NHC Product Descriptions

Tropical Cyclone Public Advisory

The Tropical Cyclone Public Advisory contains a list of all current watches and warnings on a tropical or subtropical cyclone. It also gives the cyclone position in terms of latitude and longitude coordinates and distance from a selected land point or island, as well as the current motion. The advisory includes the maximum sustained winds in miles per hour and the estimated or measured minimum central pressure in millibars and inches. The advisory may also include information on potential storm tides, rainfall or tornadoes associated with the cyclone, as well as any pertinent weather observations.

Public advisories are issued for all Atlantic tropical or subtropical cyclones, and for eastern Pacific tropical or subtropical cyclones that are threatening land. Public advisories are normally issued every six hours. They may be issued every two or three hours when coastal watches or warnings are in effect. Special public advisories may be issued at any time due to significant changes in warnings or in the cyclone.

The numbers 1-5 in the headers are assigned on a rotating basis by cyclone number, i.e., advisories on the first, sixth, or eleventh cyclones of the Atlantic season would be sent under the WMO header WTNT31 KNHC; advisories on the second, seventh, or twelfth cyclones of the Atlantic season would be sent under the WMO header WTNT32 KNHC, and so on.

Tropical Cyclone Forecast/Advisory

The Tropical Cyclone Forecast/Advisory contains a list of all current watches and warnings on a tropical or subtropical cyclone, as well as the current latitude and longitude coordinates, intensity, and system motion. The advisory contains forecasts of the cyclone positions, intensities, and wind fields for 12, 24, 36, 48, and 72 hours from the current synoptic time. The advisory may also include information on any pertinent storm tides associated with the cyclone. All wind speeds in the forecast advisory in given in knots (nautical miles per hour).

Forecast/Advisories are issued on all Atlantic and eastern Pacific tropical and subtropical cyclones every six hours. Special Forecast/Advisories may be issued at any time due to significant changes in warnings or in the cyclone.

The numbers 1-5 in the headers are assigned by cyclone number, i.e., advisories on the first, sixth, or eleventh cyclones of the Atlantic season would be sent under the WMO header WTNT21 KNHC; advisories on the second, seventh, or twelfth cyclones of the Atlantic season would be sent under the WMO header WTNT22 KNHC, and so on.

Tropical Cyclone Discussion

The Tropical Cyclone Discussion explains the reasoning for the analysis and forecast of a tropical or subtropical cyclone. It includes a table of the forecast track and intensity.

Tropical Cyclone Discussions are issued on all Atlantic and eastern Pacific tropical and subtropical cyclones every six hours. Special tropical cyclone discussions may be issued at any time due to significant changes in warnings or in the cyclone.

The numbers 1-5 in the headers are assigned by cyclone number, i.e., discussions on the first, sixth, or eleventh cyclones of the Atlantic season would be sent under the WMO header WTNT41 KNHC; discussions on the second, seventh, or twelfth cyclones of the Atlantic season would be sent under the WMO header WTNT42 KNHC, and so on.

Tropical Cyclone Strike Probabilities

The Tropical Cyclone Strike Probabilities give the percentage chance of a tropical or subtropical cyclone passing within 75 nm to the right or within 50 nm to the left of a specified point, looking in the direction of cyclone motion. The probabilities are give for the time periods 0-24, 24-36, 36-48, and 48-72 hours, with a 0-72 hour given by adding the indivdual probabilities together.

Tropical Cyclone Strike Probabilities are normally issued for Atlantic tropical or subtropical cyclones every six hours when the system is forecast to be within 72 hours of landfall. Special Strike Probabilities may be issued if Special Public/Forecast Advisories are issued.

The numbers 1-5 in the header are assigned on a rotating basis by cyclone number, i.e., probabilities on the first, sixth, or eleventh cyclones of the Atlantic season would be sent under the WMO header WTNT71 KNHC; probabilities on the second, seventh, or twelfth cyclones of the Atlantic season would be sent under the WMO header WTNT72 KNHC, and so on.

Tropical Cyclone Update

Tropical Cyclone Updates are brief statements issued in lieu of or preceding special advisories to inform of significant changes in a tropical cyclone or to post or cancel watches or warnings.

Tropical Cyclone Position Estimates

Tropical Cyclone Position Estimates are issued between 2-hourly intermdiate advisories whenever a tropical cyclone with a well-defined radar center is within 200 nautical miles of land-based radar in the United States. These estimates give the center location in map coordinates and distance and direction from a well-known point.

Tropical Weather Outlook

The Tropical Weather Outlook is a discussion of significant areas of disturbed weather and their potential for development out to 48 hours. It includes (when possible) a nontechnical explanation of the meteorology behind the outlook.

Tropical Weather Outlooks also include a brief descriptions of any tropical or subtropical cyclones in the region. It also includes the WMO and AFOS headers of where to find more information on an active cyclone during the first 24 hours of existence.

Tropical Weather Outlooks are issued four times a day during the hurricane season. Atlantic outlooks are transmitted under WMO header ABNT20 KNHC and AFOS header MIATWOAT. Eastern Pacific outlooks are transmitted under WMO header ABPZ20 KNHC and AFOS header MIATWOEP.

The most current Tropical Weather Outlook is found on the NHC home page page and the Tropical Cyclone Products page.

Special Tropical Disturbance Statement

Special Tropical Disturbance Statements are used to furnish information on strong formative, nondepression systems. These are usually issued for systems strong enough to produce heavy rains and strong winds that do not yet meet the criteria of tropical or subtropical cyclones. These products are transmitted only as needed.

Atlantic Special Tropical Disturbance Statements are issued under WMO header WONT41 KNHC and AFOS header MIADSAAT. Eastern Pacific Special Tropical Disturbance Statements are issued under WMO header WOPZ41 and AFOS header MIADSAEP.

The most current Special Tropical Disturbance Statement is found on the NHC/TPC home page.

Monthly Tropical Weather Summary

The Monthly Tropical Weather Summary is issued on the first of every month during the hurricane season. It describes the previous month's tropical cyclone actvity and gives details on the cyclones as known at that time. The last Tropical Weather Summary of the season gives an brief account of the whole season.

Atlantic Tropical Weather Summaries are issued under WMO and AFOS header ABNT30 KNHC and MIATWSAT. Eastern Pacific Tropical Weather Summaries are issued under WMO header ABPZ30 KNHC and AFOS header MIATWSEP.

The most current Monthly Tropical Weather Summary is found on the NHC home page.