3.5 Hurricanes, Typhoons, Tornadoes, and Tropical Dispatch Hazards

Tropical and Rotating Storm Hazards

The official syllabus explicitly includes tornadoes, hurricanes, and typhoons, including formation and dissipation. A hurricane or typhoon is a tropical cyclone named by basin; the hazards are not limited to the storm's highest surface-wind category. Dispatchers consider the full route and diversion network, including flooding, airport closure, navigation and communications outages, wind, convection, and airport emergency services.

Formation and structure

A tropical cyclone draws energy from warm ocean water and moist convection, with a sufficiently organized circulation and favorable atmospheric conditions. Adequate Coriolis effect, moisture, and limited disruptive vertical shear support development; no single water-temperature observation guarantees formation. Land interaction, colder water, dry air, or increased shear can weaken a storm, but the remnants may still produce heavy rain, low ceilings, gusts, and embedded thunderstorms.

The eye can have comparatively calm conditions while the surrounding eyewall contains intense convection and strong winds. Spiral rainbands extend outside the core and can contain thunderstorms, severe turbulence, heavy rain, wind shear, and tornadoes. A brief observation improvement near the eye or between bands does not establish a safe departure/arrival period. The weather can change rapidly with the next band or eyewall passage.

In the Atlantic and eastern North Pacific, a sufficiently strong tropical cyclone is called a hurricane; in the western North Pacific it is called a typhoon. Use the responsible official forecast center and local meteorological products. Do not apply an Atlantic product's terminology, times, or warning geography to every basin without checking the regional definitions.

Wind category is only one input

The Saffir–Simpson hurricane scale describes maximum sustained wind, not all rainfall, storm-surge, or airport hazards. A weakening storm can continue to flood an airport or destroy ground infrastructure. Gusts and convective outflow can exceed the operational crosswind capability for a particular runway even when an average reported wind seems acceptable.

For runway selection, calculate the forecast wind components for the relevant operating time, include the carrier's approved gust treatment, and check the actual aircraft/contamination limits. The demonstrated crosswind figure is not universally a certified operational limit; use the approved applicable limit. A runway aligned with the prevailing cyclone wind may become unsuitable as the circulation moves past the airport.

Dispatch assessment across the network

A destination and nearby alternate can both lie under the same broad rainband field. Picking an alternate merely outside the center track forecast may not provide adequate protection. Examine uncertainty in storm position and timing, and select a reachable airport whose weather and field conditions satisfy its actual planning minima and operational requirements.

Official forecasts and advisories

Use National Hurricane Center products in its area, applicable tropical-cyclone advisories, SIGMETs, and the local airport forecasts/observations. Track issue times and forecast periods. A track forecast describes the expected center movement with uncertainty; it does not identify an approved aviation corridor through the surrounding convection.

Satellite imagery can reveal circulation and cloud extent, but brightness alone does not quantify flight-level turbulence or safe distances. Radar has range and attenuation limitations, and data-link images are delayed. Combine the official products with observations and PIREPs rather than using a screen capture as a tactical storm-penetration plan. Coordinate strategic rerouting and expected ATC capacity restrictions before departure.

Tornadoes and supercell hazards

A tornado is a violently rotating column associated with a convective cloud and the ground. Funnel clouds and waterspouts are also urgent PIREP phenomena. A storm can be hazardous long before a tornado is observed: severe turbulence, hail, downdrafts, lightning, and rapidly shifting wind remain threats. A tornado warning is not the only information needed to avoid a severe thunderstorm.

Tornadoes can occur with supercells, convective lines, or tropical rainbands. The dispatcher must not infer that a tropical cyclone produces only smooth stratiform rain. Airborne crews avoid hazardous convection using appropriate current information and approved procedures; dispatch provides alternative routes, fuel/performance analysis, and timely updates. Do not wait for an aircraft-specific PIREP of a tornado before acting on a credible forecast or warning affecting the flight.

Worked delay and alternate scenario

A fictional destination has a cyclone rainband expected from 1800Z to 2200Z, including strong gusts, reduced visibility, and potential runway flooding. Flight ETA is 1930Z. The nearest alternate also lies in the band's expected movement, while a more distant airport is forecast to remain operational and meet planning minima. First verify destination authorization at ETA and whether any conditional-weather relief actually applies. Next compute fuel and performance for the reachable alternate and expected ATC delay, using the correct operating-category rule.

If postponing departure moves ETA outside the currently adverse period, obtain the updated forecast and field information rather than assuming the original forecast guarantees recovery. A closure NOTAM or unavailable rescue service may remain after weather improves. Rebrief the crew on storm motion, route changes, alternates, fuel limits, and the next reassessment point.

Finally, assess dissipation realistically. A cyclone crossing land may weaken in wind while continuing to generate widespread IFR conditions and embedded convection. Reopening a route or airport requires current evidence of suitable conditions and operational services. The practical-test answer should explain the hazard, the source and time window, the available alternatives, and why the selected operation remains safe and authorized.

Official References

Source check: 2026-10-12. 2026 FAA Aviation Weather Handbook; Icing operations § 121.629. For operational use, apply current issued authorizations and the assigned aircraft’s approved data.