Wet Day and Hard Forecast

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It was quite wet today over much of western Washington as a SE-NW band of precipitation set up residence across the region for hours.   Major contrasts too: from over 1.5 inches to a few hundredths.

Take a look at the precipitation map for the 24h ending 9 PM.  The dark green indicate more than an inch, while the whites are less than .1.  Amazing gradients...a few tenths in eastern WA.  Huge variation across the Sound ranging from 1-1.5 over the eastside to a few tenths over Kitsap...not the normal situation!  Even less on the coast.  The highest I spotted was 1.73 inches at Woods Creek NE of Monroe.

Here is a radar image for mid-afternoon....this was the story for four to six hours this afternoon

The yellows are moderate to heavy rain.

The origin of the precipitation was a very strong low off our coast that caused persistent southerly and southeasterly flow over our region--with bands of clouds and precipitation rotating around it...here is the upper level flow late this afternoon...the low is very strong for this time of the year.  This feature is not moving anywhere fast.
This is a VERY unusual situation.  Here is the 500 hPa forecast for tomorrow (solid lines) and what is known as the standardized anomaly....in standard deviations.  You see we are at least out four standard deviations...this pattern occurs only once  in 15,787 times...very, very rare.

  Here is a satellite picture showing you the moisture rotation around the low.  You can see the bands caught up in the flow..mainly on the eastern side of the low where there is upward motion.

These are very hard situations to forecast well...yes, we knew it was going to rain, but correctly defining and timing these bands is extremely difficult more than 6 hours ahead of time.   One day.

Looks like a another band will swing through later tonight....well, at least you don't have to water your garden this weekend.

Coal Train Help:   As I mentioned in a previous blog, a group of us would like to take observations around a few coal trains.   Does anyone know how frequently they pass through Seattle (I believe they are only full northbound)?  Are there more on certain days of the week?  Is there any way to know when one is coming a hour or so ahead of time?   Perhaps one of you living near a rail line might have some insights into this.

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