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Instrument Calibrations

As noted in the about page, I regularly check our sensors to be sure they are within specifications. Over the last couple weeks I have been conducting tests.

Temperature was right on. That’s typical, as our sensor is pretty bulletproof. I have a platinum RTD digital thermometer that’s accurate to within 0.1° F (best to check on a cloudy, windy night to eliminate radiation as a factor). I also have a laboratory-grade aspirated psychrometer with a dry bulb thermometer that’s extremely accurate. It’s analog, so the biggest challenge is reading between the lines. But my tests show the station’s thermal sensor is within 0.5° during the day which is quite good. There’s also a backup sensor on site as well. At night or on cloudy/rainy days, the two sensors are normally within 0.2° F. During sunny days, height (7 ft vs 21 ft) and shielding differences (active vs passive ventilation) can frequently lead to 1° differences in either direction. 2-3° differences are not out of the question when it’s particularly calm and sunny.

Continue reading “Instrument Calibrations”

Recent Site Changes

Earlier this week I removed the cloud icons that formed the main navigation links throughout the site. This design methodology had passed its shelf life. It also limited the font size of the embedded text. By deploying more generic buttons I was able to change its font type & size. This should make navigation clearer & easier to use.

In the weather history section, you can now click on each of the 24 hour graphs at the top for a much larger, more detailed version of the image. These images are not straight duplicates of the data in the smaller graphs and contain some custom “enhancements”. For instance, the detailed dew point and humidity graphs contain corrected & smoothed values (rolling 5 minute averages to prevent readings from jumping around too much when the air is unstable). The software that connects the weather station to the website cannot correct for sensor errors in real time. I do that immediately after the reading is taken. Then I send the corrected values to the site (current conditions, history tables). Unfortunately the smaller graphs are generated before I can access them. Note that the larger dew point and humidity graphs are still “initializing” which means that some of the data from yesterday is missing. This will correct itself by about 8 PM Saturday evening.

I also fixed a small bug whereby if you had selected metric units in the page settings of the City page (home page) AND you also selected unrounded temperatures you would only see rounded temperatures.

Website is Now in Summer Mode

Usually I wait until May 1st, but the upcoming 7-day forecast shows temperatures almost entirely above freezing with daily highs in the 40s & 50s. Some rain is possible next week. This is not what I would describe as “wintry” by U.P. standards. Since the site only has two modes, I think it’s time for “summer” mode.

This means that wind chill will no longer display in the current conditions on the City page (home page). Rain measurement will take its place to the right of temperature. However, until April 30th, you can monitor hourly wind chill via the daily table on the Weather History page.

Keep in mind that for wind chill to be calculated the temperature must be under 46° and the average wind speed must be at least 3 mph. Otherwise, the wind chill is the same as the ambient temperature. In actuality, wind chill remains very close to (if not identical to) the air temperature until the latter drops into the 20s and/or there are very strong winds.

If we get another cold spell this spring, I will return the site to winter mode temporarily. Let’s hope that’s not necessary!

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P.S. If it snows in the next 7 days, it’s officially my fault.

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UPDATE 5/9/2020: The website is temporarily back in winter mode due to the recent snowfall and cold temperatures. I anticipate by Tuesday the 12th I can return it to summer mode for good (knock wood).

Live Blog (April 12-13, 2020)

NOTE: Entries are in reverse chronological order. This page does not automatically update.

  • 4/13/20 3:50 PM
    Winds continue drifting westward, shutting down lake-effect snow production. We’ve had no measurable snow since 12 PM. Humidity has dropped to around 65%. This should spell the end of our snow storm. I see that the National Weather Service has pulled down the Winter Storm Warning that was supposed to last through tomorrow morning. Gusty winds should subside over time, especially after sunset. But do mind the lakeshore flood warning and stay clear of Lake Superior as it takes some time to settle down after winds abate. Anyway, that ought to do it for our live blog. Again, our storm total was 17.2″ as measured 1 block north of the Jacobetti Veteran’s Home near downtown Marquette.
  • 4/13/20 2:45 PM
    Some light flakes continue to fly but nothing significant. The focus now is on the wind. Even as the trough of low pressure crosses into Quebec, it continues to deepen, drawing air from areas of higher pressure, such as Marquette, toward it. How big is this system? Well, it has 5 frontal boundaries extending from it, including 2 cold fronts stretching down into the Gulf of Mexico!
  • 4/13/20 1:15 PM
    After declining for about 4 hours, winds have kicked back up in the last hour as the surface low exits the region. Gusts nearing 35 mph have been observed here. Snowfall has tapered off to light snow showers as winds have turned solidly to the northwest.
  • 4/13/20 12:20 PM
    Light snowfall. Latest measurement (10 AM – 12 PM): 2.1″. Event total: 17.2″
  • 4/13/20 10:00 AM
    Moderate snowfall. Visibility 1/4 – 1/2 mile. Snowfall measurement (7 AM – 10 AM): 1.2″. Event total: 15.1″
  • 4/13/20 9:30 AM
    Some lake-enhanced snowfall could set up soon, lasting at least into the early afternoon hours. Conditions are somewhat marginal, so not expecting too much additional if the lake gets involved. Knock on wood because this is spring in the U.P. and Mother Nature likes to take a shot at us this time of year. Currently less than 1/4 mile visibility due to blowing snow.
  • 4/13/20 8:55 AM
    Looks like we’ve bottomed out in surface pressure. Our gauge recorded 998.7 mb (29.49″) MSLP at ~ 7 AM EDT. The center of the low is located near Sault Saint Marie. It should slowly march NE into Quebec this afternoon. We should be nearing the top of the mountain in terms of winds within the next hour or two (if we haven’t arrived already).
  • 4/13/20 8:25 AM
    Moderate snowfall continues. Visibility is generally 1/4 – 1/2 mile but localized blowing snow creates near whiteout conditions at times. Gusty northerly winds (30-35 mph gusts) continue to buffet the city.
  • 4/13/20 7:30 AM
    Winds continue to ramp up over the last several hours. The peak wind gust measured so far here is 34 mph but 40 mph does not seem not out of reach by later this morning. Fortunately, the moderate to strong winds throughout this storm have kept power lines free of snow.
  • 4/13/20 7:00 AM
    Moderate snowfall. 1/4 – 1/2 mile visibility. Snowfall measurement (9 PM – 7 AM): 8.2″. Event total: 13.9″
  • 4/12/20 9:00 PM
    Moderate snowfall. 1/4 – 1/2 mile visibility. Snowfall measurement (6 – 9 PM): 3.6″. Event total: 5.7″
  • 4/12/20 7:45 PM
    Heavy snowfall continues. Visibility between 1/8th – 1/4 mile. Next snowfall measurement at approximately 9 PM.
  • 4/12/20 6:05 PM
    Visibility has dropped to approximately 1/8 mile due to heavy snowfall. 2.1″ measured so far.
  • 4/12/20 5:30 PM
    Snow is beginning to stick to roadways too now. Visibility is just over 1/4 mile.
  • 4/12/20 4:05 PM
    Snow is beginning to stick to grassy areas around our property now. Cement is wet but free of snow.
  • 4/12/20 3:25 PM
    Initial snowfall this afternoon has been melting on contact due to the relatively warm ground, but temperatures have been falling over the past couple hours.
  • 4/12/20 9:00 AM
    Expect the snow to start flying by mid afternoon. Heaviest snowfall after 8 PM. Winds should stay light to moderate until daybreak Monday.  Winds will build after that point reaching a peak in the afternoon. Blizzard-like conditions are likely as it will be snowing all day Monday. As per usual, I will report periodic measurements & observations here throughout the event. Keep checking back.