Over the weekend, nearly every part of the state experienced smoke impacts, with many air quality monitors observing unhealthy or worse conditions. Sunday's satellite image shows the swath of smoke across the state:
 |
| 20 Aug 2023 19:01Z - NOAA/NESDIS/STAR GOES-West |
Easterly winds plus smoke from both local and Canadian fires led to the poor air quality we observed over the weekend. Two fires in the Spokane area (Gray Fire and Oregon Road Fire) led to hazardous air quality in Spokane.
Outlook:
Western WA
We're already seeing improvements in western Washington with the arrival of westerly onshore winds. The smoke will likely linger through today but skies should be clear by tomorrow morning. Air Quality Alerts are in place through midnight tonight for the following counties: Island, King, Pierce, San Juan, Skagit, Snohomish, Whatcom. An Air Quality Alert is in effect until 5pm today for Clallam County.
Central and Eastern WA
Air quality will also slightly improve today in Central and Eastern Washington with southeast winds, although there is uncertainty in how much relief Central Washington will experience. Forecasted southwesterly winds tonight and tomorrow will increase smoke in the region. Air Quality Alerts comprise all Central and Eastern WA counties, and are extended through noon on Wednesday.
Expect significant clearing on Wednesday. Unfortunately, forecasted northerly winds could bring Canadian smoke to Northern Washington on Thursday and Friday. We'll update the blog as necessary.
____________________________________________________________________________________________
We observed interesting smoke dynamics in the atmosphere on Saturday as the smoke was transported higher up in the atmosphere but then mixed down to the surface. Ecology's air quality sensor at the Mt. Rainier visitor center (elevation 5400') observed elevated PM2.5 concentrations 3 hours before the closest purple air sensor at Longmire (elevation 2700') and 8 hours before the purple air sensor in Ashford (elevation 1700').
Could you help me understand how the different sensors give what seems to be quite different readings.
ReplyDeleteToday your map shows air quality near Lake Padden as reading a 62 and lists this as a low cost Purple air sensor.
However on the Purple air site the reading at what appears to be the same sensor is 97.
There were many other inconsistent readings.
What say you to help me make sense of this?
thanks
Ed
Hi Ed, the differences you see are namely due to 3 things: 1) PurpleAir defaults to a 30 min avg while EPA AirNow (shown on this site) uses a NowCast averaging which goes back several hours, 2) the correction factor selected on PurpleAir often defaults to LRAPA but EPA has their own correction (a correction is needed because low-cost sensors don't measure mass, they count particles, and raw PurpleAir data is too high), 3) PurpleAir shows all sensors while EPA selects a subset that are outside and show decent history. Please let us know if you have more questions on this topic.
DeleteFarren, Beth and all posters, thanks so much for the work you do on this. I'm all over this blog during smoke events and I'm just thinking about how if this site did not exist we would not know what to expect. Your site and cliff mass blog are my go-to resources and I just feel thankful you collect, interpret and present the data otherwise we'd all just be looking out the window at smoke and hoping for the best but with your help we can plan.
Deletethanks for that explanation.
Deleteso of the measurements which should I consider most accurate at a given time ?
thanks again
Ed
What I like to do is select the closest regulatory monitor (a circle), and then go down to the 5th bullet on the pop-up. It will automatically select "NowCast", but you can change it to "hourly concentration". That will give you the time series. There are also many tools on the Ecology dot map for regulatory monitors.
DeleteClarification on the Purple Air map default settings: Purple Air's map defaults to 10-minute averages with no correction applied, but users may see different settings if they have previously changed them and have browser cookies enabled.
DeleteThese explanations were great Farren! Thank you so much!
DeleteA day or two ago, I heard on a report that smoke might return to Western Washington later in the week. I have not seen any updates since. Do you know yet if there's much of a chance of the smoke coming back to the west side of the Cascades by next weekend?
ReplyDeleteThings are still uncertain, but it looks like the winds will shift to transport from the north Thursday/Friday--which would transport smoke to the region. Any moisture will dampen smoke production from the fires in British Columbia and the North Cascades...but how much moisture over the next few days is uncertain.
DeleteJust wondering why the smoke forecast seem to always be overly optimistic…..Case in point: The smoke forecast for this past weekend was 102-105 for Puget Sound, yet by yesterday(Sunday) evening here in Seattle the AQI was 196……Same for dispersal, frequently seems like a carrot tied to the end of a stick: Original Warning was originally to expire at midnight last (Sunday) night. Then it moved to 10:00am this morning(Monday 8/21). Now it’s 10:00 am TOMORROW(Tuesday, 8/21)….Are the smoke behavior models just not as accurate as the 24hr. Weather models? Are smoke forecasters just a more optimistic bunch than most?
ReplyDeleteHi Mark, without knowing which forecast you are referring to (e.g. the ARA outlooks, the map on this blog, or the blog posts), it's tough to address too many specifics. The forecast you mention was made Friday morning before smoke had carried into the Puget Sound, so there was uncertainty in both loading and clearing of the smoke for the days ahead. It also sounds like you are referring to the Air Quality Alert which was issued for the weekend. We would set the AQA to run until the smoke clears, but the NWS requires an end time/date when we issue an AQA. Don't pay much attention to the end time stated in AQAs because it is usually set relative to the next scheduled forecasters meeting. It's typical to set an AQA for the weekend to be reassessed on Monday morning when people are back in the office.
DeleteOtherwise, there are a few factors that cause smoke forecasts to under-predict in situations like we saw recently. 1) New fires that weren't considered when the morning forecast was made, 2) cloud cover reduces the number of fire locations included in the model (less satellite detections), 3) residual/carryover smoke is not accounted for well, 4) cloud cover reduces the ability to see fire activity from satellite imagery (for manual forecasts), 5) most AQI forecasts are for a daily average, not a daily maximum, and 6) most smoke forecasts do not consider fire behavior, they only perpetuate recent fire activity.
Farren, it's really interesting to hear you say "Don't pay much attention to the end time stated in AQAs because it is usually set relative to the next scheduled forecasters meeting." Those AQAs get shown on all sorts of weather forecast websites and weather apps. I'd bet that nearly everyone who reads an AQA (thousands of people? More? Certainly way more than the number who read the comments on this blog) thinks that the alert end time is the predicted end-of-smoke time. I'm not an expert, but my impression is that other NWS alerts (high heat, flooding, etc.), the end time is indicative of the expected end of the threat. If there's a way to make the posted end time more meaningful, you'll be improving one of your main methods of communicating with the general public!
DeleteWe would prefer to be able to issue AQA's that say "until further notice", but NWS doesn't allow that. It's important to consider that predicting smoke concentrations days into the future is exponentially more difficult than predicting meteorology. We generally follow the advice of NWS when it comes to end times, but there is a lot of uncertainty. It's not uncommon for the forecast to change as events develop. So, it's standard practice for AQAs to be revised through the duration of the event. NWS also wants AQAs only when it is expected to be Unhealthy AQI or worse, so we don't do long-duration AQAs when smoke is intermittent. Other NWS warnings also get extended (or expire early) as needed. Also consider that our state has 7 clean air agencies, 3 Ecology offices, and 3 NWS offices to coordinate with for AQAs... so if an AQA goes out on a Friday for the weekend, most state workers are unavailable to make changes to the AQA until Monday morning. Thus you will often see AQA's issued on Friday that go through Monday. On Monday, we would re-assess conditions and revise the AQA if needed.
DeleteI always learn so much from conversations like this. Thank you to the people commenting with the questions and a big thank you to Farren and Beth for the engaging replies!
DeleteAmazing intel. Was incredible to watch the transformation today over Puget Sound. Also curious Are we able to forecast smoke for the end of this week yet? Selfishly asking bc I’m hosting a large wedding outside.
ReplyDeleteWhere are you located? Winds will likely shift at the end of this week, but depends where you are.
DeleteHi Beth :) The wedding will be located at Heronswood Garden in Kingston
DeleteCurrently good air quality is forecasted for Kitsap County through the week. That said, forecasts do change, and will be updated to reflect changes in conditions. Shifting winds later this week could bring Canadian smoke back to the Puget Sound region, but how much smoke is uncertain.
DeleteLooks like it's coming back for the whole weekend again?
ReplyDeleteWe just posted an updated forecast. Moderate to USG smoke will likely impact northern counties for a couple of days, and areas near fires will be intermittently smoky.
Delete