National Weather Service Storm Spotter Training

The National Weather Service has 122 Weather Forecast Offices (WFOs) across the United States.

The mission of the National Weather Service (NWS), under the National Oceanic and Atmospheric Administration (NOAA) and Department of Commerce (DOC), is to protect life and property from natural disasters by issuing warnings and forecasts for all manners of hazardous weather, and to enhance the national economy. This mission is carried out by weather forecast offices and national centers throughout the United States and its territories.

The NWS is divided between six regions: Eastern, Central, Southern, Western, Pacific, and Alaskan. Each of these six regions are further divided between 122 Weather Forecast Offices. Each Weather Forecast Office has their own area of responsibility, which is called a County Warning Area.

From day-to-day weather forecasts, to warnings of potentially dangerous thunderstorms, the NWS is staffed 24/7/365. Each office issues public forecasts and severe weather warnings and watches for a select number of counties. Some offices only issue for counties in 1 state, while others issue for portions of 4 different states.

The NWS has approximately 160 WSR-88D radars (Weather Surveillance Radar – 1988 Doppler) positioned across our country. The majority of our radars, pictured at right, stand nearly 100 feet tall. The radar resides inside of the radome, a spherical structure designed to keep the radar operational through various atmospheric conditions.

Weather radars analyze the position and shape of objects in the atmosphere by emitting radio waves. When a radio wave encounters an object, such as the hydrometeor in the GIF below, the signal is returned and processed to the radar. A collection of these "return" signals can be composed into an image of reflectivity (precipitation), or velocity (wind), among other products. Radars cycle through an endless period of "listening" and "receiving".

Many radars are located adjacent to NWS forecast offices, while others are positioned in a way to provide optimal radar data for that particular area. The radar tower is the origination point for the radar data and consists of a transmitter, antenna, receiver, and signal processor. These parts generate and radiate Radio Frequency (RF) pulses, receive reflected energy from those pulses, and process this received energy into digital-based data. This data is then sent to our office.

The WSR-88D Open Systems Radar Product Generator (RPG) is located in each NWS office. It generates various products from the digital base data sent by the RDA. The RPG generates base products (reflectivity, velocity, and spectrum width) as well as derived products with the use of meteorological algorithms.

One of the missions of the NWS is to effectively communicate all warnings, watches, advisories, and forecasts to the public. The "one stop shop" for all of the NWS's information is on  weather.gov .

Across the United States, a network of radio stations continuously broadcast weather information 24/7/365. This free radio service is known as NOAA Weather Radio. Official information broadcasts directly from the nearest National Weather Service office. When your local NWS office issues a warning, NOAA Weather Radio delivers the message for the counties of interest.

NOAA Weather Radio uses Specific Area Message Encoding (SAME) to effectively broadcast emergency weather information to the public. This burst of information contains the county effected, type of alert, the time duration, and any extra information from the NWS. To receive SAME notifications, your NOAA Weather Radio must have enabled alarms. You can purchase your own NOAA Weather Radio online, or at many retailers. You can find your local radio frequency at:  https://www.weather.gov/nwr/station_listing 

Each NWS office provides weather information on Facebook, Twitter, and YouTube. The various social media platforms we use are helpful for on-the-go information, local weather news, and interesting tidbits!

In this section, we'll discuss what happens before, during, and after a severe weather event.

NWS meteorologists forecast the potential for severe weather anywhere from 1 to 7 days in advance. Forecasters at the NWS Storm Prediction Center (SPC) in Norman, OK issue severe weather outlooks days prior to the expected severe weather event.

Increased staffing is needed during severe weather operations at the Weather Forecast Office. During severe weather, we typically have the office full of staff members to carry out our mission to protect life and property.

Severe Weather Duties include:

• Several people watching radar and issuing warnings
• One person constantly analyzing our environment to help the radar operators
• Several people answering phone calls, posting on social media, and taking reports
• One or two people working on normal operations to keep our webpage and forecasts up to date

Each NWS office uses numerous tools and training to make warning decisions. These tools include:

• Satellite
• Radar
• Surface weather stations
• Trained spotters

Remember, for a thunderstorm to be classified as severe it must contain wind gusts greater than 58 mph, and/or hail greater than 1" diameter, and/or any tornado.

Oftentimes, severe thunderstorms will only cause minor tree damage, and perhaps rearrange your yard decorations. However, stronger severe thunderstorms with significant wind, hail, rain, and/or tornadoes can cause life-changing alterations for some.

In this short video, NWS Louisville examines a strong EF-3 tornado that struck Bowling Green, KY on December 11, 2021. Drones can deliver a unique perspective on tornado surveys, taking videos of damage not visible from the ground. In addition, drones are sometimes safer to use than on-foot surveys with significant tornado damage.

In this section, we'll discuss how severe thunderstorms form, their stages, and various types.

In this section, we'll discuss wind, hail, and the risks both present to life and property.

In this brief section, we'll discuss lightning, its dangers, and how to stay safe during thunderstorms.

It is commonly thought that when a thunderstorm has a lot of lightning it means it is severe, however lightning is not a NWS requirement for a thunderstorm to be classified as severe.

A thunderstorm can produce cloud-to-ground or cloud-to-cloud lightning.

Cloud-to-ground lightning can either be a negatively charged flash or a positively charged flash. The negative flash usually occurs between the negative charges in the lower part of the storm and the positive charges on the ground under and near the cloud base. Positive flashes usually occur between the positively charged upper levels of the storm and the negatively charged area surrounding the storm.

Tornadoes are extremely dangerous, rotating columns of air produced by a severe thunderstorm. In this section, we'll discuss tornado formation, classifications, and safety.

Before we begin our dive into tornadoes, it is important to rule out clouds that are not associated with tornadoes.

Below is an image of a shelf cloud. Spectacular, elongated, and ominous, shelf clouds are typically confused with tornado development. Fortunately, there is an easy way to distinguish a shelf cloud from a tornado-forming wall cloud. Shelf clouds span the entire horizon. The thunderstorm complexes they identify with feature straight-line wind gusts.

Another cloud often confused with tornadoes is the scud cloud. Often associated with rainshafts, scud clouds form below the main cloud base. To an uneducated bystander, scud clouds could look like a funnel or a tornado. When an air-parcel has a higher than average humidity below the main cloud base, it condensates in an awkward shape. Below is an example of a collection of scud clouds from southern Kentucky in August 2021.

Shelf clouds are often misinterpreted as wall clouds, which are a sign of tornado development. To the untrained eye, wall clouds can be easy to miss. Often in the Ohio Valley and southeastern U.S., wall clouds associated with supercell thunderstorms are rain-wrapped and impossible to see. For this reason, extreme caution should be exercised near low-visibility supercell thunderstorms!

One more distinction must be made before we can discuss tornadoes in the clearest light possible. Often before a tornado forms, a funnel cloud will lower from the base of the wall cloud. Funnel clouds are rotating, condensed columns of air that do not touch the ground. A funnel can either be a spectacular visual phenomena that does not produce into a tornado, or is a precursor to a violent tornado.

Funnel clouds can also form on days with little severe activity, given the proper atmospheric dynamics. In the images below, a funnel cloud formed east of Frankfort, Indiana on October 8, 2021. Note the elevated nature of the funnel, and relatively pleasant conditions away from the main cell. The first picture depicts the funnel cloud in its mature form, with the second and third pictures showing its decay.

Tornadoes remain one of nature's most elusive phenomena. Despite years of intensive research, there is still much to learn about tornado formation. In a nutshell, strong thunderstorms feature a horizontally rotating column below the storm. When this column of air is pivoted vertically by a strong updraft's wind shear, a funnel cloud forms. This process is known as tornadogenesis. Once the funnel cloud touches the ground, it is then considered a tornado.

There have been several significant tornado outbreaks across the country over the past several years. Let's examine a few of these events:

Heavy rainfall within a short time period usually leads to flash flooding. Sometimes, a very high-precipitation thunderstorm will create localized flash flooding in a timeframe under two hours. To differentiate the severity of the flash flood, the NWS categorizes flash flooding into flash flood emergencies and flash flood warnings.

No matter the type of warning, flash flooding can be life-threatening! If you come across a flooded roadway, turn your vehicle around. Even if the water only looks a few inches deep, a washed-out road could be lurking beneath. Every year, countless people in the United States die from flash flooding.

These photos represent the type of situation you want to avoid! Not only does driving through flooded roadways place your life in danger, it also places first responders in harm's way. This man was lucky to escape this flash flood with the help of a fire truck's ladder.

The graphics below depict averages of severe thunderstorms over a given year and month. You can clearly see that number of severe weather days varies greatly based on the year. Also, it is important to note that while severe thunderstorms are more common during the spring and summer months, many parts of the country can experience severe weather during any month of the year. Even northern states like Iowa/Minnesota can witness winter-time tornado events (like December 15, 2021), even though it is very rare that far north during that time of year.

In this section, we'll discuss the various ways to observe weather and report severe storms to us in the future.

When reporting hail, avoid referring to hail stones the size of marbles! Marbles come in many shapes and sizes, and are not as useful to us in determining how big the hail is. Use the chart above to help reference hail sizes.

Above all else, we want you to provide reports safely! Please practice the weather safety tips that we discussed in this presentation - DO NOT risk your life to get us a weather report!

If you are further interested in weather observation for the National Weather Service:

CoCoRaHS is a volunteer network of backyard weather observers of all ages and backgrounds working together to measure and map precipitation (rain, hail and snow) in their local communities. The only requirements to join are an enthusiasm for watching and reporting weather conditions and a desire to learn more about how weather can affect and impact our lives.

SKYWARN’s mission is to collect reports of localized severe weather in the U.S. These reports aid forecasters in issuing and verifying severe weather watches and warnings and to improve the forecasting and warning processes. SKYWARN consists of a network of NWS-trained storm spotters who observe and report severe weather to their local NWS office. 

 This website lists the local contacts for each NWS office .

Thank you for your time! Your storm reports will serve as a crucial piece to our operations during severe weather, and can serve as life-saving information in the community.