The following is a list of Frequently Asked Questions (FAQ) for the Storm Prediction Center. If you are looking for a specific topic please see if it has already been answered here before emailing us. If it hasn't then please email us at spc.feedback@noaa.gov. If you haven't already done so, try using our search engine to locate what you are looking for.

Roger Edwards has also created a separate FAQ devoted solely to tornadoes.

1. SPC questions

2. Watch Questions

3. Outlook Questions

4. Weather Questions

5. Tornado Questions

6. Other Questions

1. SPC questions (top)

1.1 What is the Storm Prediction Center?
The Storm Prediction Center (SPC) is one of 7 National Centers for Environmental Prediction. Our mission is to provide timely and accurate forecasts and watches for severe thunderstorms and tornadoes over the contiguous United States. The SPC also monitors heavy rain, heavy snow, and fire weather events across the U.S. and issues specific products for those hazards.

1.2 When was the SPC formed?
The Storm Prediction Center, formerly known as SELS (Severe Local Storms) Unit became an organization in 1953. SELS became the National Severe Storms Forecast Center in 1966. The name was changed to the Storm Prediction Center in 1995.

1.3 Where is the Storm Prediction Center located?
We are located in Norman, Oklahoma

1.4 Is the SPC a part of the National Severe Storms Laboratory?
The SPC is not a part of the National Severe Storms Laboratory (NSSL). We currently share a building with them however.

1.5 How can the media, or the public, tour or visit the SPC?

PUBLIC TOURS

Individual and group tours of the Storm Prediction Center are available by appointment. For more information, e-mail Peggy Stogsdill (SPC Administrative Officer) at peggy.stogsdill@noaa.gov, telephone/voice mail (405)579-0707.

MEDIA REQUESTS

Note that we may occasionally be unable to schedule tours when staffing could be insufficient to handle them -- especially during peak severe storm months of April-June. These may have to be limited, postponed or canceled in the event of severe weather outbreaks.

2. Watch Questions (top)

2.1 What is a Severe Thunderstorm or Tornado Watch?
A Severe Thunderstorm Watch outlines an area where hail 3/4 inch diameter or larger hail and damaging thunderstorm winds are expected to occur during a three to six hour period. A Tornado Watch includes the large hail and damaging wind threats, as well as the possibility of multiple tornadoes. Typical watches cover about 25,000 square miles, or about half the size of Iowa.

2.2 How many watches do you issue in a year?
The SPC issues approximately 1000 watches each year.

2.3 Do you issue warnings?
The SPC only issues watches. Your local National Weather Service office issues warnings for your area. Try this page to help you find the nearest office to you.

2.4 What's the difference between a watch and a warning?
A watch means severe weather is possible during the next few hours, while a warning means that severe weather has been observed, or is expected soon.

2.5 Does the SPC issue all severe weather watches and warnings?
The SPC issues all Severe Thunderstorm Watches and Tornado Watches. All warnings are issued locally (see Question 2.3)

2.6 Why are watches not issued for all severe storms? Many severe thunderstorms affect only a small area for a short period of time, making watches impractical. Watches are issued primarily for areas where significant severe weather is possible, or the severe weather threat is expected to persist for many hours.

2.7 I noticed the wording "THIS IS A PARTICULARLY DANGEROUS SITUATION" in some of your watches. What does this mean?
The "particularly dangerous situation" wording is used in rare situations when long-lived, strong and violent tornadoes are possible. This enhanced wording may also accompany severe thunderstorm watches for intense convective wind storms.

2.8 Do you forecast hurricanes and tropical storms?
We do not forecast tropical weather. That is done by the Tropical Prediction Center.

2.9 Where can I get a list of the points used for watch locations?
You can find a table containing these locations (sorted by LAT/LON) here or (sorted by Station IDs) here.

2.10 What is the yellow watch status line and how is it interpreted?
When the SPC determines where the severe weather threat continues within a severe thunderstorm or tornado watch, we issue a watch status message. This message indicates where the severe weather threat remains from our perspective.

Think of the watch status line like our outlook lines. Whenever and wherever a line is drawn, the threat for severe weather can be found to the right of that line. That is why outlooks are drawn with arrowheads. This allows a user to quickly see the direction of the line in order to determine the threat focus.

For watch status lines, the same idea holds true. When a watch box is issued, the original threat is contained within the entire watch box area. Weather conditions rapidly change in a severe weather environment and as time goes on, adjustments need to be made by the SPC forecasters to highlight the remaining severe weather threat.

As adjustments are made to the watch box, a user will see a yellow line with an arrowhead, denoting the direction of the line, drawn within it. This indicates that a continued severe weather threat can be expected to the right of the yellow watch status line within the watch box. In essence, this is how the SPC "shaves" off parts of the watch box.

This gives emergency managers, weather forecast offices, and the general public guidance as to where the threat remains for severe weather.

3. Outlook Questions (top)

3.1 I don't understand the time that you use on your products. Is it some type of military time or something?
The time you see on our products is Universal Coordinated Time (also known as Greenwich Mean Time). Please visit this link for more information about UTC.

3.2 Where can I find a list of the abbreviations and contractions that I see in the Convective Outlooks?
We have a page devoted to the abbreviations and acronyms that you'll find in our products.

3.3 What do the Slight, Moderate, and High risk categories in the Convective Outlook mean?
We have a complete discussion of the risk levels in our description of the SPC products.

3.4 Where can I get a list of the points used for outlook area definitions?
You can find a table containing these locations (sorted by LAT/LON) here (sorted by Station IDs) here.

4. Weather Questions (top)

4.1 How does the National Weather Service define severe weather?
There are many forms of hazardous, or severe weather. The primary mission of the National Weather Service is to provide forecasts and warnings for the protection of life and property. Forecasts can range from the climate and seasonal outlooks for agricultural interests provided by the Climate Prediction Center (www.cpc.ncep.noaa.gov), to the daily county forecasts for the public issued by local NWS offices. The NWS issues warnings for heavy snow, freezing rain, high winds, flash flooding, river flooding, thunderstorms, tornadoes, tropical storms, and hurricanes. In a broad sense, these are all defined as severe weather as any of them can and do pose a threat to life and property.

4.2 How does the National Weather Service (NWS) define a severe thunderstorm?
The term severe thunderstorm refers to a thunderstorm producing hail that is dime size, 0.75 inches in diameter or larger, and/or wind gusts to 58 mph or greater, and/or a tornado. Although lightning can be deadly it is not a criterion for what the NWS defines as severe thunderstorm since any ordinary thunderstorm can produce a lot of lightning. Also, excessive rainfall may lead to flash flooding, but heavy rain is not a criterion for a severe thunderstorm.

4.3 What is organized severe weather and why is it more important than non-organized severe weather?
To some degree, all thunderstorms are organized. We refer to "organized" severe storms as those which persist for several hours and we are able to forecast consistently. The most long-lived, intense tornadoes and largest hail are usually produced by supercell thunderstorms, while the most serious convective wind storms are produced by bow echoes. The most serious severe storms tend to form in areas where the vertical wind shear is relatively strong and has particular characteristics, while shorter-lived storms are most common when vertical wind shear is weak.

4.4 What environmental parameters are most often observed with organized severe weather?
In general, severe thunderstorms form in areas where moisture, instability, and lift are present. Additionally, long-lived severe thunderstorms are often associated with strong vertical wind shear (e.g., winds that change direction and increase in speed with height). Unfortunately, thunderstorm initiation is not well-understood, and weather observations are too widely spaced to detect all important features.

4.5 Can you tell me what the weather will be like on XXX date? or Is it going to rain today?
We do not have the time or resources to service individual requests like this. Please try your local NWS office.

4.6 Do you have any information about lightning?
The National Severe Storms Lab. has a great FAQ about lightning.

4.7 Do you have any general information about thunderstorms?
NSSL also has a great FAQ about thunderstorms.

4.8 Can you give me details on a particular hailstorm, thunderstorm or tornado which hit on a certain date? Or can you tell me about hail or wind damage for the last 20 years in a certain place?
No. We don't have the resources or manpower to fulfill every local weather information request we receive. However, the National Climatic Data Center (http://www.ncdc.noaa.gov) does provide local weather event information -- both in an interactive online website and through a publication called Storm Data.

5. Tornado Questions (top)

5.1 What is a tornado?
This is the first question in the tornado FAQ. Please read the information there.

5.2 How many violent tornadoes occur in a year?
Please see Question ? in tornado FAQ

5.3 What is the Fujita scale (F-scale)?
Please see the discussion in the tornado FAQ

5.4 How many tornadoes occur in a year?
Please see the Climatology section in the tornado FAQ

6. Other Questions (top)

6.1 Why do the probability values on the experimental probabilistic outlooks
always appear relatively low?
The probability values represent the chance of severe weather within 25 miles of a point, which is about the size of a major metropolitan area. Though severe storms tend to receive a large amount of media coverage, severe weather is rare at any one location. A 25% chance of a tornado within 25 miles of a point represents a significant severe weather threat. Think of how often tornadoes occur close to you on days with thunderstorms, and the relatively low probabilities begin to make more sense!

6.2 Where can I get information on building a safe room in
my house to help protect our family from tornadoes?
A structural engineer or contractor can help you plan a safe room or shelter for your home.Other tips on tornado safety are also provided by the Federal Emergency Management Agency.

6.3 What is NOAA Weather Radio and how can it help to protect me?
NOAA Weather Radio is a broadcast system which is available 24 hours a day that continuously plays the latest warnings, watches, and forecasts. These radio broadcasts can save your life in severe weather situations. For further information please refer to the this page.

6.4 How does someone become a meteorologist (at the SPC or elsewhere)?
Usually, a Bachelor of Science (B.S.) degree in Meteorology is required to enter the field and work as a forecaster. Some course work and experience can also be gained in the military, especially the Navy and Air Force. Many forecasters continue on to graduate school and acquire advanced degrees (M.S. and PhD) in meteorology, atmospheric science, mathematics, and computer science. Additional information about meteorology education can be found on our Links page.

6.5 How can I get a job at the SPC or in meteorology?
See http://www.nssl.noaa.gov/faq/metcareer.shtml

6.6 How can I become a professional storm chaser?
Very few people make a living as storm chasers. The vast majority of people who chase storms do so as a hobby in their spare time, often at a cost of hundreds or thousands of dollars a year. To become a professional storm chaser, you must be able to consistently acquire and successfully market your storm photographs and video. You may also develop enough skill to have others pay to ride along with you on chases. However, it takes many years to become a safe and successful storm chaser, and the market for storm chase pictures/video and tours is quite competitive. The best way to approach storm chasing is to ride along with more experienced chasers for a few years, and practice severe storm forecasting at every opportunity.

If you could not find an answer to your question
then please email us at spc.feedback@noaa.gov

Acknowledgments:Thanks to Rich Thompson and Greg Carbin for answering many of the questions. Thanks also to Roger Edwards for answering so many questions personally through email.