Rain off and on, but without ‘nowcasting’ it's hard to pinpoint

Oct 7, 2011

Forecasters aren’t perfect, but we can be pretty sure of the rain falling this morning.

The cooler temps and heavier rain are a few weeks early, forecaster Cliff Mass told KPLU’s Keith Seinfeld, but the front dropping this rain will move through by mid-day today leaving Saturday mostly dry with rain returning that evening through Sunday morning.

But this could all be off by a few hours either way, because the official forecasters only publish every six hours. And those forecasts are used by nearly all the different weather Websites and news organizations.

“Forecasts aren’t perfect and one of the big problems we often have are timing errors -- things coming in a little faster or slower. This is by several hours, and so you get this problem where there is a difference between the forecast and what’s actually happening. And that make people criticize my profession,” Mass said. “One essential problem is that the forecasts are only made on a regular schedule, and typically this is every six hours.”

‘Nowcasting’

The future of weather forecasting is "nowcasting," he said.

“I think the weather service needs to do it more. In nowcasting we use all the observations we have – the radar, the satellite information – to continuously update the forecast.”

As it is, the National Weather Service only publishes its forecasts every six hours.

There is a trade-off, though. If the NWS focuses more on continuous updates, then there will be less focus on the longer-term forecast.

On the Web:

Ask Cliff Mass a question: go to our Facebook page and post a question for Cliff or join the conversation on someone else’s question. Cliff says he will jump into our Facebook page from time to time to answer some of those questions.

The weekly KPLU feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and repeats twice on Friday afternoons during All Things Considered. The feature is hosted by KPLU’s Health and Science reporter Keith Seinfeld. Cliff Mass is a University of Washington Professor of Atmospheric Sciences and renowned Seattle weather prognosticator.