Fire Whirl Evolution Observed during a Valley Wind-Sea Breeze Reversal

Table 1

Numbers used to calculate the convective Froude number in two cases: up-valley wind case (1st row) and sea breeze wind case (2nd row). 𝑈_𝑓 represents ambient wind speed, 𝑈_𝑓 forward rate of fire spread, 𝑔 gravity, 𝜃 potential temperature, Δ𝜃 mean perturbation temperature near the region of intense heating, 𝑊_𝑓 fire line depth, and 𝐹_𝑐 convective Froude number.

𝑈𝑓; (ms^−1)	𝑆𝑓; (ms^−1)	𝑔; (ms^−2)	𝜃; (K)	Δ𝜃; (K)	𝑊𝑓; (m)	𝐹^2𝑐
2.2	0.5	9.8	301	36	4	0.61
4.1	0.75	9.8	299	36	5.5	1.73