The Weather at Glassverket

Observations at 18.04.2014 12:33:42 LT

OAT 10.3°C · WIND 041° / 7.8 kts · GUST 022° / 17.4 kts · QNH 1013.9 hPa · UV 2.6 · SR 756 W

Forecast for the next 12 hours

Actual Weather Report

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        DATA FROM THE DAVIS VANTAGE PRO2 PLUS/DFARS WEATHER STATION
               Received on 18.04.2014 @ 12:33:42 local time
      LOCATION: Moss, Norway (N 59°25.945'  E 010°38.752'  /  JO59hk)
           SUNRISE and SUNSET occur at 05:56 & 20:41 LOCAL TIME
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TEMPERATURE and HUMIDITY
 Outside Air Temperature ..... : 10.3°C  /  50.6°F
 THSW Index .................. : 11.7°C  /  53.0°F
 Dew Point Temperature ....... : -0.6°C  /  31.0°F
 Relative Humidity ........... : 48 %

BAROMETER
 Barometric Pressure (QNH) ... : 1013.9 hPa  /  29.94 inHg
 Barometric Trend ............ : Barometric pressure is rising rapidly.

WIND (present: gentle breeze, gust: fresh breeze)
 Present Wind Velocity ....... : 041° at 7.8 kts  /  4.0 m/sec.  /  9 mph 
 10-Minute Wind Gust ......... : 022° at 17.4 kts  /  8.9 m/sec.  /  20 mph 
 Average  2-Minute Wind Speed  : 10.0 kts  /  5.1 m/sec.  /  11.5 mph 
 Average 10-Minute Wind Speed  : 8.4 kts  /  4.3 m/sec.  /  9.7 mph 

UV INDEX and SOLAR RADIATION
 UV Index .................... : 2.6
 Solar Radiation ............. : 756 watts/m2

RAINFALL
 Present Rainfall Rate ....... :    0.0 mm  /  0.00 in per hour
 Rainfall Last 24 Hours ...... :    3.0 mm  /  0.12 in
 Rainfall Since Midnight ..... :    0.8 mm  /  0.03 in
 Rainfall Last Rainstorm ..... :    3.8 mm  /  0.15 in (from 17.04.2014)
 Rainfall April .............. :   44.2 mm  /  1.74 in
 Rainfall This Year .......... :  252.4 mm  /  9.94 in

EVAPOTRANSPIRATION
 Since Midnight .............. :    1.3 mm  /   0.05 in
 April ....................... :   28.0 mm  /   1.10 in
 This Year ................... :   80.5 mm  /   3.17 in

GENERAL FORECAST
 Partly cloudy and cooler.

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 NOTE: Reported rainfall of 0.2 mm may be caused by condensation
       in the rain collector.
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 Data proudly brought to you by WOSPi and a very dedicated Raspberry Pi.


	  

Min/max Values

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        DATA FROM THE DAVIS VANTAGE PRO2 PLUS/DFARS WEATHER STATION
               Received on 18.04.2014 @ 12:24:24 local time
      LOCATION: Moss, Norway (N 59°25.945'  E 010°38.752'  /  JO59hk)
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TEMPERATURE  (Today's MIN @ 02:09 LT, MAX @ 11:46 LT)
 Today       MIN   6.3°C / 43.3°F          MAX  10.1°C / 50.2°F
 April       MIN  -0.7°C / 30.8°F          MAX  14.6°C / 58.3°F
 This Year   MIN -10.7°C / 12.7°F          MAX  17.4°C / 63.4°F

DEW POINT    (Today's MIN @ 10:00 LT, MAX @ 00:05 LT)
 Today       MIN  -1.7°C / 29°F            MAX   3.9°C / 39°F
 April       MIN  -6.7°C / 20°F            MAX  10.0°C / 50°F
 This Year   MIN -13.3°C / 8°F             MAX  10.0°C / 50°F

HUMIDITY     (Today's MIN @ 11:40 LT, MAX @ 02:17 LT)
 Today       MIN 47 %                      MAX 86 %
 April       MIN 25 %                      MAX 96 %
 This Year   MIN 18 %                      MAX 97 %

BAROMETER    (Today's MIN @ 00:00 LT, MAX @ 12:21 LT)
 Today       MIN  998.3 hPa / 29.48 inHg   MAX 1013.5 hPa / 29.93 inHg
 April       MIN  994.9 hPa / 29.38 inHg   MAX 1027.4 hPa / 30.34 inHg
 This Year   MIN  978.7 hPa / 28.90 inHg   MAX 1036.6 hPa / 30.61 inHg

WIND SPEED   (Today's MAX @ 09:06 LT)
 Today       MAX 23.5 kts / 27.0 mph / 12.1 m/sec. / Strong breeze
 April       MAX 26.1 kts / 30.0 mph / 13.4 m/sec. / Strong breeze
 This Year   MAX 30.4 kts / 35.0 mph / 15.6 m/sec. / Near gale

UV INDEX and SOLAR RADIATION
 Today       MAX UV Index  3.1 @ 11:52 LT      MAX SR  782 W/m2 @ 11:52 LT
 April       MAX UV Index  3.1                 MAX SR  802 W/m2
 This Year   MAX UV Index  3.1                 MAX SR  802 W/m2

RAINFALL RATE
 Today       MAX   0.8 mm/hour  / 0.03 in/hour at 02:04 LT
 April       MAX  11.4 mm/hour  / 0.45 in/hour
 This Year   MAX  62.2 mm/hour  / 2.45 in/hour

 NOTE: The rainfall rate does not indicate long-lasting rainfall at the
       recorded rate. Rainfall of 0.2 mm may indicate condensation in the
       rain collector.
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CONSOLE and SYSTEM STATUS INFORMATION
 Firmware Date ....... : Dec 11 2012
 Firmware Version .... : 3.12
 ISS Battery Status .. : OK (0)
 Console Model ....... : Vantage Pro/Vantage Pro2 (16) ID: 6312
 Console Voltage ..... : 4.0
 Console Temperature . : 20.5°C / 68.9 °F   RH: 34 % 
 Console RXCHECK ..... : TOT:2895, LST:19, RESYNC:0, CONT:355, CRC:8 
 Software Version .... : 20140205-RPi
 System Uptime ....... : Running since Wed Feb  5 09:45:06 2014 LT.
                         72 day(s), 2 hour(s), 39 minute(s), 24 second(s).
 Cycle ............... : 161641
 RPi SoC Temperature . : 35.8°C
 Data Packet Format .. : LOOP + LOOP2
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 Data proudly brought to you by WOSPi and a very dedicated Raspberry Pi.


	  

Cameras

Nearby web cameras are provided by the Port of Moss. Please note that these cameras seem to have some reliability issues and may not always be available. Also, the camera feeds require a proprietary H.264 decoder (feel free to try talking Moss Havnevesen KF into publishing simple JPG images instead - for the benefit of the human race): Moss Havnevesen KF.

There's also a rather nice view available from mellos.no.

Data Plots and Histograms

The usual click-to-enlarge concept applies. Enlarged images open in new windows.

Note that the update frequency for the data plots varies. Some are updated at 10-minute intervals, others four times a day or only once a day.

24-hr data plot

24-hr wind data plot

Monthly rainfall histogram
Rainfall per month
Rainy days per month
Min/max temperatures
Max daily solar and UV radiation
One week of barometric pressure recordings
Long-term wind direction plot

System Description

Weather data is collected using a Davis Instruments Vantage Pro2 Plus weather station. The weather station console is interfaced to a Raspberry Pi model B running homemade software which queries the weather station, reads the binary-coded console data stream and uploads the decoded weather report to an external web server. With a little help of SED, weather data is also output to a locally attached flatscreen display (normally switched off, though).

The software on the RPi also stores weather data on a SD card for later analysis. As such, the system provides functionality which is equal to or better than the proprietary WeatherLink software available from Davis Instruments.

There is no Davis Instruments software or hardware involved in extracting weather data from the Vantage Pro2 Plus weather station, it's all done in my own software, called WOSPi. That's short for Weather Observation System for the Raspberry Pi. There is a rather detailed description of the WOSPi software available for download in PDF format. You can download the documentation right here. A slideshow presentation of weather data is also available, intented to run continously on a tablet computer.

Although my weather station works fine, I can no longer recommend a Davis Instruments weather station to anyone else. Davis Instruments made a design change in 2012, affecting new console units - effectively leaving them totally useless without further investments in expensive Davis Instruments hardware. Luckily, my console is of the old breed (firmware version 1.90), whereas the new firmware (version 3) which is fitted to new consoles requires an original Davis Instruments data logger (or an appropriate workaround) in order to start communicating over the serial line. Davis Instruments claims that this design change was mandated by hardware upgrades. After a bit of effort looking into the details of what's really going on, it's sad to see that the company is repeatedly serving lies to its customers. This PDF document may be of particular interest. Luckily, weather enthusiasts will be able to find other manufacturers of fine weather stations.

Weather data is fed into Weather Underground at regular intervals. Station ID is ISTFOLDM6.

The WOSPi software also generates an APRS-compliant weather report for use with UIView-32, etc. Presently, this weather report is updated at 10-minute intervals only.

There's a log of system events available here. It may or may not contain items of interest to the general audience.

Davis Vantage Weather Station.
The Raspberry Pi provides an embedded Linux platform, running on the ARM1176JZFS processor provided by the Broadcom BCM2835 chip. The ARM processor runs steadily at 700 MHz, and the entire thing draws less than 700 mA provided by a 5V USB power supply. Power consumption is minimal and the device is allowed to run H24 (the power requirement for the RPi is 700 mA, whereas the actual power consumption in the present configuration is significantly less).

The software was originally developed for the BeagleBone development board (Ångstrøm Linux running on the Texas Instruments ARM Cortex-A8 processor). Stability issues related to corruption of the microSD card proved to be a major concern with the BeagleBone. Even with major modifications to the Ångstrøm distribution, the microSD card became corrupt after a month of operation.

The mighty Raspberry Pi.
Testing and proof-of-concept programming was carried out on a Windows 7/64-bit system by means of the PowerBASIC Console Compiler v. 6 (PB/CC). PB/CC was chosen in favor of PB/Win due to ease of debugging and no need to spend time coding a GUI. Also, the PowerBASIC language provided extremely flexible and easy-to-use serial communications routines.

PowerBASIC to the rescue.
As the PowerBASIC compilers are available only for the Win32 and MS-DOS platforms, the implementation on the BeagleBone/Raspberry Pi was done using the Python programming language, offering much-appreciated degrees of flexibility and structure. Python has proved to be an excellent development platform for this project. Moving from the BeagleBone to the Raspberry Pi only required minor modifications of the program code.

Python - it just works.
From the home network, presently set up as a 100 MBit/s cabled ethernet, weather data is transferred to an external web server by means of a 40 Mbit/s synchronous fiber-optic connection provided by Viken Fibernett AS/AltIBox. Who cares for copper/xDSL (or, even worse: hybrid fiber-coax/HFC) when the best option is available at a reasonable cost?

AltIBox, high-speed internet via fiber-optics - directly to the home.
Other tools and technologies which have been used extensively during the development of annoyingdesigns.com and back-office subsystems: GNU Emacs, PHP, gnuplot, SED (who can live without it?), CSS and the Debian (RPi) and Ångström (BB) Linux distributions. Code documentation was carried out using Doxygen. Also, the Windows Calculator application (used in "Programmer View") proved to be useful, as did EditPad Pro (no surprise, really - who can stand Notepad for more than a day?). The funniest encounter while working on this project was the CRC calculation used by the Vantage Pro2 weather station, requiring a Python implementation of the CCITT-16 algorithm.

Oh, I have to admit - for a quick backup of the RPi SD card, I stick to an Apple Powerbook / iMac. Whichever comes first. Anyway, the BSD system on either of these allows for efficient SD card imaging. Life isn't too hard with a *nix clone within reach.

And ... these pages should display just fine on the iPhone/iPad.

Apple's iPad.


RasPi P1 connections.

The Raspberry Pi with the connections made to the P1 expansion header. For simplicity, I opted for a 3.5mm stereo phono jack to serve as connector between the RasPi and the Davis console. Only three connections are required for simple serial communications: GND, TX and RX.


The RasPi fashionably boxed up.

Indeed a nice case from Barch Designs - available from piholder.com.


The RasPi in operation.

The Raspberry Pi in operation, squeezed in below the display. While a display isn't really required, this one was a nice gift from my employer - it would have been such a waste to send off a perfectly operational flatscreen display to the dump. And - yes, there's a SD card holder, too - for storage of weather data.


Davis console. And two screwholes, where the BeagleBone used to be.

The Davis weather station console is normally left all by itself, only connected to an external DC power supply and the Raspberry Pi. The 3.5mm stereo phono jack is hooked up to the expansion connector at the rear of the console. The phono jack makes it easy to insert a patch cable between the console and the RPi.


SED deserves a moment or two of fame.

Oh. SED. Why do so many people ignore your beauty?


No doubt about it.


Location

The location is in maidenhead locator JO59hk, or - also with respect to the WGS84 datum: N59° 26' E010° 39'.

The following map resources are available:

Other Weather Resources

Weather Data Explained

This section explains the various parameters output by the Davis Vantage Pro2 Plus weather station.

Humidity

Humidity itself simply refers to the amount of water vapor in the air. However, the total amount of water vapor that the air can contain varies with air temperature and pressure.

Relative humidity takes into account these factors and offers a humidity reading which reflects the amount of water vapor in the air as a percentage of the amount the air is capable of holding. Relative humidity, therefore, is not actually a measure of the amount of water vapor in the air, but a ratio of the air's water vapor content to its capacity.

It is important to realize that relative humidity changes with temperature, pressure, and water vapor content. A parcel of air with a capacity for 10 grams of water vapor which contains 4 grams of water vapor, the relative humidity would be 40%. Adding 2 grams more water vapor (for a total of 6 g) would change the humidity to 60%. If that same parcel of air is then warmed so that it has a capacity for 20 grams of water vapor, the relative humidity drops to 30% even though water vapor content does not change.

Relative humidity is an important factor in determining the amount of evaporation from plants and wet surfaces since warm air with low humidity has a large capacity to absorb extra water vapor.

Wind Chill

Wind chill (often called wind chill factor) is the felt air temperature on exposed skin due to wind. The wind chill temperature is never higher than the air temperature, and the wind chill is undefined at higher temperatures (above 10°C).

THSW Index

The THSW index (temperature/humidity/sun/wind) uses humidity, temperature, sunshine and wind data to calculate an apparent temperature of what it "feels" like out in the sun. The derived temperature is called the THSW index. The THSW index is available when the outside temperature is above 10°C.

Dew Point Temperature

Dew point is the temperature to which air must be cooled for saturation (100% relative humidity) to occur, providing there is no change in water vapor content.

The dew point is an important measurement used to predict the formation of dew, frost, and fog. If dew point and temperature are close together in the late afternoon when the air begins to turn colder, fog is likely during the night. Dew point is also a good indicator of the air's actual water vapor content, unlike relative humidity, which takes the air's temperature into account. High dew point indicates high water vapor content; low dew point indicates low water vapor content. In addition a high dew point indicates a better chance of rain, severe thunderstorms, and tornados.

You can also use dew point to predict the minimum overnight temperature. Provided no new fronts are expected overnight and the afternoon relative humidity is greater than or equal to 50%, the afternoon's dew point gives you an idea of what minimum temperature to expect overnight, since the air can never get colder than the dew point. Dew point is equal to air temperature when humidity = 100%.

Rainfall

The Vantage Pro2 incorporates a tipping-bucket rain collector in the sensor suite that measures 0.2 mm of rain for each tip of the bucket. The station logs rain data in the same units it is measured in.

Rain rate calculations are based on the interval of time between each bucket tip, which is each 0.2 mm (EU version).

Condensation threshold

The construction of the Vantage Pro2 rain collector may cause rainfall readings of 0.2 mm / 0.01" when condensation droplets occur on the surface of the rain collector. The default behavior of the WOSPi software is to filter out rainfall readings below a predefined condensation threshold, typically 0.2 mm / 0.01". As such, typical morning condensation on the rain collector will not increase the count of rainy days per month.

Storm rain

Storm rain is the amount of rain in a continous period of rainfall, with an amount of leeway for beginning and end. A rainstorm begins when 0.5 mm of rain has fallen in a 24-hour period, and continues until 24 hours have passed without 0.5 mm of rain.

Barometric Pressure

The weight of the air that makes up our atmosphere exerts a pressure on the surface of the earth. This pressure is known as atmospheric pressure. Generally, the more air above an area, the higher the atmospheric pressure. This means that atmospheric pressure changes with altitude. For example, atmospheric pressure is greater at sea level than on a mountaintop. To compensate for this difference and facilitate comparison between locations with different altitudes, atmospheric pressure is generally adjusted ("reduced") to the equivalent sea level pressure. This adjusted pressure is known as barometric pressure.

In reality, the Vantage Pro2 Plus weather station measures atmospheric pressure. When you enter your location's altitude into the station parameters, the Vantage Pro2 Plus stores the necessary offset value to consistently translate atmospheric pressure into barometric pressure.

Barometric pressure also changes with local weather conditions, making barometric pressure an extremely important and useful weather forecasting tool. High pressure zones are generally associated with fair weather while low pressure zones are generally associated with poor weather. For forecasting purposes, however, the absolute barometric pressure value is generally less important than the change in barometric pressure. In general, rising pressure indicates improving weather conditions while falling pressure indicates deteriorating weather conditions.

Barometric Trend

Change rates, as reported by the Vantage Pro2 Plus weather station:
	PRESSURE CHANGE     ACTUAL
	DESCRIPTION         PRESSURE CHANGE RATE
	Rapidly             >= 2.0 hPa / 3 hr
	Slowly              >= 0.7 hPa and < 2.0 hPa / 3 hr
      

Solar Radiation

What we call "current solar radiation" is technically known as Global Solar Radiation, a measure of the intensity of the sun's radiation reaching a horizontal surface. This irradiance includes both the direct component from the sun and the reflected component from the rest of the sky. The solar radiation reading gives a measure of the amount of solar radiation hitting the solar radiation sensor at any given time, expressed in Watts/sq. meter (W/m2). Sensor range is 0-1800 W/m2.

Ultraviolet (UV) Radiation

Energy from the sun reaches the earth as visible, infrared (IR), and ultraviolet (UV) rays.

Excessive exposure to UV rays can cause health problems, such as sunburn, skin cancer, skin aging, cataracts, and can suppress the immune system. The Vantage Pro2 Plus helps analyze the changing levels of UV radiation and can advise of situations where exposure is particularly unacceptable.

The UV readings do not take into account UV rays reflected off snow, sand, or water, which can significantly increase your total exposure. Nor do your UV readings take into account the dangers of prolonged UV exposure. The readings do not suggest that any amount of exposure is safe or healthful. Do not use the Vantage Pro2 Plus to determine the amount of UV radiation to which you expose yourself. Scientific evidence suggests that UV exposure should be avoided and that even low UV doses can be harmful.

The Vantage Pro2 Plus can displays the UV Index, an intensity measurement first defined by Environment Canada and since been adopted by the World Meteorological Organization. UV Index assigns a number between 0 and 16 to the current UV intensity. The US EPA categorizes the Index values as shown in the table below. The lower the number, the lower the danger of sunburn. The Index value published by the U.S. National Weather Service is a forecast of the next day's noontime UV intensity. The index values displayed by the Vantage Pro2 Plus are real-time measurements.

	NUMERIC      
	VALUE        ACTUAL MEANING 
	0-2          Low UV radiation
	3-4          Moderate UV radiation
	5-6          High UV radiation
	7-9          Very High UV radiation
	10+          Extreme UV radiation
      

Evapotranspiration (ET)

Evapotranspiration (ET) is a measurement of the amount of water vapor returned to the air in a given area. It combines the amount of water vapor returned through evaporation (from wet surfaces) with the amount of water vapor returned through transpiration (exhaling of moisture through plant stomata) to arrive at a total.

Effectively, ET is the opposite of rainfall, and it is expressed in the same units of measure (inches or millimeters). The Vantage Pro2 Plus uses air temperature, relative humidity, average wind speed and solar radiation data to estimate ET, which is calculated once an hour, on the hour.

Weather Forecast

The Davis forecasting algorithms are based on readings and trends from a single point of reference only. It has no other data from which to draw, hence the forecast will not be very accurate.

The Davis forecasting algorithm is probably an implementation of a slightly modified Zambretti algorithm.

Disclaimer

Please keep in mind that annoyingdesigns.com does not provide weather or image data for any professional purposes. As such, it is not recommended to use data from annoyingdesigns.com for crop-critical decisions regarding irrigation planning or anything else which could possibly ruin your day.

You probably get the message - if not, here it is in a different wrapping: you're using data from this system entirely at your own risk.

If you are troubled by Davis Instruments Corp. firmware version 3.xx in your Vantage Pro2 weather station, you may want to consider this easy-to-apply fix.

Contact information

Torkel M. Jodalen
Pb. 1036 Jeløy
NO-1510 Moss
Norway

Tel. (+47) 69 25 20 33  /  92 42 20 20