Friday, January 29, 2016

Weather Station problems Oregon Scientific WMR100

This is a technical write up describing the problems I've been having with my primary weather station in Northeast Shoreline, the one I use for my historic data. The station is an old Oregon Scientific WMR100 that has been in service now at it's current location since September 29th, 2008.

Couple of weeks ago I started to notice a temperature issue with the station.  It was reading on average about 8-10°F higher than surrounding personal and professional weather stations. After doing some reading I learned that sometimes the internal components get corrosion or wet (housing is not water proof, only water resistant) and this typically causes a 10 degree rise in accuracy.

Wednesday night I brought down the station mast and removed the station for service, at first I attempted fresh batteries and a full hard reset to see if that would bring it back to normal, no such luck. So, I brought it inside and begin taking it apart.

The WMR100 sensor array partially disassembled and opened up.

Nothing was terribly exciting inside the unit other than a couple dozen spiders and a lot of spider webs, insect remains and other related debris. I cleaned everything up but didn't find any apparent cause of the temperature inaccuracy that I was able to see upon visual inspection. The sensor it's self has some kind of bronze glass thermistor or thermocouple bead, the PCB displayed "TH" for the abbreviation of the temperature sensor component. It is also using a resistive type humidity sensor element. Since the sensors in the little white box were full of spider webs, I brushed them all off with an old toothbrush and some isopropyl alcohol.  This was wrong, as it destroyed the relative humidity accuracy for several days, it appears to have recovered now.  I briefly got the temperature accuracy to match the indoor temperature where I was working on it, but when I got it all re-assembled it was settling for about 5 degrees hot again.  Disassembled and re-assembled again attempting to figure out why but it wouldn't leave the 5 degrees hot range.

So at this point in time it's close, appears to be anywhere from 3-5°F warmer than surrounding stations. At this time I am not in the position to replace this with the same or better model but eventually I plan to upgrade to a Davis Vantage Pro 2 cabled, wireless doesn't provide a good smooth constant stream of data so wind gusts can easily be missed, as they often are with wireless units.

If I get some more time this weekend or next week I'm going to take the station back down again and see if there was something I missed that might be causing the accuracy issue with temperature, the humidity sensor seems to have recovered on it's own.  I read that resistive humidity sensors sometimes take a day or two to outgas after contamination.

At this time, for temperature data I am relying on my secondary station I have set up in Lake Forest Park, on my webpage the data can be accessed under the "LFP Data" link in the navigation bar.

Wednesday, September 11, 2013

Late season heat wave

Today and tomorrow the region is under the spell of a small but late season heat wave.  With an unusually warm August, and stormy I might add, we are followed with this in September.  Seatac broke the daily record high today of 93°F, old record was set in 2009 at 87°F. 

To compare, in Shoreline today's high was 90°F, in September 11th, 2009 it was 85°F.  Possibly the result of how summers work around here during a cold PDO? 

Wednesday, January 2, 2013

December 18th, 1990 Snow Event

Also known as the Arctic Express, Mother of all Convergence Zone's and Seattle's December Blizzard.  This storm was not only my first most vivid memories of any weather event but probably one of the biggest influences on why I am so interested in weather today.  I never wish property damage, injury or death to anyone, however, I would love to observe a storm like December 1990 again as an adult where I am more capable of documenting and photographing such an event.

Heaviest snow fall I've ever witnessed started at about lunch time on this day.  I could be wrong but if memory serves 8 inches fell within a half hours time.  After that we had lighter snow fall for the rest of the afternoon.  Near as I could tell there was a little over a foot of snow when I left school, I remember it coming all the way up to my knees (I was a little boy at the time.)  When I had gotten home from school that afternoon the power was out, and it didn't return until mid day the next day.  I remember just after it got dark that there was a bright flash and a very loud thunderclap, snow was coming down pretty hard again during this time.  As darkness completely fell I wasn't able to tell from inside if it was still snowing because the power was out everywhere around us, no street lights or porch lights to watch for falling snow under.  It was an early start to the school districts winter vacation and the ground remained covered in snow until it was time to go back to school after New Years Day. 

Stories and photos from the storm are difficult to find and I've noticed particularly out of all the news articles I can dig up, like with many events, The then unincorporated King County, (Shoreline School District) now City of Shoreline was largely left out of the picture.  I've been unable to find what the snow depths were or any other details other than based on my own memory as a child.
My own artwork inspired by the December 1990 snow, created 1997.

One thing I haven't been able to find at all, is a surface analysis map of the region on December 18th, 1990, around noon time.  Everything I've read and researched says it was a Puget Sound Convergence zone storm, biggest one probably ever observed by modern instrumentation.  All the stories go, that a cold air mass in British Columbia moved closer and closer to the US border, when during the afternoon the cold air rushed into the Puget Sound generating a convergence zone.  Such convergence zone would not be the conventional kind where Westerly wind moving around the Olympics meets in the middle of the Puget Sound, but instead a convergence of warm moist air to the south colliding with the cold arctic air pouring into the Puget Sound.  We had a similar but not nearly as strong convergence in December 21st, 2008. 

I can only imagine right now that in order to generate that pattern you would have to have a strong high pressure over Western Canada with a deep low pressure sliding south off the coast of Western Canada and Washington before changing into an eastern direction just south of the Puget Sound or through Oregon.  A similar situation was occurring in December 2008, however the pressure gradients were not nearly as strong or in quite the same directions and paths.

Was it really a blizzard?  The current criteria for a Blizzard is falling snow, with winds exceeding 35mph gusts causing a reduction in visibility to less than a quarter mile, for 3 hours or longer.  We had winds gusting to 50-70mph, after the heaviest snow had already fallen, was it still snowing?  Hard to say due to blowing snow but I do remember visibility being cut down quite a bit.

Temperatures started in the low 40's in the morning and then quickly dropped to the low 20's in the afternoon as the snow started falling.  Temperatures at Sea-Tac (Not Shoreline) never broke freezing again until Christmas Day.  Lows ranged in the teens with highs in the mid 20's.  After December 25th another surge of arctic air blew in and resulted in a wider spread snow storm for the region before everything begin to thaw starting around New Years Day.

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One of my goals with this blog, is to have all of the major arctic or snow events, documented in one place that has occurred in the greater Seattle area, in an effort or attempt to identify any patterns associated with the snow events.  I suspect it's actually several global patterns and local patterns combined that make the perfect recipe for a snow disaster for this region.

Tuesday, January 1, 2013

New webpage and URL

I have a new URL for my webpage, http://www.shorelineweather.com

Also have written a new layout, hope everyone likes it.   You can also get to it by clicking on the home button above.  New navigation bar to incorporate the blog with the web page.

Sunday, September 9, 2012

Weather Station outage August 31st - September 2nd

Data from the weather station from the Afternoon of August 31st, 2012, through the evening of September 2nd, 2012 is void, due to a typical bug with the WMR100 receiver.  Station was reset September 2nd to resume normal data logging.  Sourcing data for archive in Weather Watcher reports from Shoreline Central Market's weather station.

Monday, August 13, 2012

Raingauge tipped on accident.

Sunday evening at about 5pm I was untangling an extension cord on the deck, which happens to be the same deck that the rain gauge is mounted on.  In the process I accidentally bumped the rain gauge, which caused it to register 0.09 inches of rainfall.  This data is false, as we had a bright and sunny day with no precipitation.

Sunday, August 5, 2012

Summer is here

Recorded a high temperature Saturday afternoon of 87.3°F, first time we've gone past 85°F since August 15th, 2010.  A possible high above 90°F is in line for us Sunday afternoon.