Bureau of Meteorology weather data

Overview

• The aim of this lesson is to learn how to retrieve weather data from the Bureau of Meteorology (BOM) using an API (Application Programming Interface).
• An API is simply a URL that will automatically request data from a server.
• In this example we will extract rain data from the daily weather forecast.
• The daily weather forecast includes rain forecast data up to 7 days in advance.
• We will use this data for our smart rainwater tank.
• Smart rainwater tanks need to know rain events up to 7 days in advance so that they can discharge tank water before a storm arrives.

Learning Objectives

• Learn how to use the Developer tools in a Web Browser to find an API
• Learn how to use an API with HTTP Request node in Node-Red
• Learn how to extract data from a larger data sets using the function node
• Learn how to prepare data for a chart node

Obtaining BOM rain forecast data

• This lesson will demonstrate how to extract data from the Bureau of Meterology using an API (Application Programming Interface).

Find Bureau of Meteorology API for daily weather forecast data

• Open a Web Browser.
• Enter the search term weather.bom.gov.au

• Select Melbourne VIC as the weather location.

• Ensure that Development Tools is selected under Preferences for your Browser settings.
• Under the Develop menu select Connect Web Inspector.
• This will open up an addition window to show some of the inner-workings of the web page.

• In the Development Tools window click on the Network Tab.
• Refresh the web browser.
• In the window on the left search for a file named daily
• Daily holds data related to current and future weather forecasts including 7 day rain predictions.
• You can scroll in the Previous window to see all the retrieved data presented in JSON format.

• If the mouse hovers over daily the link to the API will appear.
• In this instance it is - https://api.weather.bom.gov.au/v1/locations/r1r0fs/forecasts/daily
• You can copy this link and enter it into a Web Browser to test that it works.

Retrieve BOM data using Node-Red HTTP-In node

• Create a flow in Node-Red using the nodes:
  • Inject – timestamp
  • http request – this will request data using the daily API
  • debug – to display the output of the API in the debug window

• Double click on the HTTP request node and enter the following details.
• To copy the API request from the Web Browser use the right mouse button Copy function.
• Paste the API into notepad or a text editor to ensure that it has copied correctly.
• You may need to paste the API into a text editor on the Raspberry Pi.
• Failing this, enter the API directly.
• Ensure that the Return is a parsed JSON Object
• Give the Name - BOM daily

• Deploy the program then click on the input to the inject node to run the program.
• The output should appear in the debug window on the right.
• Click on the small expansion arrows to show more of the data content.

Collecting Day 0 rain data

• Add a function node and debug node and arrange the nodes as shown below.

• Double click on the function node and enter the following code.
• The code will extract day 0 (zero) max rainfall and place it in the variable rain.
• Name the function node Day 0 (zero) rain

• Deploy the code.
• Clear the Debug window and then click on the inject node to run the program.
• Your output will be different because it will be based on the daily weather forecast.
• This result shows that today (day 0) there will be a maximum of 2.2 mm of rain.

Collecting Day 1 rain data

• Copy the Day 0 rain function node by entering the shortcut Ctrl+C
• Enter Ctrl-V to paste a copy of the node.
• Then double click on the new function node to edit it.