Traditional ensemble probabilities have difficulty providing meaningful information for storm scale fields such as updraft helicity, which can significantly vary over short distances. Neighborhood probabilities, discussed within this article from the Storm Prediction Center, provide a means through which to evaluate probabilistic information for such storm scale fields. The neighborhood ensemble probability fields available from this page are generated using an approach which considers a radius of 40 km around each grid point when determining whether a given threshold is "met". This is done by finding the maximum value of a given parameter within 40 km of each model grid point. This information is then evaluated across the four member ensemble in order to determine the probability of occurrence for a particular parameter and threshold. These probabilities are based upon the four concurrent members, where each member has equal weighting in the calculation. For example, if one of four solutions satisfies the given criteria the probability would be 25% (if two of four, then it would be 50%).

Click here for configuration information on each member.

DISCLAIMER: The mesoscale prognostics depicted on these pages may not be  available at all times. The accuracy or reliability of the data is not guaranteed nor warranted in any way. The data is provided as is and should not be used as the sole resource for decision making. Mesoscale forecast guidance is best interpreted by a professional meteorologist who is familiar with the particular modeling system, including any model biases.