An Overview of Meteorological Forecasts and the Generation of Kinetic Analysis Hazard Data

As a leading provider of global tropical cyclone hazards and impacts information, Kinetic Analysis Corporation (KAC) is committed to offering you high-quality, high-resolution data for active events on a timely basis. All of this starts with a thorough understanding of the hazards associated with a tropical cyclone (wind, storm surge, waves, and rainfall). In this blog post, we provide readers with a high-level understanding of how KAC generates near real-time tropical cyclone hazard data.

We first collect forecasts from global and regional meteorological agencies. Across the globe, multiple meteorological agencies produce and update forecasts on a regular basis for active tropical cyclones. The World Meteorological Organization has defined agencies for all the ocean basins that experience tropical cyclones [1, 2, 3]. These agencies include six Regional Specialized Meteorological Centers (RSMCs) along with four Tropical Cyclone Warning Centers (TCWCs) [3]. The six RSMC’s include the National Hurricane Center (NHC) in Miami, the Central Pacific Hurricane Center (CPHC) in Honolulu, Fiji’s Tropical Cyclone Center in Nadi, the Meteo France branch on La Réunion, the Typhoon Warning Center in Tokyo, and the Indian Meteorological Department in New Delhi, India [1, 2, 3]. Each RSMC issues official tropical cyclone forecasts for their respective regions (Figure 1); for example, the National Hurricane Center has jurisdiction over the North Atlantic basin and the eastern Pacific basins, whereas Meteo France La Réunion issues forecasts for the southwest Indian Ocean [2, 3]. The four TCWCs are located in Jakarta, Indonesia, Melbourne, Australia, Port Moresby, Papua New Guinea, and Wellington, New Zealand [3].

Figure 1: Regional Specialized Meteorological Centers (RSMC’s) from which forecast data and updates are acquired for active tropical cyclone events. Image borrowed from: https://www.nhc.noaa.gov/aboutrsmc.shtml

Despite the various agencies issuing different forecasts for their respective regions, these forecasts are standardized in certain respects. For example, all tropical cyclone forecasts are based on meteorological observations collected by a variety of sources located across the world [4]. These include satellites, weather balloons (Figure 2), buoys, and surface weather stations [4]. The data provide a snapshot of the atmosphere that forecast agencies use as the initial conditions for their models of the ocean and atmosphere, and that scientists use as guidance when generating a forecast. Measurements are typically gathered every 6 hours at what are known as synoptic times (00, 06, 12, and 18 Universal Time Coordinated or UTC). In 1972, UTC, which is based on atomic measurements, replaced Greenwich Mean Time (GMT), which is based on the annual average solar day [5]. Historically, the solar day was defined as the annual average time between the sun crossing a set meridian, in this case, 0° longitude, or the Prime Meridian, which crosses the Royal Observatory Greenwich. The annual average time is used as the time interval changes over the course of a year.

The timing of weather observations (and thus the subsequent issuance of weather forecasts) follow UTC time so that observations everywhere occur at the same moment. Synchronous observation times help with the creation of the initial conditions that best approximate the state of the atmosphere and will, in principle, result in the global weather models generating the most accurate forecasts.

Figure 2: Weather balloons contain instruments, known as radiosondes, that take measurements as they climb through Earth’s atmosphere (https://www.weather.gov/ilx/ua-tour).

Figure 3: ASOS, which stands for Automated Surface Observing Station, is a standardized system for taking surface weather observations. Currently, hundreds of these exist throughout the United States; different nations have similar systems in place for the collection of surface-based meteorological measurements. Image borrowed from: https://www.weather.gov/asos/.

The data collected at synoptic times are used directly by forecasters and in a variety of weather forecast models. These models essentially work by using the initial conditions – the observations and measurements described earlier – to solve complicated mathematical equations that describe the evolution of the atmosphere with time. The models provide the basis that many forecasters use to create their predictions. Once a forecast is issued by an RSMC, the forecasts are then distributed through the Automated Tropical Cyclone Forecasting (ATCF) system as well as other channels such as the World Meteorological Organization Global Telecommunication System (GTS).

            The production and release of KAC data depends upon the release of agency forecasts and model guidance. As soon as a new forecast or model guidance is available, in a matter of minutes our system downloads and standardizes them for use by our custom oceanic and atmospheric models. These models then use the forecast data to generate a series of detailed geospatial hazard layers. Our standard production product has a resolution of 60 arcseconds (~2 km) and includes geospatial data for the maximum sustained winds, storm surge inundations, cumulative rainfalls, and significant wave heights associated with all active tropical cyclones. One such hazard layer for the wind speed, generated during Hurricane Ian in 2022, is shown in Figure 4. The wind speeds represent 1-minute sustained winds at 10 meters elevation and, in contrast to those forecast by NHC, are adjusted for surface roughness and topography. 

Figure 4: Hazard layer for the wind speed generated by Kinetic Analysis Corporation’s internal ocean and atmospheric modeling. The hazard layer is based on official forecast data from the National Hurricane Center and has been processed through our internal ocean and atmospheric model to produce a 2-kilometer resolution depiction of the forecast wind field for Hurricane Ian. The colored polygons indicate the level of wind that a location may see based on the forecast, and the highlighted blue polygon illustrates the specific locations that may see winds of 125-130 mph.

It is this high-resolution, detailed, and global view that has enabled us to help clients around the world in a variety of sectors. But how exactly are these hazard layers obtained from the forecast? What internal processes take place in KAC’s coupled ocean-atmosphere model to produce the hazards at such a detailed level?

In our next blog post, we will provide a deeper dive into KAC’s hazard modeling capabilities and the ways in which we generate our hazard information. Stay tuned!

References

1.     https://www.nhc.noaa.gov/aboutrsmc.shtml

2.     https://community.wmo.int/en/latest-advisories-rsmcs-and-tcwcs

3.     https://community.wmo.int/en/tropical-cyclone-regional-bodies

4.     https://www.noaa.gov/stories/6-tools-our-meteorologists-use-to-forecast-weather

5.     https://www.noaa.gov/jetstream/time