Thursday, November 06, 2008

Nor Cal Winter Weather Prediction

Sunday, November 2, 2008 (SF Chronicle) Lore says it'll pour - early, that is Tom Stienstra, Chronicle Outdoors Writer (11-01) 18:46 PDT -- There's a saying in nature, "Birds never lie." There's another that goes: Onion skins very thin, mild winter coming in; Onion skins thick and tough, coming winter cold and rough." And those fuzzy caterpillars: I've seen a half dozen with thick, full coats in the past two weeks on mountain trails in Northern California. There's more: A phenomenon in the ocean has formed called the Madden-Julian Oscillation. There's also a linked interface between ocean temperatures and coastal land temperatures in Humboldt County that can predict weather. And to time the arrival of storms, pay close attention to moon cycles. I've received a lot of requests for my annual long-range weather forecast/guess for winter, and this is it: Nature's signs mean a wet late fall and early winter, with significant storms arriving around the new moon of late November (Thanksgiving Day), and just prior to the full moon in early December (Dec. 8-10 looks promising). After a dry period in the early New Year, January and February will bring about average precipitation. I don't expect a terribly wet spring in March and April. The final result for winter will be about average rainfall, wetter in the beginning, a bit drier at the end, This is why: -- Birds never lie: The annual migration of sandhill cranes to the Woodbridge Ecological Reserve near Lodi and snow geese to Sacramento Wildlife Refuge near Willows is right on schedule. The timing of these migrations is often a reliable weather predictor. -- Onion skins: The thickness of skins from onions grown in the San Joaquin Valley looks pretty average. -- Caterpillars: Those furry coats indicate early, heavy precipitation is on the way. -- Ocean/land temperatures: A reliable theory I've developed is that when ocean temps and coast land temps are the same, the storms wheel right in. That's the case right now in Humboldt County, so look for wet weather. When the ocean is colder and the land is warmer, it often acts like a blockade and pushes the storms into Oregon, which creates periods of drought, like this past spring. In the mountains, the effect of global climate change probably will have snow lines higher than normal for many storms - about 4,000 feet elevation in the north state and about 4,500 feet in the Sierra Nevada. There is one piece of real science that supports this forecast: Weather experts have identified the formation of the Madden-Julian Oscillation offshore in the Pacific, which typically lasts about 50 days. This forms very wet storms propelled to the Pacific Coast. So wherever the jet stream delivers the storm highway this late fall and early winter, those storms could be very wet. Last year's forecast, published on Oct. 28, hit the bulls-eye: "The Bay Area and Northern California will get a lot of rain through December and early January, then lighten considerably, with an early, warm spring, especially in the San Joaquin Valley. Southern California will face continuing drought."

No comments: