TornadoesThis feature layer, utilizing data from the National Oceanic and Atmospheric Administration (NOAA), displays tornadoes in the United States, Puerto Rico and U.S. Virgin Islands between 1950 and 2022. Per NOAA, "A tornado is a narrow, violently rotating column of air that extends from a thunderstorm to the ground. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Tornadoes can be among the most violent phenomena of all atmospheric storms we experience. The most destructive tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. (Supercells can also produce damaging hail, severe non-tornadic winds, frequent lightning, and flash floods.)"EF-5 Tornado (May 22, 2011) near Joplin, MissouriData currency: December 30, 2022Data source: Storm Prediction CenterData modifications: Added fields Calculated Month and DateFor more information: Severe Weather 101 - Tornadoes; NSSL Research: TornadoesSupport documentation: SPC Tornado, Hail, and Wind Database Format SpecificationFor feedback, please contact: ArcGIScomNationalMaps@esri.comNational Oceanic and Atmospheric AdministrationPer NOAA, its mission is "To understand and predict changes in climate, weather, ocean, and coasts, to share that knowledge and information with others, and to conserve and manage coastal and marine ecosystems and resources."

Tornado TracksThis feature layer, utilizing data from the National Oceanic and Atmospheric Administration (NOAA), displays tornadoes in the United States, Puerto Rico and U.S. Virgin Islands between 1950 and 2022. A tornado track shows the route of a tornado. Per NOAA, "A tornado is a narrow, violently rotating column of air that extends from a thunderstorm to the ground. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Tornadoes can be among the most violent phenomena of all atmospheric storms we experience. The most destructive tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. (Supercells can also produce damaging hail, severe non-tornadic winds, frequent lightning, and flash floods.)"EF-5 Tornado Track (May 3, 1999) near Oklahoma City, OklahomaData currency: December 30, 2022Data source: Storm Prediction CenterData modifications: Added fields Calculated Month and DateFor more information: Severe Weather 101 - Tornadoes; NSSL Research: TornadoesSupport documentation: SPC Tornado, Hail, and Wind Database Format SpecificationFor feedback, please contact: ArcGIScomNationalMaps@esri.comNational Oceanic and Atmospheric AdministrationPer NOAA, its mission is "To understand and predict changes in climate, weather, ocean, and coasts, to share that knowledge and information with others, and to conserve and manage coastal and marine ecosystems and resources."

Tornadoes are columns of air that spin at a high rate of speed. They are small in scale but can be very violent. The area affected by a tornado's passage is between about 40 and 400 metres in width and between 1.7 and 36 kilometres in length. During a tornado the damage is due to wind as well as an extremely sudden drop in pressure. Tornadoes vary in intensity, measured on the Fujita or F scale, graduated from 0 to 5 based on the level of damage. The main season for tornadoes is from April to October, and every province is subject to the risk of tornadoes. This layer shows some of the major tornadoes that happened in Canada since the beginning of the 20th century to 1999.

Although tornadoes can occur throughout the year, prime time for twisters in the U.S. is spring and early summer. Larger symbols show more violent tornadoes. Zoom into the map to see approximate tornado tracks.

The National Weather Service issues warnings for severe weather that are imminent or actively occurring. This layer shows shorter-term warnings for the following events:Special Marine Warnings - potentially hazardous weather conditions of short duration (up to 2 hours) that may include sustained winds or gusts of 39 mph or greater, hail 0.75” or greater in diameter, or waterspouts.Severe Thunderstorm Warnings - storms with winds of 58 mph or higher or hail 1” or greater in diameter.Tornado Warnings - imminent or active tornados.Extreme Wind Warnings - surface winds of 115 mph or greater associated with non-convective, downslope, derecho, or sustained hurricane winds are expected to occur within one hour.Flash Flood Warnings - conditions are favorable for flash flooding. It does not mean that flash flooding will occur, but it is possible.SourceCurrent Warnings: https://www.weather.gov/source/crh/shapefiles/CurrentWarnings.tar.gzSample DataSee Sample Layer Item for sample data during Weather inactivity!Update FrequencyThe service is updated every 5 minutes using the Aggregated Live Feeds methodology.Area CoveredContiguous United StatesWhat can you do with this layer?Customize the display of each attribute by using the Change Style option for any layer.Query the layer to display only specific types of weather watches and warnings.Add to a map with other weather data layers to provide inside on hazardous weather events.Use ArcGIS Online analysis tools, such as Enrich Data, to determine the potential impact of weather events on populations.This map is provided for informational purposes and is not monitored 24/7 for accuracy and currency.If you would like to be alerted to potential issues or simply see when this Service will update next, please visit our Live Feed Status Page!

A violent tornado outbreak occurred on December 10-11, 2021 in the Midwest US. One of the tornadoes, known as the Quad-State tornado, tracked across four states and devastated the downtown area of Mayfield, KY, producing high-end EF-4 damage. The data here provides a series of wind speed and direction time histories of the Quad-State tornado for 44 damaged residential houses in Mayfield, KY, which can be useful for detailed forensic analysis of the residential building damage. The data was generated using a software that performs a treefall pattern analysis method, developed by the first author. In addition to the many structural damage, the tornado damaged a large number of trees in the Mayfield area. The fall direction of the damaged trees displayed a converging pattern, caused by a rotational wind flow, which is a typical indicator of a tornado. The converging treefall pattern then can be analyzed to characterize the tornadic flow and estimate the wind field (i.e., treefall pattern analysis method). The treefall pattern analysis method simulates a series of tornadoes using an idealized Rankine vortex model and generates a virtual treefall pattern, which is used to compare to the treefall pattern observed in the field and iterated until the "best-matching" pattern is found. In order to reduce the uncertainty in the estimates, the translational speed of the tornado was estimated based on tracking the motion of the vortex signature from the nearest NEXRAD radar, and the Radius of Maximum Wind (RMW) and decay exponent of the Rankine vortex model were estimated based on the structural damage. Then, the software was used to estimate the rest of the vortex parameters and wind time history (e.g., wind speed and direction) at selected locations. More detailed description on the parameter estimation and software will be published later in the NIST Technical Note.

Project Severe Weather Archive of the Philippines (SWAP) issues its 2nd Data Release, labelled as SWAP DR2. The temporal extent of the data is now from 1968 to Present. SWAP DR2 currently features the following;

1. Geographic decimal coordinates i.e. latitude-longitude pairs is revised and improved to 5 decimals for accuracy purposes. A single-point coordinate system is applied throughout the archive. The coordinates were placed on a wellknown infrastructure it impacted such as hospitals, convenience stores, or schools etc. within the area of interest. However, difficult cases were tallied only on the town-level in which a severe weather event (SWE) occurred and seen,

2. Added additional columns e.g. island partitions, designated month and year, and a status indicator whether the documentions as attached is (a) Active, (b) Preserved - for newspapers mostly, and (c) Inactive,

3. Significant uptick to the number of SWEs. Exhaustively reviewed/checked each cases. However, some older cases still requires checking and extensive researching in other repositories e.g. libraries etc. This will be another goal over the next update(s)/major releases,

4. An article/preprint is now available in arXiv acting as a foundational paper of Project SWAP and is imported to this page. We also devised a 'Hail Scale' that can be used as an initial guideline based from previous researches. To check this simple hail scale, kindly view/read the preprint as attached in this release,

5. On the EF ratings of tornadoes, these were initial ratings from careful considerations throughout the project based on presented evidences from the documentation columns. A more thorough and rigorous survey/assessment is REQUIRED to rectify these initial ratings. On the other hand, most of the waterspouts were rated as EF0 with confidence,

6. SWAP DR2 also feature proximity rawinsonde observations (RAOBs or proximity sounding profiles) from few cases as queried and analyzed through SounderPy of Gillett (2024). Please see the zip file attached in this posting. A CSV and CM1 input file of these soundings will also be included over the next incremental update soon, and

7. A technical report will also be available soon for Project SWAP.

This project can be important to uncovering the Philippine's convective and kinematic setting on various timescales, essentially creating a climatological baseline to further understand both mesoscale processes and long term climate linkages. However, any analyses using this archive will require careful consideration of biases therein, many of which we have discussed in the preprint attached in this release.

File inclusion of SWAP DR2;

• 3 standard CSV file formats containing tornadoes, hail, and waterspout reports (can easily imported to Pandas or GeoPandas),

• 3 documentation files containing hyperlinks/sources/evidences. Our OFFICIAL LOGO is also unveiled in these documentations. This includes few, basic data visualization of each severe weather phenomena,

• 2 zip files containing SWAP DR2's proximity soundings (either observed or from ERA5 Reanalysis queried in SounderPy as mentioned before), limited to several cases of tornadoes and hail events, and

• A preprint manuscript tackling SWAP DR2 and establishing a Climatological Baseline for Severe Weather Events in the Philippines. We are aiming to have the paper be published to a journal as well.

Kindly see the table below for the versions of Project SWAP and other details. If you have comments, kindly use the SWAP Contact Form below.

This dataset consists of Level 3 weather radar products collected from Next-Generation Radar (NEXRAD) stations located in the contiguous United States, Alaska, Hawaii, U.S. territories and at military base sites. NEXRAD is a network of 160 high-resolution Doppler weather radars operated by the NOAA National Weather Service (NWS), the Federal Aviation Administration (FAA), and the U.S. Air Force (USAF). Doppler radars detect atmospheric precipitation and winds, which allow scientists to track and anticipate weather events, such as rain, ice pellets, snow, hail, and tornadoes, as well as some non-weather objects like birds and insects. NEXRAD stations use the Weather Surveillance Radar - 1988, Doppler (WSR-88D) system. This is a 10 cm wavelength (S-Band) radar that operates at a frequency between 2,700 and 3,000 MHz. The radar system operates in two basic modes: a slow-scanning Clear Air Mode (Mode B) for analyzing air movements when there is little or no precipitation activity in the area, and a Precipitation Mode (Mode A) with a faster scan for tracking active weather. The two modes employ nine Volume Coverage Patterns (VCPs) to adequately sample the atmosphere based on weather conditions. A VCP is a series of 360 degree sweeps of the antenna at pre-determined elevation angles and pulse repetition frequencies completed in a specified period of time. The radar scan times 4.5, 5, 6 or 10 minutes depending on the selected VCP. During 2008, the WSR-88D radars were upgraded to produce increased spatial resolution data, called Super Resolution. The earlier Legacy Resolution data provides radar reflectivity at 1.0 degree azimuthal by 1 km range gate resolution to a range of 460 km, and Doppler velocity and spectrum width at 1.0 degree azimuthal by 250 m range gate resolution to a range of 230 km. The upgraded Super Resolution data provides radar reflectivity at 0.5 degree azimuthal by 250 m range gate resolution to a range of 460 km, and Doppler velocity and spectrum width at 0.5 degree azimuthal by 250 m range gate resolution to a range of 300 km. Super resolution makes a compromise of slightly decreased noise reduction for a large gain in resolution. In 2010, the deployment of the Dual Polarization (Dual Pol) capability to NEXRAD sites began with the first operational Dual Pol radar in May 2011. Dual Pol radar capability adds vertical polarization to the previous horizontal radar waves, in order to more accurately discern the return signal. This allows the radar to better distinguish between types of precipitation (e.g., rain, hail and snow), improves rainfall estimates, improves data retrieval in mountainous terrain, and aids in removal of non-weather artifacts. The NEXRAD products are divided in two data processing levels. The lower Level 2 data are base products at original resolution. Level 2 data are recorded at all NWS and most USAF and FAA WSR-88D sites. From the Level 2 quantities, computer processing generates numerous meteorological analysis Level 3 products. The Level 3 data consists of reduced resolution, low-bandwidth, base products as well as many derived, post-processed products. Level 3 products are recorded at most U.S. sites, though non-US sites do not have Level 3 products. There are over 40 Level 3 products available from the NCDC. General products for Level 3 include the base and composite reflectivity, storm relative velocity, vertical integrated liquid, echo tops and VAD wind profile. Precipitation products for Level 3 include estimated ground accumulated rainfall amounts for one and three hour periods, storm totals, and digital arrays. Estimates are based on reflectivity to rainfall rate (Z-R) relationships. Overlay products for Level 3 are alphanumeric data that give detailed information on certain parameters for an identified storm cell. These include storm structure, hail index, mesocyclone identification, tornadic vortex signature, and storm tracking information. Radar messages for Level 3 are sent by the radar site to users in order to know more about the radar status and special product data. NEXRAD data are provided to the NOAA National Centers for Environmental Information (NCEI) for archiving and dissemination to users. Data coverage varies by station and ranges from May 1992 to 1 day from present. Most stations began observing in the mid-1990s, and most period of records are continuous.

On the evening of 28 March 2000, two tornados struck Fort Worth, Arlington, and Grand Prairie, Texas. The Fort Worth Tornado touched down west of the city, and moved through the downtown area. The tornado was rated an F2 on the Fujita scale at its strongest point. The Arlington tornado started as an F3, and varied from F2 to F0 throughout its 6.5 mile track. The damages from these tornados was estimated at $450 million in the Fort Worth area. 5 F2's, and 8 F0-F1's. While southern Louisiana's annual average for tornados is 13 (1950-1995), it hosted 12 tornados on 1-2 January. All of the tornados were indicated by WSR-88D radars in Lake Charles and Fort Polk,

Louisiana. The average lead time was an impressive 24 minutes. There was one fatality in Texas, but, given the severity of the outbreak and the fact that it happened overnight, it is fortunate that there were not more people injured or killed.

For more information, see: http://data.eol.ucar.edu/codiac/projs?COMET_CASE_028