What Pilots Need to Know About AIRMETs and SIGMETs

The East Coast has had more than its fair share of severe weather lately. Rain, thunderstorms, hail, wind and tornadic activity present true hazards to pilots, especially in light aircraft. Aircraft pilots need to know how to interpret AIRMETs and SIGMETs to keep themselves and others safe ahead of all weather conditions.

SIGMETs

• Refer to Significant Meteorological activity
• Issued for lines of thunderstorms, embedded thunderstorms, heavy intensity storms which cover at least 40% of an area, tornadoes, winds of 50 knots or higher, or hail 3/4" or larger (these are called Convective SIGMETs)
• Also issued for volcanic activity, dust storms, sandstorms, severe turbulence, and icing (non-convective SIGMETs)
• Scheduled bulletins are issued hourly (additional updates issued as necessary)
• Will say "None" if no activity is forecast or observed
• If severe weather is anticipated, SIGMET will tell you what kind(s) of weather, when it's expected, how fast it's moving, what areas are affected, and when an update will be issued
• Have a maximum valid time of 2 hours

AIRMETs

• Issued for weather that may be hazardous to light aircraft and VFR pilots, but is less severe than a SIGMET
• Refers to moderate icing, moderate turbulence, surface winds of 30 knots or more, mountain obscurations, or IFR conditions
• Expire after 6 hours

What should you do if issued an AIRMET or SIGMET?

Avoid flying in SIGMETs at all costs. These are serious weather conditions that can put you in severe danger. Cancel your flight, change your flight plan, or wait it out. Although you can usually legally fly through a convective SIGMET, why would you risk it?

Think carefully about flying in AIRMETs. These weather conditions can still be dangerous, but you can avoid the risk by adjusting your flight plan or taking the necessary precautions.

What about "outlook" versus "active"?

SIGMETs and AIRMETs can be issued for active (observed) or outlook (forecasted) weather conditions.

Outlook SIGMETs can contain just as much dangerous weather as an active storm. Keep an eye on which directions and how fast the storm is expected to move, and amend your flight plan or wait it out.

Being close to the edge of a storm can also make it tempting to push your luck. But SIGMETs don't always show all of the convective weather. There is often a larger outlook area outside the perimeter of the active area!

In general, play it safe. Don't take unnecessary risks by flying into dangerous weather.