Frequently Asked Questions

What is UTC, GMT, or Z time?

– By international agreement, the local time at the prime meridian or 0 degrees longitude, which passes through Greenwich, England. Since there are 15 time zones across the world, UTC acts as a reference time for the scientific community. The terms Coordinated Universal Time (UTC), Zulu (Z), and Greenwich Mean Time (GMT) are equivalent. All of the analysis and forecast products are based on this reference time. This longitude is the line that separates the eastern and western hemispheres.

How do I determine when a chart was disseminated? When is the forecast on the chart for?

– "ISSUED" is the time and date for when this product was disseminated by the forecaster
– "VALID" is the time and date for when the forecast depicted will represent the weather conditions