![]() ![]() Values over 3,000-4,000 are considered extremely unstable, often indicative of a high-end severe weather event. Measured in Joules per kilogram (j/kg), values near or over 500-1,000 j/kg are often about the low-end needed for widespread severe weather chances. If CAPE is zero, the atmosphere is stable. ( return to top) Key tornado indices via the Storm Prediction CenterĬAPE, or Convective Available Potential Energy, is among the necessary ingredients for storms. Where winds shift, fronts or boundaries can be found. ![]() In general, winds with a lengthy southerly component will efficiently transport moisture northward. In many warm-season cases, that means a southeasterly wind or close. A critical component in tornadogenesis is “backing” low-level winds. When it comes to tornado forecasting, the quick items to look for in actual station observations that aren’t explicitly in the features map include: surface winds and temperatures, as well as dew points (more detail on that below). The chart above is a simple one, and similar to the general surface feature map just above. Weather observations are critical to any severe storm forecast. observations, including wind speed and direction Other features that help produce tornadoes include wind shift zones like the warm front (red lines with half-circle bubbles pointing in the direction of movement), surface trough/dry line (dashed orange line, often connected to a low), and in some cases the cold front (blue line with arrows pointing in the direction of movement). ![]() When it comes to tornadoes, your classic setups involve a low pressure system (little red L above) to the northwest or west of the area of primary severe risk. Tomorrow’s tornado probability ( outlook)ĭay three severe weather outlook | Days 4-8 severe weather outlookĬollege of DuPage | NASA Regional Viewer (Visible, Infrared, Water Vapor) Current surface conditionsĪ surface feature analysis often tells the basic story of any weather setup. Tornadoes also occur in severe thunderstorm watches fairly frequently. Watches, either tornado (red) or severe thunderstorm (blue), indicate that storms are likely to pose the highlighted threat. Severity is up from there, from short-lived in slight to more persistent in enhanced, long-lived in moderate, and exceptional in high. In a marginal risk, one might expect mostly non severe storms, with perhaps an isolated severe weather incident. Levels increase from there to “slight” (SLGT), then “enhanced” (ENH), to “moderate” (MDT), and finally “high” (HIGH). Organized categorical risk of severe storms begins with “marginal” (MRGL). See also: Maximum tornado probabilities by month and yearĢ%, Marginal | 5%, Slight | 10%, Enhanced (hatch = EF2+ greater risk) | 15%, Moderate (as above) | 30%, Moderate (if no hatch) | 30%+, High (hatch = EF2+ greater risk)Ĭurrent outlook areas, radar, and convective watches T he following tornado probabilities correspond to each SPC storm risk category. If a hatched area is included in the image, which is only done with probabilities of 10 percent or higher, strong tornadoes are more of a concern than normal. The probability of a tornado within 25 miles of a point. The key things to know from the experts, select images for more info at source Nav SPC tornado/severe risks | Satellite/surface observations | Key ingredients | General links | NWS office links | Warnings Tornado risk overview – Storm Prediction Center Forecast basics Identifying and understanding ingredients | Search for boundaries and gradients | Looking for what could go wrong :: Spotting basics Tornado shapes and sizes | Tornadic radar signatures ![]()
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