Meteorology · Forecasting & Routing
The '1-2-3 rule' used with a forecast tropical cyclone track refers to:
- AIssuing three forecasts per day
- BA three-knot reduction in speed per hour
- CMaintaining radio watch on three frequencies
- DThe 100/200/300-nautical-mile forecast-error buffers added around the 24/48/72-hour forecast positions✓ Correct
Explanation
The 1-2-3 rule adds the typical forecast-track error — roughly 100 nm at 24 hours, 200 nm at 48 hours, and 300 nm at 72 hours — around the forecast positions to define a danger area to avoid. It builds a margin for track uncertainty.
Authority: Bowditch (Pub. No. 9)
Practice the full Meteorology bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Meteorology questions
- Atmosphere & Pressure
Standard atmospheric pressure at sea level is approximately:
- Atmosphere & Pressure
One millibar (mb) is equal to:
- Atmosphere & Pressure
A barometer that is falling rapidly most likely indicates:
- Atmosphere & Pressure
On a surface weather chart, isobars spaced very close together indicate:
- Wind
By convention, a wind is named for:
- Wind
In the Northern Hemisphere, the Coriolis effect deflects moving air: