HOUSTON — Living in Houston comes with its benefits. It also comes with the daily possibility that severe weather could strike at any moment.
One of the many jobs of the Storm Prediction Center is to provide warnings to areas it thinks will be hit by severe weather days in advance.
One of the ways the SPC does that is by designating threat levels for certain areas in danger of certain weather events.
What do the SPC threat levels mean?
In order of risk and severity, here are the five risk categories and what each of them means, according to the SPC:
- Marginal (Dark green): This initial level means isolated severe thunderstorms are possible. Storms would likely be limited in how long they last, how much area they cover and how intense they become.
- Slight (Yellow): A slight risk means scattered severe storms are possible, though they'd likely be short-lived and not have widespread coverage over an area. While they might not be as persistent, these storms could still produce isolated intense conditions.
- Enhanced (Orange): Under enhanced conditions, numerous severe storms are possible. This level is marked by more persistent and widespread storms, a few of which could be intense.
- Moderate (Red): Jumping to a moderate risk level means more widespread severe storms are likely, and they could be long-lived and intense.
- High (Magenta): An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes or a long-lived derecho-producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage. This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe (i.e., violent tornadoes or very damaging convective wind events).
What defines severe weather?
The National Weather Service defines a severe thunderstorm as any storm that produces one or more of the following elements:
- A tornado.
- Damaging winds or speeds of 58 mph (50 knots) or greater.
- Hail 1 inch in diameter or larger.
The SPC further defines significant severe thunderstorms as any storm that produce one or more of the following elements:
- A tornado produces EF2 or greater damage.
- Wind speeds of 75 mph (65 knots) or greater.
- Hail 2 inches in diameter or larger.
What is the SPC?
(Wording from the SPC website)
The Storm Prediction Center (SPC) is part of the National Weather Service (NWS) and the National Centers for Environmental Prediction (NCEP). 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 for hazardous winter weather and fire weather events and issues specific products for those hazards. We use the most advanced technology and scientific methods available to achieve this goal.
