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Storm Data FAQ Page
When does data become available?
Due to the amount of time it takes to collect, validate, and enter post Storm Data information, the National Climatic Data Center (NCDC) regularly receives Storm Data from the National Weather Service (NWS) approximately 60-90 days after the end of the data month.
The NWS has 60 days to submit their data files to the NWS Headquarters in Silver Spring, MD. The NWS Headquarters (NWSHQ) then collects all of the data files from the 124 NWS Forecast Offices (NWSFO). The NWSHQ then uses several algorithms to prepare the Storm Data product into the integrated database. The NCDC receives a copy of this database approximately 75-90 days after the end of the month. A publication and archive are produced and the Storm Events Database is then updated within 90-120 days after the end of the month
Where does the data come from?
NCDC receives Storm Data from the National Weather Service. The National Weather service receives their information from a variety of sources, which include but are not limited to: county, state and federal emergency management officials, local law enforcement officials, skywarn spotters, NWS damage surveys, newspaper clipping services, the insurance industry and the general public.
How accurate is the data?
Storm Data Disclaimer:
Storm Data is an official publication of the National Oceanic and Atmospheric Administration (NOAA) which documents the occurrence of storms and other significant weather phenomena having sufficient intensity to cause loss of life, injuries, significant property damage, and/or disruption to commerce. In addition, it is a partial record of other significant meteorological events, such as record maximum or minimum temperatures or precipitation that occurs in connection with another event. Some information appearing in Storm Data may be provided by or gathered from sources outside the National Weather Service (NWS), such as the media, law enforcement and/or other government agencies, private companies, individuals, etc. An effort is made to use the best available information but because of time and resource constraints, information from these sources may be unverified by the NWS. Therefore, when using information from Storm Data, customers should be cautious as the NWS does not guarantee the accuracy or validity of the information. Further, when it is apparent information appearing in Storm Data originated from a source outside the NWS (frequently credit is provided), Storm Data customers requiring additional information should contact that source directly. In most cases, NWS employees will not have the knowledge to respond to such requests. In cases of legal proceedings, Federal regulations generally prohibit NWS employees from appearing as witnesses in litigation not involving the United States.
How are the latitude and longitudes determined?
Storm data is entered into the database as a distance in miles and a direction on 16-point compass scale from a known location, usually a town or city. Example: 4.5 miles ESE Atlanta. The NWS uses a database of over 106,000 cities and towns including their latitudes and longitudes. Using an algorithm, the location 4.5 miles ESE of Atlanta can be derived from the known latitude and longitude of Atlanta. These latitude and longitude pairs are generated by the NWS and populated into the database. The latitude and longitude are in DMS (degrees, minutes, seconds) format.
How are the damage amounts determined?
The National Weather Service makes a best guess using all available data at the time of the publication. The damage amounts are received from a variety of sources, including those listed above in the Data Sources section. Property and Crop damage should be considered as a broad estimate.
Why is there no lightning strike information?
At this time, the only lightning data contained within Storm Data are lightning events that result in fatality, injury and/or property and crop damage. These events are reported to the NWS for inclusion into the Storm Events Database. If you need information on lightning strikes that do not result in this criteria, you can obtain the lightning strike data from Vaisala here: Vaisala Lightning Strike Data
How are tornadoes counted?
Tornadoes may contain multiple segments. A tornado that crosses a county line or state line is considered a seperate segment. Also, a tornado that lifts off the ground for less that 5 minutes or 2.5 miles is considered a seperate segment. If the tornado lifts off the ground for greater than 5 minutes or 2.5 miles, it is considered a seperate tornado. Tornadoes reported in Storm Data and the Storm Events Database are in segments. For official tornado counts by state, please use the Annual Summaries, found here: NCDC Annual Summaries or use the monthly counts at the Storms Prediction Center here: Storms Prediction Center Tornado Data