JACKSONVILLE, Fla. – As the June 1st 2018 Atlantic Hurricane season draws near, the National Hurricane Center has made forecast changes it hopes will save lives and property. There are six upgrades that will provide you with a more detailed and accurate forecast.
The NHC Public Advisory will now discuss forecast information beyond 48 hours.
The NHC Public Advisory is a text product that contains a list of all current coastal watches and warnings and gives pertinent storm information, including general forecast and hazard (storm surge, wind, rainfall, tornadoes, surf) information. The forecast information contained within the advisory will now include information beyond 48 hours. Previously, these advisories were limited to a discussion of a tropical cyclone’s track and intensity forecast through 48 hours. This change will allow public advisories to discuss the track and intensity forecast routinely through 72 hours, and allow the flexibility to discuss the forecast through 5 days when conditions warrant.
The format of Weather Prediction Center (WPC) Public Advisories on inland tropical depressions will now mirror the format of NHC Public Advisories.
WPC Public Advisories provide users with meteorological information on decaying tropical or subtropical systems that have moved inland over the conterminous U.S. and have the potential to produce heavy rainfall and flash flooding. WPC will issue Public Advisories on these inland systems when winds drop below tropical storm strength and the system is not forecast to regain tropical storm intensity or re-emerge over water. The format for WPC Public Advisories on these systems will now mirror the format of the NHC Public Advisories and will contain the same sections (Summary, Watches and Warnings, Discussion and Outlook, Hazards, and Next Advisory). WPC Public Advisories will also contain forecast positions for these systems.
NHC will begin issuing 48-hour hurricane-force (64-kt) wind radii forecasts.
NHC will begin issuing hurricane-force (64-knot) wind radii forecasts at the 48-hour forecast time. These wind radii will be provided in the Tropical Cyclone Forecast/Advisory Message (TCM). Previously, the NHC provided hurricane-force wind radii forecasts out to 36 hours. The NHC Forecast/Advisory will now include a forecast of tropical-storm-force (34-knot) and 58-mph (50-knot) wind radii out to 72 hours and hurricane-force (64-knot) wind radii out to 48 hours. These radii forecasts provide the forecast maximum extent of these winds in each quadrant of the storm.
The NHC Arrival Time of Tropical-Storm-Force Winds graphics will become operational in 2018.
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.
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 graphic would be more appropriate for users who are willing to risk not having completed their preparations before the storm arrives.
Annual update to the track forecast error cone.
The size of the tropical cyclone track forecast error cone for the Atlantic basin will be smaller this year, but a little larger at the longer forecast times in the East Pacific. The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of imaginary circles placed along the forecast track (at 12, 24, 36 hours, etc.). The size of each circle is set so that two-thirds of historical official forecast errors over the previous five years (2013–2017) fall within the circle.
New reconnaissance vortex message format.
In June of 2018, NHC will change the reconnaissance Vortex Data Message format. This product is transmitted from NOAA and Air Force hurricane hunter aircraft and issued under AWIPS headers MIAREPNT2, MIAREPPN2, and WMO headers URNT12 URPN12 for both KNHC and KWBC site IDs. The format changes below will enhance the utility of the Vortex Message by including important parameters previously not provided, or provided only optionally in the comment section, and by improving the organization of the message.