Synoptic-Scale Precursors to Tropical Cyclone Rapid Intensification in the Atlantic Basin

Table 4

Permutation test results showing the percentage of significance at the 95% confidence level for the variables and associated level used for the SVM and logistic regression models, compared to the percentage of significance regardless of height. For comparison purpose, the percent significance for divergence is included to show why it was not chosen. Larger percentages suggest better discrimination ability.

Variables examined	Level(s)	% significance
	(hPa)
SST	1000	58.8
Specific humidity	1000–100	46.0
Specific humidity	1000	50.0
Specific humidity	925	77.0
Specific humidity	850	58.2
Specific humidity	700	35.0
Potential temperature	1000–100	81.4
Potential temperature	1000	39.0
Potential temperature	925	50.0
Potential temperature	850	65.0
Potential temperature	700	89.0
Vorticity	500	33.3
Pressure vertical velocity	1000–100	17.8
Pressure vertical velocity	850	18.8
Pressure vertical velocity	700	14.5
Pressure vertical velocity	500	12.1
Pressure vertical velocity	200	20.6
Vertical shear	200–850	82.5
Divergence	200	11.1