That’s the National Weather Service radar map for the Bay Area right now. That area of yellow and orange is heavy rain, and its moving pretty much straight east from the Pacific.
Temperature Inversion
You know the old rule: Temperature declines as you gain elevation. Here’s an adjunct to that: Except when it doesn’t. It’s fairly common in the San Francisco Bay Area to have cool marine air trapped under a layer of much warmer air. It can be a startling experience to start a walk in the cool damp air in our flatlands neighborhood and cross suddenly–in the matter of just a few feet–into very warm, much drier air.
There’s a beautiful case in point this morning. The lower elevations around the Bay are cocooned in a blanket of cool, moist air. Here in Berkeley, one station has the temperature as 58 degrees Fahrenheit and 91 percent relative humidity. That’s at an elevation of 361 feet–probably up on campus. At the 1,300-foot level in the hills, less than five miles away as the crow flies, it’s 78 F. with 29 percent humidity. Further afield, atop Mount Diablo (about 20 miles to the east; elevation 3,849), it’s 82 F. and 8 percent while at the base of the mountain (in Clayton, 518 feet) it’s 67 F. and 44 percent.
Potrero Avenue: PM Clouds
The other end of the day. Looking south on Potrero from Mariposa. Another warm evening, one that prompted me to run up to the top of Potrero Hill after I left work to watch the city and the sky. (And I mean run: I passed a cyclist who was struggling up the upper part of San Bruno Avenue. We said hi to each other, and she said, “You go!”)
Berkeley: AM Clouds
We at Infospigot Information Services are great fans of the evening sky, but we’re not often out and about to report on dawn-time sky conditions. This morning was the exception to that rule. According to the National Weather Service area forecast discussions, there’s some sort of low spinning off the coast and sending in a stream of moisture from the southwest, which takes shape as unusually high, fluffy, and abundant clouds hereabouts (are typical cloud cover in the summer months is a dense bank of low stratus). It’s also a warm, muggy morning, also atypical of our Mediterranean climatic regime.
Lake Night
In the Bay Area this summer, everyone has bemoaned the prolonged presence of the thick marine overcast that keeps the coastal locales cool. And it does seem to have been a little cooler than normal if you’re anywhere along the bayside (inland’s another story). Chicago, too, has had a relatively cool summer; it’s been six weeks or so since the last official 90-degree reading. That will change today — it’s before noon and the temperature is already pushing 90. The weather service has issued heat advisories from Chicago south and severe thunderstorm warnings from Chicago north.
Though it didn’t officially hit 90 yesterday, the day did feature the high humidity that makes Chicago great. It creates a heat that seems to envelop you, then go through you. I spent most of the day in the North Side Brekke place, comfortably air-conditioned. I did take a short midday walk up Western Avenue, though, and then after dinner walked the mile and a half over to the lake. I got there about 10 o’clock, and there were lots of people hanging out on the beach, the one cool spot in the city. Fireworks were going off to the south somewhere; to the northeast, lighting flashed through the clouds. (The shot above was on the shore where Columbia Avenue ends. )
Lake Night
In the Bay Area this summer, everyone has bemoaned the prolonged presence of the thick marine overcast that keeps the coastal locales cool. And it does seem to have been a little cooler than normal if you’re anywhere along the bayside (inland’s another story). Chicago, too, has had a relatively cool summer; it’s been six weeks or so since the last official 90-degree reading. That will change today — it’s before noon and the temperature is already pushing 90. The weather service has issued heat advisories from Chicago south and severe thunderstorm warnings from Chicago north.
Though it didn’t officially hit 90 yesterday, the day did feature the high humidity that makes Chicago great. It creates a heat that seems to envelop you, then go through you. I spent most of the day in the North Side Brekke place, comfortably air-conditioned. I did take a short midday walk up Western Avenue, though, and then after dinner walked the mile and a half over to the lake. I got there about 10 o’clock, and there were lots of people hanging out on the beach, the one cool spot in the city. Fireworks were going off to the south somewhere; to the northeast, lighting flashed through the clouds. (The shot above was on the shore where Columbia Avenue ends. )
Summer Rainbow
I’ve long been a fan of photographic panoramas. Once a long time ago, we went to the farm near Dyersville, Iowa, where “Field of Dreams” was filmed, and I took a series of shots of the baseball field from the farmhouse porch. When I got the pictures back, I spent a while creating a mosaic of the shots, then had them mounted and framed as a present for my dad. I think he’s still got it hanging on his wall. One of the unexpected artifacts in the pictures was a guy who was walking along the right-field and first-base line; he appears in several shots in the “panorama.”
Nowadays, I’m sure there’s some sort of really good software that helps you stitch together digital pictures. Me, I have an application for the Mac called DoubleTake that does an OK job. One of the first things you realize when using it, though, is that it can’t really give you a seamless rendering of more than two shots. Not that I mind–I’m not a pro and I’m taking pictures with a pocket-sized camera.
But every once in a while, I wish I had the equipment, the knowledge, and the other wherewithal that would knit together with my enthusiasm for wide-angle scenes. Case in point: This evening just before sunset, we got an exceedingly rare July rainfall. The sun was below the edge of the clouds, and as soon as the rain started falling–very lightly–I knew we’d see a rainbow. And in a few minutes, there it was: a full arch and a full “double” image. The colors on the descending legs were so bright they appeared fluorescent. I ran in the house and got the beat-up Casio and shot away. I shot away knowing that I wouldn’t capture the real brilliance of the light and that I’d need three shots, minimum, to get the full expanse of the rainbow.
So that’s where that image up there comes from (click for a larger image–the full size is 2400×900-some pixels). To make the rainbow look continuous, I compromised on the bottom edge of the pictures, where you can see some strange things happening with trees and houses.
On to the next experiment. (And if you want to check out a panoramic picture system, take a look at this.)
Evaporation
When you read California’s daily water-storage reports and pore over the columns of data–for instance, from Lake Shasta, the state’s largest reservoir–you happen across this one: EVAP. It’s a record of how much water escapes the lake by changing state from liquid to gas. We’re schooled very early on in our science education about the hydrologic cycle. You know, the process by which water evaporates from oceans, lakes, rivers, and your scotch on the rocks, is transported into the atmosphere to fall as rain or snow, and then is evaporated and carried into the sky once more. Still, it’s one thing to know that a theoretical process is operating out there in the world somewhere and another to see its monumental workings in a statistical read-out.
Go back to Lake Shasta. I’ve been to the dam that holds it back, and I’ve driven past it dozens of times. It sprawls in an endless series of bays and inlets — old river courses — among the mountains that wall off the northern end of the Central Valley. The lake is usually ringed by a collar of brilliant orange-red soil, the upper margin of which marks the reservoir’s high-water mark. That ring is a sort of drought gauge: the more of it you see, the lower the lake is and, generally, the drier the state is.
One thing I don’t think when I drive past Shasta is that I’m watching a massive machine pumping millions of gallons of water into the sky. But that’s what it is. According to the summary from the Department of Water Resources California Data Exchange Center, yesterday the lake lost about 316 cubic feet of water per second through evaporation. Here’s what that is in household terms:
–A cubic foot of water is 7.48 gallons, so the lake was leaking 2,363.68 gallons into the atmosphere every second; three seconds’ worth at that rate would be more water than we’ve ever used in our Berkeley household in an entire month.
–Every minute, 141,820.8 gallons evaporated. In rough terms, the evaporation rate was 1 acre-foot every two minutes and 15 seconds. That’s a generous annual supply of water for two water-guzzling U.S. household.
–Every hour, 8,509,248 gallons of water — about 26.1 acre-feet — departed the lake. That’s enough to submerge a football field to a depth of 20 feet.
–For the day (and the evaporation rate is a 24-hour average), the lake lost 204,221,952 gallons, or 627 acre-feet. That’s a minor part of the reservoir’s net change for the day–the overall level fell by 7,271 acre-feet, mainly through water released for power generation–and it’s a tiny fraction of the lake’s current storage, about 3.15 million acre-feet.
Last stat for now: the process of evaporation is highly dependent on local weather, just like the grade-school lesson on the water cycle would suggest. When it’s warm, more water evaporates as the surface layer of lake water heats up. When it’s cool, the process slows. For the past month, the highest daily evaporation rate was 362 cubic feet per second, in the midst of a spike of very hot weather. The low point was 14 CFS, during a stretch of cool, rainy weather.
Snow Again
Here’s what that Friday morning snow in Mount Shasta looked like. Not sure when it started, but it was over by 10 a.m. By noon, it was turning into a nice day. I spent the afternoon on a ranch north and east of town, and it was dry and warm there.
Snow
Drove up to Mount Shasta last night and didn’t get in until very late. I’m up here to do a radio story on a recent Nature Conservancy land purchase that aims to restore some valuable salmon spawning streams up here. But the news right now, as I look out my window onto Mount Shasta Boulevard, is that there’s a steady and from a lowlander’s perspective pretty heavy snow falling. I don’t think it will last long, but I didn’t really expect to see it. It’s beautiful, and I’m hoping that it won’t get in the way too much of my handling a tape recorder and microphone. Pictures later.