NHC Text Product Descriptions
Download the NHC Product Description User's Guide for all tropical cyclone-related products.
Contents
World Meteorological
Organization (WMO) and AWIPS (in parenthesis) headers:
WTNT31-35 KNHC (MIATCPAT1-5) – Atlantic
WTPZ31-35 KNHC (MIATCPEP1-5) – E. Pacific
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 and eastern Pacific tropical or subtropical
cyclones. Prior to 2008, public advisories for eastern Pacific tropical or subtropical cyclones were issued only when the cyclones threatened land.
Public advisories for Atlantic tropical cyclones are normally issued every six
hours at 5:00 AM EDT, 11:00 AM EDT, 5:00 PM EDT, and 11:00 PM EDT (or 4:00 AM EST, 10:00 AM EST, 4:00 PM EST, and 10:00 PM EST).
Public advisories for Eastern Pacific tropical cyclones are normally issued every six
hours at 2:00 AM PDT, 8:00 AM PDT, 2:00 PM PDT, and 8:00 PM PDT (or 1:00 AM PST, 7:00 AM PST, 1:00 PM PST, and 7:00 PM PST).
Intermediate public advisories may be issued every 3 hours when coastal watches or warnings are in effect, and every 2 hours when coastal watches or
warnings are in effect and land-based radars have identified a reliable storm center. Additionally, 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.
See Example
World Meteorological
Organization (WMO) and AWIPS (in parenthesis) headers:
WTNT21-25 KNHC (MIATCMAT1-5) – Atlantic
WTPZ21-25 KNHC (MIATCMEP1-5) – E. Pacific
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 at 0300, 0900, 1500, and 2100 UTC (learn about UTC time).
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.
See Example
World Meteorological
Organization (WMO) and AWIPS (in parenthesis) headers:
WTNT41-45 KNHC (MIATCDAT1-5) – Atlantic
WTPZ41-45 KNHC (MIATCDEP1-5) – E. Pacific
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.
Tropical Cyclone Discussions for Atlantic tropical cyclones are normally issued every six
hours at 5:00 AM EDT, 11:00 AM EDT, 5:00 PM EDT, and 11:00 PM EDT (or 4:00 AM EST, 10:00 AM EST, 4:00 PM EST, and 10:00 PM EST).
Tropical Cyclone Discussions for Eastern Pacific tropical cyclones are normally issued every six
hours at 2:00 AM PDT, 8:00 AM PDT, 2:00 PM PDT, and 8:00 PM PDT (or 1:00 AM PST, 7:00 AM PST, 1:00 PM PST, and 7:00 PM PST).
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.
See Example
World Meteorological
Organization (WMO) and AWIPS (in parenthesis) headers:
FONT11-15 KNHC (MIAPWSAT1-5) – Atlantic
FOPZ11-15 KNHC (MIAPWSEP1-5) – Eastern Pacific
FOPA11-15 PHFO (HNLPWSCP1-5) – Central Pacific (issued by CPHC)
The Tropical Cyclone
Surface Wind Speed Probabilities text product provides probabilities, in percent,
of sustained wind speeds equal
to or exceeding 34-, 50-, and 64-knot wind speed thresholds. These wind speed
probabilities are based on the track, intensity, and wind structure forecasts and uncertainties
from the National Hurricane Center
and the Central Pacific Hurricane Center and are computed
for coastal and inland cities as well as offshore locations (e.g., buoys).
These text products are issued on all Atlantic and eastern Pacific tropical and subtropical
cyclones every six hours at 0300, 0900, 1500, and 2100 UTC (learn about UTC time).
Special tropical cyclone surface wind speed probabilities may be issued at any time due to significant changes in warnings or in the cyclone.
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 FONT11 KNHC; probabilities on the second, seventh, or twelfth cyclones of
the Atlantic season would be sent under the WMO header FONT12 KNHC, and so on.
Three types of tropical cyclone wind speed probability values will be created
during 2006. Not all of these values will be distributed or placed on the Internet.
For each probability value, the event in question is a sustained (one-minute average)
surface (10 m) wind speed of at least a particular threshold value (34, 50, or 64 kt)
at a specific location.
Cumulative – These values tell you the overall probability the event will
occur sometime during the specified cumulative forecast period (0-6 hours, 0-12,
0-18, etc.) at each specific point. These values are provided in both the text and
graphical formats.
In the text product, the numbers are in parentheses.
The graphical products depict
only cumulative values. The text product is transmitted
to users via normal NWS dissemination methods. The graphic is available on the internet from the
National Hurricane Center and the
Central Pacific Hurricane Center.
Individual – These values tell you the probability the event will start
sometime during the specified individual forecast period (0 - 6 hours, 6-12, 12-18,
etc.) at each specific point. These periods are individual, since nothing that
occurs before or after the specified period affects the probability. These values
are provided only in the text NHC product. They are the values outside of the
parentheses (cumulative values are in the parentheses). The term "individual" also
makes a clear distinction from the cumulative period values for users.
Incremental – These values tell you the probability the event will occur
sometime during the specified forecast period (0 - 6 hours, 6-12, 12-18, etc.) at each specific
point. These values are incremental since they can increase in value by accounting for the
possibility the event might start in an earlier period and still be occurring in the specified
period.
See Example
Note: View a more detailed description of the wind speed probabilities products.
List of Cities by Basin: Atlantic – Eastern Pacific –
Central Pacific – Western Pacific
World Meteorological
Organization (WMO) and AWIPS (in parenthesis) headers:
WTNT61-65 KNHC (MIATCUAT1-5) – Atlantic
WTPZ61-65 KNHC (MIATCUEP1-5) – E. Pacific
Tropical Cyclone Updates (TCUs) 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. No structured issuance schedule exists for these update statements.
When a TCU is issued to change the status of a tropical cyclone (e.g., from a tropical storm to a hurricane), or to update storm intensity, location, or motion
information, the TCU will include a storm summary section identical in format to the storm summary section found in the TCP.
A TCU may be issued without a storm summary section to provide advance notice that significant changes to storm information will be conveyed shortly, either
through a subsequent TCU or through a Special Advisory. TCUs issued to convey changes to watches or warnings also will not require a storm summary section.
See Example
World Meteorological
Organization (WMO) and AWIPS (in parenthesis) headers:
WTNT51-55 KNHC (MIATCEAT1-5) – Atlantic
WTPZ51-55 KNHC (MIATCEEP1-5) – E. Pacific (rarely issued)
Tropical Cyclone Position Estimates are issued between 2-hourly
intermediate public 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.
See Example
World Meteorological Organization (WMO) and AWIPS (in parenthesis) headers:
ABNT20 KNHC (MIATWOAT) – Atlantic
ABPZ20 KNHC (MIATWOEP) – E. Pacific
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. The Outlook also
provides the chance of development (in percent, from 0 to 100 in ten percent increments) of each disturbance discussed in the outlook.
The NHC issues Special Tropical Weather Outlooks when important changes with areas of disturbed weather need to be conveyed before the
next scheduled release of the Tropical Weather Outlook (TWO). The Special TWO can also be used on a recurring basis for disturbances
outside of the normal hurricane season when routine TWOs are not issued. Special TWOs are issued under the same product headers as
the TWO and they will supercede the previously issued regular or special TWO.
Please note the (Special) Tropical Weather Outlook has a companion Graphical Tropical Weather Outlook that will be updated at the same time.
Tropical Weather Outlooks also include a brief descriptions of any tropical or subtropical cyclones in the region. It also includes the WMO and
AWIPS headers of where to find more information on an active cyclone during the first 24 hours of existence.
During hurricane
season, Tropical Weather Outlooks are issued four times a day. Atlantic outlooks are issued at 2:00 AM EDT, 8:00 AM EDT, 2:00 PM EDT, and 8:00 PM EDT. They are transmitted
under WMO header ABNT20 KNHC and AWIPS header MIATWOAT.
Eastern Pacific outlooks are issued at 5:00 AM PDT, 11:00 AM PDT, 5:00 PM PDT, and 11:00 PM PDT. They are transmitted under
WMO header ABPZ20 KNHC and AWIPS header MIATWOEP.
The products will be issued one hour earlier for both basins during Standard Time. The most current Tropical Weather Outlook is found on the NHC home page.
See Example
Special Tropical Disturbance Statement
Effective May 15 2009, the National Hurricane Center has discontinued the issuance of Special Tropical Disturbance Statements. The following products are no longer issued:
WONT41 KNHC (MIADSAAT) – Atlantic
WOPZ41 KNHC (MIADSAEP) – E. Pacific
Special DSAs were formerly issued when important changes in areas of disturbed weather over tropical or subtropical waters needed to be conveyed before the next scheduled release of the
Tropical Weather Outlook. Effective May 15 2009 the information formerly provided in DSA statements will be available through the issuance of Special Tropical Weather Outlooks (TWOs).
These product changes result in no degradation of service but provide a more efficient delivery of the same information to users of NHC products.
Users wishing to continue receiving the information previously provided through DSAs will need to use the Tropical Weather Outlook (TWO) products that are described immediately
above (see example).
World Meteorological Organization (WMO) and AWIPS (in parenthesis) headers:
WTNT81-85 KNHC (MIATCVAT1-5) – Atlantic
WTPZ81-85 KNHC (MIATCVEP1-5) – E. Pacific
The Tropical Cyclone Watch/Warning text product (TCV) is based upon the Valid Time Event Code
(VTEC). It summarizes all new, continued, and canceled tropical cyclone watches and warnings
issued by the National Hurricane Center (NHC) for the U.S. Atlantic and Gulf coasts, Puerto Rico, and U.S. Virgin Islands.
Beginning in 2008, the TCV will also include areas of southern California from Los Angeles to the United States/Mexico border.
Once watches and/or warnings are in effect for the areas mentioned, updates will be issued by the NHC at a
minimum of every six hours at the regular advisory issuance time of 5:00 AM EDT, 11:00 AM EDT, 5:00 PM EDT, and 11:00 PM EDT
(or 4:00 AM EST, 10:00 AM EST, 4:00 PM EST, and 10:00 PM EST). TCVs for special advisories will
be issued for the same circumstances that apply for a standard advisory.
When active, the most current Tropical Cyclone Valid Time Event Code (VTEC) product can be
found on the NHC home page.
Additionally, a more detailed description about this product can be found at the TCV
overview page. An overview of the VTEC program is available at
http://www.nws.noaa.gov/om/vtec/.
See Example
World Meteorological Organization (WMO) and AWIPS (in parenthesis) headers:
FKNT21-25 KNHC (MIATCANT1-5) – Atlantic
FKPZ21-25 KNHC (MIATCAPZ1-5) – E. Pacific
The Aviation Tropical Cyclone Advisory is issued to provide short term tropical cyclone forecast guidance for
international aviation safety and routing purposes. The TCA lists the current TC position, motion, and
intensity, and includes 6, 12, 18, and 24 hour forecast positions and intensities. Position and intensity information
for forecast hours (+06, +12, +18 and +24) is derived from interpolated forecast information – intensity is
rounded to the nearest 5 knots.
Issuance of the Aviation Tropical Cyclone Advisory occurs every six hours at the regular advisory issuance time of 0300,
0900, 1500, and 2100 UTC (learn about UTC time). For 2008, the bulletin's information is valid at
the routine advisory times (0300, 0900, 1500 and 2100 UTC) and is not anchored to the synoptic times. TCAs for
special advisories will be issued for the same circumstances that apply for a standard advisory.
See Example
Hurricane Local Statement (HLS)
These statements are NOT produced at the National Hurricane Center, but can be found through links in the NHC storm table when an active tropical cyclone threatens U.S. land.
Local National Weather Service Weather Forecast Offices (WFOs) produce these local statements to keep the media, local
decision makers, and the public current on present and anticipated storm effects
in their area. The hurricane local statements contain essential hurricane or
tropical storm information in a condensed form, but expand on the storm's potential
effects on the local area and on any actions declared by local emergency managers.
Local weather statements generally present the following:
- A lead statement
- A sentence detailing the counties, parishes, or cities covered by the statement
- Watches and/or warnings in effect and the counties or parishes to which they apply
- Recommended precautionary actions and the times they should be completed
- Storm surge and storm tide information, including the times that various heights are expected, present heights, and their locations
- Present winds and the expected time of onset of tropical storm or hurricane-force winds
- Tornado, flood, flash flood, rip current, beach erosion, and inland high wind potential
- The time of the next statement
- Information on the probability of hurricane or tropical storm conditions may also be included. An example section of a hurricane local statement is provided below.
See NWS Weather Forecast Office locations to find your local office.
World Meteorological Organization (WMO) and AWIPS (in parenthesis) headers:
ABNT30 KNHC (MIATWSAT) – Atlantic
ABPZ30 KNHC (MIATWSEP) – E. Pacific
The Monthly Tropical Weather Summary is issued on the first day of every month during the
hurricane season. It briefly describes the previous month's
tropical cyclone actvity and gives a table of basic meteorological
statistics, such as the dates of occurrence and estimated peak intensity, for all of the season's tropical cyclones to date. Narrative summaries for
individual cyclones are no longer included as of 2009, although brief descriptions for records of interest may be provided.
Users requiring comprehensive information on each tropical cyclone including synoptic history, meteorological statistics, casualties and damages,
and the post-analysis best track (six-hourly positions and intensities), are encouraged to consult the end of season tropical cyclone reports.
Atlantic tropical cyclone reports are available at www.nhc.noaa.gov/2008atlan.shtml and Eastern Pacific tropical
cyclone reports are available at www.nhc.noaa.gov/2008epac.shtml.
Atlantic Tropical Weather Summaries are issued under WMO and AWIPS header
ABNT30 KNHC and MIATWSAT. Eastern Pacific Tropical Weather Summaries are
issued under WMO header ABPZ30 KNHC and AWIPS header MIATWSEP.
The most current Monthly Tropical Weather Summary is found on the
NHC home page.
See Example
These reports are available in the archives section of the NHC website
The National Hurricane Center's Tropical Cyclone Reports (formerly called Preliminary
Reports) contain comprehensive information on each storm, including synoptic history,
meteorological statistics, casualties and damages, and the post-analysis best
track (six-hourly positions and intensities). Tropical cyclones include depressions,
storms and hurricanes. Tropical depressions listed in the table
of contents are those that did not reach tropical storm strength.
Tropical Cyclone Reports (TCRs) are composed after a tropical cyclone has reached its end of life, and all pertinent data has been
gathered and analyzed. Once completed, the TCRs are posted to the archives section of the NHC website.
|