Wednesday, April 6, 2016

Heat Storm Hits the Northwest

You heard of heat waves, an extended period of much above normal temperatures.

But tomorrow we will have something else, what I will call a HEAT STORM, a short pulse of torrid temperatures.

The average high right now at Seattle Tacoma Airport is 57F.  Tomorrow might well get into the lower 80s...and perhaps higher.  Roughly 25F above normal, with daily records falling all over the place. 

But there is a range of forecasts--let's look at them.

The UW highest resolution forecast model--the raw prediction--is very warm.
At 8 AM tomorrow (Thursday).  The warmest temperatures are on the western slopes of the Cascades and coastal mountains, consistent with easterly (offshore) flow.
 By 11 AM, temperatures in those areas are ABOVE 80F (white)
 Much above 80F temperatures are widespread over western WA at 5 PM.

We can plot the temperatures and winds at Seattle Tacoma Airport produced by the model,which is called meteogram, with time in UTC (GMT).
Unbelievably warm, withtemperatures surge to around 90F!  The winds show this heat storm is associated with a pulse of easterly flow.

Possibly the best predictor of local temperatures in such situations is probcast (, a UW project that does sophisticated statistical post-processing of an ensemble of many local weather forecasts.  It is going for 84F. 

The Weather Channel has excellent forecasts, but does not have the advantage of the uber-high resolution predictions available locally.   There forecast is more conservative (79F):
The National Weather Service?  82F

How about the National Weather Service short-range ensemble (SREF)?  Lots of higher resolution forecasts (see below).  Looks like roughly 81F.

The bottom line is that many locations will see temperatures climbing into the low 80s tomorrow...which is really quite extraordinary for early April.   We should surpass some daily records.

The cause of all this warmth?  A high amplitude ridge or area of high pressure over the West Coast (see upper level map at 5 AM Thursday).

This configuration brings in warm air aloft, as well as low-level easterly flow with reduces cool marine influences and forces downslope warming. 

As I have discussed several times, there is no reason to expect that this ridge or high pressure has anything to do with global warming, or that anthropogenic  (human-caused) warming will cause more ridges like this.  In fact, climate models suggest just the opposite:  increasing greenhouse gases will lessen the amplitude of such waves.   Perhaps global warming is contributing 1-2F of a temperature anomaly of 20-30F.


Westside guy said...

I remember an early April somewhere around 1990 (plus or minus a couple years) when it supposedly got into the upper 70s or low 80s around here. Thing is, I was in the middle of the Greenland ice sheet at the time, and could only read about it in sporadic letters I'd receive from my wife.

I was experiencing... somewhat colder temperatures than that. :-D

Arnie said...

Interesting post. How frequently would one expect to see an anomaly of 20-30F? Is this a once a decade level anomaly?

K.R. Burgess said...

@Westside guy.
You said,"I was in the middle of the Greenland is sheet" around 1990?

My question is; When did you become frozen,in the ice sheet?
Who found you,and how long did it take to thaw you out?


Ricksea said...

"Perhaps global warming is contributing 1-2F of a temperature anomaly of 20-30F." When are you going to discuss the difference between "average" and "tail events"? Like you said yourself a while ago, even assuming a Gaussian model (not obvious), and an estimated variance unaffected by warming human-induced or not (estimating the variance of a non stationary complex system like the weather is really not the most reliable statistical operation), a relatively small shift in the mean makes extreme events much more likely.

p206.1981 said...

According to the California Weather blog the west coast ridge has increased in frequency over the last several decades:

"Between 1948 and 2015, however, we found that this West Coast ridge has become notably more pronounced and increasingly persistent from month to month.... We confirmed that regionally-enhanced warming of the lower atmosphere is primarily responsible for the observed increase in the average strength of the West Coast winter ridge... because temperatures along the West Coast warmed much more than those in adjacent regions, the overall increase in middle atmospheric pressure reached a local maximum there."

Matt Thompson said...

Just to add to what Ricksea stated, please read

I have to completely disagree with this post, because it is clear that these swings are getting worse. Extreme heat, then followed by extreme rains in Seattle from Oct. 1st well into March this year and extreme snow storms in the mountains (193 inches in December at Snoqualmie Pass, including 112 inches in one week, this is extreme for one month up there, much less one week!). Logically it can be said that climate change is causing more severe swings in our weather, period.

Ansel said...

I have to agree with Matt. It does seem like the swings are getting greater. But I cautiously remind myself that it takes years of recording and analysis to verify any trend in the climate.

Gj said...

27oC in Hagensborg, BC (near Bella Coola) at 5:00 pm. Measured with a thermometer in a Stevenson Screen. More impressive were temps above 10oC @ 8,500 ft in the Monarch Icefield region in the early pm.

Matt Thompson said...

Ansel: You are correct about needing time to verify trends, and collect data. But a lot of data has been taken from carbon record and ice coring, to get temps and CO2 from past years; upon which models are being built. I agree again that we do need more data, but I also believe the trend is upward on temps. I hope in 20 years we see that is not correct about temps, that it was a blip, but sadly, I don't think this will be the case. 14 out of the 15 most warm years on record have occurred since 2000

Again logic would dictate that the trend is for warmer average temps, thus more extreme weather possibilities.

Ansel said...

Matt, I probably should have mentioned that whatever the extremes, one need only look at the glaciers in our local mountains- which are "natural averagers"- to see that the climate is getting warmer and/or drier.