Initial import of NavSea pbf project

tasks/test2.md

@@ -0,0 +1,83 @@
+# NavSea Weather Server
+Step-2 测试：GFS Downloader
+
+创建文件：
+
+gfs_downloader.py
+
+------------------------------------------------
+
+import os
+import requests
+from datetime import datetime
+
+BASE_URL = "https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod"
+
+FORECAST_HOURS = [
+0,3,6,9,12,15,18,21,24,
+27,30,33,36,39,42,45,
+48,51,54,57,60,63,66,
+69,72
+]
+
+OUTPUT_DIR = "data/grib"
+
+os.makedirs(OUTPUT_DIR, exist_ok=True)
+
+
+def get_cycle():
+
+    now = datetime.utcnow()
+
+    hour = (now.hour // 6) * 6
+
+    cycle = f"{hour:02d}"
+
+    date = now.strftime("%Y%m%d")
+
+    return date, cycle
+
+
+def download_file(url, path):
+
+    if os.path.exists(path):
+        print("skip", path)
+        return
+
+    print("downloading", url)
+
+    r = requests.get(url, stream=True)
+
+    if r.status_code != 200:
+        print("failed", url)
+        return
+
+    with open(path, "wb") as f:
+        for chunk in r.iter_content(1024*1024):
+            f.write(chunk)
+
+
+def main():
+
+    date, cycle = get_cycle()
+
+    print("cycle:", date, cycle)
+
+    for fh in FORECAST_HOURS:
+
+        fh_str = f"{fh:03d}"
+
+        filename = f"gfs.t{cycle}z.pgrb2.0p25.f{fh_str}"
+
+        url = f"{BASE_URL}/gfs.{date}/{cycle}/atmos/{filename}"
+
+        output = os.path.join(
+            OUTPUT_DIR,
+            f"{date}_{cycle}_f{fh_str}.grib2"
+        )
+
+        download_file(url, output)
+
+
+if __name__ == "__main__":
+    main()