Predicting the Mighty Ocean

The Tropical Analysis and Forecast Branch (TAFB) is the largest part of the National Hurricane Center (NHC) in Miami. TAFB forecasters predict winds and waves, and issue marine warnings year-round for 10,000,000 square nautical miles over the tropical North Atlantic Ocean, Gulf of Mexico, Caribbean Sea, and tropical Northeast Pacific Ocean. These marine warnings account for tropical storms and hurricanes as well as winter storms, trade wind gales, and severe gap-wind events. Our team of 17 full-time federal employees issue these products under the auspices of both NWS and the International Maritime Organization, year-round 24 hours a day. TAFB has developed robust impact-based Decision Support Services in the last few years to become a trusted core governmental partner to the U.S. Coast Guard in support of their life-saving mission. TAFB also supports the Hurricane Specialists Unit (HSU) within NHC, which issues the tropical cyclone advisories.

Click on the link below for the latest on tropical cyclone activity in the Atlantic and Pacific Basins:

In the fall of 1965, the U.S. Weather Bureau, predecessor of the National Weather Service established the National Hurricane Center at Miami, Florida. The goal was to consolidate prediction and warning capabilities for tropical cyclones. Tropical Analysis Center (TAC), predecessor of TAFB was added to the National Hurricane Center two years later. At the beginning, the main mission of TAC was to perform analysis of the troposphere above the tropical oceans; leading to better understanding on the interaction of various tropospheric levels. This increased the ability to detect small scale weather features in the tropics, and predict their chances of becoming tropical cyclones. Over time, TAC evolved into today's TAFB with the added tasks mentioned at the beginning.

Most tropical cyclones form in the open ocean far away from land, where direct measurements from sensors (ground based or onboard aircrafts) and radars are not available. This makes estimating and forecasting tropical cyclone intensity difficult. On April 1st 1960, National Aeronautics and Space Administration (NASA) successfully launched the first weather observing satellite, TIROS 1. This allowed meteorologists to observe weather systems and features from space for the very first time. Subsequent satellites launched in the 60s and 70s improved tremendously on technology and capability.

In 1973, American meteorologist, Vernon Francis Dvorak developed a method by using cloud patterns observed in infrared satellite imagery to estimate tropical cyclone intensity. This famous and beneficial method is known as the Dvorak Technique. The technique uses four geophysical properties: vorticity (rotation of air), vertical wind shear (affects cloud pattern), convection and core temperature (infrared satellite imagery to the right). Despite being developed almost 50 years ago, the Dvorak Technique has withstood the test of time and is still being used today. TAFB is among the few meteorological operational units in the world that uses Dvorak Technique to estimate tropical cyclone intensity. By doing so, TAFB provides important in-house guidance to the hurricane specialists at HSU. Since its implementation, the Dvorak Technique has indirectly saved countless lives along coastal communities worldwide. It has been modified and improved as satellite technology advances over the years, and this trend will likely continue in the future.

Click on the link below to read an article published by the American Meteorological Society on the Dvorak Technique:

Two years after the infamous sinking of the Titanic, the world community gathered in 1914 at the International Convention for the Safety of Life at Sea (SOLAS) for the very first time. The convention's objective was to establish a framework of standards and guidelines to improve maritime safety. Chapter V of the Technical Provision was dedicated for Safety of Navigation, it pioneered the initial step for international agreement to provide services on meteorological forecast, ice patrol, ship routing and, search and rescue. After the establishment of the United Nations (UN) in 1941, it served as a catalyst for international cooperation on maritime safety. Two agencies were formed within the UN to supervise these tasks: The World Meteorological Organization (WMO) and International Maritime Organization (IMO). Within the Global Maritime Distress and Safety System managed by the IMO, the WMO established protocols for the Worldwide Met-Ocean Information and Warning Service (WWMIWS). Under these protocols, the world's oceans have been divided into 21 areas, called METAREAS (slide arrows to the right on the map). The meteorological agency of a designated nation will provide meteorological warnings and information for each METAREA. The U.S. is responsible for METAREA IV, the western and central Atlantic Ocean and METAREA XII, the eastern and part of the central Pacific Ocean. Within METAREAS IV and XII, TAFB is responsible for the tropical Northeast Pacific, and tropical North Atlantic, the Gulf of Mexico and Caribbean Sea, respectively (slide arrows to the left on the map).

Click on the links below to learn about the World Meteorological Organization (WMO), International Maritime Organization (IMO) and Worldwide Met-Ocean Information and Warning Service (WWMIWS):

Under mandates of the WMO, TAFB issues High Seas Forecasts for parts of the Atlantic and Pacific Oceans. In the Atlantic, it is from 7N to 31N and west of 35W, including the Gulf of Mexico and Caribbean Sea. In the Pacific, it is from the Equator to 30N east of 140W, and from the Equator to 3.4S east of 120W. The High Seas Forecast highlights areas of the ocean with significant winds, seas and weather, such as gales and rough seas, dense fog and strong thunderstorms; as well as non-weather phenomena such as smoke and volcanic ash. It uses Latitude and Longitude coordinates for area delineation, and contains a duration of 48 hours with 12 to 24-hour intervals. It is primarily for commercial cargo ships and large cruise ships travelling long distances.

Within each High Seas Forecast area, TAFB also provides a more detailed Offshore Waters Forecast. In the Atlantic, it includes the Gulf of Mexico, Caribbean Sea and western Atlantic waters. For the Pacific, it composes of waters west of Baja California, central and southern Mexico, including the Gulf of California or Sea of Cortez; and west of central America, Colombia and Ecuador, including waters near the Galapagos Islands. The Offshore Waters Forecast contains more details on winds, swell and weather within each designated Offshore Zone in a 5-day period. In addition, a synopsis is provided for each regional marine basin and headlines are used to emphasize marine warnings in impacted zones. Smaller vessels like recreational boats, private yachts and fishing trawlers are the main users of the Offshore Waters Forecast since they are more vulnerable to inclement marine conditions.

Both the High Seas and Offshore Waters Forecasts are based on marine and weather parameters grids constructed by marine meteorologists at TAFB, more information about these grids will be provided later in this presentation. Meanwhile, please drag the "Double Arrows" left and right to toggle between the METAREAS and Areas of Responsibility (AOR) of TAFB:

• Tropical Pacific High Seas Forecast Area, which contains
  • Tropical Pacific Offshore Waters Forecast Zones
• Tropical Atlantic High Seas Forecast Area, which contains
  • Tropical Atlantic Offshore Waters Forecast Zones

Click on the link below to visit TAFB's Marine Information Page for our latest marine forecast and analysis:

The U.S. Coast Guard (USCG) is a core partner of the U.S. National Weather Service (NWS). This unique relationship is bound by a signed agreement called "Memorandum of Agreement" between the USCG and the NWS. Under this agreement, the NWS is the sole provider of weather information and decision support services for the USCG. For TAFB, USCG District 7 and 8 are the main federal core partners. District 7 is responsible for Atlantic waters adjacent to South Carolina, Georgia, Florida and Puerto Rico, and also the Gulf of Mexico waters next to Florida up to the Big Bend Area. The area of responsibility for District 8 includes the Gulf of Mexico waters south of Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle. Occasionally, TAFB provides IDSS to USCG District 5 (Norfolk - Central North Atlantic), District 11 (Alameda - Eastern North Pacific), and District 14 (Honolulu - Central Pacific), where these Districts' Search and Rescue Regions intersect TAFB's marine areas of responsibility.

A key service that TAFB provides to USCG is the Spot Forecast. This is a short-term forecast in tabular format for a specific location based upon latitude and longitude. This can be short-notice request or pre-planned, depending on the requirement of the USCG mission. Short-notice missions usually involve distress or disabled vessels, ditched airplanes and emergency medical evacuation. Pre-planned missions consist of long-distance sailing with wider areal coverage, and/or longer time durations, such as law enforcement, search and rescue, and oil spill cleanup activities. Under this scenarios, TAFB might need to put together PowerPoint briefings based on the information provided by the USCG. Occasionally, TAFB will collaborate with one or more Weather Forecast Office(s) (WFO) if part of USCG missions are within 60 nautical miles of the US coastline.

When a tropical cyclone has the potential to impact resources and operations of the US Coast Guard, TAFB provides exclusive tropical cyclone briefings to District 7 and/or 8 based on tropical cyclone advisories issued by the Hurricane Specialist Unit. These briefings along with marine forecast issued by TAFB provide vital and important information for District 7 and 8 on making decision regarding to closing major sea ports, bases, relocating assets and allocating resources. The USCG work tirelessly and professionally to protect US marine interests, enforce laws, assist in disaster relief and conduct search and rescue 24 hours a day, 7 days a week. TAFB is proud to be able to provide our service to such dedicated organization.

Click on the link below to learn about USCG and their mission in the Atlantic Basin.

Click on the link below to learn about USCG and their mission in the Pacific Basin.

A surface weather chart is a snap shot of the lower troposphere. It reveals where the frontal boundaries, low and high pressures, convergent zones and other features, including tropical cyclones are. It serves as a starting point for a marine and weather forecast, providing most the initial conditions. It is also a graphical illustration of the analysis sections included within the Atlantic and Pacific Tropical Weather Discussions text products.

The NWS Unified Surface Analysis Chart to the right covers a huge area. It spans from the eastern Pacific Ocean, including Hawaii across parts of both the North and South America Continents to the Atlantic Ocean, including part of Africa. It is great teamwork among the analysts from TAFB, the Ocean and Weather Prediction Centers in College Park, Maryland, and Honolulu Forecast Office in Hawaii. The Unified Surface Analysis Chart is produced every six hours, 24 hours daily.

To provide useful information for the marine community, TAFB also produces charts on Significant Wave Heights, Winds and Waves, and Surface Features Forecast, as well as Peak Wave Period and Primary Swell Direction (graphic above). These charts serve as valuable planning tools for mariners operating and/or navigating in the ocean with older communication equipment. To highlight areas of hazardous marine conditions produced by tropical cyclones, mariners can look at the Tropical Cyclone Danger Graphics. During non-tropical cyclone season, the High Winds and Associated Seas graphics depict areas with winds 35 knots or greater along with seas above 8 feet.

Click on the links below to access the Atlantic Significant Wave Height Analysis, 72-Hour Pacific Winds and Waves Forecast, 48-Hour Atlantic Surface Forecast, and Pacific Tropical Cyclone Danger Graphics:

For mariners with high bandwidth internet access while at sea, they can access the aforementioned 5-day gridded marine forecast by TAFB via the NWS-National Digital Forecast Database Graphical Forecast page. The forecast parameters include wind speed and direction, wind gusts, wave height and marine hazards such as gales and tropical storm conditions in temporal resolution of 3 hours for day 1 to 3, and 6 hours for day 4 and 5. For those who use lower bandwidth internet at sea, they can look at the same 5-day marine forecast vis TAFB's Marine Graphical Composite Forecast Map page. In order to limit the amount of data flow, graphics here are in slightly lower resolution, and the temporal resolution is in 12 hourly.

Click on the links below to look at the 5-day marine forecast in high and lower bandwidth versions: