Tuesday, July 12, 2011

The Big Chill

During the past two weeks we have enjoy fairly nice weather over the region, a break from the cooler and wetter-than-normal conditions this spring.  I got some bad news for you...amazingly, the cool pattern is back and it isn't going away soon.  And it will rain--today.

But first a recap to make you feel better.  Here are the temperatures at Sea-Tac Airport versus the normal high (red line) and normal low (blue) line for the past two weeks.
 You will notice that most days we either just reached normal or exceeded it, plus a few days below normal, which  is...well..normal.    Most days are not normal!   Amazingly we have been drier than normal this month...a few hundredths of an inch when we usually have .3-4 inches by this time.

But something has changed--something that is obvious by scanning the sky.  Yesterday some showers moved through and today (Tuesday) we are certain to get more.  Here is the latest visible satellite picture.  It looks like winter, with clouds over the entire region and a very solid mass of clouds moving in from the southeast.


Why is this happening during a period in which the weather is usually fine?  The reason:  an anomalous upper level low has moved in just offshore.  Here is the upper level chart for this morning for the UW WRF forecasting system:


The chart shows the height of the 500 mb pressure surface (roughly 18000 ft) and you can see a deep low centered a few hundred miles off of Washington.  And upper level troughing just hangs out along the West Coast this week.  Here is Wednesday afternoon:

Saturday during the day:


And Sunday late afternoon 
 

 You get the picture...this pattern is not going anywhere according to this forecast model solution.  Last night's run had a major warm up on Monday...no longer.

One tool meteorologists use to estimate our confidence in theforecasts is from ensembles--running the models many times with slightly different starting points or physics.   The average or mean of the ensembles tends to be more skillful than any individual forecast and spread of the forecasts give you a measure of uncertainty.

Here is the ensemble-mean anomaly (difference from normal) for upper level heights (same field as above) from the National Weather Service operational ensemble system.  Blue indicates that the mean of the ensemble is lower than normal and there is a lot of blue along the west coast.  And we are not talking just about the Northwest--the entire West Coast will be cooler and cloudier than normal. 


And the spread or variation among the ensembles is relatively low (see graphic below)--thus the confidence in this cool solution is relatively high.


The ensembles do have a lot of disagreements next week---so don't sell your swim trunks yet.  But in the near term, don't plan on typical warm, sunny weather.  And keep in mind this upper level pattern is making the eastern U.S. unbearably warm...with upper 90s in New York today.

31 comments:

Scott said...

Every year you write about how it's surprisingly not nice. Why does anybody ever get surprised we have lousy "summers" anymore? Why don't the forecasters here just predict cloudy and cold with a decent chance of rain 365.25 days / year? They'd do better.

stuffradio said...

Why do you want to remind us that the East Coast is warm? We need some heat here for drying everything out, etc.

Ashley said...

Seriously considering moving east of the Cascades...ugh. I have never been mentally affected by weather like I have this year.

kaybradley said...

I think this is the weather's response to the Seattle Times headline last week about "warmer" trending ;-)

JS said...

21 years living in the Seattle area and last summer and this summer have been by far the worst I have experienced. If this is what climate change has in store for the PNW then I am out of here. What I don't understand is why it seems like when the models predict great weather 5+ days out more often than not the forecast deteriorates but it rarely seems as though the reverse is true. Is my perception correct or perhaps is it skewed by disappointment?

DaveOnFidalgo said...

Anacortes/Fidalgo Island is 65 and sunny today, the O.R.S. at work, no doubt. Went to grad school in Iowa and lived there 9 years. Believe me, we have weather paradise here year-around, regardless of the little issues that come along. Stifling, humid gulf air in the summer, bitter, sub-zero arctic air in the winter, tornadoes, blizzards, golf ball hail, ice storms, apocalyptic thunderstorms were the norm. I'll take this anytime.

Annette Stollman said...

Any idea of what is the cause of the anomalous low?

Ansel said...

Someday I'm going to break down and move out of here. I believe a person gets "imprinted" with the summers where they grow up- in my case Connecticut. I entered 2 swimming events outdoors last summer and both were cloudy. I fear that we are having "one of those summers", but I really hope I'm wrong.

Ansel

stuffradio said...

It pretty much turned a clear blue sky for me hours after my original post even though we were supposed to be rain and gloomy! :)

Tom said...

I spent $50 for a season pass to the boat launch. I have a sailboat, and there hasn't been and good weather with wind at the same time on Lake Washington. My boat is still dry, and my mood is getting worse every day as my vitamin D level continues to dwindle.

Glenn said...

Is there a larger pattern here, Dr. Mass? Anomolies are no longer anomolies when they become the new norm. Is this perhaps, a symptom of the North Pacific Decadal Oscillation? If so, do we have any idea of it's period and magnitude?

Glenn,
Marrowstone

richard583 said...
This comment has been removed by the author.
richard583 said...

... an anomalous ... low, ... generated (?) associated with the significantly cold ocean-surface waters at this point sitting off the coast and within the main NE section of the Gulf of Alaska, having facilitated an avenue for still plenty cold air mass north, south; .. that colder water also having worked to support and maintain the depth of that colder air. ?

http://www.osdpd.noaa.gov/data/sst/anomaly/2011/anomnight.7.11.2011.gif

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?vis_archive+start+2011071114+end+2011071216+interval+

richard583 said...
This comment has been removed by the author.
Westside guy said...

On the plus side, I snuck out between showers today and planted most of my winter roots bed (carrots, parsnips, beets) - this is about the best mid-July weather I could hope for, in terms of getting those plants to germinate well!

But for the tomatoes and cukes... not quite so great weather.

mike said...

So are we sure El Nina is over?? seems like the pattern since spring has not changed much to me.

Polistra said...

This is the weirdest radar picture I've ever seen. Reminds me of a cloud rake.

Screencap from this morning's radar at NWCN.COM:

http://ockhamsbungalow.com/blog27/Clipboard01.jpg

natchrl8r said...

Every year it is the same complaints: "This is the worst summer I can remember..." Memory is a funny thing. The weather has been fairly normal for early July with a bonus dry 4th! I admit that in mid-June I am pining for the warm sunshine of my youth but here that is an anomaly. I used to work at a wilderness Ranger Station and I can't count the number of times some visitor would say "We're from (Texas, Connecticut, Ontario, Chicago, Louisiana...) and it is miserable there. We just love this cool summer weather!" Hot, humid summers are fine if you are a kid playing in the water all day. Scorching arid desert is great if you are a cactus. But we have awesome summers here perfect for hiking. Tomatoes do well in a subtropical climate but you're in broccoli territory here.

OlympicRainShadow.com said...

Tuesday the Olympic Rain Shadow seemed to kick into gear here in Sequim, with a gorgeous bright sunny day, but prodigious clouds over all the mountains, and apparently over surrounding areas.

This morning, Wednesday, does not look too good. Some clearing toward Victoria.

I am with the guy who said last summer and this were some of the worst he has seen. I would bet that for the period April - July, 2010 and 2011 are two of the coldest cloudiest consecutive periods ever recorded.

And all this cloud cover is letting the snow pack just hang in there.

Mattster said...

Yes, with over a year plus of this "weather funk", it's starting to grate.

Two cold Springs and Summers in a row. With the exception of some winter weather in November, the winter didn't act much like winter either. I've spoken to other native NWers and you are not alone if this is starting to bug you. We're pretty sturdy, but over a year of weather funk is bound to put anyone in a...well, funk.

I'm always curious if the long-term forecasts somehow factor in what is "normal" for that time of year, making them less useful for "abnormal" situations.

Joseph Ratliff said...

As you state repeatedly Professor Mass, and stated again in this post...the weather is almost never "normal" here.

We've had this type of weather before, and we'll have it again I'm sure.

Enjoy the cool weather folks. :)

Lindsey said...

I really thought that with now "ENSO neutral" conditions since June, the much cooler than average conditions wouldn't persist. It is depressing and frustrating; and I echo the added irritation of no real La Nina winter, too.

wildbill said...

Off Topic. Cliff, you have deleted your wonderful weather radar link. It showed all NW radars on a zoomable map. Please bring it back or tell me where to find it.

JRF said...

I'm from the midwest and every year since moving to Seattle (8 years) I have gotten headaches in the fall (due to weather, allergies, who knows) but I have started to get them over the past week or so. Plus we just got back from 2 weeks on the east coast on July 7th - so we missed all the nice weather...I pretty much feel like we have entered fall already and I am not happy.

julie said...

Grew up east of the Cascades and go over once a month for family obligation. Have now lived in Seattle thirty five years and have acquired the metaphorical duck feet. We whine about this weather but it is very mild and livable with dry sunshine summer available a little over an hour away from Seattle. Agree with DaveOnFidalgo. People can have their uber hot humid summers in other territories. A sweater at a picnic is easier than worrying about vulnerable family members having heatstroke. Wear a little more. Hike. Enjoy the temperate ease. Or take the drive east and enjoy the nice dry heat.

lemonlye said...

I'm with the minority: 60-70F is my absolute favorite temperature range, and I've been loving the weather the past few days. Just enough rain to lull us to sleep at night and make our garden happy, with enough daytime sun breaks that we can still wear sandals and not feel too chilly. This is exactly the kind of weather that made me choose to live here!

I spent three years in the Sacramento Valley, and their long, dry, scorching summers made me want to wither up like a sad little fern. I think I have Reverse SAD. That said, this past winter/spring up here *was* long and cold and tough to get through. However, today's weather, with temperatures in the 60s, and occasional gentle showers? That's easy to live with. Glorious, even.

Unknown said...

I suppose calling it 'the big comfortable' wouldn't have worked as well. But seriously this isn't bad weather at all. Sure those cumulus clouds from the persistent low pressure this week isn't very July like. But really low to mid 70's with a mix of clouds and sun is heck of a lot better than the oppressive heat covering much of the country. Heat indexes above 120 are not pleasant. Seems like the La Nina effect hasn't quite let go of us entirely. Then again if its keeping those pesky thermal troughs at bay then so be it.

Lindsey said...

Yes yes yes: I'd say the vast majority agree that what we're experiencing now in the Pacific NW is better than much of the country is currently experiencing. But I think what many of us are saying is that we'd just like a pretty "average/normal" summer where the temps and sunshine over any particular several week period is within just a few degrees of the average. Like we've often gotten here.

TVN said...

Today is yucky indeed but yesterday was surprisingly nice. It warmed up to 74 in Redmond and was mostly sunny all afternoon. We even went out for ice cream.. Hard to imagine we're going to have to change our deck refinishing plans this weekend but the extneded forecast looks nice at this point.

Deb Fitz said...

Gonna go out to my garden and shoot my tomato plants to put them out of their misery...

Unknown said...

This is good for the glaciers, which have been retreating for so many years. Glacier Peak is a disaster zone.