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Frequently Asked Questions (FAQ)

The following is a list of Frequently Asked Questions (FAQ) for the Storm Prediction Center, maintained by Roger Edwards, David Imy and Jay Liang. 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 visit the SPC feedback page. If you haven't already done so, try using our search engine to locate what you are looking for.

We also have a separate FAQ devoted entirely to tornadoes, and another for derechos.

1. SPC questions
1.1 What is the Storm Prediction Center?
1.2 When was the SPC formed?
1.3 Where is the Storm Prediction Center located?
1.4 Is the SPC a part of the National Severe Storms Laboratory?
1.5 How can the media or the public tour or visit the SPC?
1.6 What is the SPC copyright information and web links exchange policy?
1.7 How does SPC forecast severe weather?

2. Watch Questions
2.1 What is a Severe Thunderstorm or Tornado Watch?
2.2 How many watches do you issue in a year?
2.3 Do you issue warnings?
2.4 What's the difference between a watch and a warning?
2.5 Does the SPC issue all severe weather watches and warnings?
2.6 Why are watches not issued for all severe storms?
2.7 I noticed the wording "THIS IS A PARTICULARLY DANGEROUS SITUATION" in some of your watches. What does this mean?
2.8 Do you forecast hurricanes and tropical storms?
2.9 Where can I get a list of the points used for watch locations?
2.10 What is the watch status line (line with an arrow inside a watch) and how is it interpreted?
2.11 Who clears watches?
2.12 What do the watch probability numbers mean? How are these different from outlook probabilities?
2.13 Do you have an e-mail or text messaging service for watches and warnings?

3. Outlook Questions
3.1 What is this "Z" time that you use all over your outlooks and also in other SPC forecasts?
3.2 Where can I find a list of the abbreviations and contractions that I see in the Convective Outlooks?
3.3 What do the Slight, Moderate, and High risk categories in the Convective Outlook mean?
3.4 What do the outlook probabilities mean?
3.5 Why do the probability values on the outlooks seem so low?
3.6 What is that nameless green line on Day-1 and Day-2 SPC outlook graphics?
3.7 Where can I get a list of the points used for the Convective Outlook Areal Outline product?
3.8 What do the points in the Convective and Fire Weather Outlook Areal Outline product mean?

4. Weather Questions
4.1 How does the National Weather Service define severe weather?
4.2 How does the National Weather Service define a severe thunderstorm?
4.3 What is organized severe weather and why is it more
important than non-organized severe weather?

4.4 What environmental parameters are most often observed
with organized severe weather?

4.5 Can you tell me what the weather will be like on a specific date? or Is it going to rain today?
4.6 Do you have any educational information about lightning?
4.7 Do you have any general information 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?
4.9 What is a derecho and where do I learn more about them?
4.10 Where can information be obtained on the occurrence of lightning from a past storm event?

5. Tornado Questions
5.1 What is a tornado?
5.2 How many tornadoes occur in a year?
5.3 What is the Enhanced Fujita scale?
5.4 How many tornadoes and tornado deaths occur in a year?
5.5 How does SPC forecast tornadoes?
5.6 Do you have some tornado safety tips?
5.7 How many tornadoes have there been in my state or county?

6. Other Questions
6.1 Why did some severe weather not show up on your reports list? How do I get a list of reports for a particular place or period of time?
6.2 Where is your lightning page? How do I get lightning data?
6.3 Where can I get information on building a safe room in my house to help protect our family from tornadoes?
6.4 What is NOAA Weather Radio and how can it help to protect me?
6.5 How does someone become a meteorologist (at the SPC)?
6.6 How can I get a job at the SPC or in meteorology?
6.7 How can I become a professional storm chaser?
6.8 How are the latitude and longitude numbers expressed on the storm reports page and how can I depict this information at mapquest.com or maps.google.com?
6.9 What are the 3-letter IDs in the Storm Reports Comment section?
6.10 What are the differences between the regular and the raw Storm Reports CSV files?
6.11 What are the differences between the filtered and the unfiltered Storm Reports?
6.12 How do I unsubscribe SMS/Email alerts?
6.13 SPC/University of Oklahoma Career Experience Program
6.14 The Local Storm Reports shown on the NEW webpages www.spc.noaa.gov/exper/reports/ at SPC appear to have more information. What is different?

7. Fire Weather Questions
7.1 What is a Critical Fire Weather Area?
7.2 What is the difference between Critical and Extremely Critical in the Fire Weather Outlook?
7.3 What is a Dry Thunderstorm Critical Fire Weather Area?
7.4 Do you issue fire weather watches or red flag warnings?
7.5 Where can I find historical information about wildfires?
7.6 What criteria does SPC use for its fire weather forecasts?


1. SPC questions (top)

1.1 What is the Storm Prediction Center?
The Storm Prediction Center (SPC) is one of nine 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. For more information on SELS and SPC history, please see this brief overview page and/or this PowerPoint poster (29 MB).

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 are co-located with them and some other NOAA National Weather Service organizations such as Norman Weather Forecast Office, Radar Operations Center, and Warning Decision Training Branch.

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

PUBLIC TOURS
Tours of the National Weather Center (NWC) in Norman, located on the south University of Oklahoma campus, will be offered on Mondays, Wednesdays and Fridays at 1 p.m. Each tour will last approximately 45 minutes. The tour provides a comprehensive overview of the NWC and the units housed within including NOAA's Storm Prediction Center, the Norman National Weather Service Forecast Office, and the National Severe Storms Laboratory as well as the OU School of Meteorology, the NWC observation deck, classroom and laboratory facilities. You must make reservations for a public tour, as space is limited! If you have more than 8 people in your group, please schedule a group tour (see next paragraph). If you have special needs, please note those needs when you make reservations. To reserve a spot on a tour, please contact the NWC Professional Staff Office at tours@nwc.ou.edu or call (405) 325-1147.

GROUP TOURS (35 max)
Tours of the NWC will be offered for groups on Tuesdays and Thursdays between 9 a.m. and 5 p.m. and will last 1 to 1.5 hours. K-12 tours will only be available at 10am or 1pm on Tuesdays or Thursdays. The Group tour is similar to the Public tour, but allows for extra question and answer time. A complete list of names for your group must be submitted prior to the tour. For Group tours, contact the NWC Professional Staff Office at tours@nwc.ou.edu or call (405) 325-1147.

SPECIALTY TOURS(35 max)
If you are interested in a more detailed tour focused on a specific unit or subset of units in the NWC building, please call the following:

For NOAA Weather Partners (National Severe Storms Laboratory, Norman National Weather Service Forecast Office, Storm Prediction Center, Warning Decision Training Branch and/or the Radar Operations Center) contact Daphne Thompson at Daphne.Thompson@noaa.gov or by phone at (405) 325-6892.

MEDIA REQUESTS
Interviews with SPC staff, TV shoots and photo shoots by members of the media should be arranged first through Keli Pirtle, NOAA Public Affairs, (405) 325-6933, or email Keli.Pirtle@noaa.gov. If Keli is unavailable, the backup contacts for urgent media inquiries are Greg Carbin (SPC Warning Coordination Meteorologist) at spc.wcm@noaa.gov, (405) 325-2080, or Peggy Stogsdill (SPC Administrative Officer) at Peggy.Stogsdill@noaa.gov, (405) 325-2067.

1.6 What is the SPC copyright information and web links exchange policy?
We are pleased that you find our web site useful and you are certainly welcome to link to any of our pages.
Information on government servers is public domain, unless specifically annotated otherwise, and may be used freely by the public. NWS data and products form a national information data base and infrastructure which can be used by other government agencies, the private sector, the public and the global community. We encourage innovative and constructive uses of NWS data and products, particularly when they contribute to the protection of life and property and the enhancement of the national economy.
While you are free to use NWS data and products, a few words of caution are in order. First, NOAA and NWS logos and names cannot be used in a manner that implies an endorsement or affiliation with NOAA/NWS. As NWS information changes rapidly in response to weather and climate events, special attention should be given to the date and time of the data and products being displayed. In addition, NWS information may not be modified in content and then presented as official government material. NWS is providing this data as is and the user assumes any risk related to using this data. And in no event is NWS liable to you or anyone else due to your use of this data.
Finally, as required by 17 U.S.C. 403, third parties producing copyrighted works consisting predominantly of the material appearing in NWS web pages must provide notice with such work(s) identifying the NWS material incorporated and stating that such material is not subject to copyright protection.
We do not provide reciprocal links. Our linking policy requires that any links outside of the U.S. government meet very specific standards and requirements. The data must not be available from Federal agencies, must be necessary for and material to the presentation of agency information, and that the contents of the linked pages meet Section 515 Information Quality standards and comply with Department of Commerce restrictions on lobbying.

1.7 How does SPC forecast severe weather?
That's a simple question with a complex and ever-changing answer. The ways we make a forecast vary from event to event, as much as the weather itself, and depends on the timing, location and intensity of the hail, thunderstorm wind and tornado threats. This PowerPoint poster (9 MB) gives a summary of some of the tools and concepts we use in making forecasts.

2. Watch Questions (top)

2.1 What is a Severe Thunderstorm or Tornado Watch?
A Severe Thunderstorm Watch outlines an area where an organized episode of hail 1 inch diameter or larger and/or damaging thunderstorm winds are expected during a three to eight 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. Click here to view a video clip on What is a Watch?

2.2 How many watches do you issue in a year?
The SPC issues approximately 1000 watches each year. Of course, the precise number varies from year to year, depending on weather.

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 well organized or 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? What is the criteria for a PDS watch?
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 exceptionally intense and well organized convective wind storms. PDS watches are issued, when in the opinion of the forecaster, the likelihood of significant events is boosted by very volatile atmospheric conditions. Usually this decision is based on a number of atmospheric clues and parameters, so the decision to issue a PDS watch is subjective. There is no hard threshold or criteria. In high risk outlooks PDS watches are issued most often.

2.8 Do you forecast hurricanes and tropical storms?
We do not forecast tropical weather. That is done by the National Hurricane Center. We do issue tornado watches for inland portions of tropical cyclones when conditions may develop that favor multiple tornadoes.

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 watch status line (line with an arrow inside a watch) and how is it interpreted?
When a watch is issued, the original threat is contained within the entire watch area. When the SPC determines where the severe weather threat continues within a severe thunderstorm or tornado watch, usually on an hourly basis, we issue a watch status message. Unless the whole watch area remains valid, the status report includes points on a line that indicates where the severe weather threat remains from our perspective. The severe weather threat is to the right of that line, as in our outlooks. As adjustments are made to the watch, you will see that yellow "status" line shift across the original watch area. This gives emergency managers, weather forecast offices, media and the general public guidance as to where the threat remains for severe weather.

2.11 Who clears watches?
It is up to the local NWS forecast offices -- not SPC -- to clear or keep counties within the watch once SPC has issued it. Also, only local NWS offices can cancel a watch. Our status lines (described above) are just for guidance purposes to describe the remaining threat area.

2.12 What do the watch probability numbers mean? How are these different from outlook probabilities?
Watch and outlook probabilities have different meanings and should not be compared to each other. Probability numbers for watches tell you the chance that a certain kind of severe weather or combination of severe events (say, 2 or more tornadoes, or 6 or more combined severe hail/wind events) will happen in the whole watch. This is much different from outlook probabilities, which describe the chance of severe weather within 25 miles of any point in the outlook. For more details on outlook probabilities, go here.

Watch probabilities are tagged as Low, Moderate or High. This also is different than how the outlook risks are tied to their probability numbers. For watches, the "Low" category contains probability values ranging from less than 2% to 20% (F2-F5 tornadoes), less than 5% to 20% (all other probabilities), "Moderate" from 30% to 60%, and "High" from 70% to greater than 95%.

2.13 Do you have an e-mail or text messaging service for watches and warnings?
SPC does not offer this type of services. However, there are several private weather companies that do take NWS watches, warnings and other official weather bulletins and send them to individual e-mail addresses, cellular numbers or pager numbers. We can't endorse any one of them in particular (hence, no web links), but feel free to check with weather vendors online. More information can be found: www.weather.gov/subscribe.

3. Outlook Questions (top)

3.1 What is this "Z" time that you use all over your outlooks and also in other SPC forecasts?
The time you see on our products is Universal Coordinated Time (UTC) (also known as Greenwich Mean Time (GMT) or Zulu in military parlance -- hence the "Z" abbreviation). We do this for simplicity since the SPC forecast domain covers multiple time zones across the entire 48 contiguous U.S. states, and since all official weather records for scientific use are stored by Z time. It doesn't change with time zone or with daylight versus standard time, so Z makes an efficient and standardized way to communicate a common time reference, no matter where you are. Please visit this link for a conversion table. Another good site to visit regarding the UTC/GMT/Z time and your local time is US Naval Observatory Master Clock Time (Javascript must be enabled).

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?
Slight, moderate and high risks represent progressively larger threat for organized severe storm episodes. These risks and their graphical labels (SLGT, MDT, HIGH) are based directly on the numerical probabilities of severe weather that we provide with every outlook. See question 3.5 below for more.

3.4 What do the outlook probabilities mean?
For the day-1 outlook graphics, the percentage lines enclose the chance that the given type of severe weather (tornado, hail or damaging thunderstorm wind) will happen within roughly a 25 mile radius of any given point inside that line. For Day-2 and Day-3, the probabilities cover all severe storm hazards together. Categorical (SLGT, MDT, HIGH) labels are tied directly to the probability numbers as defined in this table for Day-1, in this table for Day-2 and this one for Day-3 outlooks.

3.5 Why do the probability values on the outlooks seem so low?
The probability values represent the chance of severe weather within about 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 uncommon at any one location. Your chance of getting a tornado on any random day are very small, climatologically speaking. Put in that context, even a 10% chance of a tornado within 25 miles of a point means a much bigger threat than usual, and should be taken seriously. Think of how often tornadoes normally happen close to you on any given day, and those small-looking probabilities start to seem large by comparison!

3.6 What is that nameless green line on Day-1 and Day-2 SPC outlook graphics?
The green line is the general thunderstorm forecast line on the categorical outlook, and represents a 10% or greater probability of thunderstorms to the right of the line. We only do general thunder forecasts for Day-1 and Day-2 outlooks at this time, but may attempt day-3 general thunder forecasts on at least an experimental basis in the future.

3.7 Where can I get a list of the points used for the Convective Outlook Areal Outline product?
You can find a table containing these locations -- sorted by longitude east-west here and sorted alphabetically by station IDs here.

3.8 What do the points in the Convective and Fire Weather Outlook Areal Outline product mean?
The lat/lon numbers are expressed in decimal degrees to four decimals. For example, in the following:

   CRIT   45300143 44580165 44280242 44530391 45390559 46360575
          49000652 49030478 49000161 48370159 46820149 45300143
the first latitude is 45.30 N and longitude is 101.43 W, the second latitude is 44.58 N and longitude is 101.65 W, and so on. The latitude values are referenced as North and the longitude values are referenced as West. For longitude values equal to or greater than 100, the leading 1 is dropped.

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 at least quarter size, 1 inch in diameter or larger, and/or wind gusts to 58 mph or greater, and/or a tornado. Although lightning can be deadly, the NWS doesn't use it to define a severe thunderstorm. If it did, every thunderstorm would be severe, by definition. Also, excessive rainfall may lead to deadly flash flooding, but heavy rain is not a severe criterion either. The flood threat is handled through a separate set of watches and warnings from your local NWS forecast office.

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, are capable of multiple and/or significant severe weather events, and which 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 small-scale features that influence storms.

4.5 Can you tell me what the weather will be like on a specific date? or Is it going to rain today?
SPC doesn't produce local weather forecasts, and doesn't have the staffing to handle individual forecast requests like this. The SPC home page, along with the main page of any other NWS center or office, will give you local forecasts by city, state or ZIP code, using an entry box at upper left.

4.6 Do you have any educational information about lightning?
The National Severe Storms Lab has a great FAQ about lightning. NWS Pueblo also provides some handy links to web resources on 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?
Unfortunately, no. We don't have the resources or staffing to fulfill every local weather information request we receive. However, the National Climatic Data Center (http://www.ncdc.noaa.gov, phone 828-271-4800) does provide local weather event information -- both in an interactive online website, and for severe and extreme weather events, in a publication called Storm Data.

4.9 What is a derecho and where do I learn more about them?
A derecho is an exceptionally long-lived, widespread, severe, convective wind outbreak. Derecho producing storm systems also can contain tornadoes, but they consist mostly of (and are defined by) damaging non-tornadic wind. Sometimes a derecho results in hundreds of severe wind and damage reports spread along a swath covering multiple states, with deaths, injuries and many millions of dollars in losses. See the SPC derecho FAQ for more information and some historical examples.

4.10 Where can information be obtained on the occurrence of lightning from a past storm event?
The SPC does not maintain a database for past lightning strikes. While the NWS does not endorse any lightning vendors, there are numerous vendors of lightning detection systems and data (e.g., Vaisala's National Lightning Detection Network, WSI's U.S. Precision Lightning Network, Weather Decision Technology's Lightning Decision Support System). A complete list can be found at http://www.nws.noaa.gov/im/more.htm.

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 tornadoes and tornado deaths occur in a year?
Please see the Climatology section of the Tornado FAQ.

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

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

5.5 How does SPC forecast tornadoes?
Please see the Forecasting section in the tornado FAQ.

5.6 Do you have some tornado safety tips?
Many issues of tornado safety are also covered in the Tornado FAQ under its Safety section.

5.7 How many tornadoes have there been in my state or county?
This question is answered in the Tornado FAQ.

6. Other Questions (top)

6.1 Why did some severe weather not show up on your reports list? How do I get a list of reports for a particular place or period of time?
The listings on the SPC Storms Reports page are automatically collected from thunderstorm-related local storm reports (LSRs for short) sent out by the local NWS offices. If there was no LSR for an event, or it arrived a week or more late, the report probably won't show up here. Our storm reports list is preliminary and likely does not contain all severe weather reports for any particular event. For example, non-thunderstorm related strong wind events such as hurricanes will NOT be decoded in the SPC LSR. Storm surveys may be needed to confirm tornadoes, EF scale, find out if damage really was from a tornado or other thunderstorm winds, etc. You can search Storm Data, from the National Climatic Data Center, which provides the official, final data for severe weather reports. Storm Data takes a few months to compile, so if you need information on more recent severe weather reports, please contact your local NWS office.

6.2 Where is your lightning data page? How do I get lightning data?
We don't have a web page with lightning data. Unlike most weather data in the US, which is collected by the NWS and paid for by tax dollars, "live" lightning data is completely privatized, meaning companies collect and distribute it for a price. You won't find it for free anywhere on the web unless the provider gives them a license to do so. Lightning data (like you may see on TV weather reports) is sold on contract by companies which gather the strike points through sensors they have deployed around the country. NWS does get lightning data for internal forecast use, but because it is locked in proprietary contract, it cannot be redistributed. Commercial lightning data providers can be found using "lightning data" in a reputable Internet search engine.

6.3 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. Helpful tips on getting started with safe rooms also are provided by the Federal Emergency Management Agency.

6.4 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 NOAA Weather Radio page.

6.5 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, and NSSL maintains an online list of colleges providing meteorology degrees.

6.6 How can I get a job at the SPC or in meteorology?
See http://www.nssl.noaa.gov/faq/faq_careers.php

6.7 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.

6.8 How are the latitude and longitude numbers expressed on the storm reports page and how can I depict this information at mapquest.com or maps.google.com?
The lat/lon numbers are expressed in decimal degrees to two decimals.
For example, in the following report:

    1108 100 NEODESHA WILSON KS 3742 9568 (ICT)
the latitude is 37.42 (or 37.42N) and longitude is 95.68 (or -95.68W)
The latitude values are referenced as North, and the longitude values are referenced as West and negative. The negative signs are included in the comma separated values (CSV) files for the ease of importing into other mapping programs.
A lat/lon interface at mapquest.com: http://atlas.mapquest.com/maps/latlong.adp
Similar lat/lon interface at maps.google.com: http://maps.google.com/

6.9 What are the 3-letter IDs in the Storm Reports Comment section?
The 3-letter IDs represent the reporting WFO office for the report. For example,

QUARTER SIZED HAIL...STRONG WINDS WITH POWER OUTAGES AND VERY HEAVY RAIN. (OAX)
The report above was from (OAX) which is Omaha, NE WFO. Follow this link to see a list of all WFO IDs and Locations.

6.10 What are the differences between the regular and the raw Storm Reports CSV files?
The differences between the regular vs raw CSVs are as follows:

  1. raw CSVs capture all decoded LSRs with de-duplication of identical reports,
  2. the regular LSRs are de-duplicated based on:
    1. same occurance time
    2. same lat/lon location
    In all categories, most recently issued report of the pair is kept by comparing LSR issuance times
We noticed sometimes the comments/remarks in the LSR regarding the same event can span multiple reports. With the raw files, all comments are captured and anyone can decide how to de-dup the LSRs themselves.

6.11 What are the differences between the filtered and the unfiltered Storm Reports?
Unfiltered: On March 8, 2011, the SPC started providing unfiltered storm reports by removing space/time filtering on incoming National Weather Service (NWS) Local Storm Reports (LSRs). This approach is consistent with NWS storm-based verification methods. However, identical reports are removed from SPC logs and should not appear on the preliminary maps and lists.

Filtered: The space/time filtering had been used by SPC in an attempt to reduce duplicate reports and limit artificially inflated initial estimates of severe weather events when many reports arrived for the same event. The filtering is applied to each of the tornado, hail and wind reports separately.

The logic implemented for filtering is as follows:

  1. Same county and state
  2. Same regular expression of deaths/fatalities
  3. Spatial/Temporal differences between pairs
    1. Less than 5 miles and 5 minutes for tornadoes
    2. Less than 10 miles and 15 minutes for hail and wind reports. (the higher wind speed and larger hail size reports are kept.)
The filtering logic is applied to tornado, hail and wind reports separately. For example, a tornado report and hail report for the same location and time are kept in their respective reports.

6.12 How do I unsubscribe SMS/Email alerts?
The actual delivery of the experimental SPC products SMS/Email alerts are provided by a contractor (govdelivery.com). To unsubscribe either the SMS or Email alerts, there are two options:

  1. follow instructions on http://www.weather.gov/emailupdates/unsubscribe.php.
  2. email your mobile number or your email address used to sign up the alert service to spc.feedback@noaa.gov for manual unsubscription. (There may be some delay in processing using this method.)

6.13 SPC/University of Oklahoma Career Experience Program
The Storm Prediction Center (SPC) and OU School of Meteorology (SoM) Career Experience Program is an unpaid, “for credit” opportunity offered through the SoM. The objective is to provide the second semester junior or senior undergraduate, or first-year graduate student holding strong interests in severe weather forecasting and related research with a semester-long experience to focus their career goals and provide an opportunity to apply meteorological principles in an operationally oriented research and hands-on setting. The student will spend between 8-10 hours per week (3 credit hours of METR 3890) at the SPC working on a research project related to U.S. hazardous weather events, culminating in a term paper from the student. The student will have the opportunity to spend several days in the SPC operations area to interact with forecasters and learn about the SPC severe weather forecast process.

  1. Click here for Spring 2013 semester announcement.
  2. Click here for Spring 2013 semester application (Deadline Tuesday, November 20, 2012).

6.14 The Local Storm Reports shown on the NEW webpages www.spc.noaa.gov/exper/reports/ at SPC appear to have more information. What is different?
The Storm Prediction Center (SPC) has been decoding National Weather Service (NWS) Local Storm Reports (LSRs) in an automated fashion for about 20 years, with little change in the format and content. Historically, certain parts of the LSR had been truncated or ignored for the case of brevity. The new, experimental LSR decoder contains more information by retaining more from the listing of the report. Thus, the new changes will mean keeping the source of the report, extending the remarks section to include all 500 characters, and saving whether the report magnitude was measured, estimated, or unknown. Also, for the first time the LSR decoder will extend beyond severe weather to include winter weather related type reports from the NWS. The winter weather LSRs include the following types: Blizzard, Freezing Rain, Ice Storm, Heavy Snow, Sleet, and Snow. The new Reports page also provides search capabilities by States, and/or by County Warning Areas (CWAs) and by Time ranges.

7. Fire Weather Questions (top)

7.1 What is a Critical Fire Weather Area?
Critical Fire Weather Areas for Wind and Relative Humidity are typically issued when strong winds (>20 mph) and low relative humidities are expected to occur where dried fuels exist, resulting in a significant threat for wildfires.

7.2 What is the difference between Critical and Extremely Critical in the Fire Weather Outlook?
Critical and Extremely Critical represent progressively larger threats for wildfire spread. Extremely critical areas are issued when very strong winds and very low RH are expected to occur with very dry fuels. Extremely Critical areas will be rarely issued, similar to the very low frequency of High Risk Convective Outlooks.

7.3 What is a Dry Thunderstorm Critical Fire Weather Area?
Dry thunderstorm critical fire weather areas are typically issued when widespread or numerous thunderstorms producing little wetting rain (<0.10 in) are expected to occur where dried fuels exist. This can result in many fire ignitions, particularly in the Western U.S. during the summer.

7.4 Do you issue fire weather watches or red flag warnings?
The SPC only issues fire weather outlooks. Your local National Weather Service office issues fire weather watches and red flag warnings for your area. Try this page to help you find the nearest office to you.

7.5 Where can I find historical information about wildfires?
The National Interagency Fire Center provides information for current and historical fires at this page.

7.6 What criteria does SPC use for its fire weather forecasts?
Critical fire weather criteria document in MS-Word or PDF.

More unanswered questions? Post your questions on the Feedback page.

Acknowledgments:Current and past contributors to this FAQ (alphabetically) include Greg Carbin, Roger Edwards, Greg Grosshans, David Imy, Mike Kay, Jay Liang, Joe Schaefer and Rich Thompson. In addition to them, Jared Guyer has answered a good deal of e-mail questions through our feedback service.

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