Saturday, May 21, 2016

A significant precipitation event from the "wrong" direction

As predicted, a deep trough has formed over the West Coast, bringing cooler temperatures and precipitation.   The atmosphere has reconfigured itself during the past week, as the pesky ridge of high pressure, which brought warmth and aridity to our region, has moved to the west.

As shown by the latest (Saturday AM) infrared satellite image (see below, with my annotations), an upper low center is found over eastern Oregon, with substantial moisture rotating around it into our region.    There is a substantial EASTERLY (form the east) component of the winds and that produces upslope precipitation on the normally dry easterly slopes of the Cascades.  Eastern WA is also getting rain.

How much so far?   Here is the 24h totals ending 9 AM Saturday over central Washington.  Impressive amounts (over an inch in some locations) over the eastern slopes, will many locations wetted by more the .5 inches.  Good rain over northeast Washington.

A band of precipitation is now circling into western Washington (see radar).   My garden will be happy.

Normally dry, eastern Oregon has done very well from this event, with some eastern Cascade locations getting over 1.5 inches.

The latest WRF model forecast for the next 24 h (ending 5 AM Sunday), brings lots of rain to the central and southern Cascades, with relatively dry conditions along the coast.

There are a lot of folks worried about heat and drought this summer and potential impacts such as wildfires and poor harvests.     This event is very positive as has been the reconfiguration of the atmospheric circulation.  Eastern WA soil moistures are near normal and our reservoirs, such as those in the critical Yakima drainage are full and above normal (see below for yesterday...and that is before the today's rain).
El Nino is collapsing and the latest  NOAA CFSv2 seasonal forecast predicts wetter than normal conditions from June, July and August (spoiler alert:  the skill of these forecasts is not great).

However, with warm water still offshore, El Nino still be present, and other factors, the subseasonal forecast models are projecting warmer than normal conditions over our region this summer (see below).   Not crazy warm like last year, but .5-1 C warmer. Warm temperatures encourage evaporation and thus contribute to surface drying.


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C.P.O. said...

Eastern WA usually gets it, so WHERE'S OUR RAINSHADOW??

RLL said...

Oddly enough we are having southerly winds at this time over Sinclair Inlet in Bremerton. Cloud cover is low enough we cannot see any upper level clouds from the north. Light rain, and not a good thing for the parade going on at this time.

John said...

According to NWS Spokane,Wenatchee had more rain overnight(.71")than what normally falls in the entire month of May.

Deek said...

Its been spotty. We're still waiting for the rain in Winthrop. Our rain gauge had slightly less than 4 mm this morning. So far this month we have had 0.27 in vs a normal (to date) of 0.6 in. The average temperature is 6.2 F above normal this month although I expect this to drop with the recent coolness. The average temperature in April was 6.4 F above average. I am enjoying the cool cloudy weather.

Matter said...

Last evening I was curious about where our promised rain was. As I often do, I took a look at NWS radar and was surprise by the loop showing what I'll call retrograde weather. I then took a look at surface winds for the region from 9PM observations. Direction and velocity were all over the place. I was expecting more easterly winds based upon what I percieved the flow would be based upon the radar. As I recall most opservations were indicating S to SW winds with gust to about 15 MPH.
My grass and garden welcome the moisture. Slugs like it too.

John said...

Major thunderstorm in NW Spokane county this afternoon. 1.35"here in just a few hours.Only had .27" for the month of May until today.What a difference a little convection can make!

larchitech said...

My wife and I needed to get in a long training ride yesterday and we looked at the radar and saw that shield heading towards us so we headed to the coast and biked there. It's the first time we've gone to the coust to avoid rain.

Tim Fisher said...

I love those rainfall total maps, where do you get them? I'd make them my desktop background if I could :D

Bruce Kay said...

Another brilliant example of the stunning skill in modern weather forecasting. I think you and others called this over 5 days ago.

I was wondering if you could comment on two things:

1) How close (or perhaps better framed as how evolved) the current state of weather forecasting is to Lorenzo's old and still pertinent statement on chaos theory, that weather forecasting will always be limited (mathematically?) to a maximum of 9 days out, no matter how skilled.

2) The role and efficacy in computer modelling that has occured in this evolution.

This could be illuminating, perhaps (perhaps not for some) for the doubters (cynics rather than skeptics?) of the power and worth of computer modelling in everything we do..... such as climate science.

Patti Robinson said...

None of these rain events have dropped any precipitation on the area West of Forks. We are usually the wet ones and need it for our gardens.