Several folks have asked me whether we will break the record for the driest July in history.
Several locations, including SeaTac Airport, have had no precipitation this month, and to put it bluntly, little is predicted for many locations.
First, how much has fallen so far? For western Washington, some locations have received a bit, such as the Cascades (from some thunderstorms last week) and along the coast.
To illustrate, here is the latest UW WRF model simulation of clouds at 2 PM tomorrow.
Looks impressive, right? You can tell it is convective by the mottled appearance of the simulated clouds. Lots of mid-level cumulus.
The NOAA/NWS HRRR model is similar.
The UW extended accumulated precipitation from this morning through the end of the month (below) predicts considerable rain over coastal BC, but little over much of the Northwest, except for the far southwest that gets a piece of the monsoonal moisture streaming up from Arizona, Nevada, and Utah.
The bottom line is that SeaTac and other sites around here could easily end up with no July rainfall.
Now the shocker: this would not be any kind of record. Several previous Julys have done the same.
To show this, here is the July rainfall at SeaTac going back to around 1950. Six previous years have had a trace or zero. There does seem to be a trend towards drier Julys, something that is consistent with global warming simulations.
At least you don't have to worry about carrying an umbrella. And with dropping temperatures, the weather should be nearly perfect for outdoor recreation or a hearty barbecue.
Thanks for keeping us posted. Count me among the many who have a long list of fair-weather projects to catch up on while conditions hold (west slopes). Summers are a lot tougher in eastern Washington, and always are. My friends and relatives in the east have a lot of difficulty grasping how radically different from one-another zones are here in Pacific Northwest - the coast(s), rain shadows, and the crest. As a result, few generalizations "fit" everywhere. We get it; they don't.
ReplyDeleteHiking and trail work on south-facing slopes can get a bit warm on sunny hillsides. Give a thought to the volunteers of WTA. Been there, done that, have the T-shirts.
ReplyDeleteEast of the Cascade Crest it is very hazy – Sunday AM. The satellite view has the backward-tilting cloud band not quite reaching the Ellensburg area.
There is smoke from several fires and little wind (3 mph at KELN). The average July rain is 0.20 inches, so nothing new here.
It's a bit tricky to say just what the driest July on record for the region was. It's difficult to directly compare stations that have long PORs with those that don't; and what area constitutes "the region"? The presence of relatively large topographic relief in close proximity to the open ocean tends to divide "the region" up into sub-regions which aren't necessarily easy to compare in such a specific way.
ReplyDeleteThere 56 sites west of the Cascade Crest between the Columbia River and the Canadian border for which historical data are readily available via NWS Seattle. Among the relatively few stations with the longest PORs, July 1922 stands out as having been notably dry. The Julys of 1958 and, especially, 1960 were also very dry area wide. In the recent past, the Julys of 2013, 2017 and 2021 stand out. It should be noted, however, that none of the Julys during the aforementioned years, or any others, appears among the driest at more than 21 (2017 and 2021) of the 56 stations - a testament to the large climatic variability that occurs across "the region".
Many interior lowland locations have had completely rainless Julys with the exception, among the major stations, of KSEA and KBLI which have each bottomed out with a trace - so far.
well, it's a little difficult to break a record when the measurement line stops at zero - it's not like we could get 'negative precipitation'. also noting five out of the past six Julys (including 2024) were extremely dry.
ReplyDeleteThere might be a way to get into negatives or drought beyond zero precip if you take into account whether winter precip in the mountains fell as snow in which case it will be available to rivers as summer snowmelt or as rain in which case it just washes right out when it falls. Maybe I am wrong about that and snowmelt is just replaced by melt from whatever passes as remaining glaciers so mountain discharge is stable. I don't think so, though.
ReplyDeleteI had a somewhat weird experience with the temperature and humidity profile. A friend and I hiked to Glacier Basin (4500 feet) above Monte Cristo. It was very uncomfortably warm and humid for hiking up, even at 9 AM, and NOAA had predicted pass temps about 90. But as we returned to Monte Cristo and to town it got progressively cooler and cloudy. There was, however, no rain or thunderstorm despite the fact that we were in the heart of the traditional Cascades convergence zone. The weird thing was, how much hotter it was in the high country than in the valley. Must have been one of those "super inversions" that prevented significant convection.
ReplyDeleteCliff, where the heck did the system we saw this morning come from. There was no mention of it. Woke up to thunder, smelled like rain, couple new fires.
ReplyDeleteWhat happened to summer? Highs in 60s yesterday, Brrr. Hopefully we can back to 80s soon. summer just started and I hate to think it's over already.
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