竜巻アラート is a free lifestyle app developed by 日本気象株式会社. It is designed to notify users of the possibility of tornadoes in their selected region through pop-ups and notification bars. Users can choose their region either by selecting a city or by using their current location. The app aims to help users stay safe from the dangers of tornadoes.

In addition to the alert feature, users can also access the "Tornado Prediction Map" and "Pinpoint Weather" on the detailed screen through the "お天気ナビゲータ" website. However, it is important to note that the app's support will end in November 2020, and no further updates or bug fixes will be provided.

The app displays the tornado risk level in three stages: the possibility of tornadoes occurring at the moment, the possibility of tornadoes occurring within the next hour, and when the possibility of tornadoes is low. Users can customize their settings, including region selection, automatic updates, notification intervals, and notification settings such as time, sound, vibration, and LED.

The tornado prediction data used in the app is based on the Tornado Occurrence Probability Nowcast provided by the Japan Meteorological Agency. The predictions are updated every 10 minutes for the next hour. There are two levels of prediction: Level 2 indicates a possibility of severe gusts, while Level 1 indicates a possibility of intense gusts. The app notifies users if Level 1 or higher is predicted for their selected region.

Please note that manual data updates can be done by pulling down the radar screen, and poor network conditions may affect the delivery of notifications.