Weather Oops

Two weeks back, went way out on a limb, thrill seeker that I am, and predicted the end of the 2017-2018 rainy season here in Bay Area. It rarely rains much after March, was the impeccable logic used.

Oops.

Current radar rain map as of 9:00 a.m. Thursday. 

The system moving our way:

A ‘Pineapple Express’ situation: tropical moisture from around Hawaii heading straight at us, getting sucked up into a swirly Gulf of Alaska storm hitting British Columbia, Washington and Oregon. 

Current prediction is for an inch or more of rain in the lowlands, 2 to 4 inches in the mountains and hills by Saturday morning. Rain at the Casa de Moore supposed to start tonight. The odd part: as of now (these things change) the storm is moving north east in such a way as to miss Southern California entirely.

Should rake across the Sierra pretty solidly from north to south. Since (as of now) that norther colder storm isn’t supposed to push very far south, the snow level will be very high, like 7,000 or even 8,000 feet in most of the Sierra. The ski resorts will be happy for the most part, but this won’t help the snowpack any lower down. Unless the cold air pushes down south, which it sometimes does. More rain is predicted for next week as well, but with the high level of uncertainty that accompanies forecasts more than 3 days out.

So, um, yea, looks like April will be a bit rainier than average this year.

My original estimate was that we’d come in with something like 75% of average rainfall for the year here in Contra Costa County. We’re sitting at 73.5% right now, based on a weighted average across the 30 rain gauges of the local flood control district. An inch or two more rain will bring that up past 80%, which is only panic zone if your panic threshold is very low. Snowpack affect too early to call.

For those new to my local weather obsession, I got into this because 1) California’s state hobby seems to be panicking over droughts, which seem to be defined, roughly, as any water situation that’s not as good as the better situations we’ve seen over the last 30 or 40 years; 2) there’s a bunch of good current data available (I really do need to send that fan letter to the Contra Costa Flood Control District, which throw tons of great stuff up on the Web for free – brings a tear to me eye!); 3) it is apparently required by law for bureaucrats and media-critters to mention climate change no matter what happens, good, bad or average.

It is in my self-appointed role as Science! monitor that I aggregate these things and point out the odd fact, such as that the really good data really only goes back 30-40 years. Before that, we had somebody manually spot-checking snow depth or rain gauges or thermometers in a very few locations across a huge, very geologically diverse state – and even that only goes back maybe 150, 175 years. Everything else we think we know are reconstructions based on assumptions – nothing wrong with that, per se, as long as we remember such reconstructions are really not a lot better than educated but still rough guesses. We must factor in a high level of uncertainty.

Think of this weather thing as a case study in how an amatuer can think his way through the scientific evidence.