Wetand News

I have been hearing from a lot of folks suggesting that our weekends have been wetter than our weekdays , and asking me whether this was true. So is it true?  Are the weather gods preferentially punishing Puget Sound residents over the weekend? Are the weather gods punishing us? Let's find out!  To do this, I secured the daily precipitation statistics at Seattle-Tacoma Airport for May and June so far--43 days in all. For the full period , there was 4.04 inches at Sea-Tac for . 09 inches per day . For the 31 weekdays, there was 1.72 inches in the rain gauge, or .05 inches per day But for the 12 weekend days , there was 2.32 inches or .19 inches per day . Yikes! It is true!  The weekends have been wetter, with nearly FOUR TIMES MORE PRECIPITATION PER DAY THAN DURING THE WEEKDAYS. Good reason to complain.  But is this a real effect or just chance? There have been a number of investigations of this serious topic, a recent one led by one of my ex-students:  Prof

As I discussed in >a previous blog , there is little evidence of transmission of COVID-19 in outside air, with a substantial and growing literature documenting the lack of risk for virtually any activity in the outside air. Empty parks in Seattle But now, there is even more compelling and powerful evidence of the lack of COVID threat in outside air, even in a worse-case situation:  the lack of surge in COVID cases following the large protests in Seattle and other cities. The protests represent the opposite of responsible social distancing, with large crowds of hundreds or even thousands packed in close together.   People are screaming, chanting and singing:  activities that are optimal for spraying virus-laden droplets into the air.  Many, but not all, of the protesters are wearing masks, with most of them using the less effective cloth ones.  And tear gas causes people to cough and expel large quantities of mucus and droplets.  If you want to spread a dangerous virus, y

With all the challenges we have dealt with during the past months, there does appear to be some good news on one front:  there is no reason at this point to  expect an unusual wildfire season over Washington State this summer . As shown by this plot of the average number of wildfires over time in our region, we are now entering the period of typical rapid growth in the number of wildfire events (blue line shows today), with the peak in August.  There are currently no wildfires burning in our region. And the situation looking forward is quite favorable in most aspects. During the past 30 days, Washington State has been wetter than normal and the eastern quarter MUCH wetter than normal (see below).  This is very important, because the surface fuels and upper soil layers are being wet down immediately before the fire season. The National Interagency fire danger forecast for today shows low (dark green) risk. The forecast of accumulated precipitation over the next week

Another weekend, another thunderstorm--perhaps. Some modestly unstable air is approaching the region and there will be showers from Puget Sound southward,how many will have the "juice" to provide lightning and thunder? The latest visible satellite photo (7:12 AM)  shows a large fields of convective showers, produced by instability in the vertical,  over the Pacific Ocean (the showers are indicated by the "popcorn-looking features).   A star is shown over Seattle for orientation. We can get an idea of how high these showers are (and thus their intensity) by viewing an infrared satellite image at the same time. This imagery shows the temperatures of the cloud tops, with taller clouds being cooler (see below)--the green colors are the highest. Clearly, some convective clouds--like cumulus/cumulonimbus-- out there, but right now none are producing lightning (we would pick that up with our lightning sensors). All these instability clouds are there because two

Announcement: Online Talk:  The Mathematics of Weather Prediction, Sunday, June 7 at 1 PM. I will be giving a talk on the how mathematics is used in weather prediction that will be available online (Zoom).  This is part of the "Math Hour" outreach of the UW Department of Mathematics and is directed to middle and high school students, but should be interesting and accessible to a wide audience.  If you are interested, you should register  here .  If the 1 PM session fills, will do it again at 2 PM. _______ On Saturday morning, as thunder rumbled through the region, something remarkable happened:  radar and satellite imagery revealed the highest thunderstorm tops I have ever seen west of the Cascade crest, with some extending to 49, 000 ft. These were the tops of active thunderstorms, in an area where we get excited if they get to 25,000 ft. We can determine the thunderstorm tops using the local National Weather Service weather radars, which provide echo tops :  the

Saturday, for many reasons, was an extremely dark day here in Seattle. The view at 1 PM Saturday, near solar noon, was ominous and forbidding. Meteorologically, it was the darkest day during the last week of May in twenty years, according to Mark Albright, a research scientist at the UW and past Washington State climatologist. The solar radiation at the top of the Atmospheric Sciences Building at the UW was extraordinarily low, only reaching 2.82 megajoules per square meter (mega is million and joule is a unit of energy).  The day before it was almost 27...nearly ten times more! A plot of the daily solar radiation from the wonderful WSU AgWeather site showed that Saturday had the lowest solar radiation in Seattle since early March, when the day wass much shorter and sun much weaker. The reason for the low solar radiation?  The key one was the extremely deep and persistent clouds that hung over us the entire day, something evident in the visible satellite image at

As predicted, the second.....and probably more potent...line of thunderstorms is now moving northward near the Oregon/WA border. The latest visible satellite image (4:26 PM) shows several major, strong convective systems entering Washington State.  The one on the right has good radar coverage from the Pendleton, Oregon NWS radar, but the western one is in the well-known radar hole over the eastern slopes of the Cascades. The radar image at the same time (below), shows intense radar returns with the eastern storms (red colors), but the western systems have poor coverage so we don't know how strong they are.  Since they are heading for the Cascades and western WA, this is not good. Over the past half hour, lightning sensors have shown massive lightning in these storms (see below, each strike is shown by an "X") There are some strikingly strong winds with this line of thunderstorms, with some gusts reaching 60-70 mph! (see the max gusts over the past hour b