my backyard is not the measure of water conditions in the state. The news reports are full of stories on the incredible snowpack that has built up in the Sierra Nevada in the last few weeks, with single storms producing six feet of snow or more.

The critical Sierra Nevada snowpack sits at between 109% and 135% of normal (measuring from north to south), with a statewide average of 123%. If no more snow fell, our season would end at 84% of normal. It's a comfortable place to be.

But no water planner is ever comfortable. With so much snow in the mountains, the reservoir water masters always have to worry about the possibility of a big atmospheric river storm, the kind that combines the extreme low pressure of an Arctic storm with a stream of extremely humid air out of the tropics. Like the one that could happen this week. In a worst case scenario, such a storm could cause rain at high elevations, melting much of the snowpack and raising the specter of flooding downstream.

And that is why the Tuolumne River came alive this week. For many months, the river has remained at an unnaturally low flow of about 200 cubic feet per second, a minimal amount. There are large reservoirs upstream, especially Hetch Hetchy and Don Pedro, and the operative mode is to save as much water as possible. During the recent storms, inflow to Don Pedro reached as high as 8,000 cubic feet per second, but outflow remained at 200 cfs.

Last week the river was dramatically higher, flowing at 2,000 cubic feet per second. The water masters are clearing out some storage space in Don Pedro in case of a flood emergency. It looks like they intend to go as high as 3,500 cfs in the next few days. Certainly not a flood (it would have to reach 9,000 cubic feet per second for that), but enough to clear the channel of invasive water hyacinth, and enough to make one feel the river is closer to a natural seasonal condition.

It's a nice time of year to walk the Tuolumne.