Although forecasting skill is dramatically better than even 20 years ago, sometimes predictions are less skillful.
Such a situation occurred on Friday and Saturday over western Washington.
The National Weather Service forecast on FRIDAY MORNING for the high temperature that day in Seattle was for highs in the upper 70s to low 80s (see below). For Saturday, mid-70s to lower 80s.
What were the actual highs at SeaTac airport? 73 on Friday and 70 on Saturday.
Ouch. Major errors.
The NWS errors reflected problems with the numerical forecast models. Here are the temperature forecasts made Thursday morning from the UW ensemble (many forecasts) prediction system. The solid black line is the average of many forecasts (which is usually very skillful), and the orange dots are the observed temperatures.
The forecasts were excellent on Thursday, but FAR too warm on Friday and Saturday. Other modeling systems had similar errors.
The models did not have sufficient clouds, which are potent sources of cooling, since they reflect the sun's radiation back to space.
Here is the simulated (infrared) satellite image (from the forecast) on Saturday at 2 PM. Just some scattered clouds over western Washington.
Reality? A potent band of relatively thick clouds moving around the offshore low. Not good.
There are also issues of simulating them correctly, with model descriptions of cloud processes (called cloud microphysics) having substantial problems, something I am working on.
Plenty of work for meteorologists over the next few years to address these smaller-scale cloud physics issues. Or we can hope Machine Learning solves it all.😊
It feels that forecasters need to inject some of the randomness evident in the forecast. Some measure of uncertainty to let the public know, “we’re really not sure about this one.”
ReplyDeleteThanks for the explanation, Dr. Mass, and good luck cracking that microphysics nut!
ReplyDeleteI think it's the work of Sleepy Joe Biden and the Do Nothing Democrats who through their deep state operatives, continue to seed clouds around the nation
ReplyDeleteI like the machine learning remark. Deep learning algorithms (mostly linear algebra) aren't new, but the compute power is finally coming. UW is a research powerhouse and thus well positioned.
ReplyDeleteThere has been a persistent theme of this in the fall. I remember vividly same time of year. a prediction citing a week of sun, and it was otherwise. On a major level. In summary autumn/late summer forecasts Take with a grain of salt
ReplyDeleteGood observation. I've also noticed this time of year into about late October is a tough time for the models. The change of seasons as well as features like West Pacific typhoons and energy in the westerlies can really amplify the upper level pattern. The big high pressure systems get stuck over the West coast of North America when there's a vortex over Hudson Bay and a deep low in the Bering Sea. Pattern lock. Often the models will show large scale pattern changes (like the demaplification of the jet stream or the breakdown of a ridge) too soon, sometimes by a week or two!
DeleteI was mentioning this to my wife recently. Landscape and other types of outdoor photography are my main hobby, and I prefer to shoot in bad weather. (I change my clothes, not my plans.)
DeleteThis time of year, however, knowing when to plan a shoot feels like a game of chance. There seem to be multiple disconnects between the forecast models and facts on the ground:
- Getting locked into persistence forecasts that miss a pattern change until it's practically standing in the doorway.
- Advertising a pattern change about 5 days out -- day after day after day after ...
- Completely missing the boat on convergence zone activity (which requires a major upgrade to my raingear and my lens choices.
- REALLY screwing up with thunderstorm activity (I get better heads-up watching for convective debris streaming south to north over Seattle than I get from any of the forecast models )
Things seem to improve considerably by mid -October, but for the next few weeks my plan is to plan for anything, even if that means hauling around a car full of gear I probably won't need.
Hi Cliff,
ReplyDeleteWhat is the basis for the statement that forecasting of temperature, precipitation, etc. (as opposed to 500 mb heights) is dramatically better than 20 years ago? Thanks.
Mike
Mike.... take a look at the stats on the WPC website. Shows substantial improvement for several variables. ...cliff
DeleteGood science. Evaluate the problem - work the solution.
ReplyDeleteI wasn't even looking at the NWS forecast for Saturday, as I kept an eye on it as I was going to be outdoors all day. The Weather Underground forecast essentially called it correctly as it usually does.
ReplyDeleteI bet the diffuse smoke is the culprit.
ReplyDelete