Meteorological Consulting Services
A Precipitation Frequency Estimate (PFE) is a depth of precipitation, occurring over a specific a duration of time, at a specific location that has a particular probability of occurring in any given year. For example, a storm that drops 4.57 inches of precipitation in a 24-hour period in Denver, Colorado represents a 100-year 24-hour PFE. The 100-year terminology means a precipitation event of this magnitude occurs, on average, every 100-years, which is termed an Average Recurrence Interval (ARI). From a probabilistic perspective, a precipitation event with an ARI of 100-years equates to a 1% chance of occurring in any given year; this is known as the Annual Exceedance Probability or AEP.
PFEs serve as a fundamental resource that allow the estimation of design rainfall events and ensuing floods in order to optimize planning and design of engineering projects. PFEs provide engineers and hydrologists the needed information to build and efficiently operate safe hydraulic infrastructure (e.g., culverts, bridges, dam spillways, stormwater/drainage systems, mines, nuclear power plants, industrial plants, etc.). Projects of this nature are of great importance given the costs, lives at risk and potential property damage associated with hydrologic structure failures. The demand for improved precipitation statistics is driven by clients developing safe, efficient and cost-effective water retaining structures through risk-based analyses instead of a traditional deterministic (single design number) approach.
This shift in philosophy and regulation towards risk-informed decision making is being driven by regulatory agencies around the world, including the U.S.’s Federal Energy Regulatory Commission (FERC) which says deterministic (single value) hydrometeorological approaches are no longer adequate for ascertaining the risks associated with dams and nuclear power plants. Typically, to evaluate potential hydrologic-related failures of a structure, PFEs well beyond 10,000 years are required. The computation of PFEs, with uncertainly bounds, for events that have a 0.00000001% chance of occurring in any given year require large data sets, unique statistical skills and sophisticated methods. We are nationally-recognized experts in the development of regional precipitation-frequency (PF) analyses, Probabilistic Flood Hazard Analysis (PFHA) using stochastic flood modeling (e.g., Stochastic Event Flood Model or SEFM) and gridded storm analyses for historical extreme events and near real-time hydrologic modeling efforts. We currently have projects underway emphasizing the use of precipitation frequency results in Risk-Informed Decision Making for a number of state and local clients. Trust the MetStat team in computing these precipitation analytics for your project.
The World Meteorological Organization defines probable maximum precipitation (PMP) as “the greatest depth of precipitation for a given duration meteorologically possible for a given size storm area at a particular location at a particular time of year, with no allowance made for long-time climatic trends.” PMPs represent a deterministic precipitation value that conveys no randomness or uncertainty. The PMP is a single precipitation value for a specific watershed that may be used to compute the Probable Maximum Flood (PMF), which is the largest flood, considering snow melt and other applicable factors, that could conceivably occur. PMP and PMF are worst-case scenarios that have traditionally been used to design and safely operate hydraulic infrastructure (e.g., dam spillways, tailing dams at mine sites, nuclear power plants, industrial plants). Generalized PMP values for the United States are available in a series of Hydrometeorological Reports (HMRs) published between 1963-1994. Rely on MetStat to re-evaluate/re-compute PMPs for the following reasons:
- The HMRs themselves recommend site-specific PMP studies in areas with complex terrain where the generalized PMP values should be refined.
- Although based on the best available data and science at the time (1960s-1970s), the HMRs are simply outdated. Updated PMP studies leverage much larger data sets, new techniques and far greater computing power.
- Re-licensing of dams and nuclear power plants often require a hydrologic assessment to ensure the structure is adequate for conveying the PMF, which requires a PMP analysis.
- In some areas of the world, PMPs simply do not exist, but regulatory agencies require them for any new construction.
From site-specific to regional PMP studies, our team is equipped with the knowledge, experience and data sets to perform PMP studies worldwide.
MetStat is also capable of providing hydrologic modeling studies as well as a variety of services in support of hydrologic modeling studies. In addition to the model inputs provided by our storm analysis and precipitation frequency products, MetStat operates the Stochastic Event Flood Model (SEFM), a stochastic flood model capable of developing flood-frequency relationships.
Since 1994, MetStat has been trusted with a variety of interesting, challenging and unique projects. Equipped with large databases, countless scripts/programs and skillful team members, MetStat is accustomed to taking on a variety of meteorological consulting, including forensic analysis, climate mapping and climate change assessments, and other miscellaneous projects. Our extensive internal databases of storm data, precipitation observations, and Numerical Weather Prediction (NWP) amounts to several terabytes of disk space for use in various consulting applications. We also utilize Amazon Web Services (AWS) cloud computing and storage solutions to store our data, as well as operate highly adaptable virtual computer systems that scale to any size of job.
Our team has over 100 years of combined experience and hails from a variety of disciplines, including academic, government and private industry backgrounds in weather, climate, hydrology, regulatory, and statistical fields. Our rich blend of backgrounds provides our team with a well-rounded and helpful perspective.
Our comprehensive understanding of precipitation and hydrology allows us to develop reliable techniques to blend weather radar data together with observed data to reconstruct weather events to support a wide variety of purposes, including legal, insurance, modeling, and design. In fact, given our extreme rainfall/precipitation specialty, we are on the World Meteorological Organization (WMO) extreme precipitation evaluation committee, which is responsible for assessing the validity of potentially new world record rainfall intensities.