The HLS is unique among Hazard formatters in that it utilizes the combo map. You use this feature the same as in other formatters in that you group zones with like impacts in mind and in the order you want them to appear in the HLS. It is important to keep the groups to the smallest number possible to keep the overall HLS length down.

Both the timing of landfall as well as potential impact categories should both play a role in determining how to break out your groups. The farther out you are from impact, generally the fewer breakouts you should force. Potential track error is about 50 miles in the watch timeframe, so factor that into your decision. And with the formatter designed to give only general impact statements and no specific values, this approach works.

But as you approach landfall, the groupings should be made with like impacts in mind as the group size will be used to determine the values given for the zone with respect to wind and surge values and therefore determine the category it uses to pull the impact statement. If you choose too large a grouping, you can wash out potentially higher wind speeds and surge values and inadvertently downplay the threat.

See the 17-minute video on an Overview of the HLS for an introduction to using the HLS formatter.

For more information on tropical operations and how to handle an HLS formatter failure, view this video.