Rio Piedras Weather Station

This page is updated every hour (approximately 15 minutes after the hour) as described below.
Last update: Wed Mar 10 01:15:00 AST 2010.

• Current conditions in Rio Piedras
• Last-minute conditions
• Historical Data (sample plot)
• Station Specifications and Location
• Station Status
• How it is done
• Back to Home page

Current Conditions in Rio Piedras

at 01:14	Temperature (°F)	Humidity (%)	Dew Point (°F)	Pressure (in)	Heat Index (°F)	12-24 Hour Forecast
Now	71.8	92	69.4	29.96 Falling slowly	68.3	Partly cloudy
Hi Time	72.5 00:00	93 01:04	69.9 00:18	29.99 00:00	69.6 00:00
Lo Time	71.6 00:51	91 00:00	69.2 00:51	29.96 00:49	67.6 01:04

(If a parameter lies outside the measurable range of the station, either the single character '?' or two '??' appear instead of the value, indicating a value above or below the allowed range, respectively. If the symbol 'NA' appears instead, it indicates no value received from the sensor. Any of these can be an indication of a malfunction of the corresponding sensor.)

Rain Wind Gust Ave Now 0.0 in/h Now Calm Calm Today 0 in Hi Time 2 mph 00:22 Yesterday 0.2 in

Sun rise set Today 06:37 18:34 Tomorrow 06:36 18:34

Hourly Summary

Previous dates summaries

Mar 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1
Feb 28 , 27 , 26 , 25 , 24 , 23 , 22 , 21 , 20 , 19 , 18 , 17 , 16 , 15 , 14 , 13 , 12 , 11 , 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1
Jan 31 , 30 , 29 , 28 , 27 , 26 , 25 , 24 , 22 , 18 , 17 , 16 , 15 , 14 , 13 , 12 , 11 , 10 , 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

How it is done

The data is currently collected by the Cabled Vantage Pro Plus weather station manufactured by Davis. It was bought in May 2003 from Scientific Sales Inc, which at that time had the lowest price we found. After a few months of testing and writing the software, the station was installed permanently and, since 1 January 2004, that is the data that is published here. Prior to that, the station used was a WM-918 weather station manufactured by Oregon Scientific. We keep the description of that station for reference purposes, and the station is still working and collecting data, but the data is not being published.

The Vantage Pro consists of an outside temperature and humidity sensor, an anemometer, a rain collector, a solar radiation sensor and an UV sensor, all of them connected to the integrated sensor suite (ISS). It comes with a small console, to which the ISS is connected by a 4-wire telephone cable, and which also contains a pressure barometer, as well as an indoor temperature and humidity sensor. In addition to collecting the data from the sensors, the embbeded software in the console calculates various derived quantities such as the dew point, heat index and various others. The Vantage Pro takes samples from the sensors at different intervals depending on the sensor (see below), and the data is sent to the computer via a serial port every 2 seconds.

The station is connected to a computer that runs continuously, using FreeBSD. (When the project started the computer was running Debian/GNU Linux, but we have changed to FreeBSD since the summer of 2000.) A small daemon program vprod , which we wrote (in C) for this purpose, reads the data from the console every time it is sent to the computer via its serial port. The program reads and updates its data internally every time (every two seconds) that the console sends a transmission. In the current setup, the data is logged to a file every minute, although by a simple change of a directive in a run-time configuration file it can be made to log at any other specified time interval.

The rest of the work is done by a set of scripts. The main script, written in awk, makes a pass through the log file, and collects the current, maximum and minimum values for each relevant parameter corresponding to the current date. The output of this script is a set of sed commands, which are then applied to a template html file to produce the html file that you are reading, and to another template file that is then input to the gnuplot program to do the graphs.

The main awk script, as well as the associated sed comands, are actually invoked automatically, every hour, by a shell script that is run as a cron job. In addition, after updating the html and plot files with the new data, the shell script makes a connection to our web host and transfers the html and plot files. In the way it is set up now, the files are updated locally in the station computer as described above and then transfered to our web server account every hour. We may change this in the future. The data is also uploaded (hourly) to the wunderground weather station project.

In addition to the hourly update, at the end of the day another script writes an hourly summary of the day's data to an html file, and inserts an appropriate link to it in the main file. The data file is transfered to our web server in the last transmission of the day, just before midnight. In this way, the previous data for everyday since this project started, is available online.

In addition, all the data is archived, on a weekly basis, in a PostgreSQL database. This archive method provides very comprehensive data retrieval and analysis mechanisms, that can be conveniently adapted to many different requirements. The data can be made available upon request, in various formats, and can be used for any purpose.

The satellite images are obtained using the Hamtronics ''R139 Weather Fax Receiver''. The receiver is conected to a Quadrifiliar Helix Antenna, acquired from Software Systems Consulting . Both of these pieces of equipment are built especially for NOAA-type polar orbiting satellite reception and together they work nicely. The audio output of the receiver is connected to the sound input of a laptop running Windows 98, and the images are received and decoded using wxtoimg.

There are currently three satellites that are worth following: NOAA 12, 15 and very recently 17. I restrict the automatic scheduling of satellite reception to those passes in which the maximum elevation is at least 25 degrees. With that cut, I typically get 2 images per day from each satellite: either 1 or 2 in the early morning and 1 or 2 more in the afternoon or evening. Therefore, in the evening, I set up the laptop to receive the early morning images, and then before going to work I turn everything off. In the afternoon, I set it up again to get the late afternoon or evening images.

For advanced planning, I use a separate program that I wrote, in C, for calculating and predicting satellite orbits. That program runs on the FreeBSD machine, and it allows to process the images from the laptop in an automatic fashion. After a given pass, the laptop stores the decoded images in a directory that actuakky resides in the FreeBSD machine, but which is mounted on the laptop via Samba. Then, by a set of scripts, the image files are massaged, an index.html file is created, and everything is packed in a form suitable for uploading to the web server.

In Dec 2002 the receiver stopped working (no output from it), I contacted Timestep and, following their suggestion, I sent it to them on 3 Jan 2003 for repair. It was finally returned to me on 11 Mar 2003. Unfortunately, it was apparently in the same state as when I had sent it. After repeated attempts to find out from Timestep what was wrong with it and what had ben repaired, they admitted that nothing was repaired; nothing was wrong at all, according to them. I continued to insist that the radio was not working, they suggested a few checks, none of them turned useful information and, in their own words, they ``gave up''. To cut the losses (I had paid for the shipping, back and forth, and the ``repair'', a total of slightly more than $100), I gave up too, and bought the Hamtronics.

Station Specifications

Console Status and Diagnostics - Wed Mar 10 01:15:00 AST 2010