The confidence in weather forecasts is not always the same.
Sometimes all the models lock onto a forecast, suggesting uncertainty is low and meteorologists can have confidence in their predictions.
But in other situations, uncertainty is large, with large differences among the forecast guidance.
The wind forecast for tomorrow over central Puget Sound is a good example of such an uncertain forecast.
One of the key tools of meteorologists for exploring uncertainty is viewing the forecasts from many weather model simulations, something called an ensemble.
Below is the ensemble of forecasts for wind gusts in Seattle for forecasts starting early Friday.
The predictions for Saturday are all over the place!
The key issue producing uncertainty is the path and intensity of a weak low-pressure center approaching the region.
The updated American model solution on Friday evening has a low approach coast and then passes across northern Puget Sound (see below for forecast at 5 AM Saturday.
I suspect very few will lose power tomorrow. However, the approaching low will dump ever more rain over the region on Saturday morning. Showers will greatly decline on Sunday and Monday, and Tuesday should be mainly dry.
Talking of rain, today's moist southwesterly flow produced profound contrasts for precipitation across the Olympics (below). For the period from midnight through 8 PM Friday, there were 2-3 inches on the southwest side of the barrier and only .01 in Port Townsend. That is quite a rain shadow.
Note that the largest rainfall totals are not at the high elevations but in the lower foothills of the mountains, where the moist air was initially forced to rise.
Interesting stuff. The most interesting part of the NWS forecast is the Forecast Discussion in which meteorologists talk about the models and what they're seeing and what it means. The technical stuff goes over my head, but I come away with a pretty good idea of what to expect within a given window of time as well as watching the forecast 'evolve' as models come into alignment. If you accept that this is a less than perfect science, forecasting, even a week or so out is pretty accurate and usable for us outdoor enthusiasts.
ReplyDeleteIt's already quite simplified but you could always use ChatGPT to simplify it more. If you want to read a really technical discussion that is really meant for the experts, check out the Joint Typhoon Warning Center under the section "Prognostic Reasoning". I clicked on it before and had a good laugh because it was basically another language to me. Talk about confusing, it's really only for meteorologists.
DeleteThis article reminds me of John Coleman's old Chicago forecasts of A, B, and C confidence.
ReplyDeleteThat concept could be worth dusting off and putting to use again to properly convey forecast uncertainty to the general public in an understandable way.
DeleteInteresting! I've been watching the radar and also the full-disk satellite images as this thing as played-out. Nature does take its own course, huh? Gotta love it - so, so complex.
ReplyDeleteThanks for the clear breakdown!
ReplyDeleteTrying to sneak through from Port Townsend to Sandpoint ID next weekend (ish) via Snoqualamie Pass. Was thinking of leaving very early on Saturday the 6th. With the waves you see coming, does this seem logical, or is there a better window? Not skilled driving on icy roads. Thank you!!
ReplyDelete