Precipitation: Subtle and Uncertain

fogWeather shapes our lives. We celebrate when the weather is good although that might mean mild and sunny for the soccer game or a rainy day when we desperately need it. We watch the Weather Channel forecast and the satellite image for what?s headed our way. Our climate is changing but it?s the seasonal weather that gets out attention.

Seems like we?ve had quite a few heat waves so far this year and it?s only mid-summer. Recently the temps soared to the high 90?s and low 100?s in some places and remained high even at night. The next day brought fog so thick it dripped from the trees. I could almost hear the trees absorbing the moisture. We know that redwoods thrive along the coast because of the fog. Have you ever wondered how much water a tree can get from this source?

Fog drip is precipitation that forms when fog droplets condense on the needles or leaves of trees. Redwoods especially are extremely efficient producers of fog drip but other conifers like Douglas fir and pines can collect quite a bit as do large madrone leaves. According to Dr. Todd Dawson, author of ?Redwood? by the National Park Service, ?A relatively small 100 foot tall redwood can gather the equivalent of four inches of rain in a single evening.?

Dawson?s studies have found that Doug firs along our coast produced anywhere from 7-27 inches of fog drip each year. He measured the fog drip below a single tanoak at a whopping 59 inches of precipitation along the Northern California coast. This summer moisture can provide as much as half the water coming into a forest for over a year. Trees can absorb a small amount of water through their needles and leaves, too. Every little bit helps in our summer dry climate.

Because of the water that accumulates below the trees many plants like our native Western Sword fern, the small Epipactis orchid and Phantom orchid are found in these unique conditions.

Fog drip occurs every summer. Ask Mark Twain said or whoever really penned the saying, ?The coldest winter I ever saw was the summer I spent in San Francisco?.

But what about this upcoming winter?s rainfall forecast? What?s the latest on our chances of El Nino coming to visit and bringing some nice soaking rainfall with it?

According to the National Weather Service at NOAA our hopes are dimming but not altogether gone that the drought will be eased with this winter?s rain. What started out as much warmer than normal Pacific Ocean temperatures last May indicating a strong El Nino effect has not changed much since. The Weather Service Center is still predicting that sea surface temperatures will be warmer than usual – the phenomenon known as El Nino-but the effect will be only ?weak to moderate?.

That?s because the Pacific Ocean temperatures near the International Date Line have not continued to rise since earlier this year when they were well about average. While strong El Nino weather patterns usually create more rain for California, weaker El Nino?s typically don?t bring more rains to the region.

The Center said that there is now a 70% chance El Nino will develop by the end of the summer and an 80% chance that one will develop by the early winter. Unfortunately, Northern California isn?t likely to get a bump with a moderate event but Southern California just may benefit anyway.

Hopefully, we?ll be on the winning side of these forecasts. Water conservation will always be a part of our lives. Start planning now the changes you want to make in your garden this fall.

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