A script that downloads wind forecast data from NOAA NHC

dload-nhc-wind-probs.R

# Copyright 2017, James Molyneux
# MIT License, http://www.opensource.org/licenses/mit-license.php

# Load the rvest package
library(rvest)

# Naviagate to the site and obtain the form
site_url <- "http://www.nhc.noaa.gov/gis/archive_wsp.php"
my_session <- html_session(site_url)
site_form <- html_form(my_session)[[3]]

# Set form value to the year you'd like
my_form <- set_values(form = site_form, year = "2017")

# The form's url is NULL by default, which causes errors. So I 
# set the url to be the same as the session's.
my_form$url <- my_session$url

# Submit the form
data_page <- submit_form(my_session, my_form, submit = "year")

# Find all of the links on the new page
page_links <- read_html(data_page) %>% 
  html_nodes("a") %>% 
  html_attr("href")

# Find all the links to just the forecast data
data_links <- page_links[grepl(pattern = "forecast/", page_links)]

# Create a set of links to download from
download_urls <- paste0("http://www.nhc.noaa.gov/gis/", data_links)

# Create a set of destination file names
dest_filenames <- paste0("~/Downloads/", basename(download_urls))

# Download the files! (This seems to download
# all the files at once, fyi)
download.file(download_urls, dest_filenames)