Modifiers matching circumstance:

• historical,
• stressful,
• catastrophic,
• unforeseen,
• unfortunate,
• unique,
• personal,
• negative,
• unforeseeable,
• extraordinary,
• relevant,
• extreme,
• bad,
• threatening,
• special,
• unexpected,
• common,
• exceptional,
• verifiable,
• severe,
• external,
• exigent,
• unusual,
• unavoidable,
• involuntary,
• individual,

Simple categories matching exigent:

• circumstance,