The climate prediction enterprise is a humbling one.
Sure, forecasting techniques have gotten much better, however often they disappoint, significantly for tough conditions like this morning’s snow occasion.
The mannequin runs on Friday indicated that Puget Sound nation was on the sting for sn ow, each by way of temperature and precipitation.
Beneath is the precipitation forecast (quantity of liquid water predicted for the 24h ending 4 AM today–Saturday. No precipitation over Seattle’s japanese suburbs and round 0.15 inches over the western facet of northwest Seattle.
With the everyday ratio of 10 to 1 for snow to rain quantities, NW Seattle ought to have had solely had about 1.5 inches at most. Substantial parts of north Seattle had 4 inches. For moist snow, the ratio is even lower–so there was clearly a considerable underestimate of precipitation.
Listed here are the noticed quantities for a similar interval. Ouch.
Rather more precipitation than predicted over Seattle and the japanese suburbs
The fashions had predicted a pointy japanese fringe of the rainfall (over Seattle), however as proven by the radar final evening round midnight, a broad space of precipitation prolonged over the area.
What made this case significantly disturbing, was that our main device for recognizing climate prediction outliers…..ensemble prediction operating the mannequin many instances, every barely differently–did not successfully decide up on this moist answer.
The determine beneath reveals the expected precipitation at SeaTac for the various ensemle members (the assorted strains) and precise precipitation is proven by the purple circles. Solely considered one of two dozen ensembles obtained it proper. The common of all of the ensembles, the ensemble imply, proven in black, predicted lower than half of the noticed precipitation.
It is a fairly massive and weird failure for such a brief forecast. In any case, one can study from failures and I will probably be examing this one fastidiously.
Lastly, an enchanting facet of this occasion was the intense variability of the snow, pushed by temperature variations with top.
Areas in Seattle close to sea stage had solely a light-weight dusting, whereas just some miles away there was 4-5 inches of heavy, moist snow.
Sobered by this failure I drove round Seattle this morning. Close to sea stage on Sand Level Method (NE ninetieth), there was nothing.
However as a drove to Lake Metropolis , just a few hundred ft above SL, it was all white with just a few inches of slush. By Aurora avenue, round 4 inches.
Sunday’s Snow Occasion
Clouds and precipitation are beginning to swing northward across the low-pressure space off of California (see newest infrared satellite tv for pc picture).
The most recent mannequin runs brings some gentle snow into Oregon and southern Washington tomorrow, as illustrated by the entire predicted snow accumulation by means of 1 AM Monday.
I’m beginning to get uninterested in these marginal snow conditions……
