Climate.gov Data Snapshots: Historic Probability of Severe Weather
Principal Investigator(s): View help for Principal Investigator(s) National Oceanic and Atmospheric Administration
Version: View help for Version V2
Name | File Type | Size | Last Modified |
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data | 06/24/2025 09:03:PM | ||
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application/pdf | 11 MB | 06/17/2025 06:08:PM |
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application/pdf | 1.3 MB | 06/17/2025 06:08:PM |
Project Citation:
National Oceanic and Atmospheric Administration. Climate.gov Data Snapshots: Historic Probability of Severe Weather. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2025-06-24. https://doi.org/10.3886/E233242V2
Project Description
Project Title:
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Climate.gov Data Snapshots: Historic Probability of Severe Weather
Summary:
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This upload includes two additional files:
* Historic Probability of Severe Weather _NOAA Climate.gov.pdf is a screenshot of the main Climate.gov site for these snapshots (https://www.climate.gov/maps-data/data-snapshots/data-source/historic-probability-severe-weather )
* Cimate_gov_ Data Snapshots.pdf is a screenshot of the data download page for the full-resolution files.
Q: Where is severe weather likely at this time of year?
A: Shading
on each map reflects how often severe weather occurred within 25 miles
during a 30-year base period. The darker the shading, the higher the
number of severe weather reports near that date. For this map, severe
weather encompasses tornadoes, thunderstorm winds over 58 miles per
hour, and hail larger than three-quarters of an inch in diameter.
Q: How were these maps produced?
A: For
each day of the year, scientists plotted reports of severe weather from
1982 to 2011 on a gridded map. To reveal the long-term patterns of
these events, they applied mathematical filters to smooth the counts in
time and space. Keep in mind that severe weather is possible at any
location on any day of the year.
Q: What do the colors mean?
A: Shaded
areas show the historical probability of severe weather occurring
within 25 miles. Meteorologists estimated these probabilities from
severe weather reports submitted from 1982-2011. For each day of the
year, scientists plotted reports of severe events onto a map marked with
grid cells 50 miles on a side. For each grid cell, they counted the
number of years with at least one report, and divided by the total
number of years. To reveal the long-term patterns suggested by this
relatively small dataset, they used statistical methods to smooth the
data. For instance, to smooth clusters of events in time, a mathematical
filter replaced the value in every grid cell with a 15-day average.
Another filter extended report locations over a 25-mile-wide circle to
indicate the probability that the event could have occurred at other
points within that area.
Q: Why do these data matter?
A: Knowing
when and where severe weather tends to occur through the year promotes
preparedness. Residents who are alert to the possibility of severe
weather are better able to respond in ways that keep them safe. These
data can also help emergency response personnel plan for when and where
their services may be necessary.
Q: How did you produce these snapshots?
A: Data
Snapshots are derivatives of existing data products: to meet the needs
of a broad audience, we present the source data in a simplified visual
style. NOAA's National Weather Service Storm Prediction Center produced
the Severe Weather Climatology files. To produce our images, we obtained
the climatology data as a numpy array, and ran a set of scripts to
display the mapped areas on our base maps with a custom color bar.
Additional information
Data for
these images represents an update and extension of work first put forth
by Dr. Harold Brooks of the National Severe Storms Laboratory.
References
Brooks, H. E., C. A. Doswell, III, and M. P. Kay, (2003) Climatological estimates of local daily tornado probability, Wea. Forecasting, 18, 626-640.
Source: https://www.climate.gov/maps-data/data-snapshots/data-source/historic-probability-severe-weather
This upload includes two additional files:
* Historic Probability of Severe Weather _NOAA Climate.gov.pdf is a screenshot of the main Climate.gov site for these snapshots (https://www.climate.gov/maps-data/data-snapshots/data-source/historic-probability-severe-weather )
* Cimate_gov_ Data Snapshots.pdf is a screenshot of the data download page for the full-resolution files.
Original Distribution URL:
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https://www.climate.gov/data/SevereWeather--Daily--Historic-Probability-of-Severe-Weather--CONUS/
Scope of Project
Subject Terms:
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severe weather;
climate;
climate change;
weather history
Geographic Coverage:
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United States
Time Period(s):
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1982 – 2011
Data Type(s):
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images: photographs, drawings, graphical representations
Collection Notes:
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One image for each day of the year.
Data is divided in to folders by image resolution -- full size (zip), kml (zip, broadcast (png), small (png), and large (png). Occasionally there may be one image missing in a particular size but available in another size.
Data downloaded from climate.gov 6/15/2025 - 6/16/2025 (small, large, and full resolution) and 6/21/2025 (others).
Data is divided in to folders by image resolution -- full size (zip), kml (zip, broadcast (png), small (png), and large (png). Occasionally there may be one image missing in a particular size but available in another size.
Data downloaded from climate.gov 6/15/2025 - 6/16/2025 (small, large, and full resolution) and 6/21/2025 (others).
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