BIG STORM POSSIBLE FOR NORTH BAY ON MONDAY
THE BIG PICTURE
The various forecast models are struggling to make sense of our fall weather pattern, with wild swings from one day to the next. But the most trustworthy medium range forecast models are starting to look significantly wetter for next week.
If the current trends hold, this could bring the North Bay its first soaking rainstorm of the season.
Here’s the latest, as of Wednesday the 8th.
The European, Euro AI, Canadian and GFS models are all showing low pressure digging south over California from Friday the 11th into the middle of next week, at least. This will bring a lot of cool air to California, along with chances for rain.
How much rain arrives depends on the intensity of low pressure, how far south it tracks, and what route it takes to reach us. If its track is over the ocean, we get more rain. Over land, less rain.
CLUSTERING
The ensemble forecast models test out lots of different variables that could impact our future weather. These are reflected in the different ensemble “members.” Forecasters look for trends, or clusters in the models where all the various forecast runs are coming together on a similar solution.
So, what are they saying?
Here is a look at the forecast runs from the European model as of Wednesday, showing rainfall from the likely storm next Monday and Tuesday. Dark red is the heaviest rainfall outlook. Do you see any similarities, or clustering?
What’s pretty obvious is that around three quarters of the “members” agree on a storm arriving and digging pretty far south next Monday and Tuesday. That’s called clustering, and that gives forecasters more confidence in the overall outlook.
And that is reflected in the current deterministic model forecasts.
RAINFALL OUTLOOK
Although the Friday-Saturday storm is now expected to bring only showers (this could change), the 2nd one due to arrive on Monday the 13th and last through Tuesday the 14th is trending wetter in the European, Euro AI, and other models.
First the European outlook for rain through next Wednesday.
Then the European ensemble, taking lots of model runs into account.
Both of them now have much of the North Bay receiving an inch or more of rain.
The Canadian model (below) is especially wet, which is almost certainly overdoing rainfall. Meantime the GFS is drier, which is also an outlier. It should be noted that the GFS often plays catch up with the other major models.
CONCLUSION
With so many variables at work, rainfall estimates are sure to change over the next 5 or 6 days, but you can see where the current thinking is going.
And the models agree that low pressure systems passing over the state will bring lots of cool air to California through mid-October.
So, confidence is growing for a significant storm for next Monday the 13th, and for cool weather ahead. We could certainly use the rain, so we’ll keep watching trends for the North Bay and keep you updated.
Author: newsofthenorthbay
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