The eight hazard classes

Eight classes, one published record

Every forecast run labels each district with one of eight hazard classes. Each class has its own season, its own physics proxy and its own limits. The full methodology for each class is published on its hazard page.

Flood

• Season: June to September (monsoon); peak in July to August.
• Scored from: Riverine and monsoon flooding, scored from how much rain falls and how hard it falls.

Flash Flood

• Season: March to May (pre-monsoon convection) and June to September.
• Scored from: Short-duration, high-intensity flooding: the burst case of the rainfall proxy.

Tropical Cyclone

• Season: April to May and October to November; the post-monsoon window is the more destructive.
• Scored from: Wind-driven coastal hazard: sustained wind above 50 km/h, with the rain it carries.

Drought

• Season: November to April (dry season), most acute in the Barind and the south-west.
• Scored from: Heat load against the rainfall the horizon is expected to bring.

Heat Wave

• Season: March to June; the pre-monsoon window.
• Scored from: Exceedance above 30 °C, plus persistence.

Cold Wave

• Season: December to February, concentrated in the north and north-west.
• Scored from: How far the minimum falls below 16 °C, plus persistence.

Fire

• Season: March to May, before the monsoon; also the December to January dry spell.
• Scored from: Vegetation and burn risk from heat, wind and drying.

Severe Local Storm

• Season: March to May (Nor'wester / Kalbaishakhi), plus pre-monsoon squall lines.
• Scored from: Squall wind plus a convective downpour.

Where the classes share limits

Two limits apply across the board. The published confidence is the model's own score over the eight classes and is reported as uncalibrated: it is not a probability. And the rainfall classes carry no hydrology, so a high score says how much rain a district saw, not whether a river will breach.