JeffreyGreenII
commented
8 months ago Potential Data Sources
Rain
Liquid precipitation (this is their language, not mine) data may be derived from the Weather Prediction Center (WPC) in the form of Quantitative Precipitation Forecasts (QPF) and Probabilistic Quantitative Precipitation Forecasts (PQPF) products.
Documentation on both can be found here:
Furthermore, there is additional rain-related dashboards and forecasts, such as the Excessive Rainfall Forecast and Significant River Flood Outlook products.
Snow
Winter weather precipitation may be derived from the WPC's Winter Weather Forecast (WWF) product (Documentation for the WWF product). The WWF breaks down it's precipitation forecasts into 2 categories:
- Snowfall
- Freezing rain
Data Formats & Availability
Rain
Formats
The QPF's are available as GRIB2, Shapefile, and KML formats (seen here), while PQPF's seem to only be available via the GRIB2 format (seen here).
Availability
For brevity's sake, I will cover only the GRIB2 type of forecast format offered for QPF, to give context to the type of forecast breakdowns offered. QPF's seem to be available for a 7-day period with differences between the first 3 days of forecasts and the last 4 days of forecasts. For the first 3 days, each forecast covers 6 hour spans (eg, 00-06 hour forecast, 06-12 hour forecast, ..., 30-36 hour forecast, etc.). However, there also exists longer span reports for the first three days, as well, offering 24/120/168 hour span forecasts, such as 24/48/72 hours. Lastly, the 5-day and 7-day forecasts are only available via 120 hour and 168 hour forecasts.
While PQPF's only seem to project out 3 days or 72 hours, providing a 6 hour, 12 hour, 24 hour and 72 hour forecast.
Snow
Formats
The WWF seems to also offer GRIB2, Shapefile and KML formatted files (seen here for Shapefile/KML links and individual forecast links offer GRIB2 format download links).
Availability
The WWF seems to only predict precipitation amounts out by 3 days or 72 hours, but offer 1 day, 2 day, and 3 day forecasts.
Collecting the data
All data seems to be hosted as individual files, each containing some or all of the specific forecast, which are hosted via an FTP server.
To collect the 7-day forecast of each of these would require fetching between 1-7 forecast files (depending on the granularity of the forecast data within each file) per data point (ie, 1-7 QPF or PQPF forecast files, 1-7 snowfall forecast files, and/or 1-7 freezing rain forecast files).
Below are the FTP server locations of the aforementioned forecast files:
Finding the forecast files on the FTP
While I'm not certain the exact naming strategy for all forecast files, the strategy for most files on the FTP server seem to follow a pattern as such:
p{$length_of_forecast}m_{$date_of_forecast}{$hour_of_forecast}f{$end_time_of_forecast}Where:
$length_of_forecastpertains to the span of hours covered (ex,p06m_...likely covers a 6 hour window)$date_of_forecastpertains to the day for when the forecast begins (ex, if the forecast was calculated on 2024 Jan 7, this would read20240107$hour_of_forecastpertains to the hour for when the forecast begins (ex, if the forecast was calculated at 05:18, this would read06, as the forecasts are calculated every 6 hours, rounding the up to the nearest hour of when the forecast was generated)$end_time_of_forecastis the end time of the forecast. So if this reads54and the$length_of_forecastwasp06m, then this report covers hours48through54from when the forecast was calculated. So if the forecasts$date_of_forecastand$hour_of_forecastreads2024010712, this forecast was calculated to start at noon (timezone unknown) for 2024 Jan 7, and provides forecasted conditions for for the hours of 2024 Jan 9 @ noon to 2024 Jan 9 @ 6p.
Parsing the data
At present, I'm not sure how to use any of these data types (GRIB2, Shapefile, or KML) to collect the necessary data about predicted rainfall.
KCRHA expects this alert to be able to collect information on precipitation (measurements in inches) for both predicted rainfall and snowfall forecasts.