End of Summer, Another Dry Water Year, & Looking For Rain

9pm Tuesday…

Since I last posted, we’ve seen August give way to September. Labor Day Weekend has come and gone too, a nice “end to summer” with abundant sunshine but no hot weather.

Of course meteorologically we just finished summer which runs from June to August. In Portland, Summer 2021 was just barely edged out by a slightly hotter Summer 2015. By 0.1 degree! Basically it was tied with 2015 for hottest summer on record at PDX.

In Salem, Eugene, Medford, & Redmond it was the hottest on record. As I’ve mentioned many times, Salem’s climate record is excellent, going back to the late 1800s. This summer was a scorcher!

This was our 9th consecutive warm/hot summer; of course not all of those were “hot”. Last year is a good example, just a bit warmer than average. 2012 was the last time we had a “cool” summer, mainly due to a very cool June. But 2015, 2018, & 2021 have been blazing hot. Portland has seen (so far) 24 days at/above 90 degrees. That’s at the higher end, but we’ve seen more in 2015 and 2018.

Salem has seen 39 days that warm; a new all-time record there. Eugene also set a record…41 days at/above 90 degrees!

Of course the drought continues… Portland has only seen .05″ rain in just under 3 months. And the six month period from early March through early September is the 2nd driest six-month stretch on record. Summer & early fall 1987 were slightly drier.

This means we are seeing another very dry “water year”. By the way, a water year is a term used throughout the Western USA. Since most precipitation falls in the cold season (straddling two calendar years), it makes sense to look back at wet seasons separately, which means starting the “water year” on October 1st each year and ending September 30th. We’ve got three weeks left this year. Right now it’s the driest since the 2000-2001 drought year…in Portland. We haven’t seen a wet year since 2016-17. Of course we could easily pick up 2″ rain the 2nd half of September, but even then it would be a much drier than normal year. Typically we get about 36″ in Portland each year.

Do we have any rain ahead? Not really, at least nothing significant through mid-month. A weak system drops a few showers tonight, then mainly or all dry through at least next Tuesday/Wednesday. Take a look at the ECMWF ensemble forecast chart for the next two weeks. It shows 24 hour rainfall. Each thin horizontal line on upper part of chart shows one of the 51 ensemble members. Time goes from now (left) to two weeks out (right).

Notice almost no members produce .10″ or more through the middle of next week, instilling high confidence that we’ll be dry through the 15th. But you’ll also notice around the 18th or so a lot of ensemble members say we could actually see rain. I’m not saying this is the case, but every few Septembers we get a big soaking the 2nd half of the month. In fact 3 of the past 4 Septembers we’ve picked up at least 2″ rain during that time.

It would be wonderful (and mainly finish the fire season) if we could get 2″ of rain in valleys plus 4″ in mountains the last ten days of the month.

One more note, it’s also obvious that we’re making a turn toward more typical (cooler) September temperatures starting Thursday. The same morning ECMWF model ensembles show temperatures consistently in the 70-80 degree range the next 10+ days. Summer is over…but warm early fall weather is here for awhile longer

Chief Meteorologist Mark Nelsen

51 Responses to End of Summer, Another Dry Water Year, & Looking For Rain

  1. Ken in Wood Village says:

    I decided to go back and pay for a weather site since we are starting to get into Fall and Winter season. The past 6 months have been very uneventful so I saved some money…lol.

    I have been looking at the GFS and Euro models on and off for the past couple of hours and one thing that does stand out is the Jetstream. The GFS is a little more aggressive because I’m seeing winds close to 200 knots. With the Jet being this strong, even if we had High pressure move in, it won’t stay around for long.

    The Low that is suppose to come in next weekend, I found were it’s coming from. It’s just North of Taiwan right now. It’s Tropical Storm Chanthu. With it being a Tropical Storm, I’m thinking those characteristics of being a TS could stay with it by the time it hits the PNW. I believe we need to keep a watchful eye on how this storm develops when it approaches PNW. I don’t think it would be like the Columbus Day Storm but I did notice the Jet is strong (about 138 knots) and maybe that could influence the storm when it approaches the Coast.

    What I believe is, we are going into a active pattern. It’s been awhile but I think we could be going into were we have storm after storm hitting the PNW. One reason why I say this is because of the Jetstream. The Jet seems to want to push the High pressure systems out of the way to allow storms to move in. I’ll see if my hunches are correct!!

    • Hank says:

      Im pretty sure the low pressure that is going to it us is the one north of japan right now which is not a tropical storm. But i agree with what you’re saying, Also im curious, which pay for weather site is the one you use?

      • Ken in Wood Village says:

        I looked at the model again. Your right, it’s the Low your talking about. Sometimes it’s a little hard to know what your looking at with the models. I wish they had names for the landmasses…lol.

        I’m using weathermodels.com website. I tried using weatherBELL before, it’s a little more complex than what I’m use to.

        I still think we will have an active pattern because of the Jet. It will be interesting to see how active the Jet becomes this year. If it’s very active (strong) then we could be seeing storm after storm. I think this could be just the start of a strong Jet.

      • tim says:

        In September 2013 we have a series of strong storms that hit the west coast then completely dead the rest of the fall could this be the same setup?, well see.

  2. Jake says:

    I really hope this rainstorm verifies with the intensity suggested because here’s what pine trees are starting to look like:


    • Jake says:

      I’ve never seen a drought like this before in tandem with such heatwaves. Clearly some of those trees are not coming back next Spring

  3. Joshua Lake Oswego says:

    The 00z is the wettest run yet. >1’’ from Bellingham to Eugene through next Saturday. >2’’ from PDX to Salem. Mid-50s for a high on Saturday.

    No chance this verifies, but it’s fun to look at.

    • Oliver Watson says:

      So sad that we are saying no chance this verifies. All we are talking about is a little above normal rain for September, not an epic 2 foot snowstorm and 0 degree temps. Sad times we live in

      • Joshua Lake Oswego says:

        Don’t take my word for it. Hard not to be pessimistic though. The 00z GEM brings the trough in much further south too. If we get a good widespread soaking, I will be very happy. Still almost a week to go. Lots of time for details to be ironed out.

    • tim says:

      Looks like a one storm event then bone dry the rest of the month, I hope this isn’t the setup for the fall/winter more dry then wet.

  4. tim says:

    My neighbors on the south side of my house has three months of garbage piled up in there back yard waiting to be burned once the burn ban is lifted they don’t pay for garbage take out, you guys in portland should have no problem seeing the thick black smoke it’s gonna look and smell nasty, so much for clean air after the first rain.

  5. Joshua Lake Oswego says:

    The 12z GFS digs the trough further south like on the 00z. A real beaut. We need to get the Euro back on board.

  6. tim says:

    The 00z says one “storm” next weekend then ridging afterwords, not surprised one bit.

  7. tim says:

    Cliff mass new post on major rain event next weekend but this flow is coming from the WNW so lot of rain shadowing for Puget sound and Willamette valley, boring.

    • tim says:

      And of course models always overdue the rainfall amounts anyways so take the total amount and cut it in half at lest.

      • Joshua Lake Oswego says:

        Saying half is giving the models too much credit unless we are within a couple of days. 10th percentile on the ensembles is the magic forecasting tool.

  8. Roland Derksen says:

    I haven’t added up my water year total for 2020-21 yet, but I don’t expect to be a particularly dry year- we had a lot of rain in December and January this past winter.

  9. W7ENK says:

    Lots of rain this morning on the back side of the Cascades and out into Central Oregon. Cloudy here, but not a drop to be had on this side of the mountains.

  10. tim says:

    Forget la nina, Neutral years are the best we see our biggest storms, flooding, Artic outbreaks, Windstorms, ect and the way enso is looking I say we have a good chance of a Neutral winter instead.

  11. JERAT416 says:

    With how dry we have been the last 5 or 6 months, how have we avoided water restrictions?

  12. tim says:

    Cpc has us cooler then normal long term, if this was a year ago it would be showing normal temps instead in the same pattern since noaa bump up the average daily hi’s this year.

    • Andrew says:

      Thanks for sharing. Can anyone elaborate on what we tend to see here with the second of consecutive la niña winters? I recall some discussion last year that the second la niña tends to drive certain trends in our weather but don’t recall specifics. Thanks!

  13. Patrick b says:

    Thank you, Mark. This is one blanked up one

    Summer, it’s been nothing like I have seen before, is there any thing in the long range for rain? In my opinion its getting really importan

  14. Anonymous says:

    The Euro and GFS currently in agreement on a storm hitting us 10+ days out 😍

    I know it’s way too early, but just seeing the two models come to agreement on major precipitation makes me want to do a little dance.

  15. W7ENK says:

    Seattle got a thunderstorm last night.

    WTF?!? Why can’t we get anything???

  16. Paul D says:

    End of summer? That’s funny! When it stays below 80 for a week, I’ll begin to believe summer is gone.

  17. Zach says:

    Todays 12z Euro delivers a nice wildfire showstopper at the end.

    • tim says:

      Once again the crazy 18z is showing a wet storm around the 20th only for it to dry up once that date arrives.

  18. Opie says:

    Stronger than usual trade winds (blue and purple) are a leading indicator of La Niña, so even though the 3.4. region has been warming recently, I’m still confident of La Niña conditions a few months out.

    NOAA will update its forecast tomorrow – second Thursday of each month.

    • tim says:

      Because la Nina is getting a very late start and that’s assuming it’s gonna happen the effects la Nina might not happen until mid to late winter at best.

  19. Roland Derksen says:

    Some light showers here this morning, and perhaps more tomorrow. I can’t say we’re in a drought situation anymore, what with the 0.69 inch amount we had on the 4th . We could certainly use more rain though.

  20. Anonymous says:

    Looks like only a single location got measurable rain last night and I’m wondering if even that is a fluke: https://or.water.usgs.gov/non-usgs/bes

    Not at all surprising. I also wouldn’t be surprised if the storm coming in on the 18th never reaches the valley.

    I’ll take this comfortable sunshine though as long as we don’t get anymore smoke.

  21. W7ENK says:

    Woke up at 2:50am to an incredibly light pit-pat of raindrops out my window. Few and far between, only lasted a couple of minutes, and wasn’t anywhere near enough to wet the pavement, let alone register anything in either of my rain gauges.

  22. Mark, my summer was a bit strange but yet interesting. In June the first half of the month I had 1.93 inches of rain which seeming came out of no where based on how dry the March to August period has been. In the second half here in Southeast Tacoma I reached 105 degrees which tied the all time high here set back in July 2009,

    July and August were rather boring. Nothing spectacular with temperatures and next to NO precipitation or at least anything significant on any one day. July only a trace here and August just a meager 0.06 inches.

    I know the NOAA CPC has a La Nina in their projections and based on 1.2 negative forecast I did see I tend to think this one will be a bit beefy so put that thought in the Nelsen vault for later viewing please.

  23. tim says:

    Summer is over but it’s not unusual to get a burst of warm weather in October, 70’s are very common the first half of the month.

  24. W7ENK says:

    Lots of moisture just off the Coast this evening, even some lightning in it about 200 miles offshore, straight out from Tillamöök. Will probably evaporate entirely as the front pushes inland overnight and into the morning hours, but just in case, I’ll be pulling the cushions off the lawn furniture before I go to bed. 🤷🏼‍♂️

  25. tim says:

    And that’s why we ignore the 18z it’s always wrong, the drought continues.

    • Joshua Lake Oswego says:

      The 00z GFS looks fantastic for you and all of western WA mid/late next week. Oregon is left out per usual.

      • tim says:

        Not really, this pattern looks like a NW flow which means a classic Olympic rain Shadow effect for central Puget sound.

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