Rainy Day… Again?!?
Wednesday, June 1st, 2011
It’s June 1 and I got thoroughly soaked on my bike ride into work today. By now in the San Francisco bay area, we’re usually into a spring pattern of mild, sunny days that have school kids and working adults thinking about playing hooky and heading for the beach. But for the last three months we’ve had what seems like relentless cold, rainy weather–more dead winter than a mere 20 days till official summer.
I gave our local National Weather Service meteorologist, Tom Evans, a call to ask him what’s up with the weather (all the while controlling the irrational desire to blame him for my miserable bike ride this morning). He confirmed that our weather, indeed, has been unusual with higher than normal rainfall, especially for a La Nina year. “We’ve been getting a lot of weather systems from the Northwest, picking up moisture from the tropics that’s giving us heavier rain periods than we usually see.”
Let’s back up a second and talk about La Nina which I have some familiarity with from a webcast project I did years ago. Perhaps less well-know than it’s opposite twin El Nino, La Nina refers to cooler than normal water temperatures in the equatorial Pacific Ocean off the coast of South America. This cooler water disrupts normal climate patterns, with warmer, drier weather than normal in the Southwest and cooler, wetter weather in the Northwest. In the bay area, climate patterns could go either way, but usually tends to the warmer, drier side. But not this year. Tom did a little study and found only three La Nina winters in the last 50 that have been significantly wetter than normal in the bay area: 1955-56, 1973-74 and 2010-11. This year has been a real doozy. Our rainfall has continued into May (and now June) with an accumulated total in San Francisco of over 30 inches or 175% of normal. We’ve had mountain snowfall at nearly twice the normal accumulation and it kept snowing in the Sierras, even into May when the annual Amgen Tour of California bike race had to cancel its first stage in Lake Tahoe because it *snowed* nearly a foot that day.
According to Tom and NOAA’s National Centers for Environmental Prediction (NCEP) office, we are transitioning away from La Nina to a neutral ocean condition so maybe there’s a glimmer of hope that we’ll have some kind of spring… but not right away. On the NCEP website comes this ominous statement: “Atmospheric circulation anomalies associated with La Nina remain significant.” In plain English, Tom Evans says there’s nothing in the current condition of the atmosphere that will force a change in the jet stream. That means additional cool, rainy weather will be moving in as if on a conveyer belt over the next several days with another strong storm predicted for Friday. “The good news is that the Climate Prediction Center is telling us we should have a normal summer this year, but we have to get into a summer pattern first… it might be awhile yet.”







indicating to consumers that the fishery maintains a healthy population, doesn’t damage the environment, and is effectively managed. That appears to be the case for this Norwegian operation, which claims it only harvests 1% of the Antarctic krill population each year, but environmentalists are disgruntled with the Marine Stewardship Council in general for relying on consultants paid by the fisheries without taking into enough consideration the work of independent scientists and the growing realization that most of the world’s marine fisheries are not sustainable and indeed that most commercial stocks are on the 
That’s bad news for the tourists shivering in their shorts at Fishermans Wharf, but great news for a bicycle commuter like me who rides to the southeast end of the city to catch her train home. The 20 mph afternoon sea breeze that pushes me to my destination is a familiar weather pattern for most ocean communities, especially in summer. This pattern is caused when temperatures in the inland valleys warm up in the sun, causing air to rise and expand, creating a low-pressure region. Meanwhile, air over the cool ocean sinks and compresses, creating a relatively high-pressure region. Air flows from high to low pressure, creating what cyclists and tourists experience as wind. The greater the pressure difference, the stronger the wind.



