Storm Prediction Center
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Storm Prediction Center logo
The Storm Prediction Center is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service, which in turn is part of the National Oceanic and Atmospheric Administration (NOAA) of the U.S. government. Until October 1995, the SPC was known as the National Severe Storms Forecast Center (NSSFC).
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Overview
The SPC is responsible for identifying the risk of severe weather that may cause damage, then issuing a severe thunderstorm watch, tornado watch, or mesoscale discussion. The SPC also issues severe weather forecasts for up to two days in advance. Watches issued by the SPC are generally no less than 50,000 square miles in area and are normally preceded by a mesoscale discussion.
Severe weather outlooks
Several times daily, the SPC issues categorical and probability forecasts. They are labelled and issued by day. Day 1 outlooks refer to the current day and include graphics relating the probability of tornadoes, hail, wind, and severe weather in general. Day 2 outlooks refer to tomorrow's weather and only include a general overview with a probability graph. Finally, Day 3 outlooks refer to the day after tomorrow, and include the same "break outs" as the Day 2 outlook.
Critical areas (often referred to as "hatched areas" because of their representation on Day 1 outlooks) refer to an increased or imminent threat of severe weather. For example, a critical area on the "Hail" graphic would be hatched to indicate an imminent threat of large hail within that region.
Local forecast offices of the National Weather Service, radio and television stations, and emergency planners often use the forecasts to gauge the potential severe weather threats to their areas.
Mesoscale discussions
Mesoscale discussions (or "MD"s) generally precede a tornado watch or severe thunderstorm watch. They're designed to give forecasters an update on a region that is becoming a severe weather threat. (However, it's important to note that these discussions are often associated with other events such as blizzards or freezing rain.)
The discussions generally break down a smaller area for review than is given in the severe weather outlook. If a mesoscale discussion is issued and the weather trend for that area continues, a weather watch is generally issued in one to three hours for roughly the same area.
External links
- SPC (http://www.spc.noaa.gov)