The Mariners' 1-2-3 Rule, or "Danger area", is indicated by shading. The 1-2-3 Rule, commonly taught to mariners, refers to the rounded long-term NHC forecast errors of 100-200-300 nautical miles at 24-48-72 hours, respectively. The contour defining the shaded area is constructed by accounting for those errors and then broadened further to reflect the maximum tropical storm force (34 knot) wind radii forecast at each of those times by the NHC. The NHC does not warrant that avoiding these danger areas will eliminate the risk of harm from tropical cyclones.
Users operating in the vicinity of these systems are advised to continually monitor the latest Forecast/Advisories from the NHC and proceed at their own risk. Areas are also shaded for systems in which NHC forecasters believe there is an adequate chance of tropical cyclone formation within the next 48 hours.
About Alternates - E-Mail Advisories - RSS Feeds
Latest Advisory - Past Advisories - About Advisories
Latest Products - About Marine Products
Tools & Data
Satellite Imagery - US Weather Radar - Aircraft Recon - Local Data Archive - Forecast Verification - Deadliest/Costliest/Most Intense
Learn About Hurricanes
Storm Names Wind Scale - Prepare - Climatology - NHC Glossary - NHC Acronyms - Frequently Asked Questions - AOML Hurricane-Research Division
About NHC - Mission/Vision - Other NCEP Centers - NHC Staff - Visitor Information - NHC Library
National Weather Service
National Centers for Environmental Prediction
National Hurricane Center
11691 SW 17th Street
Miami, Florida, 33165-2149 USA
Page last modified: Thursday, 29-Sep-2016 23:26:17 UTC