Capability 02 · Probability Assessment — A Field Guide

How to think about wildfire probability.

This page is a methods guide, not a scoreboard. It walks through how a defensible wildfire-probability assessment is actually conducted — what evidence to start from, which environmental signals to layer on, and how to combine and communicate them honestly. There are no live scores here: probability work is legacy work, built on the historical record.

Read this first

A probability is not a prediction — and it is not live. Probability assessment asks how strongly a place resembles the places where fire has historically occurred. It is an archival exercise: dated, versioned, and revisited — never a tracker of active fires, and never the sole basis for emergency, insurance, or land-use decisions. This platform deliberately does not track live fire response.

Step one · the evidence

Start from the historical record

The honest anchor for any probability statement is what has already happened. Before touching a model, assemble the record and interrogate it.

Fire perimeterswhere & how often
Map every recorded burn. Recurrence is the strongest single signal — fire-prone ground tends to stay fire-prone, because the conditions that made it burn persist.
Ignition recordswhere fires start
Starts cluster along human corridors — roads, communities, infrastructure. Ignition density tells you where the sparks are, independent of whether they grew.
Fire frequencythe starting point
Count what the record shows: how many fires, over how much area, across how many years. That observed rate is the starting point — the environmental factors below only adjust it up or down, and every adjustment should have a stated reason.
Step two · the modifiers

Layer on the environment

The record shows where fire has occurred. The next question is whether the vegetation and rainfall at a place today still look like the conditions that carried those fires.

Fuelsthe carrier
In Hawaiʻi the main carriers are nonnative fuels — invasive grasses above all, but alien shrubland and forest burn too. Ask what fraction of the ground these fuels cover, and how continuous that cover is.
Rainfallthe slow variable
Rainfall over the preceding months — 1-, 3-, 6-, and 12-month windows — sets how much of the fuel has cured. The same vegetation carries fire very differently after a dry winter than after a wet one.