Automated Tropical Cyclone Forecasting System

The need for a more modernized method for forecasting tropical cyclones had become apparent by the mid-1980s. At that time Department of Defense was using acetate, grease pencils, and disparate computer programs to forecast tropical cyclones.[1] The ATCF software was developed by the Naval Research Laboratory for the Joint Typhoon Warning Center (JTWC) beginning in 1986,[2] and used since 1988. During 1990 the system was adapted by the National Hurricane Center (NHC) for use at the NHC, National Centers for Environmental Prediction and the Central Pacific Hurricane Center.[2][3] This provided the NHC with a multitasking software environment which allowed them to improve efficiency and cut the time required to make a forecast by 25% or 1 hour.[3] ATCF was originally developed for use within DOS, before later being adapted to Unix and Linux.[2]

ATCF image of Nabi's (2005) previous track, forecast track, along with tropical storm, storm, and hurricane-force wind radii depicted, from 18z on September 5

An a-deck is a data file that contains a listing of available forecast aid projections for a storm's 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 a-deck name 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 increase to around 1 megabyte in size.[4]

A b-deck is a data file that contains the history of past storms' center locations, intensity, and other parameters at the six hourly synoptic times: 0000, 0600, 1200, and 1800 UTC. The files can contain information outside of synoptic hours, such as the time of landfall. During hurricane season, these files contain the best operational estimates of these parameters, and are known as the operational best tracks. Once the season has completed, the files are updated with revised information after the storm history has undergone a careful review by forecasters and other experts. The post-season files are known as the best tracks. The real-time portion of this web site will always feature the operational best tracks (the ones which have not undergone any review).[4]

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.[4]

This is an Atlantic Objective Aid message for a tropical disturbance which was in the Gulf of Mexico on June 7, 2014 at 00z, generated from input into ATCF. Note its identifier is AL902014, meant for a tropical disturbance (Invest-90L) in the North Atlantic Ocean during 2014

Systems within ATCF are identified with the basin prefix (AL, CP, EP, IO, SH, SL, WP) and then followed by two digit number between 01 and 49 for active tropical cyclones,[5] which becomes incremented with each new system, and then the year associated with the system (e.g. EP202015 for Hurricane Patricia). Numbers from 50 through 79 after the basin acronym are used internally by the basin's respective Tropical Cyclone Warning Centers and Regional Specialized Meteorological Center.[6] Numbers in the 80s are used for training purposes and can be reused. Numbers in the 90s are used for areas of interest,[7] sometimes referred to as invests or areas of disturbed weather, and are also reused within any particular year. Their status is listed the following ways within the associated data file: DB – disturbance, TD – tropical depression, TS – tropical storm, TY – typhoon, ST – super typhoon, TC – tropical cyclone, HU – hurricane, SD – subtropical depression, SS – subtropical storm, EX – extratropical systems, IN – inland, DS – dissipating, LO – low, WV – tropical wave, ET – extrapolated, and XX – unknown. Times used are in a four digit year, month, day, and hour format.[5]

In the 1990s, other countries developed similar tropical cyclone forecasting software. The Bureau of Meteorology in Australia developed the Australian Tropical Cyclone Workstation. The Canadian Hurricane Centre developed Canadian Hurricane Centre Forecaster's Workstation.[2]