Meteorological Summer is Over… But Summer-Like Weather Continues

Blue skies on full display from my yard 🙂 (9/1/20)

Although “traditional” or astronomical summer doesn’t end until September 22 (when fall begins), meteorological summer has officially ended. Meteorological summer spans the months of June through August.

Meteorological seasons were created to help aid in keeping consistent climatological data that could accurately be compared from year to year (there’s some variation in astronomical seasons). More can be read on this topic here.

Below is a snapshot of temperatures for the months of June through August. The highest temperature recorded for the summer at Paine Field occurred on August 16, with a temperature reaching 100 degrees! This was only the second time a triple-digit temperature has been recorded at Paine Field, with the first coming on July 29, 2009. August 16 was also when we had some thunderstorms in the area 🙂 ⛈ Two high temperature records were broken: June 23 with 77 degrees and August 16 with 100 degrees.

Figure 1: Temperature snapshot for meteorological summer at KPAE (2020)
Figure 2: Accumulated precipitation for June through August at KPAE

In terms of precipitation (shown above), we ended just slightly below average, with 3.55 inches compared to the average 4.05 inches. 2020 actually ended at number 10 in terms of the most precipitation during a meteorological summer! I’m not complaining ¯\_(ツ)_/¯

For fall lovers like me, the goal is in sight… but we aren’t quite there yet. We still have a stretch of summer-like weather to contend with.

Figure 3: GFS Ensemble temperature forecast for KPAE

The GFS ensemble members average near 80 degrees for the next several days at KPAE (ensemble averages tend to be more skillful than individual members). After that, it shows a spike in temperatures on Wednesday and Thursday of next week, with high temperatures in the mid-to-upper-80s. This still has time to change as it is still a ways away, but it’s worth keeping an eye on.

However, other models like the Euro do not go as warm as the GFS does. Take a peak at the Euro ensemble daily high/low temperature forecast:

Figure 4: Euro daily high/low temperature for KPAE

This still shows a spike in temperatures next Tuesday through Thursday, but not nearly as warm as the GFS.

But regardless of exactly how high temperatures get in the greater Everett area, it will still be warm. A ridge of high pressure setting up shop over the area will help contribute to the heat.

It is also possible that a thermal trough develops, which is responsible for most of our heat waves.

The great Cliff Mass describes this phenomenon in an old blog post found here. Here is an excerpt from it:

A lobe of high pressure extends inland of us, forcing offshore flow.   This offshore (easterly) flow starts over the heated interior of the continent and then gets even warmer when it sinks down the western slopes of the Cascades.   The result is that a tongue of warm air extends northwestward out of the southwest–generally northward from the interior valley of CA or the intermountain West—towards our region.   Each day it moves farther northward and strengthens.  And since warm air is less dense, a pressure trough (area of low pressure) extends northward with the warm air. 

As already mentioned, models disagree on exactly how warm it will get over the next several days. But I think it’s safe to say that it’ll still feel like summer for awhile–in terms of both temperature and dryness.

Figure 5: GFS ensemble for 24 hour precipitation at KPAE

None of the GFS ensemble members show a drop of rain until late next week, and even then, it’s a small amount. The Euro shows a mostly dry next several days, as well. Good news for those who never want summer to end. Take advantage of it while you can! It won’t last forever 😉

Summer Rain Making Brief Comeback

With an average total precipitation accumulation of 1.05 inches, the month of August is the second driest month of the year at Paine Field. At the time of writing this, the monthly total at KPAE is 0.51 inches, slightly behind the normal 0.56 inches. However, over the next few days, we could double our monthly total as the first atmospheric river of the season heads our way.

Figure 1: Integrated Water Vapor Transport forecast; darker colors show areas of more moisture

Figure 1 shows the setup of the atmospheric river, with the moisture aiming right at Washington. To read more about atmospheric rivers, click here.

Through the above visible satellite animation courtesy of NWS Seattle, you can see clouds associated with the incoming system poised to take aim at us.

For August, some of the rainfall totals across Western Washington look to be quite impressive.

Figure 2: Euro model for accumulated precipitation through Saturday evening

Areas especially near the Olympics look like they’ll get a good soaking, with some places approaching 2 inches!

Closer to home, the Euro model shows Everett to having just over a quarter inch. But when you look at the Euro ensemble (shown in Figure 3 below), the average (which is generally more skillful than individual members) is approaching a half inch.

Figure 3: Euro ensemble for total accumulated precipitation for KPAE

For the rain lovers out there (🙋‍♀️), enjoy it while it’s here because we are still in one of the driest times of the year, and the dry comes back full swing afterwards with not much more rain expected in the next couple weeks (at least at this time–it can change still).

Figure 4: 24 Hour Precipitation accumulation for KPAE (Euro ensemble)

It’s like a little taste of fall and winter weather in the midst of summer…but it makes me really excited for the cooler and wetter days ahead of us! Fall is coming… just gotta wait a little while longer!

Are you excited for Fall? Let me know in the comments below!

Has Summer Finally Arrived in Western Washington?

After what has seemed like a dreadful start to summer (at least to some), it seems like summer has finally started in the area.

Overall, since meteorological summer began in June, temperatures have been mostly in the 60s and low 70s, as illustrated in the figure below. In fact, at least at Paine Field, the temperature has not yet reached 80 degrees. On average, the first 80-degree day of the year is June 12—so we’re a little behind schedule! The last time it’s been at least this far into summer without an 80-degree day was 2012 (when the first 80 degree day occurred on August 4th)!

Figure 1: Daily temperature data from Paine Field Airport (KPAE) since June 1

In terms of precipitation at KPAE, we are actually slightly below the average accumulation of 2.53 inches since June 1st, with a total of 2.34 inches. However, when you look at the number of days with non-zero amounts of rain, it tells a different story. We are currently at 23 days of rain in the same time span.** And many of those days were on a weekend!

Figure 2: Number of days of rain at KPAE during the above time span

As you can see, this year ranks number 2 for the most amount of days of rain in the available data. So even though the rain didn’t amount to much, we’ve seen more days of rain than usual.

But now it seems like we’ve flipped a switch and summer has finally arrived. And for the most part, it looks like it’s here to stay for awhile.

Figure 3: Euro model of 24-hour rain for KPAE

The above figure shows that besides a small blip of rain expected on Friday, we are supposed to be primarily dry for most of the forecast period, which will no doubt make many people happy. Even some of the most stout rain lovers are ready to have a little bit of real summer-like weather. I’ll admit it’s been a little nice to go outside without worrying about getting rained on.

Thanks to a nice ridge of high pressure setting up shop in the area, temperatures for the rest of the week will be quite comfortable, primarily in the low-to-mid 70s in the Everett area…which is just right, in my opinion. Tomorrow (Wednesday) looks to be the warmest day of the week. Some areas in Western Washington could even reach the low 80s! Friday’s temperature should drop slightly associated with the weak system that looks to bring a bit of rain over the area.

According to most recent models, next week is when more of the heat could make its way back. There’s still time for things to change but it’s definitely something to keep in mind looking ahead.

In the meantime, enjoy the summer weather and get outside…safely of course! It looks like the warm and dry weather is here to stay for awhile.

**Note: one of the precipitation daily values is missing from the 2020 official data, but in combing over other sources of data, I believe it did rain on that day. That would put the number of days with precipitation at 24.

April 2020 Recap and Stormy Weekend Potential

April 2020 is now in the books, and what a month it was (obviously not just relating to weather). We started the month with drier than normal conditions (you can read more about that here), and ended with slightly wetter than normal conditions. The graph below clearly supports that the total precipitation for the last 10 days of April was above normal at Paine Field.

Figure 1: Rain accumulation data for 4.21.20 to 4.30.20

In total, however, we were still unable to make up for the deficit at the start of the month, and we still ended up below average for the whole month (see Figure 3 below).

Here is a graphic that shows an overview of the temperatures for the month at Paine Field. No records were broken in terms of highs or lows, as illustrated by each blue bar staying within the bounds of the shaded red and blue areas. However, the average high temperature was just slightly above average.

Figure 2: Temperatures at Paine Field for April 2020

To summarize the month, take a look at the following graphic. It is important to note here that in the temperature category, the first column of data (“average”) refers to what actually happened in April 2020, while the second column is the average over several years of data.

Figure 3: April 2020 Summary at Paine Field

Shifting gears here, it is officially May, and after a great start to the month today, things start to get a little bit exciting.

After a weak system moves in overnight, a stronger one moves in Saturday, which brings with it rain and the potential for thunderstorms. The Storm Prediction Center (SPC) has included the area in the general thunderstorm category. Parts of Eastern Washington are even included in the “marginal” category of severe storms.

CAPE (Convective Available Potential Energy) values are forecast to be quite decent for our standards. Take a look at 21z tomorrow (which is 2 PM local time):

Figure 4: CAPE values according to the NAM for 2 PM Saturday

This run of the NAM puts 649 J/kg of CAPE at Paine Field, which is decent for our neck of the woods. NE Oregon and SE Washington looks to be a great setup for thunderstorms, some of which could be severe.

As a side note, in order for a thunderstorm to be considered “severe,” it must “contain one or more of the following: hail one inch or greater, winds gusting in excess of 50 knots (57.5 mph), or a tornado” (according to NOAA).

The primary threat for our neck of the woods should be wind gusts, so make sure to secure loose objects that could get potentially carried by strong gusts. The following graphic is for 3 PM tomorrow, showing wind gusts according to the NAM. Gusts of 36 mph are shown for KPAE, but it easily could exceed that if a strong storm develops.

Figure 5: NAM wind gusts at 3 PM tomorrow

The strength of storms that we get is contingent on whether we get sun breaks. The sun greatly destabilizes the atmosphere through surface heating–which enhances upward motion and thus, storms. If we get enough of a sun break tomorrow, our chances of thunderstorms will go up.

The chance for thunderstorms should decrease as the sun goes down because of the lack of surface heating from the sun. However, the chance again returns on Sunday. Although, the risk seems to be greater on Saturday.

If you see anything exciting, send it to me by posting it on my Facebook page or tagging me on Twitter!

I’m hoping that we get some action tomorrow, and I know I’m not the only one…here’s to some exciting weather to start out the month of May!

Showery Saturday On Tap For Western Washington

After a wet Wednesday and some showers on Thursday, today has been a break in the rain. We are currently in between systems–but the break won’t last long.

First, here’s an update on the monthly precipitation after this first system in a train of them expected to hit the area:

Figure 1: Monthly precipitation for KPAE (blue) and KSEA (black)
Figure 2: Monthly departure from average precipitation for KPAE (green) and KSEA (orange)

Paine Field is only slightly below average at this point. Sea-Tac is still around 1.3 inches below average, but the next series of systems should help chip away at the deficit.

The first system arrives early Saturday morning, as another front rams into us:

Figure 3

It will be quite the soggy start to our Saturday morning, but thankfully, there shouldn’t be a lot of people out and about at that time (because, let’s face it, people STILL can’t drive in the rain).

The main front is out of here by the afternoon, but some scattered post-frontal showers should remain for the much of the day. Some of these could be locally heavy and could even contain a stray bolt of lightning or some hail. There is a little bit of instability to work with, as shown below in the CAPE values.

Figure 4: CAPE (Convective Available Potential Energy) values for KPAE

CAPE indicates the amount of fuel available for a thunderstorm to form and is a measure of the instability in the atmosphere. The “large” spike is for Saturday afternoon. The values here are generally minuscule compared to other areas of the country, especially the mid-west (to compare, values for tomorrow in South Texas could exceed 1000), but it still might be enough to get an isolated thunderstorm.

Besides the isolated chance of a thunderstorm, westerly (west to east) winds could trigger a PSCZ or Puget Sound Convergence Zone (click here to read up on this common PNW phenomenon). This, too, has the potential to spark (no pun intended) a stray bolt or two. I know many lightning lovers (including myself) are crossing their fingers.

Sunday will be another short break in the action, with partly to mostly cloudy skies at Paine Field. Emphasis on short. Because by Sunday night into Monday, another front is due over the area, again bringing rain. This “system-then-short-break” pattern could continue into next week. Updates to come on this.

Now that our “normal” April showers seem to be back on track, maybe our May flowers will be that much better. 🙂

Abnormally Dry April About to Turn Wet

water droplets on clear glass

Much of this month has been the taste of Spring that many of us has needed as a sort of mood-booster during these uncertain times. There has been plenty of dry weather and sun to go around.

In fact, this mostly dry start is abnormal. Take a look at these charts showing the minimum 20 day precipitation total at both KSEA and KPAE:

Table 1
Table 2

These tables show the driest starts to the month of April on record for both Sea-Tac and Paine Field, respectively. Since records began in 1948, this has been the second driest start to the month of April at Sea-Tac…the driest since 1951! Paine Field isn’t quite as impressive, but it still sits at number 7 (although most of that total fell on April 18th).

This has been great to go outside for some walks or bike rides as we all continue to do social distancing. I know I’ve taken advantage of it by going on many bike rides!

Unfortunately (or fortunately, depending on who you are), our weather pattern is about to shift.

The first system is on deck by tomorrow, packing quite a punch for this April’s standards. You can see it on visible satellite imagery, lurking in the eastern Pacific.

Figure 1: Satellite image taken around 3:30 PM on 4.21.20

Take a look at the following GIFs, showing the 3-hour precipitation totals as the system moves into the area:

Figure 2: 12z Euro run of 3 hour precipitation for 4.22.20
Figure 3: 12z GFS run of 3 hour precipitation for 4.22.20

Much of the state looks to take a hit, with even Eastern Washington getting in on the action.

Figure 4: Euro Ensemble showing 24 hour QPF (accumulated rainfall) for KPAE

Figure 4 above suggests that this system could be one of the wetter ones on tap for the area in the next week or so. But it also shows that it’s not the only system on its way.

Showers decrease gradually throughout the day Thursday, with a mini ridge of high pressure taking shape. This should help keep Friday mostly dry, with the exception of some scattered showers. Yet, another system arrives late Friday into Saturday, with potentially a third following it (things could certainly change a week out from now). You can see the three spikes in the 24-hour QPF in Figure 4 corresponding to each system. The GFS shows similar spikes, as shown below.

Figure 5: GFS Ensemble showing 24 hour QPF for KPAE

By next week, both models are suggesting we could add an additional 2 inches of rainfall to our April total at Paine Field. The Euro and the GFS don’t agree as much at Sea-Tac, with the GFS showing just over an inch while the Euro is near the 2 inch mark.

If those totals came into fruition, our April rainfall deficit could be completely erased. To give some perspective, the normal rainfall for the month of April is 2.58 inches at Paine Field and 2.71 inches at Sea-Tac.

During this time, high temperatures should be close to normal.

This month has given all the sun-lovers something to rejoice over…but now it’s the rain-lovers’ turn!

They Say “April Showers Bring May Flowers”… So Where Are The Showers?

The majority of this month has been quite pleasant weather-wise. The sun and dry weather has served as a mood-booster for so many people in the midst of the COVID-19 pandemic. But it still begs the question…where is the rain?

Here is the Paine Field precipitation accumulation graph so far for the month of April.

Figure 1: Accumulated precipitation for KPAE, via NOAA

With the exception of some trace rainfall on April 11, all the rainfall has occurred in the first few days of the month, amounting to just 0.35 inches. The normal amount for this period is 1.48 inches.

When looking at the same graphic for Sea-Tac, we get a similar story.

Figure 2: Accumulated precipitation for KSEA, via NOAA

Except here, there has only been 0.01 inches of accumulated rainfall. You can hardly even see the green line on the graphic.

To put this into perspective, take a look at this tweet.

Much of California has been getting hammered by storms and rainfall and has significantly more than us here in western Washington. Even areas of Arizona have more than Sea-Tac! Wow.

So why has our weather been so nice recently? It has been the result of a ridge of high pressure that has been acting as a block, preventing storms from making it to our region. (You can read more about this in Cliff Mass’ blog, found here.)

And, spoiler alert, this nice weather is likely to continue through the rest of the week.

Highs today should be in the mid-to-upper 60s for most of us.

Overnight tonight, clouds begin to increase as onshore flow (i.e. from west to east) develops. As a result, Wednesday morning has a chance to start cloudy. But as the figure shows below, clouds should burn off by the afternoon. Because of the cloudy start, Wednesday’s highs could be slightly lower than today’s.

Figure 3: Cloud cover percentage (darks = less clouds, lights = more clouds)

Thursday and Friday look to be the warmest and nicest days of the week, with highs in the low 70s possible!

Figure 4: GFS high/low temperatures for KPAE
Figure 5: GFS high/low temperatures for KSEA

It should be perfect to go outside and go on bike rides, walks, and the like… of course maintaining social distancing 🙂

Some models/ensemble members of models show a chance for light showers on Saturday, but if anything falls, it likely won’t amount to much. Models are also suggesting the chance of some rainier weather next week, but it’s too far in advance to know for sure.

In the meantime, enjoy the sunny weather!

Sunny and Dry This Week… But Please Stay Home

This week, for the first time in forever (or so it seems), it should be dry and the sun should be out at times for much of Western Washington. But that doesn’t mean you should be going out to public parks and beaches to enjoy it.

The last time it got super nice, people flocked to parks and beaches, hardly taking any consideration for social distancing. Exhibit A:

Figure 1: Tweet originally found here

Please, for the sake of those around you (especially the most vulnerable), don’t do this. If you go outdoors, do not congregate in places with a lot of people (yes, that includes certain hiking trails). Try to stick with walks and bike rides around the neighborhood, always maintaining distance from others.

Okay, rant over (sorry about that).

It will be tempting at times to want to go out to these public places, though. Take a look at the daily temperatures at Paine Field in Everett according to the GFS (i.e. American) ensemble.

Figure 2: Temperature GFS Ensemble for KPAE

Much of the week will see highs in the mid-to-upper 50s, while the low 60s are possible by the end of the week. For native Washingtonians like me, that is almost t-shirt weather. The European model doesn’t show temperatures quite as warm, but are still in the mid-to-upper 50s. Temperatures closer to Seattle and Sea-Tac look to be a touch warmer than Everett, as shown below.

Figure 3: Temperature GFS Ensemble for KSEA

Not only is it supposed to be warmer, but it’s also supposed to be dry. Take a look at this:

Figure 4: 24-Hour Precipitation GFS Ensemble for KPAE
Figure 5: 24-Hour Precipitation GFS Ensemble for KSEA

All of the above GFS ensemble members are not showing the chance of rain until Saturday… BUT, there’s still plenty of time for that to change in the coming days.

Even though it’ll be warmer and dry, it won’t be 100% sunny the whole week. Expect to see some cloudy to partly cloudy skies at times; but don’t worry–we should definitely see our fair share of sun. There will be plenty of opportunities to go outside for a walk or bike ride–again, keeping your distance from others!

This week, it’ll finally start to feel more like Spring after a stretch of below-normal temperatures. In this time of uncertainty, I know it will lift the moods of many people. Just like the sun always eventually comes out, even after the darkest of days, we will eventually get through this.

In the meantime, I hope you stay safe and healthy.