Hurricane center to launch, test new products in 2017

New and updated graphics will be issued during the 2017 hurricane season (Image: National Hurricane Center)

MIAMI – The National Hurricane Center will begin issuing storm surge watches and warnings operationally during the 2017 hurricane season.

Hurricane season in the Atlantic basin begins today and continues through the end of November.

Storm surge watches and warnings will be used to highlight areas along the Gulf and Atlantic Coasts of the United States that have a significant risk of life-threatening inundation from a tropical cyclone, subtropical cyclone, post-tropical cyclone, or a potential tropical cyclone.

Storm surge is often the greatest threat to life and property from a tropical cyclone, and it does not always occur at the same time or in the same location as the storms dangerous winds.

In addition, while in most cases coastal residents can remain in their homes (or in a secure structure nearby) and be safe from a tropical cyclone’s winds, evacuations are generally needed to keep people safe from storm surge. Having separate warnings for these two hazards will save lives by better identifying the specific tropical cyclone hazards communities face, and by enhancing public response to instructions from local officials.

The storm surge watch/warning areas are determined by a collaborative process between the NHC and local NWS Weather Forecast Offices (WFOs).

New in 2017: Alerts for potential tropical cyclones

The hurricane center will have the option, pending final NWS approval, to issue advisories, watches, and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land within 48 hours.

It has previously not been permitted to issue a hurricane or tropical storm watch or warning until after a tropical cyclone had formed.

Experimental time of arrival of tropical-storm-force winds graphic

The arrival of sustained tropical-storm-force winds is a critical planning threshold for coastal communities, as many preparedness activities become difficult or dangerous once winds reach tropical storm force. Frequently, this timing is estimated using the deterministic NHC track, intensity, and wind-field (size) forecasts, but such an approach doesn’t account for forecast uncertainty, and communities can be caught off guard if a storm speeds up or grows in size beyond what was forecast.

To provide guidance on when users should consider having their preparations completed before a storm, NHC will begin issuing in 2017 experimental Time of Arrival of Tropical-Storm-Force Winds graphics.

The primary graphic displays the “earliest reasonable” arrival time, identifying the time window that users at individual locations can safely assume will be free from tropical-storm-force winds. Specifically, this is the time that has no more than a 1-in-10 (10%) chance of seeing the onset of sustained tropical-storm-force winds – the period during which preparations should ideally be completed for those with a low tolerance for risk.

A second graphic will show the “most likely” arrival time – that is, the time before or after which the onset of tropical-storm-force winds is equally likely. This would be more appropriate for users who are willing to risk not having completed their preparations before the storm arrives.

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