Real-Time Guidance | About Real-time Guidance

About Real-Time Guidance

This page provides an overview of the real-time guidance system. This system monitors currently active tropical cyclones in the North Atlantic, Northeast Pacific, Central Pacific, Western Pacific, North Indian Ocean, and Southern Hemisphere basins. Note: This site does NOT currently provide information for the Mediterranean or South Atlantic basins. Once model guidance is available for a given storm, the system generates an individual page for that storm and populates with links to the latest model guidance plots, diagnostics, and observational data.

The sidebar on the right provides general information about how the real-time system works, when it updates, and so forth. Details about the contents of each section of the individual storm pages can be found in the main page below.

For information about each of the types of plots and the models and forecast aids they show, please refer to the Guide to Plots. Following some general information, each section of the individual storm pages are explained.

About information as of the most recent model cycle

This section provides a short narrative of basic details about the system at the time of the most recent model cycle (00, 06, 12, or 18 UTC). Note that this information may not match more recent information given in official warning messages from the designated warning center. Most of this information here is expanded and decoded from the very condensed format of the storm's b-deck data file. The narrative provides the following details:

Type of system. A storm can be any of the following types: "tropical wave", "tropical disturbance", "tropical depression", "tropical storm", "hurricane", "major hurricane", "remnant low", "tropical wave", or "post-tropical". In the global basins, the names for tropical cyclones may differ from the above.
STORMID. An 8-character identification code which uniquely identifies a storm by it's basin, stormnumber (of the season, for that particular basin), and the year it formed in. For more information on how to decode the STORMID, click here.
Major Basin. The major basin that the system is currently located in (even if over land). The major global basins in which tropical cyclones occur are the North Atlantic, the Northeast Pacific, the North Central Pacific, the Northwest Pacific, the North Indian, the Southwest Indian, the Southeast Indian, and the Southwest Pacific.
Latitude and longitude of the storm center that was provided to the forecast aids for this model cycle. Given in decimal form to the nearest tenth of a degree. Keep in mind that the storm position may have much more uncertainty than what is implied by the precision of a tenth of a degree.
Intensity of the storm that was provided to the forecast aids for this model cycle. Normally this is the best operational estimate of the storm's 1-minute average maximum sustained surface windspeed (in knots). Since the various forecast aids are initialized on a cycle that falls in between the official storm advisories from some warning centers, this value will sometimes be an estimate that does not correspond to earlier or later advisories. Generally, this intensity value is quite important for the resulting output of the forecast aids.
Translation speed of the storm center (in knots) and direction of motion (in degrees, 0º corresponds to North). Together, these quantities define the storm motion vector that was provided to the forecast aids for this model cycle. This can also have an important effect on the projections of various forecast aids, particularly for models which bogus the initial storm vortex.
Minimum central pressure of the storm (in millibars) that was provided to the forecast aids for this model cycle. Like intensity, this value is generally an estimate specific to the forecast cycle and may not match the values given in warning advisories before or after this time.

About track guidance plots

This section of the individual storm page provides links to several types of track guidance. The first type of plot include groups of forecast aids that are considered early cycle aids. The second type type of plot shows late cycle forecast aids. The contents of each plot type are described in more detail in the guide to early cycle track plots and the guide to late cycle track plots. Use these links to find out more about the forecast aids that are plotted therein.

In general, the individual storm page will provide a link to the most recent of each plot type. If the storm has dissipated, or for some reason updated guidance is not available, the link will point to the most recent plot available (even if the storm dissipated a long time ago). The archive link provides links to all the track guidance plots of this type for the storm.

See the sidebar to the right for more information about the schedule in which these plots are updated and how to access real-time plots for past storms.

About intensity guidance plots

This section of the individual storm page provides a link to the intensity guidance plot and to an archive which contains all of the intensity plots for the storm. The real-time guidance system currently produces two types of intensity guidance plots. The first type include the typical suite of forecast aids in the operational suite. The second type includes experimental intensity forecast aids. The contents of each plot type are described in more detail in the guide to standard intensity plots and the guide to experimental intensity plots.

About Ensemble Prediction System (EPS) track guidance plots

This section of the individual storm page provides a link to the track guidance from multiple ensemble prediction systems, allowing the user to understand the range of variability in the track forecast between the different ensemble systems. The real-time guidance system currently produces this output for the late cycle and an "extra late" cycle. The contents of this plot type are described in more detail in the guide to EPS track plots.

About probabilistic wind exceedance guidance plots

This section of the individual storm page provides links to probabilistic wind exceedance guidance plots produced by the Forecasts of Hurricanes using Large-ensemble Outputs (FHLO) model^*. This section also links to archives for each of the wind exceedance plots for the storm. The real-time guidance system currently provides FHLO wind speed exceedance probabilities based off of two underlying global ensembles and for 7 different wind speed thresholds. The contents are explained in more detail in the guide to probabilistic wind exceedance guidance plots.

^*The data incorporated herein is generated from the use of the Massachusetts Institute of Technology (MIT)’s Forecasts of Hurricanes Using Large-ensemble Outputs (FHLO) version 1.3, © MIT, used with permission. All Rights Reserved.

About ATCF data files

This section of the individual storm page provides links to various data files for the particular storm. All of the files use formats specified by the Automated Tropical Cyclone Forecast (ATCF) System. The contents of each type of data file is described below.

What is an "a-deck"?

An a-deck is a data file that contains a complete listing of all available forecast aid projections for the entire storm history. The real-time guidance system uses a subset of the track and intensity information contained in these files to create the real-time guidance plots. The name of the file, "a-deck", comes from the fact that the filenames start with an "a". Normally, all the model projections are included for the entire lifetime of the storm, so these files can get quite large (~1 MB). The files use a common format known as "ab-deck", according to the specifications of the . For more information on decoding the a-deck contents, click here.

What is a "b-deck"?

A b-deck is a data file that contains a complete history of the past estimates of the storm's center locations, intensity, and other parameters at the 6-hourly synoptic times: 00, 06, 12, and 18 UTC (note that the files can also contain information about the storm at off-synoptic periods, such as the time of landfall). During hurricane season, these files contain the best operational estimates of these parameters, and so are called the "operational best tracks". TCGP provides links to these operational b-decks from each individual storm page. The full collection for all storms is also available in TCGP's global repository.

Note that for the North Atlantic, Eastern Pacific, and Central Pacific basins, TCGP is just providing the b-decks obtained from the National Hurricane Center. For the other global basins, TCGP constructs the b-decks using information found in the tcvitals files that the U.S. Navy's Joint Typhoon Warning Center (JTWC) provides to the U.S. National Oceanagraphic and Atmospheric Administration's National Center for Environmental Prediction (NOAA/NCEP) for the purpose of initializing the model. Note that JTWC does not normally provide tcvitals files once a system has moved inland and is not expected to reemerge over water, or once a system has undergone extratropical transition.

Once the tropical cyclone season has completed, the operational centers eventually update the b-decks with revised, more accurate information after the storm history undergone a careful review by forecasters and other TC experts. Those post-season b-deck files are known simply as the "best tracks", and can be obtained directly from the operational agencies some time following the end of the tropical cyclone season for that agencies basin(s). Normally, the NHC updates their b-decks by about March or April of the following year. For Central Pacific, it could taks as much as several years before the post-season best tracks are available. Below are links where users can download post-season b-decks directly from the various U.S. agencies that produce these:

The real-time portion of TCGP will always feature the operational best tracks (the ones which have not undergone any review). Like the a-decks, the b-decks also use the "ab-deck" format of the ATCF, except that no model projections appear in the files -- the only types of lines that appear use the TECH identifier, "BEST". For more information on decoding the a-deck contents, click here.

What is a "f-deck"?

An f-deck is a data file that contains a record of the fixes of a storm's location and/or intensity. A location fix is any position estimate of the storm center. An intensity fix is any estimate of the storm's intensity. Both location and intensity fixes can be obtained by aircraft flying low-level penetrations through the storm center. Various methods that use satellite imagery or other remote sensing can also provide location and intensity fixes. The f-deck format is an ATCF format. For more information about the f-deck contents, click here

Other data formats

What is a "tcvitals" file?

A tcvitals file is a small data file that contains the current operational estimate of the storm's center location, intensity, central pressure, and several other parameters at synoptic time (00, 06, 12, or 18 UTC). The tcvital file contains almost exactly the same information that are contained in the "compute decks" in the adecks (these are the lines that have the TECH identifier of `CARQ'), but in a different format. tcvitals files are used by the National Centers for Environmental Prediction (NCEP) and many other modeling groups to begin the process of running a hurricane model. The initialization scheme of such models use the information contained in the tcvitals to put the storm in the correct location. Some more advanced initialization techniques attempt to ensure that the storm is also the correct intensity and size. For more information about the contents of tcvitals files, click here.

About aircraft reconnaissance data

Eventually this site will feature a variety of the real-time reconnaissance aircraft data. For now, this section of the individual storm page will just contain a link to a file containing all of the Vortex Data Messages for that storm.

What is a Vortex Data Message?

A Vortex Data Message (VDM) is a succinct summary of a storm's intensity and structure parameters that were measured by an aircraft flying through the storm center. More information on the contents of these files will be detailed when Phase III of this site is released.

About environmental diagnostics

Eventually, this site may feature additional diagnostic information about the storm and its environment. For now, we just provide a link to the latest SHIPS diagnostic message.

What is a SHIPS diagnostic message?

The Statistical Hurricane Intensity Prediction Scheme (SHIPS) is a forecast aid that uses a statistical-dynamical technique to project future storm intensity. The technique is not a NWP model, but rather a linear regression model that takes predictors as input, and gives an intensity projection as output. The predictors include a variety of storm parameters, such as current and recent intensity, environmental parameters such as the sea surface temperature (SST) along the projected storm path, the environmental vertical wind shear along the storm's projected path, and many others quantities. Many of these are derived from another dynamical model's projection on the storm (such as NCEP's Global Forecasting System (GFS) model). The SHIPS diagnostic message is a human-readable text file which includes a summary of many of these predictors. They provide forecasters with a quick summary of how the storm's environment is expected to change if it follows the dynamical model's track (and if that dynamical model's projection of the future environment is correct). For more information about SHIPS, see the SHIPS documentation page.

General information about the real-time guidance system

What does "real-time" mean?

"Real-time" means that all of the plots in this section of the site were generated soon after the underlying data became available. The real-time plots show which data were available to forecasters at that particular stage of the forecast cycle. Once the forecast cycle has finished, plots will not be created here for that forecast cycle.

In a later phase of TCGP, we plan to release retrospective plots for historical storms. Those plots would include forecast aids that became available after the model cycle, or which were run retroactively long after the storm was gone.

Keep in mind that just because a plot was generated in real-time, it will still exist in the archives of the real-time section of this site after the storm has dissipated. Therefore, users should always check the time stamp on the top of each plot. This time stamp indicates for which time the plot is valid for.

How often are the real-time guidance plots updated?

Every six hours. When it's time to do an update, the real-time script system checks to see if there are any active storms in the basins it monitors. For each active storm, it then checks to see if there are any forecast aids to plot. If there is, it generates the real-time plots and creates an individual storm page with links to the plots. It also links to related text products at that time. Some of the observational data, such as the Vortex Data Messages, are set to update more frequently if new data are available. All guidance plots are on a 6-hour update cycle.

Exactly when does the real-time guidance system do its updating?

The real-time system updates 4 times a day: at 01, 07, 13, and 19 UTC. The system starts running around 40 minutes past the hour by starting to collect some preliminary data. At 46 minutes the hour, it starts gathering the a-decks of forecast aids and model guidance. At 50 minutes past, the system begins making the new guidance plots. Depending on how many plots there are to create, this may take a minute or two. After the plot are finished, all content is linked to the individual storm pages and the overview map is updated. Generally, content is available by 51 or 52 minutes past the hour.

Is there an archive? Where can I find past plots of real-time guidance?

At the current time, there is not an easy way to access past plots of the real-time guidance. The real-time content doesn't go away - it continues to live in the location in which it was placed, so all past content can be accessed from the original URLs. To find a particular recent storm, feel free to browse around in the basin directories, select the year, and then the storm. Iin the near future we plan to implement an archive page to facilitate easier access to past storms.

The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.