Friday, June 3, 2016

Weekend Heat Wave

We should see some very warm temperatures this weekend, and certainly some daily records will fall.  But the heat will be short-lived and more temperate conditions will return on Monday.

A strong upper level ridge (high pressure) has been in over our region and will continue to amplify for the next day.     Here is the 500 hPa (around 18,000 ft) heights (like pressure) for 5 PM Saturday to illustrate.  Huge, broad ridge over the West Coast.   In contrast, a cool trough is over the eastern U.S.


This ridge brings warmer temperature aloft and the development of a thermal trough that will progressively extend up the West Coast.

Here is the 24 h forecast of sea level pressure, surface wind, and low-atmosphere temperatures (925 hPa) for Saturday at 5 PM.   There is a tongue of low pressure in western Oregon that extends into western WA...that is the thermal trough.   VERY warm temperatures in Oregon. The northern portion of the trough is associated with strong offshore and downslope flow.


A close up view of the temps at the same time shows that Portland should be over 100F on Saturday. and southwest WA will reach the 90s.   Puget Sound is cooler.  Why?  Because with the thermal trough centered south of us, there will be a north-south pressure gradient that will drive northerly winds and cooler air from north.  Low to mid 80s around Seattle.  Cooler over NW Washington.


At Sunday at 5 PM, the thermal trough will extend north and start to transition over the Cascades.  This will be the warmest day around Seattle.

 The temperature forecast for this time shows 90s around Olympia and over the eastern suburbs of Seattle, which temperature will peak around 90F.      Eastern WA will warm up on Sunday as the thermal trough starts making the move. The coast will start to cool down that day.

Monday at 5 PM is a different world.   Cooler air has moved in west of the Cascades crest and you can see the resulting strong pressure gradient over the western side.   Eastern WA has warmed considerably.

The temperature at 5 PM Monday illustrates this...cooler over western WA--perhaps reaching 80F in Seattle.  But 100F in portions of the Columbia Basin.  That should ripen some crops.


Temperatures will further moderate during next week, dropping into the 60s by Wednesday.

16 comments:

Kevin said...

Will it work to cool off on Sunday with a hike in the Cascades? Or will it be too hot in the mountains, too?

William said...

Hi Cliff,

It seems that during my time living in the Pacific Northwest we hear about record highs each year but rarely hear about record lows. Has this been a trend during the last decade, and if so, do you have any data to support my suspicions?

Respectfully,
Bill

Dave said...

At Seaside Oregon for a conference and it was over 80°F at 08:30

Rebecca Timson said...

Check out: www.washington.edu/news/2013/07/19/nighttime-heat-waves-quadruple-in-pacific-northwest/. Cliff can update and comment. I think he might have addressed this before (?)

Unknown said...

There is a long black cloud over lake washington...is that the thermal trough? Or is that an exhaust cloud from the traffic kerfluffle with the I 90 bridge bottling west bound?

cyd corujo said...

There is a long black cloud over lake washington...is that the thermal trough? Or is that an exhaust cloud from the traffic kerfluffle with the I 90 bridge bottling west bound?

Westside guy said...

Hey this isn't about the heat... but I'm wondering if I just saw some noctilucent clouds a few minutes ago. They looked a lot like sparse cirrus clouds, but even though it was almost 10:00, the clouds were a pretty bright white against the rather dark sky.

Here Goes Nothing said...

I think babies born in the 1980's and forward have barely experienced record breaking lows. This is a national trend.

Cascadian Engineer said...

Good to hear this won't be a repeat of last year. I've spent the past couple days hiding inside with my air conditioning set at 60.

sunsnow12 said...

"I think babies born in the 1980's and forward have barely experienced record breaking lows. This is a national trend."

Can you support that with any data?

I just ran a quick look at Seattle in December. 18 of the 31 days have record lows registered since 1980. 7 of those have been since 2008 - a winter where we had almost 2 feet of snow. When December rolls around, should I make a blanket statement about how cold it is getting?

There are plenty of stats that show the earth is warming. Claiming a generation has "barely experienced" record lows nationwide is not one of them.

Matt said...

Bill, 54 straight record highs n Seattle since the last record low in Feb, 2011.

sunsnow12 said...

As noted I just did December for SeaTac (and only December), went through the NWS reports day by day. December 5th, 2013 was recorded as a record low of 23. So not sure where the "since the last record low in Feb, 2011" comes from. (http://www.atmos.washington.edu/climate/clisea/20131206.clisea)

I don't doubt we have had more record highs than lows but what is your source on that Matt? I would also be interested in how the dates are distributed.

Dominic Holdem said...

sunday was glorious! more, please.

Organic Farmer said...

False.. think polar vortex, some very cold spells further east on a national scale

Mark said...

Sunsnow12. You are correct about Dec 5, 2013. But if you look at the Intellicast dataset it says 23F Dec 5, 1956.

http://www.intellicast.com/Local/History.aspx?month=12

The Intellicast has not been recently updated. My guess is that the 23F in 2013 tied the record daily low rather than set a new record daily low.

You are both correct.

The Intellicast data set is interesting because it includes pre-SeaTac data gathered by the NWS when it was located in the Federal building in downtown Seattle. The Feb bldg. data is probably biased high because of its urban location. Note the record max for Dec 5 on the Intellicast data set.

The Western Regional dataset is regularly updated:
http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?wa7473


sunsnow12 said...

The claim was "54 straight record highs n (sic) Seattle since the last record low in Feb, 2011." It was actually 3 days in a row of record lows in February of 2011: 2/23, 2/24, 2/25, and the Intellicast data shows them all with a record low from 1962. The Intellicast data is wrong and completely out of date to be making this kind of claim.

Tying a record becomes the new record. That is standard NWS protocol. The claim, again, was "since the last record low in Feb, 2011". To illustrate that protocol, here is the most recent daily report from December 5th, 2015: http://www.atmos.washington.edu/climate/clisea/20151206.clisea Note the record low value does not say 1956, but rather 2013. 1956 is not noted at all.

One of the recent record breaking highs (May 2nd) was a tie: http://www.atmos.washington.edu/climate/clisea/20160503.clisea but you will note it also is registered as a record for the date.

Again, I don't doubt that we have seen substantially more record highs than lows over the last few years. But we are not "both correct". Data is data. It is critically important that it remains completely objective.