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Public Information Statement
National Weather Service Miami FL
522 PM EDT Mon Apr 20 2026

To:        Subscribers:
           -NOAA Weather Wire Service
           -Emergency Managers Weather Information Network
           -NOAAPort
           Other NWS Partners and NWS Employees

From:      Jamie Rhome, Deputy Director
           National Hurricane Center

Subject:   Hurricane Threats and Impacts (HTI) Mosaic Testing on
April 21, 2026 (backup date: April 23, 2026)

The National Weather Service (NWS) Weather Forecast Offices
(WFOs) in Honolulu, Hawaii, San Juan, Puerto Rico, and all WFOs
in the contiguous United States that can issue tropical storm and
hurricane hazards will commence with Hurricane Threats and
Impacts (HTI) threat grid mosaic testing on Tuesday, April 21,
2026.  Testing will begin at approximately 1500 UTC.  Test
activities will take approximately 1 hour.  However, NWS
dissemination systems may take up to an hour and a half to purge
all test data.  All test data is expected to be cleared by 1730
UTC.

In the event that the test needs to be postponed, due to weather
or another event, the testing will instead commence at the
affected offices on April 23, 2026.

For the test, HTI grids will be created for tropical Wind Threat,
Flooding Rain Threat, Tornado Threat, and Storm Surge Threat
(where applicable) at each participating WFO. Those grids are
stitched together into storm-scale HTI graphics. The HTI Mosaic
graphics are available in Keyhole Markup Language (KML) format on
the following webpage:
https://www.weather.gov/hti

The mosaics are also available through the National Digital
Forecast Database and on web pages hosted by the Weather Forecast
Offices (WFOs) affected by tropical cyclones. These webpages
include WFO Tropical Webpages and Graphical Hazardous Weather
Outlook (GHWO) Webpages.

GHWO Webpages use the following URL format, where XXX should be
replaced with the 3-letter identifier for the WFO of interest
(note that WFO Honolulu does not have a GHWO webpage):
https://www.weather.gov/erh/ghwo?wfo=XXX

WFO 3-letter identifiers and the respective NWS Region that each
WFO belongs to is listed at the following page:
https://www.weather.gov/pimar/CWAbyWFO

NWS Eastern, Southern, and Western Region WFO Tropical Webpages
use the following URL format, where XXX should be replaced with
the 3 letter identifier for the WFO of interest:

NWS Eastern Region WFOs:
https://www.weather.gov/XXX/tropical#hti

NWS Southern Region and Western Region WFOs:
https://www.weather.gov/srh/tropical?office=XXX#hti

The Tropical Webpage for WFO Honolulu can be found at:
https://www.weather.gov/hfo/hti

User information about HTI can be found here:
https://www.weather.gov/media/srh/tropical/HTI_Explanation.pdf

More specific details on HTI can be found in the Product
Description Document:
https://www.weather.gov/media/srh/tropical/PDD_HTI.pdf

Periodic software and hardware testing in preparation for
tropical cyclone events will continue during the remainder of
2026.

For more information, please contact:

Robert Garcia
Warning Coordination Meteorologist
National Weather Service Office
Miami, FL
robert.garcia@noaa.gov

National Public Information Statements are online at:
https://www.weather.gov/notification/

NNNN

$$

RAG