Saturday, February 3, 2018

The Heavy Rain/Flooding Event Begins

An unusual heavy rain and flooding event has now begun, and if the forecasts are correct, it will be an amazing example of the prowess of modern numerical weather prediction.

The 6 PM radar says it all..with a plume of moisture moving into our region from the Northwest.

Let me show you the latest forecasts for 24h total precipitation.   For the 24-h period ending 4 AM Sunday, there is heavy precipitation along the western slopes of the Cascades (as much as 2-5 inches, black color), with an extension over Whidbey Is. and Port Townsend.  I have never seen an extension of heavy rain away from the mountains like that.

 The next 24-h  (through Tuesday at 4 AM) is just crazy, with some locations getting  up to 5 inches of additional precipitation.

And believe it or not, even more the next 24 hr under sustained northwesterly flow.
The 48-h total ending 4 PM Monday is just amazing, with the highest amounts hitting 10 inches (in a very small area) Not the profound rainshadow to the SE of the Olympics.   They will get essentially nothing. And dry just to the east of the Cascade crest.  Such huge precipitation contrasts make Northwest meteorology fascinating.

As I noted in my earlier blog, the maximum precipitation is lower down the slopes than usual, with enhanced low-level blocking of approaching air by the Cascades causing air to rise sooner than normal--thus pushing the precipitation to the west.

The NOAA/NWS River Forecast Center in Portland has revved up their warnings and is going for moderate flooding (blue dots) on several rivers draining the western slopes of the Cascades. Flood stage will occur on several more.


Many of the locations will get very close to a major flood, as illustrated by the river flow prediction for the Snoqualmie River near Carnation. 


If you want to see something impressive go Snoqualmie Falls on Monday or Tuesday.   In any case, you can choose to be entirely dry or completely drenched on Sunday....

31 comments:

Ellen Falconer, LMP said...

Port Townsend is getting inundated. Unusual indeed! And more on Sunday...

Tom Butler said...

Looks like another data point supporting the SPU study showing increasing probabilities of intense precipitation events.

Cliff Mass said...

Tom,
Seattle is not getting much precipitation from this event. And that SPU study has serious flaws...perhaps I will blog about that sometime..cliff

TrueBlue said...

Cliff, could you comment on the article in the Seattle Times claiming that the city has gotten heavier rains in the past 15 years, and that this is evidence of human-caused cimare change? I'm skeptiical.

Flying Bear said...

Friday through Sunday totals (so far) for our farm in Langley on Whidbey Island is 1.37 inches. Not a PWS record breaker, but certainly a bigger rain event than we've had in a while.

Rebecca Timson said...

Operating at Stevens Pass today, but with 5 chairs closed and no night skiing. Limited operations at Crystal too.

ginnaville said...

Somebody else took our rain, but that's okay. The NWS pinpoint forecast for our neighborhood (4 SSE Renton) for last night was 3/4 to 1 inch of rain, but I never heard any rain before going to bed, or any downpour during the night. The closest CWOP to me (EW0259) reports zero rain between 8:30 pm Saturday and 6:30 am Sunday, then a brief shower of .04 inch after 6:30 am. A CWOP several miles to the north reports similar numbers in the same time frame. Actually, it was a very quiet night out here.

Gpacharlie said...

Amazing rain shadow has spared North Bend and Snoqualmie. Will you be doing a post on this (unusual?) rain shadow? Winds this am were steady east to west and strong. Could you describe what factors caused this downdraft? Thanks

John Marshall said...

We aren't supposed to be getting rain shadowed on the NE side of the Olympics today (forecasted rainshadow only on SE), but even after the front came through at noon Sunday, we've only managed to get 0.04" since Saturday near Sequim.

I was hoping for a gullywasher given my property is drier this winter than it has been in recent years and more rain would be nice. Instead, we are sitting inside low stratus clouds at 1000' and just foggy. But heck, the moss is growing like crazy this year. It likes the fog.

I'll continue hoping for a good rain before this winter ends, but apparently not from this one.

sunsnow12 said...

Cliff, please blog on the SPU pr release.

I'm surprised SPU didn't say "it was really hard to stand up with a straight face" when they released it - like they did at the end of the 2001 water year (Seattle Times, 9/30/2001 "Worst Drought Fears a Washout...")

This stuff needs to stop... and yet it just keep going, year after year. Why is that?

nutso fasst said...

Will this event topple Diablo Dam's 3-day record of 13.42" set in 1975?

About the "heavier rains in the past 15 years" claim from Seattle Times...

Yes, there were heavier rains at SeaTac during the past 15 years than any period since 1945.

Record 3-day precipitation for SeaTac is 6.07" in 2003, record 1-day is 5.02" in 2003. Records were set between 2003 and 2006. Since then, intensity went to below 1950s levels.

As for total winter precipitation, 2015-16 is tops at 24.63", 1998-99 2nd at 22.77", and 1950-51 3rd at 22.7".

A few miles SE at Kent, record 3-day rainfall of 11" occurred in 1949, with 6" falling in one day. The only 3-day rainfall in the top 10 occurring this century was in 2003, with 5.69"--5.02" of which fell in one day.

Record total winter precipitation at Kent was 30.7" in 1949-1950 (and that's with 69 days of missing data!). Total in 1933-34 was 26.38" and 2015-16 is in 3rd place with 24.24".

Alex said...

Heavy rain in the Redmond area last night, but nothing earth shattering. Now it's quite clear and sunny. Climate change my arse.

Hal said...

My closest Weather Underground station for my place in Kent reports 0.18" for yesterday, and 0" today. So perhaps other places in the region are seeing high activity, but not here.

John said...

Quite windy in the Snoqualmie Valley area at 5:20 pm...

floater said...

I logged 1.10" betwixt 11 a.m. Sat. 2/3 - & - 11 a.m. Sun. 2/4 ... a NICE & NOT "normal" amount for here in Greenbank - on Central Whidbey Island.
So far in Feb. we've had 1.68" - and hope for MUCH more !

Matter said...

Spent the weekend at Mason Lake, SE of the Olympics. While Saturday had extremely light precipitation, like a small drop every 30 to 40 seconds, for most of the day, there was no gulley washing event there. Satalite and Radar clearly showed rain shadowing was going on. Sunday was beautiful and blustery. Home rain gauge in Rainier Beach picked up .28” inch.

Donald Strong said...

Please Cliff, tell us it's not so.

Joe said...

Cliff, it seems, at least for the area from Bellevue to Mill Creek, the huge rain event didn't materialize. Was that area in a "donut hole" or did the rain gods have mercy on us for that day? We changed our plans from outdoors to indoors because of the forecast. When we came out a couple of times during the day, the weather in Bellevue and Mill Creek was quite nice.

nutso fasst said...

Correction to previous comment: record 3-day precip at SeaTac was in 2006, not 2003.

Owen Bamford said...

obviously these reports are from the local(Seattle?) station, but how are the data collected for the big models? Does every country's weather stations allow access by NOAA or UKMET ? How many reports go into a model? are the satellites reporting to their owners only?
It would be nice to think that if I phone in a report about snowfall as a spotter that it contributes to a world view, but I assume that those data are combined before being passed on to the supercomputers. So really my question is "who owns the weather data?"

Stickerbush said...

I think the forecasters missed this one, other than some misty rain on Saturday, it's been rather dry in the lowlands, not the heavy rains that were predicted.

J said...

Human caused, nah. Climate changing? Sure. Climate isn't a constant. The last time I checked, the Sun drives the weather of our planet. Humans changing weather? Arrogant and Ig-norant for sure. Ignoring what is obvious, you just happen to be alive during the time when climate is changing, or did you just not notice it never is constant?

J said...

Also, why not comment on the fact that we've had between 12-15 inches of rain in the first 5 weeks of the year? Of course, it depends on location. Also, maybe mentioning the rest of the country and world would create an interesting conversation. Cold, cold, cold everywhere. Yes, the west is being spared for now, but most everywhere has seen a truly bitterly cold winter. It's probably been since the Dalton minimum that we've seen such cold for sustained periods of time. Or you can say, nothing to see here.

Tom Butler said...

Seems like an awful lot of wind the last three days. Is that related to the high that is steering the river directly west?
Also, nutso according to the SPU report: Seattle has been hit with at least 4 inches of rain in 24 hours several times since SPU started keeping track — in 1981, 1986, 2003, 2007 and 2010. These were previously considered 100 year storms by SPU based on historical data.

Unknown said...

Rain shadow or not, Snoqualmie Falls looked impressive this afternoon ...

Unknown said...

A picture and a video from this afternoon at the falls... -Rob

https://1drv.ms/f/s!Ahzk1f4PyELv71vSSLVERHVoYQaI

nutso fasst said...

Tom Butler: "These were previously considered 100 year storms by SPU based on historical data."

Please refer me to the historical data on which such considerations were based.

Seattle is not the 'canary in the coal mine' for anthropogenic effects on NW climate, much less global climate. There are weather stations outside Seattle's urban spread with records that contradict the claims in the Seattle Times article.

Suggest you read this memorandum very carefully and then tell me if you honestly believe you can "expect" an event in Seattle every x number of years based on 40 years of data:

http://climatechange.seattle.gov/wp-content/uploads/2018/01/Seattle-IDF-Curve-Update-TM_12-29-2017.pdf

sunsnow12 said...

Cliff -

Are you not going to review what went wrong here? You predicted - and the local media came out with a lot of scary headlines - that "Many of the locations will get very close to a major flood". You reported "The NOAA/NWS River Forecast Center in Portland has revved up their warnings and is going for moderate flooding (blue dots) on several rivers draining the western slopes of the Cascades."

Where did this happen? http://water.weather.gov/ahps2/index.php?wfo=sew

No river came close to a major or even moderate flood, in fact only a few made it into "minor" flooding (minimal or no property damage) and every river is receding at this point. That's not "many" and it's not "major". It's not even "moderate".

I am not downplaying the importance of notifying the public but misses like this can damage credibility as you have pointed out many times. It just does not seem like you to gloss this over. What did you learn?

Tom Butler said...

Well nutso we can start with http://www.climate.washington.edu/events/2009floods/

and then for the detailed analysis: http://www.mgsengr.com/downloads/ExtendedTimeSeriesReport_WSDOT.pdf

And your question as to whether to expect a rain event every x number of years indicates a lack of understanding of statistics. I expect the probability of a rain event in any given year to increase based on their analysis (I prefer the L Moments approach) and on papers that Cliff has published showing that climate modeling predicts an increase in heavy rain events Climateworkshop 92104-1.ppt.

Wantabeclimatologist said...

Hi, it looks like the destruction was secondary to a Williwaw weather event. Just a thought from a southwestern New York resident.

Wantabeclimatologist said...

From the destruction, it looks like they experienced a Williwaw weather event.