Future Coastal/Lakeshore Flooding and Storm Surge Messaging

PROPOSAL

The NWS is proposing to put all coastal and lakeshore flood and storm surge information issued by WFOs into one text product - the CFW. 

If this change is made, all users will be able to find coastal/lakeshore flooding information in the CFW during any type of weather event (tropical or non-tropical) and severity (life-threatening to nuisance flooding). The high surf, rip current, and beach hazard information currently in the CFW would move to a new product to be determined at a later date. The Local Tropical Cyclone Watch/Warning VTEC (TCV) product would become a wind-only product that focuses on the delivery of tropical storm and hurricane watches and warnings, but a complete picture of all tropical hazards would continue to be provided in the Hurricane Local Statement (HLS) text product. Additional information on the change to the proposed TCV and an opportunity to provide feedback can be found here. The CFW content would change slightly to include more detailed geographic information about the flooding hazards, their potential impacts and how to prepare for them.

The NWS is proposing that WFO-issued coastal/lakeshore flood watches/warnings/advisories and storm surge watches/warnings would all be alerted geographically using polygons. 

By providing polygon data with the issuance of storm surge and coastal/lakeshore flood hazards, the NWS can be much more detailed when describing the locations in danger of coastal flooding. This change will require users to go to a separate web link to get detailed hazard polygon vertex latitude/longitude points as they would be too lengthy to provide in the text message directly.  This web link as well as one that pointed to a web-based map of the hazard polygon would be provided at the bottom of the future CFW product. Most importantly, the NWS could eventually better refine the areas that receive a Wireless Emergency Alert (WEA) on individual mobile devices from the issuance of a storm surge warning for life-threatening coastal flooding during a tropical cyclone event, reducing the chance that people receive the alert that are not in harm’s way.

BACKGROUND

Currently, the NWS Weather Forecast Offices (WFOs) issue coastal and lakeshore flood watches/warnings/advisories via the Coastal/Lakeshore Hazard Message (CFW) text product (note that lakeshore flood information is only provided for the Great Lakes).  Meanwhile, when there is life-threatening coastal flooding known as “storm surge” from a tropical storm or hurricane, WFOs issue storm surge watches/warnings via a Local Tropical Cyclone Watch/Warning (TCV) text product.  The CFW and TCV text products provide similar information about coastal/lakeshore flooding, but in two different formats.  See the side by side examples below for coastal flooding of the same magnitude from tropical and non-tropical events.

In addition to the differences in the text products, the NWS currently alerts coastal/lakeshore flood and storm surge hazards differently geographically. Below is an example from a hurricane event where a gridded storm surge warning was issued for life-threatening coastal flooding while NWS zone-based (generally the size of a county) coastal flood advisory and coastal flood statement hazards were issued on either side for flooding that’s a threat to property and for nuisance flooding, respectively.  Notice the warning for life-threatening storm surge is depicted on a 2.5 km grid that is tailored to the threatened area while the coastal flood hazards are depicted across the large NWS zone area and not tailored to the threatened area.

NOTE: Lakeshore flood hazards are only issued for the Great Lakes

Please submit your feedback on the proposed changes here or send an email to Tropical.Program@noaa.gov.