FLASH HailTrack Hail Forecast - Predictive

Retrieve hail prediction data for forecast periods.

This API provides high-resolution hail prediction data for the next hour which are output by a proprietary deep learning model.

Key Features:

• Coverage: 20°W to 55°W, -130°N to -60°N (CONUS)
• Horizontal Resolution: ~1-km horizontal grid spacing (3500 x 7000)
• Temporal Resolution: 5-minute updates
• Products: Hail size and arrival time predictions

Parameters:

• product (required): Type of prediction data
  • hailsize: Hail size predictions
  • hailarrival: Hail arrival time predictions
• cfcache (optional): edge cache control, False fetches fresh data (default: True)

Response Format:

Returns a GeoJSON FeatureCollection of filled contour polygons covering the CONUS domain.

• type: "FeatureCollection"
• features: Array of hail contour polygon features
• init_time: When the model was initialized (UTC, "YYYY-MM-DD HH:MM:SS")
• valid_time: Valid time for the prediction (UTC, "YYYY-MM-DD HH:MM:SS")

Feature Properties (hailsize):

Each hail size feature includes:

• init_time: When the model was initialized (UTC, "YYYY-MM-DD HH:MM:SS")
• valid_time: Valid time for the prediction (UTC, "YYYY-MM-DD HH:MM:SS")
• hail_mm: Lower bound of the contour band in millimeters (e.g., 6.35)
• hail_in: Lower bound of the contour band in inches (e.g., 0.25)
• label_mm: Human-readable mm label (e.g., "6 mm")
• label_in: Human-readable inch label (e.g., "0.25 in")

Feature Properties (hailarrival):

Each arrival feature includes:

• init_time: When the model was initialized (UTC, "YYYY-MM-DD HH:MM:SS")
• valid_time: Valid time for the prediction (UTC, "YYYY-MM-DD HH:MM:SS")
• arrival_min: Minutes until hail arrival, 1 means imminent (<10 min), otherwise 10–55
• label: Human-readable label (e.g., "Imminent (<10 min)" or "30 min")

Error Responses:

• 400 Bad Request: Missing or invalid parameters
• 401 Unauthorized: Invalid or missing authentication token
• 500 Internal Server Error: Unexpected server error

Use Cases:

• Vehicle and agricultural loss mitigation
• Proactive roof and property damage response
• Insurance claim preparation and validation
• Terminal and enroute aviation threat assessment
• Emergency dispatch pre-positioning

curl -X GET "https://example.com/hailstone/?cfcache=True&product=hailsize"

{  "type": "FeatureCollection",  "forecast_time": "2026-04-27 17:00:00",  "valid_time": "2026-04-27 17:30:00",  "features": [    {      "type": "Feature",      "geometry": {        "type": "Polygon",        "coordinates": [          [            [              -98.5,              35.2            ],            [              -98.3,              35.2            ],            [              -98.3,              35.4            ],            [              -98.5,              35.4            ],            [              -98.5,              35.2            ]          ]        ]      },      "properties": {        "forecast_time": "2026-04-27 17:00:00",        "valid_time": "2026-04-27 17:30:00",        "hail_mm": 6.35,        "hail_in": 0.25,        "label_mm": "6 mm",        "label_in": "0.25 in"      }    }  ]}