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NHC Tropical Cyclone Graphical Product Descriptions


Download the NHC Product Description User's Guide for all tropical cyclone-related products.

Contents

 


Tropical Cyclone Track Forecast Cone and Watches/Warnings

Tropical Cyclone Track and Watches/Warnings 
image example

This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC's forecast intensity for that time:

D: Tropical Depression – wind speed less than 39 MPH
S: Tropical Storm – wind speed between 39 MPH and 73 MPH
H: Hurricane – wind speed between 74 MPH and 110 MPH
M: Major Hurricane – wind speed greater than 110 MPH

NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast "cone", the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.

It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Cumulative Wind History Graphic described below.

Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in graphical form and in tabular form for selected locations and forecast positions.

Graphics 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).

Graphics 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 graphics also will be updated when intermediate public advisories are issued, and special graphics may be issued at any time due to significant changes in warnings or in the cyclone.

Note:  A detailed definition of the NHC track forecast cone is also available.


Tropical Cyclone Surface Wind Speed Probabilities

Tropical Cyclone Surface Wind Speed Probability Grahic image example

Three types of tropical cyclone wind speed probability values are created for each forecast/advisory package, but not all of these values are 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 kt...39 mph, 50 kt...58 mph, or 64 kt...74 mph) 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.

Graphics 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).

Graphics 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).

Special graphics may be issued at any time due to significant changes in warnings or in the cyclone.

Note:  A more detailed description of these probability products is also available.


Tropical Cylone Surface Wind Field

Tropical Cyclone Wind Field image example

This graphic shows the areas potentially being affected by the sustained winds of tropical storm force (in orange) and hurricane force (in red). The display is based on the wind radii contained in the latest Forecast/Advisory (indicated at the top of the figure). Users are reminded that the Forecast/Advisory wind radii represent the maximum possible extent of a given wind speed within particular quadrants around the tropical cyclone. As a result, not all locations falling within the orange or red shaded areas will be experiencing sustained tropical storm or hurricane force winds, respectively.

In addition to the wind field, this graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The white dot indicates the current position of the center of the tropical cyclone, and the dashed line shows the history of the center of the tropical cyclone.

Graphics 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). Graphics 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).

Special graphics may be issued at any time due to significant changes in warnings or in the cyclone.

Note:  Please read the Tropical Cyclone Surface Wind Field full product description.


Cumulative Wind History

Tropical Cyclone Cumulative
Wind Distribution image example

This graphic shows how the size of the storm has changed, and the areas potentially affected so far by sustained winds of tropical storm force (in orange) and hurricane force (in red). The display is based on the wind radii contained in the set of Forecast/Advisories indicated at the top of the figure. Users are reminded that the Forecast/Advisory wind radii represent the maximum possible extent of a given wind speed within particular quadrants around the tropical cyclone. As a result, not all locations falling within the orange or red swaths will have experienced sustained tropical storm or hurricane force winds, respectively.

Graphics 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).

Graphics 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).

Special graphics may be issued at any time due to significant changes in warnings or in the cyclone.


2-Day Graphical Tropical Weather Outlook

Graphical Tropical Weather Outlook Example Image
Example Graphical Tropical Weather Outlook for the Atlantic basin.
(Click to see an interactive example with mouseovers)

The 2-Day Graphical Tropical Weather Outlook (TWO) depicts significant areas of disturbed weather and their potential for development during the next 48 hours. The 2-Day Graphical TWO also shows the locations of any active tropical cyclones. The location of areas of disturbed weather on the graphic are denoted by an X and numbered, with text discussions for each disturbance given beneath the graphic.

The potential for tropical cyclone formation for each disturbance within the next 48 hours will be indicated by the color of the X; yellow indicates a low probability of development (0-30%), orange indicates medium likelihood (40-60%), and red indicates a high likelihood of development (70-100%).

The graphic is interactive; users can mouse over cyclones or disturbances in the in the graphic and pop-up windows will appear with cyclone advisory information or the text Outlook discussion for that disturbance. Clicking on a tropical cyclone symbol will take the user to a new web location that contains all advisories and products for the cyclone. Clicking on a disturbance will take you to a zoomed satellite image of that disturbance. Information on the motion and potential impacts of each disturbance is available in the text descriptions but is not displayed graphically.

The Tropical Weather Outlook is issued every six hours from 1 June–30 November for the Atlantic Basin and from 15 May–30 November for the eastern North Pacific Basin at 0000, 0600, 1200, 1800 UTC. Local issuance times are shown in the table below.
Basin Local Issuance Times During Daylight Savings Time Local Issuance Times During Standard Time
Atlantic
(1 June–30 November
2:00 am EDT
8:00 am EDT
2:00 pm EDT
8:00 pm EDT
1:00 am EST
7:00 am EST
1:00 pm EST
7:00 pm EST
Eastern North Pacific
(15 May–30 November)
 5:00  am PDT
11:00 am PDT
 5:00  pm PDT
11:00 pm PDT
 4:00  am PST
10:00 am PST
 4:00  pm PST
10:00 pm PST

The 2-Day Graphical TWO is usually available shortly after the text TWO has been issued, but occasionaly there might be a slight delay for the updated graphic to appear on the NHC website. For this reason, users are reminded that the text TWO may show updated information a few minutes prior to the 2-Day Graphical TWO.

A special TWO may be issued at any time when important changes in areas of disturbed weather over tropical or subtropical waters need to be conveyed before the next scheduled release of the TWO.

Note:  A more complete description of the Graphical Tropical Weather Outlook can be found here.


5-Day Graphical Tropical Weather Outlook

5-day Graphical Tropical Weather Outlook Example Image
Example Graphical Tropical Weather Outlook for the Atlantic basin.
(Click to see an interactive example with mouseovers)

The 5-day Graphical Tropical Weather Outlook (TWO) became operational in 2015. This graphic provides formation potential for individual disturbances during the next 5-day period. The areas enclosed on the graph represent the potential formation area during the forecast period.

The areas are color coded based on the potential for tropical cyclone formation during the next 5-days. Yellow indicates a low probability of development (0-30%), orange indicates medium likelihood (40-60%), and red indicates a high likelihood of development (70-100%).

The location of existing disturbances is indicated by an X. If the formation potential of an existing disturbance does not include the area in which the disturbance is currently located, an arrow will connect the current location of the disturbance to its area of potential formation. Areas without an X or not connected by an arrow to an X indicate that the disturbance does not currently exist, but is expected to develop during the 5-day period.

The graphic is interactive; users can mouse over disturbances in the in the graphic and pop-up windows will appear with cyclone advisory information or the text Outlook discussion for that disturbance. Clicking on a disturbance will take the user to a graphic that shows only that disturbance. Active tropical cyclones are not depicted on this graphic.

The Tropical Weather Outlook is issued every six hours from 1 June–30 November for the Atlantic Basin and from 15 May–30 November for the eastern North Pacific Basin at 0000, 0600, 1200, 1800 UTC. Local issuance times are shown in the table below.
Basin Local Issuance Times During Daylight Savings Time Local Issuance Times During Standard Time
Atlantic
(1 June–30 November
2:00 am EDT
8:00 am EDT
2:00 pm EDT
8:00 pm EDT
1:00 am EST
7:00 am EST
1:00 pm EST
7:00 pm EST
Eastern North Pacific
(15 May–30 November)
 5:00  am PDT
11:00 am PDT
 5:00  pm PDT
11:00 pm PDT
 4:00  am PST
10:00 am PST
 4:00  pm PST
10:00 pm PST

The graphical TWO is usually available shortly after the text TWO has been issued, but occasionaly there might be a slight delay for the updated graphic to appear on the NHC website. For this reason, users are reminded that the text TWO may show updated information a few minutes prior to the graphical TWO.

A special TWO may be issued at any time when important changes in areas of disturbed weather over tropical or subtropical waters need to be conveyed before the next scheduled release of the TWO.

Note:  A more complete description of the Graphical Tropical Weather Outlook can be found here.


Tropical Cyclone Storm Surge Probabilities (0 - 20 feet)

P-SURGE Heights Example Example Static example of the Probabilistic Storm Surge Heights output. Note that the actual product is interactive with pan and zoom capability.

The Tropical Cyclone Storm Surge Probabilities products are created for the Gulf of Mexico and Atlantic coastal areas of the continental United States. This product is intended to provide users with information which enhances their ability to make preparedness decisions specific to their own situations.

The product on the NHC website has changed for the 2014 season. Heights now are expressed in feet above ground level (AGL), and includes tides. The graphic shows probabilities, in percent, of storm surge exceeding various thresholds. The range of thresholds now are at 1-foot intervals with a minimum value of 0 feet and a maximum value of 20 feet.

This storm surge graphic is based upon an ensemble of Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model runs using the National Hurricane Center (NHC) official advisory and accounts for track, size, and intensity errors based on historical errors. Additional information on the SLOSH model can be found at: http://www.nhc.noaa.gov/surge/slosh.php.

The emergency management community is the primary target audience. However, this product will also be widely used by other federal, state, and local government agencies; the media; maritime interests; and the general public.

The product is available on the NHC website when a hurricane watch or hurricane warning is in effect for any portion of the Gulf or Atlantic coasts of the continental United States. Updates to the product are produced about one hour after the issuance of routine NHC tropical cyclone advisories 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).

The data are available in GRIB2 format in the National Digital Guidance Database (NDGD) via HTTP and FTP.

More probabilistic surge products can be found at MDL's web page.

Note:  More information on the Tropical Cyclone P-SURGE graphics and model model can be found here.


Tropical Cyclone Storm Surge Probabilities (exceedance)

P-SURGE Exceedance Example Example Static example of the Probabilistic Storm Surge Exceedance output. Note that the actual product is interactive with pan and zoom capability.

The Probabilistic Tropical Cyclone Storm Surge Exceedance products are created for the Gulf of Mexico and Atlantic coastal areas of the continental United States. This product shows storm surge height including tides, in feet above ground level (AGL), such that there is an N percent chance of exceeding it, where N ranges from 10 to 50 in intervals of 10 percent. The 10 percent exceedance height, for example, is the storm surge height including tides, above ground level (AGL), such that there is a 10 percent chance of exceeding it.

The storm surge graphics are based upon an ensemble of Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model runs using the National Hurricane Center (NHC) official advisory and account for track, size, and intensity uncertainty from historical errors. Additional information on the SLOSH model can be found at: http://www.nhc.noaa.gov/surge/slosh.php.

The emergency management community is the primary target audience. However, this product will also be widely used by other federal, state, and local government agencies; the media; maritime interests; and the general public.

The product is available on the NHC website when a hurricane watch or hurricane warning is in effect for any portion of the Gulf or Atlantic coasts of the continental United States. Updates to the product are produced about one hour after the issuance of routine NHC tropical cyclone advisories 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).

The data are available in GRIB2 format in the National Digital Guidance Database (NDGD) via HTTP and FTP.

More exceedance products can be found at MDL's web page.

Note:  More information on the Tropical Cyclone P-SURGE graphics and model model can be found here.

U.S. Rainfall QPF from WPC

Example of the WPC QPF Rainfall graphic

This graphic is created by the NWS/NCEP Weather Prediction Center (WPC) and shows rainfall potential for the United States when a tropical cyclone threatens land. The graphic is displayed as a Quantitative Precipitation Forecast (QPF), which shows rainfall totals for a specified time period, based on forecaster discretion. For more rainfall information, visit WPC Quantitative Precipitation Forecasts.



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Page last modified: Tuesday, 02-Jun-2015 13:18:04 UTC