The Automated Tropical Cyclone Forecasting System (ATCF) is a piece of software originally developed to run on a personal computer for the Joint Typhoon Warning Center (JTWC) in 1988,and the National Hurricane Center (NHC) in 1990. ATCF remains the main piece of forecasting software used for the United States Government, including the JTWC, NHC, and Central Pacific Hurricane Center. Other tropical cyclone centers in Australia and Canada developed similar software in the 1990s. The data files with ATCF lie within three decks, known as the a-, b-, and f-decks. The a-decks include forecast information, the b-decks contain a history of center fixes at synoptic hours, and the f-decks include the various fixes made by various analysis center at various times. In the years since its introduction, it has been adapted to Unix and Linux platforms.
A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician. Unlike large costly minicomputer and mainframes, time-sharing by many people at the same time is not used with personal computers.
The Joint Typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command located in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South Pacific Ocean, and Indian Ocean for all branches of the U.S. Department of Defense and other U.S. government agencies. Their warnings are intended for the protection of primarily military ships and aircraft as well as military installations jointly operated with other countries around the world.
The National Hurricane Center (NHC) is the division of the United States' National Weather Service responsible for tracking and predicting tropical weather systems between the Prime Meridian and the 140th meridian west poleward to the 30th parallel north in the northeast Pacific Ocean and the 31st parallel north in the northern Atlantic Ocean. The agency, which is co-located with the Miami branch of the National Weather Service, is situated on the campus of Florida International University in University Park, Florida.
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.The ATCF software was developed by the Naval Research Laboratory for the Joint Typhoon Warning Center (JTWC) beginning in 1986, 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. 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. ATCF was originally developed for use within DOS, before later being adapted to Unix and Linux.
The United States National Centers for Environmental Prediction (NCEP) delivers national and global weather, water, climate and space weather guidance, forecasts, warnings and analyses to its Partners and External User Communities. These products and services are based on a service-science legacy and respond to user needs to protect life and property, enhance that nation's economy and support the nation's growing need for environmental information. The centers form part of the National Weather Service.
The Central Pacific Hurricane Center (CPHC) of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central Pacific region: from the equator northward, 140°W–180°W, most significantly for Hawai‘i. It is the Regional Specialized Meteorological Center (RSMC) for tropical cyclones in this region, and in this capacity is known as RSMC Honolulu.
DOS is a family of disk operating systems, hence the name. DOS primarily consists of MS-DOS and a rebranded version under the name IBM PC DOS, both of which were introduced in 1981. Other later compatible systems from other manufacturers include DR-DOS (1988), ROM-DOS (1989), PTS-DOS (1993), and FreeDOS (1998). MS-DOS dominated the x86-based IBM PC compatible market between 1981 and 1995.
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.
The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix mega is a multiplier of 1000000 (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities.
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).
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.
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,which becomes incremented with each new system, and then the year associated with the system. 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. Numbers in the 80s are used for training purposes and can be reused. Numbers in the 90s are used for areas of interest, 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.
A Regional Specialized Meteorological Centre is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as part of the World Weather Watch.
An invest in meteorology is a designated area of disturbed weather that is being monitored for potential tropical cyclone development. Invests are designated by three separate United States forecast centers: the National Hurricane Center, the Central Pacific Hurricane Center, and the Joint Typhoon Warning Center.
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.
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone.
A Pacific hurricane is a mature tropical cyclone that develops within the eastern and central Pacific Ocean to the east of 180°W, north of the equator. For tropical cyclone warning purposes, the northern Pacific is divided into three regions: the eastern, central, and western, while the southern Pacific is divided into 2 sections, the Australian region and the southern Pacific basin between 160°E and 120°W. Identical phenomena in the western north Pacific are called typhoons. This separation between the two basins has a practical convenience, however, as tropical cyclones rarely form in the central north Pacific due to high vertical wind shear, and few cross the dateline.
A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern, central, and western. The Regional Specialized Meteorological Center (RSMC) for tropical cyclone forecasts is in Japan, with other tropical cyclone warning centers for the northwest Pacific in Hawaii, the Philippines and Hong Kong. While the RSMC names each system, the main name list itself is coordinated among 18 countries that have territories threatened by typhoons each year A hurricane is a storm that occurs in the Atlantic Ocean or northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a tropical cyclone occurs in the south Pacific or Indian Ocean.
Tropical cyclones are unofficially ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basin(s) they are located in. Only a few scales of classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but some alternative scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
A tropical cyclone forecast model is a computer program that uses meteorological data to forecast aspects of the future state of tropical cyclones. There are three types of models: statistical, dynamical, or combined statistical-dynamic. Dynamical models utilize powerful supercomputers with sophisticated mathematical modeling software and meteorological data to calculate future weather conditions. Statistical models forecast the evolution of a tropical cyclone in a simpler manner, by extrapolating from historical datasets, and thus can be run quickly on platforms such as personal computers. Statistical-dynamical models use aspects of both types of forecasting. Four primary types of forecasts exist for tropical cyclones: track, intensity, storm surge, and rainfall. Dynamical models were not developed until the 1970s and the 1980s, with earlier efforts focused on the storm surge problem.
The Dvorak technique is a widely used system to estimate tropical cyclone intensity based solely on visible and infrared satellite images. Within the Dvorak satellite strength estimate for tropical cyclones, there are several visual patterns that a cyclone may take on which define the upper and lower bounds on its intensity. The primary patterns used are curved band pattern (T1.0-T4.5), shear pattern (T1.5–T3.5), central dense overcast (CDO) pattern (T2.5–T5.0), central cold cover (CCC) pattern, banding eye pattern (T4.0–T4.5), and eye pattern (T4.5–T8.0).
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; while in the south Pacific or Indian Ocean, comparable storms are referred to simply as "tropical cyclones" or "severe cyclonic storms".
Tropical cyclone forecasting is the science of forecasting where a tropical cyclone's center, and its effects, are expected to be at some point in the future. There are several elements to tropical cyclone forecasting: track forecasting, intensity forecasting, rainfall forecasting, storm surge, tornado, and seasonal forecasting. While skill is increasing in regard to track forecasting, intensity forecasting skill remains nearly unchanged over the past several years. Seasonal forecasting began in the 1980s in the Atlantic basin and has spread into other basins in the years since.
The Hurricane Databases (HURDAT), managed by the National Hurricane Center, are two separate databases that contain details on tropical cyclones, that have occurred within the Atlantic Ocean and Eastern Pacific Ocean since either 1851 or 1949.
The following is a glossary of tropical cyclone terms.
The 1951 Pacific hurricane season ran through the summer and fall of 1951. Nine tropical systems were observed this season.
Typhoon Haiyan's meteorological history began with its origins as a tropical disturbance east-southeast of Pohnpei and lasted until its degeneration as a tropical cyclone over Southern China. The thirteenth typhoon of the 2013 Pacific typhoon season, Haiyan originated from an area of low pressure several hundred kilometers east-southeast of Pohnpei in the Federated States of Micronesia on November 2. Tracking generally westward, environmental conditions favored tropical cyclogenesis and the system developed into a tropical depression the following day. After becoming a tropical storm and attaining the name Haiyan at 0000 UTC on November 4, the system began a period of rapid intensification that brought it to typhoon intensity by 1800 UTC on November 5. By November 6, the Joint Typhoon Warning Center (JTWC) assessed the system as a Category 5-equivalent super typhoon on the Saffir-Simpson hurricane wind scale; the storm passed over the island of Kayangel in Palau shortly after attaining this strength.
Hurricane Genevieve, also referred to as Typhoon Genevieve, was the fourth-most intense tropical cyclone of the North Pacific Ocean in 2014. A long-lasting system, Genevieve was the first one to track across all three northern Pacific basins since Hurricane Dora in 1999. Genevieve developed from a tropical wave into the eighth tropical storm of the 2014 Pacific hurricane season well east-southeast of Hawaii on July 25. However, increased vertical wind shear caused it to weaken into a tropical depression by the following day and degenerate into a remnant low on July 28. Late on July 29, the system regenerated into a tropical depression, but it weakened into a remnant low again on July 31, owing to vertical wind shear and dry air.
Typhoon Kim, known in the Philippines as Typhoon Osang, was the second typhoon in a week to directly affect the Philippines during July 1980. Like Typhoon Joe, Kim formed from the near equatorial monsoon trough in the northwestern Pacific Ocean on July 19. The disturbance tracked quickly westward-northwest underneath a subtropical ridge, reaching tropical storm strength on the July 21 and typhoon strength on July 23. After developing an eye, Kim began to rapidly intensify, and during the afternoon of July 24, peaked in intensity as a super typhoon. Several hours later, Kim made landfall over the Philippines, but the storm had weakened considerably by this time. Throughout the Philippines, 40 people were killed, 2 via drownings, and 19,000 others were directly affected. A total of 12,000 homes were destroyed and 5,000 villages were flooded. Less than a week earlier, the same areas were affected by Joe; however, Kim was considered the more damaging of the two typhoons. Land interaction took its toll on Kim, and upon entering the South China Sea, the storm was down below typhoon intensity. Kim continued northwestward but its disrupted circulation prevented re-intensification, and it remained a tropical storm until hitting southern China July 27 to the northeast of Hong Kong, where only slight damage was reported. Later that day, Kim dissipated.
A tropical cyclone tracking chart is used by those within hurricane-threatened areas to track tropical cyclones worldwide. In the north Atlantic basin, they are known as hurricane tracking charts. New tropical cyclone information is available at least every six hours in the Northern Hemisphere and at least every twelve hours in the Southern Hemisphere. Charts include maps of the areas where tropical cyclones form and track within the various basins, include name lists for the year, basin-specific tropical cyclone definitions, rules of thumb for hurricane preparedness, emergency contact information, and numbers for figuring out where tropical cyclone shelters are open.